Cranes, lifts, and scaffolding are three types of equipment that, in different ways, enable employees to effectively perform work from heights. Cranes lift and lower loads and move them horizontally, aerial lifts are vehicle-mounted devices used to elevate personnel, and scaffolding refers to temporary support structures. Using this equipment safely and effectively requires knowledge and training in the hazards involved, such as falls and electric shocks.
Mobile cranes in the construction industry
- OSHA regulates cranes in the construction industry under 29 CFR 1926 Subpart CC, which applies to a wide array of equipment that is power-operated and can hoist, lower, and horizontally move a suspended load.
For employees who operate or work around cranes or derricks, it’s critical that they understand and comply with the necessary work practices established by their company to keep them safe from crane accidents.
Employees should have a basic understanding of electricity and the clearance distances necessary to minimize danger when working near power lines or other electrical sources. An understanding of the hazards associated with crane assembly/disassembly, rotating superstructures, energized equipment, and falls is also key to overall safety.
Scope/Who must comply
The Occupational Safety & Health Association (OSHA) regulates this at 29 CFR 1926 Subpart CC — Cranes and derricks in construction.
OSHA’s Subpart CC applies to power-operated equipment, when used in construction, that can hoist, lower, and horizontally move a suspended load. Such equipment includes, but is not limited to:
- Articulating cranes (such as knuckle-boom cranes),
- Crawler cranes,
- Floating cranes,
- Cranes on barges,
- Locomotive cranes,
- Mobile cranes (such as wheel-mounted, rough-terrain, all-terrain, commercial truck-mounted, and boom truck cranes),
- Multi-purpose machines when configured to hoist and lower (by means of a winch or hook) and horizontally move a suspended load,
- Industrial cranes (such as carry-deck cranes),
- Dedicated pile drivers,
- Service/mechanic trucks with a hoisting device,
- A crane on a monorail,
- Tower cranes (such as a fixed jib, i.e., “hammerhead boom”; luffing boom; and self-erecting),
- Pedestal cranes,
- Portal cranes,
- Overhead and gantry cranes,
- Straddle cranes,
- Sideboom cranes,
- Derricks, and
- Variations of such equipment.
Employer requirements
- Employers are responsible for providing a safe work environment for their employees, including determining safe ground conditions, assessing hazards in the work zone, inspecting equipment to keep it in good working order, and training employees in proper procedures.
Employers are responsible for minimizing hazards to the extent possible and providing employees with the knowledge and resources to work safely in and around mobile cranes.
Determine ground conditions
Employers must determine whether the ground is sufficient to support the anticipated weight of hoisting equipment and associated loads.
The term “ground conditions” means the ability of the ground to support the equipment (including slope, compaction, and firmness).
Assess hazards
Employers must assess hazards within the work zone that would affect the safe operation of hoisting equipment, such as those of power lines and objects or personnel that would be within the work zone or swing radius of the hoisting equipment.
Ensure equipment is safe
Employers must ensure that the equipment is in safe operating condition by performing required inspections.
Train employees
Employers must train employees in the work zone to recognize hazards associated with the use of the equipment and any related duties that they are assigned to perform.
Crane operator requirements
- Crane operators must be certified, but employers should also evaluate them to make sure they have the necessary skills.
The employer must ensure that each operator is trained, certified/licensed, and evaluated before operating any equipment covered under 29 CFR 1926 Subpart CC.
Operator qualification requirements
Being certified doesn’t necessarily make an operator qualified. The most important way to determine an operator’s qualifications is through evaluation during the certification process. The Occupational Safety & Health Association (OSHA) has determined that an employer evaluation is necessary to determine the qualifications of an operator.
Just as a driver’s license doesn’t qualify an employee to operate all types of vehicles, certification doesn’t mean that an operator can use all types of cranes. Ultimately, there are two major issues associated with certified operators who switch to new equipment or tasks without evaluation:
- A certified operator who switches tasks involving the same crane type with different controls could lack the skills to operate new controls.
- An operator assigned to unfamiliar tasks might not have the expertise required to manage or avert accidents or risks inherent during crane operation.
Operator certification requirements
Before the evaluation process begins, operators must be trained and certified in operating either a specific crane type or a crane type with a specific rated capacity. Although employers are required to provide each operator-in-training with sufficient training, certification can be acquired through:
- Licensing from a state or local government,
- A certification by an accredited crane operator testing organization, or
- An audited employer program.
Third-party certification is portable. If an employee acquired certification from a previous employer, that certification is acceptable. However, employers are still required to evaluate an operator with certification, whether from a third party or not.
Until employees pass evaluation, they must be considered operators-in-training and must not use equipment without supervision.
Evaluation of operator qualification
The evaluation process should be performance-oriented. For operators to learn successfully and safely, a competency evaluation is critical. The requirements for the evaluation process have important advantages:
- The process allows a newly hired operator to run the equipment while a new employer gauges the operator’s knowledge, operating skills, and training needs.
- It also allows experienced and certified operators to become accustomed to performing new crane operations or operating different equipment while being evaluated by the employer for that purpose.
(Note: Employers are not required to comply with the evaluation process if operators are using derricks, side-booms, and cranes with a capacity of 2,000 pounds or less.)
Many incidents occur because an operator doesn’t have the equipment-specific knowledge to safely operate a crane. For this reason, OSHA has determined that accidents can be reduced if employers evaluate the operators’ skills and knowledge, as well as their ability to recognize and avert risk necessary to operate the equipment. Employees’ capabilities with the following should be evaluated:
- Safety devices and operational aids;
- Software and the size and configuration of the equipment; and
- Hoisting activities such as blind lifts, personnel hoisting, and multi-crane lifts.
The evaluation can be done by a qualified operator who has already passed evaluation or by an agent. If the employer decides to use an agent, the requirements for evaluation still apply and should be enforced.
An operator who successfully passes evaluation can operate equipment without supervision unless doing so would require different skills, knowledge, or ability to reduce risk. There may be many times when operators switch to new tasks or equipment. In those cases, a new evaluation should be performed to reduce the risk of injury to the operator or employees around the crane and equipment.
Operator documentation, retraining, and validation
- Employers should document operator evaluations and provide retraining as necessary or requested.
- If an operator was certified by a now-defunct organization, employers should check the expiration date of the certification and search online to confirm the legitimacy of the organization.
Employers should document each evaluation, providing:
- The operator’s name;
- The evaluator’s name and signature;
- The date; and
- The make, model, and configuration of equipment used in the evaluation.
Keep the documentation available on the worksite for the duration of the operator’s employment.
(Note: If an operator was hired prior to December 10, 2018, employers are allowed to rely on previous documentation and evaluations rather than conducting new ones.)
If there is an indication that an operator may need retraining, then the employer must provide retraining based on the topic(s) in question. Sometimes, an operator might forget information needed to safely operate equipment, and an accident could occur.
Of course, retraining won’t always happen because of an accident. If an operator indicates a lack of clarity about something, retraining is required. Retraining is ongoing. After the initial evaluation, operator retraining should be required as needed.
Validation of operator certification
As mentioned above, operators can be certified through a crane operator testing organization. These certifications are issued only after the operator has demonstrated through written and practical tests the knowledge and skills required to operate a crane.
In some cases, employers may hire an operator whose certification was acquired through a nationally accredited organization that no longer exists. In these cases, how can an employer ensure sure their operators are adequately certified?
It’s actually an easy question to answer, and options for solving the problem are available.
- Expiration date. There may be an expiration date on the certification. Before restarting the certification process or finding a new testing organization, an employer can check to see if the operator’s current certification identifies an expiration date. This can give some time to look for new testing organizations.
- The regulations. In the Occupational Safety & Health Association’s (OSHA) operator training, certification, and evaluation regulation, the Agency states that a certification issued by an accredited crane operator testing organization is valid for 5 years. If the operator knows when the certification was acquired, the regulations can be used to figure out when it expires.
If an operator’s certification may not really have been issued by a nationally accredited organization, the best way to proceed is to do some digging and find information on the organization. Just because the organization no longer exists doesn’t mean information on its credibility or history isn’t available.
All findings should be clearly documented. Having information ready for immediate evaluation can prove useful should an OSHA inspection occur.
Ground conditions
- Adequate ground conditions for a crane involve the ground’s slope, compaction, and firmness; if any of these is lacking, the crane might tip over.
- The job’s CE is responsible for assessing ground conditions pre-project and arranging measures to improve ground conditions as needed.
The typical construction crane can weigh many tons. Putting this weight on the ground at a construction site can lead to all sorts of problems. The most serious could be crane tip-over caused by the ground underneath the crane giving way.
The Occupational Safety & Health Association (OSHA) has determined that failure to have adequate ground conditions is a significant crane safety problem.
The term “ground conditions” is defined as the ability of the ground to support the equipment. Three key factors are involved in ground conditions:
Adequate ground conditions are essential for safe operations because the crane’s capacity and stability depend on those conditions being present. There are two key problems regarding ground conditions:
- Equipment is often brought on-site by a subcontractor who has little control over ground conditions and lacks any knowledge of hidden hazards.
- The company that does have control over the ground conditions, and could be aware of hidden hazards, may not have the expertise to know what changes are needed to make the area suitable for safe crane operation.
Stability and support
The requirements for ensuring adequate ground support apply both when assembling a crane and during actual crane operation.
The three ground support requirements are:
- Ensure the ground is firm, drained, and graded.
- Supply enough supporting materials, if needed, to keep the crane stable. “Supporting materials” is defined as blocking, mats, cribbing, marsh buggies (in marshes/wetlands), or similar supporting materials or devices. Such materials typically help to distribute the load of the crane over a broad area and/or assist in leveling the equipment.
- Verify that the crane’s “degree of level” is met. This is the crane manufacturer’s specifications for how level the crane must be.
The responsibility for determining if the ground conditions are safe falls to the job’s controlling entity (CE). The CE is defined as an employer who is a prime contractor, general contractor, construction manager, or any other legal entity that has the overall responsibility for the project’s planning, quality, and completion.
Before any equipment is brought to the jobsite, the CE must possess and examine information (such as site drawings, as-built drawings, and soil analyses) to see if there are hazards beneath the crane setup area. If there are hazards identified in those documents, or if the CE has identified other hazards, then the CE must inform the crane user and operator of the hazards.
If the CE is not familiar with the crane or with the ground conditions at a particular jobsite, then the CE is responsible for having someone who is familiar with those requirements:
- Ensure that ground preparations necessary to meet the requirements in 1–3 above are met; and
- Inform the user and the operator of the location of hazards beneath the equipment setup area (such as voids, tanks, and utilities) if:
- Those hazards are identified in documents (such as site drawings, as-built drawings, and soil analyses) that are in the possession of the CE (whether at the site or off-site); or
- The hazards are otherwise known to that CE.
If there is no CE for the project, the ground support requirements in 1–3 above must be met by the employer who has authority at the site to make or arrange for ground preparations.
Assembly and disassembly
Before beginning assembly/disassembly (A/D), the A/D director has to determine whether ground conditions are adequate to support the equipment during that activity. If the A/D director or the operator determines that ground conditions do not meet the ground support requirements, that person’s employer must have a discussion with the CE regarding the ground preparations that are needed so that, with the use of suitable supporting materials/devices (if necessary), the ground support requirements can be met.
Power-line safety
- For safety’s sake, all power lines should be considered to be energized and uninsulated until confirmed otherwise.
- Cranes must either maintain a minimum distance from power lines at all times, or other safety measures (such as having the lines de-energized) must be taken.
All power lines should be considered to be energized unless the utility owner/operator confirms the line has been, and continues to be, de-energized and visibly grounded at the jobsite. In addition, power lines should be presumed to be uninsulated unless the utility owner/operator or a registered professional engineer — who is a qualified person with respect to electrical power transmission and distribution — confirms that a line is insulated.
The Occupational Safety & Health Association’s (OSHA) 29 CFR 1926 Subpart CC requires employers to use a very specific and systematic approach to deal with the hazards of power lines.
(Note: Some of these requirements do not apply to work covered by Subpart V — Power Transmission and Distribution.)
When working near all voltages, the basic procedure is:
- Identify the work zone, assess it for power lines, and determine how close the crane could get to them. The employer has the option of doing this assessment for the area 360 degrees around the crane or for a more limited, demarcated area.
- If the assessment shows that the crane could get closer than the trigger distance corresponding to the voltage of the power line (20 feet for lines rated up to 350 kV, 50 feet for lines rated over 350 kV, or as determined by a qualified person for lines rated over 1000 kV), then requirements for additional actions are needed.
- The additional actions for cranes and derricks operating within the trigger distance are:
- De-energize and ground the lines, or
- Implement encroachment/electrocution prevention measures to prevent the crane from breaching the minimum clearance distance.
The employer is allowed to choose from several minimum clearance distance options.
Equipment operations — Power-line safety (all voltages)
- To minimize power-line hazards, employers must clearly mark or define the work zone and determine whether any part of the crane, load line, or load could get closer than the trigger distance.
- No part of the equipment or load is allowed beneath a power line unless that line is de-energized and visibly grounded.
In addition to frequent and periodic inspections, employers are required to inspect and test equipment to ensure it is capable of safe and reliable operation when initially set up or placed in service and after any major repairs or design modification.
The first step is to determine if power lines pose a hazard. To do this requires the work zone to be identified in one of the following ways:
- Marking boundaries with flags or with a range limit device or range control warning device. Next, the employer must prohibit the crane operator from operating the equipment past those boundaries.
- Defining the work zone as the area 360 degrees around the equipment, up to the equipment’s maximum working radius.
Once the work zone is identified, it must be determined if any part of the crane, load line, or load (including the rigging and lifting accessories) could get closer than the trigger distance to a power line.
The trigger distance is as follows:
- For power lines up to 350 kV: 20 feet
- For power lines from 350–1000 kV: 50 feet
- For power lines over 1,000 kV: The minimum clearance distance must be established by the utility owner/operator or a registered professional engineer who is a qualified person with respect to electrical power transmission and distribution. The clearance distance will be at least 50 feet.
This determination should be made with the assumption that the crane will be operated up to its maximum working radius in the work zone.
If the crane will not get closer than the trigger distance to the power line, then the employer is not required to take any further action.
However, the employer may encounter a situation where it is necessary to increase the size of the work zone. This may occur as a result of an unanticipated need to change the crane’s position or have it operate beyond the original work zone boundaries. If that is the case, the employer must reidentify the work zone and conduct a new trigger distance assessment.
Operations below power lines
No part of the equipment, load line, or load (including rigging and lifting accessories) is allowed below a power line unless the employer has confirmed that the utility owner/operator has de-energized and (at the jobsite) visibly grounded the power line. Exceptions are listed in paragraph 1926.1408(d)(2).
Cranes within 20 feet of the power line
- If a crane could get within 20 feet of a power line, there are three options to minimize this hazard: de-energize and ground the line, rearrange the site (if possible) to maintain a 20-foot clearance, or use the minimum clearance distance corresponding to the line’s voltage.
If the crane could get closer than 20 feet to a power line, one of the three following options must be chosen.
Option 1 — De-energize and ground
Confirmation is received from the utility owner/operator that the power line has been de-energized and visibly grounded at the jobsite. This option is the safest and minimizes the possibility the crane would become energized if it did contact the line. If this option is chosen, the employer does not have to implement any of the other encroachment- or electrocution-prevention measures.
However, there are drawbacks to this. One is the time lag due to the amount of time needed to arrange for the utility owner to de-energize and ground the lines. Another is that when the construction project is small, the cost to de-energize and ground the lines can be excessive in comparison to the cost of the job.
Option 2 — Maintain 20-foot clearance
This option requires a minimum 20-foot clearance be maintained at all times. (If the work requires a closer approach than 20 feet, then Option 3 must be used.) The advantage of using this option is that employers don’t have to determine the exact voltage of the power lines; they only have to determine it is not more than 350kV.
To help make sure the 20-foot distance is not breached, the following precautions are required:
- Planning meeting. A planning meeting must be held with the crane operator and other workers who will be in the area of the equipment or load. During the meeting, the location of the power line(s) and the steps that will be used to prevent intrusion closer than 20 feet must be reviewed.
- Tag lines. If used, they must be non-conductive.
- Warning line. An elevated warning line, barricade, or line of signs should be erected that is in view of the operator. It must have flags or other high-visibility markings to make it easier to see.
- The warning line (or barricade or line of signs) must be 20 feet from the power line. If the crane operator can’t see it, a dedicated spotter must be used.
- Additional safeguards. In addition to the above, at least one of the following must be implemented. (These requirements do not apply to Subpart V — Power Transmission and Distribution work.)
- Proximity alarm set to give sufficient warning to prevent encroachment.
- Dedicated spotter.
- Range control warning device that is set to give sufficient warning to prevent encroachment.
- Limiting device set to prevent encroachment.
- Insulating link installed between the end of the load line and the load.
Option 3 — Follow Table A clearance
For this option, the employer must determine the power line’s voltage (by getting the voltage from the utility owner/operator), then determine whether any part of the crane, load line, or load (including the rigging and lifting accessories) could get closer to the power line than the minimum approach distance allowed in Table A.
When making this determination, assume the crane will be operated up to its maximum working radius when in the work zone, and comply with the minimum clearance distances in Table A. Note that, depending on the voltage, minimum clearance distances can be closer than the 20-foot clearance required for Option 1.
Table A — Minimum clearance distances |
---|
Voltage (nominal, kV, alternating current) | Minimum clearance distance (feet) |
---|
up to 50 | 10 |
over 50 to 200 | 15 |
over 200 to 350 | 20 |
over 350 to 500 | 25 |
over 500 to 750 | 35 |
over 750 to 1,000 | 45 |
over 1,000 | As established by the utility owner/operator or a registered professional engineer who is a qualified person with respect to electrical power transmission and distribution. |
The utility owner/operator must provide the requested voltage information within two days of the request.
If the crane could get closer to the power line than the minimum approach distance allowed in Table A, the same precautions mentioned in Option 2 apply.
Power-line safety (all voltages) — Equipment operations closer than the Table A zone
- Working closer than the Table A distance is allowed under three conditions: the work is impossible otherwise, the line can’t be de-energized, and an expert determines a minimum distance that’s specific to the site.
There are requirements in place to protect employees from contact with power lines. The requirements consist of prerequisites and criteria that apply when work must be done closer than the minimum clearance distance specified in Table A of 1926.1408.
Working closer than the minimum approach distance allowed in Table A is highly discouraged.
However, there is an exception if the following three requirements are met:
- The employer determines it is not possible to do the work without breaching the minimum approach distance in Table A.
- The employer determines after consultation with the utility owner/operator that it is not possible to de-energize and ground the power lines.
- The power-line owner/operator or a registered professional engineer (who is a qualified person with respect to electrical power transmission and distribution) determines the minimum clearance distance that must be maintained to prevent electrical contact, specific to on-site conditions. Some factors that must be considered include:
- Conditions affecting atmospheric conductivity;
- Time necessary to bring the equipment, load line, and load (including rigging and lifting accessories) to a complete stop;
- Wind conditions;
- Degree of sway in the power line;
- Lighting conditions; and
- Other conditions affecting the ability to prevent electrical contact.
The next step is to have a planning meeting that includes the employer and utility owner/operator to determine the procedures that will be followed to prevent electrical contact and electrocution. At a minimum, there are 12 procedures that must be included, per 1926.1410(d)(1) through (d)(12), and these procedures must be documented and immediately available on-site.
Traveling under or near power lines with no load
Equipment traveling under or near power lines with no load is covered at 1926.1411. The minimum clearance distances in Table T must be maintained. For traveling in poor visibility, a dedicated spotter should be used if needed, along with additional precautions.
Danger of getting close to or touching equipment and load
- The possibility of getting close enough to the power line to act as a ground is called “touch potential.”
When cranes are operating near overhead power lines, the crane, load line, or load could come into contact with the lines. If that happens, the electric current will pass through the equipment to the ground.
Anyone touching the crane in this situation will act as a ground, and the electric current will pass through the person. Even if the person doesn’t touch the equipment, the ground near the crane will be energized and present an electrocution hazard.
The Occupational Safety & Health Association (OSHA) refers to this hazard as “touch potential.” Touch potential is the voltage between the energized object and the feet of a person in contact with the object. It is equal to the difference in voltage between the object and a point some distance away.
Note that the touch potential could be nearly the full voltage across the grounded object if that object is grounded at a point remote from the place where the person is in contact with it. For example, a crane that was grounded to the system neutral and that contacted an energized line would expose any person in contact with the crane, or its uninsulated load line, to a touch potential nearly equal to the full voltage of the power line.
People should avoid approaching or coming into contact with any equipment that is operating, or any load being moved, near power lines.
Danger of an energized zone
- If a crane touches a power line, current will pass into the ground, putting anyone standing nearby at risk.
If a crane comes into contact with a power line, the current will pass through the equipment to the ground. This unintentional grounding, more commonly known as a ground fault, enables voltages to be impressed on the “grounded” object that is faulting the line. A person could be at risk of injury during a fault simply by standing near the grounding point.
The Occupational Safety & Health Association (OSHA) refers to this hazard as “step potential.” Step potential is the voltage difference between the two feet of a person standing near an energized grounded object. It is equal to the difference in voltage, given by the voltage distribution curve, between two points at different distances from the electrode.
OSHA recommends that anyone who is not directly involved in the operation being performed should keep away from areas where hazardous step or touch potentials could arise. Anyone on the ground in the vicinity of transmission structures should stay at a distance where step voltages would be insufficient to cause injury.
Common grounding procedures
- Work being done near transmitter towers or power lines must have precautionary measures in place for dissipating voltage.
- Employees who are attaching grounds are at risk of shock and should have adequate protection.
A common method of grounding, which the Occupational Safety & Health Association (OSHA) recommends in 1926 Subpart O — Motorized Vehicles, Mechanical Equipment, and Marine Operations for work near an electrical charge, includes:
- Providing the equipment with an electrical ground directly to the upper rotating structure supporting the boom; and
- Attaching ground jumper cables to materials being handled by boom equipment when electrical charge is induced while working near energized transmitters. Crews must be provided with nonconductive poles having large alligator clips or other similar protection to attach the ground cable to the load.
It’s important to understand that work being performed near transmitter towers or power lines (where an electrical charge can be induced in the equipment or materials being handled) must have precautionary measures implemented to dissipate induced voltages before work is performed. Being aware of the limitations of grounding is key.
Limitations of grounding
According to the preamble to Subpart CC (page 47958 of the Federal Register dated August 9, 2010), “OSHA is aware that employees are exposed to serious electric shock hazards when they are attaching grounds in accordance with 1926.1408(f). For example, when attaching the rigging to the load or the ground to the crane, the crane and load will be energized.
“OSHA views this condition as a recognized hazard and expects employers to ensure that employees are adequately protected when they are attaching grounds. Employers who fail to properly protect their employees in this regard will, in appropriate circumstances, be subject to citation under the General Duty Clause (sec. 5(a)(1)) of the OSH Act.”
Recommended evacuation procedures
Deciding whether to remain inside the cab or evacuate after power-line contact is important, especially where there is an imminent danger of fire, explosion, or other emergency. According to OSHA, to protect crane operators against electrical shock, the following procedures are recommended:
- The crane operator should remain inside the cab until the lines have been de-energized.
- All other personnel should keep away from the crane, ropes, and load since the ground around the machine might be energized.
- The crane operator should try to remove the crane from contact by reversing direction.
- If the crane cannot be moved away from contact, the operator should remain inside the cab until the lines have been de-energized.
Limitations of insulating links, proximity alarms, and range control (and similar) devices
- Insulating links, proximity alarms, and range control devices are all useful tools for minimizing electrical risks but have their limitations.
It’s important to understand that insulating links, proximity alarms, and range control (and similar) devices all have their limitations.
Insulating links
Insulating links serve a dual purpose. They protect a rigger who is handling the load if the equipment upstream of the link makes electrical contact with a power line. They also protect employees who are upstream of the insulating link if the load makes electrical contact with a power line.
The workers who are at the greatest risk of electrocution — the riggers who handle the load — are also protected by the requirement for nonconductive tag lines.
The insulating link option that is available under 1926.1408(b)(4)(v) would not protect against encroachment (certainly a limitation), but it would provide protection to employees handling the load in the event that encroachment did occur.
Insulating links must be installed between the end of the load line and the load. When so installed, these prevent the load from becoming energized in the event the load line or other part of the equipment makes electrical contact with a power line.
Preventing the load from becoming energized helps protect riggers, who often guide crane loads manually and who are at a high risk of being electrocuted if a load becomes energized. For more information on insulating links, including the phase-in period for these devices, see 1926.1408(b)(4).
Proximity alarms
A proximity alarm is a device that warns of the equipment coming near a power line. The device must be listed, labeled, or accepted by an Occupational Safety & Health Association (OSHA) Nationally Recognized Testing Laboratory. The limitations of a proximity alarm include not being operational, or effective against electrocution, during certain phases of the assembly or disassembly process of certain types of cranes.
Range control devices
A range control warning device is a device that can be set by an equipment operator to warn that the boom or jib tip is at a certain plane or multiple planes. The device must be set to alert the operator in time to prevent the boom, load line, or load (whichever is closest to the power line) from breaching the trigger distance.
As a practical matter, the device has to be set to sound the warning before the trigger distance is reached, since the operator will need some time to react and to account for the momentum of the equipment, load line, and load.
Crane assembly/Disassembly hazards
- OSHA requires employers to comply with either manufacturer procedures or employer procedures for crane assembly and disassembly.
- Before beginning A/D, crew members must know their tasks, the associated hazards, and the hazardous locations to avoid on the jobsite.
Some mobile crane accidents happen because of improper assembly and disassembly of the crane on the jobsite. Most of these accidents could be avoided by following the crane manufacturer’s requirements for assembly/disassembly (A/D). That’s why the Occupational Safety & Health Association (OSHA) requires the employer to comply with all manufacturer prohibitions applicable to assembly and disassembly, and use either:
- Manufacturer procedures for assembly and disassembly, or
- Employer procedures for assembly and disassembly.
Manufacturer procedures are generally the first choice. Employer procedures may be used only where the employer can demonstrate that the procedures used do the following:
- Prevent unintended dangerous movement and collapse of any part of the equipment,
- Provide adequate support and stability of all parts of the equipment, and
- Position employees involved in the A/D operation so that their exposure to unintended movement or collapse of part or all of the equipment is minimized.
Employer procedures must be developed by a qualified person.
Synthetic slings are an exception. Employer procedures can’t be used during rigging if the employer uses synthetic slings. Rather, the synthetic sling manufacturer’s instructions, limitations, specifications, and recommendations must be followed.
Proper assembly procedures
Accidents during A/D are often caused by:
- Misunderstanding or confusion by employees as to their tasks and how they are to be performed, or
- Failure to recognize potentially dangerous areas in and around the equipment.
The details of these tasks, and the location of danger areas that workers need to keep out of, often vary from one machine to another. The A/D director is responsible for making sure that the crew members know this essential information before starting the A/D process.
Crew instructions
Before beginning A/D operations, the A/D director must make sure that the crew members understand:
- Their tasks,
- The hazards associated with their tasks, and
- The hazardous positions and locations that they need to avoid.
Before a crew member takes on a different task, or when adding new personnel during the A/D operations, the crew instruction requirements listed above must be met. Crew instructions must be given first.
Capacity limits
Rated capacity limits must not be exceeded for loads imposed on the equipment, equipment components (including rigging), lifting lugs, and equipment accessories. This prohibition applies during all phases of A/D.
In some cases, the crane being assembled is used to install its own counterweights (which can create a capacity limit risk). Early in this process, when few counterweights are in place, the crane’s capacity will be so limited that swinging beyond a certain point, or booming out beyond a certain point, may cause it to overturn.
Note that where an assist crane is being used during the A/D of another crane/derrick, the requirements for rated capacity during operations must be met.
Blocking material
- Blocking, also known as cribbing, is material used to support equipment or components and distribute loads to the ground.
- OSHA requires that the “size, amount, condition, and method of stacking the blocking” be “sufficient to sustain the loads and maintain stability.”
Proper blocking plays an important role in assembly/disassembly (A/D) safety. Blocking is used in a variety of circumstances to compensate for minor ground sloping and to enhance stability by spreading out the area over which forces from the load are transferred to the ground. It is used to help support assembled equipment (usually placed under outrigger pads) and during A/D to support components.
Blocking that is undersized, insufficient in type or number, in poor condition, and/or stacked in an unstable manner could lead to a failure of support and unplanned movement or collapse of the equipment or component.
The Occupational Safety & Health Association (OSHA) defines “blocking” (also referred to as “cribbing”) as “wood or other material used to support equipment or a component and distribute loads to the ground…typically used to support latticed boom sections during assembly/disassembly and under outrigger floats.” (1926.1401)
When blocking is used to support lattice booms or lattice components, the failure to place it in the correct location could have several dangerous consequences. For example, incorrect placement could cause part of the lattice boom/component to bear too much force and damage it.
Damage to the boom/component could compromise structural integrity and, in some cases, may not be immediately noticed. If the assembly process were to continue, the boom/component could fail.
Improper blocking location may also result in a failure to provide adequate support of the boom/component. One example is blocking used to provide support to a boom section, such as after pins are removed. If the blocking is in the wrong place, once the pins are removed, unplanned movement or collapse could result.
OSHA’s regulatory requirement is stated simply as, “The size, amount, condition and method of stacking the blocking must be sufficient to sustain the loads and maintain stability.” (1926.1404)
Verifying assist crane loads
- Before A/D, the loads that will be used on an assist crane must be verified using either calculations or direct testing.
An assist crane is a crane used to assist in assembling or disassembling a crane. When using an assist crane, the loads that will be imposed on the assist crane at each phase of assembly/disassembly (A/D) must be verified (before A/D begins) with at least one of the following methods:
- Option 1. The weight of the load must be determined from a source recognized by the industry (such as the load’s manufacturer), by a calculation method recognized by the industry (such as calculating a steel beam from measured dimensions and a known per foot weight), or by other equally reliable means. When requested by the operator, this information must be provided to the operator prior to the lift.
- Option 2. The operator must begin hoisting the load to determine, using a load weighing device, load movement indicator, rated capacity indicator, or rated capacity limiter, whether it exceeds 75 percent of the maximum rated capacity at the longest radius that will be used during the lift operation. If it does, the operator must not proceed with the lift until the weight of the load is verified.
At times, resulting loads on assist cranes during the A/D process are not properly anticipated. For example, when a boom is being disassembled in a cantilevered position, an assist crane is sometimes used to help support the boom. In some instances, the load is within the assist crane’s rated capacity prior to pin removal but exceeds its rated capacity once the pins are removed, causing a collapse.
Boom and jib pick points
- To handle booms and jibs safely, pick points must be chosen and installed so as to result in the boom/jib being at the intended angle.
The point(s) of attachment of rigging to a boom (or boom sections, or jib or jib sections) must be suitable for preventing structural damage and allowing safe handling of these components. Damage could compromise structural integrity and, in some cases, may not be immediately noticed. If that component is used, the boom/component could fail.
Safe handling of the boom/jib or boom/jib sections requires using pick points that will result in the boom/section being at the intended angle (90 degrees to the load line or some other intended angle) when hoisted.
For example, if the boom/section is intended to be horizontal, and only one pick point is going to be used, the pick point must coincide with the center of gravity. If the boom/section is intended to be at some other angle, a pick point would need to be identified that would generate that angle. Failing to do this could cause unintended movement during connecting or disconnecting the boom/section.
Center of gravity
- Maintaining stability during A/D may require identifying the center of gravity of the load so that the rigging can be balanced.
Often the method used for maintaining stability during assembly/disassembly (A/D) depends on supporting or rigging a component (or set of components) so that it remains balanced throughout the lift. In such instances, the A/D director is required to identify the center of gravity of the load.
One example of a situation where it would be necessary to identify the center of gravity is if the A/D crew is relying on an assist crane to suspend a component in a horizontal position. In this case, the center of gravity must be identified in order to correctly install the rigging.
If the center of gravity is not identified before installing the rigging, employees might try to compensate by riding on the section/component while it is being moved into place, which is quite dangerous. Also, in such a situation, if the component gets “hung up,” it can move unexpectedly when freed.
Some methods for maintaining stability do not depend on rigging or supporting the component to attain horizontal balance. For example, if two adjoining sections of a boom are being disconnected from each other, and both sections are supported at all four end points by blocking, then identifying the center of gravity may not be necessary.
There may be instances where the A/D method being used requires the identification of the center of gravity, but the employer can’t get sufficient information to make that identification. If the center of gravity cannot be identified, precautions must be taken to prevent unintended dangerous movement.
Stability upon pin removal
- Boom sections, suspension systems, and components must be rigged or supported so that they stay stable when the pins are removed.
The boom sections, boom suspension systems (such as gantry A-frames and jib struts), and components must be rigged or supported to maintain stability upon the removal of the pins.
The Occupational Safety & Health Association (OSHA) defines “boom suspension systems” as “a system of pendants, running ropes, sheaves, and other hardware which supports the boom tip and controls the boom angle.” (1926.1401)
The process of pin removal is particularly hazardous. Potential energy in these sections, systems, and components can be released suddenly during pin removal, resulting in unanticipated movement ranging from shifting to collapse. Even small movements can result in injury, including amputations; larger movements and collapses can cause fatal injuries.
The key to preventing these injuries and fatalities is ensuring that the sections/components remain stable upon the removal of the pins. Instability can have a variety of causes, including improper A/D sequencing, improper rigging, incorrectly designed support, blocking failures, and ground compression.
Addressing specific hazards
- The A/D director is responsible for addressing known hazards of the operation.
- These may include ropes and pendants getting snagged, counterweights striking employees, and equipment losing backward stability.
The assembly/disassembly (A/D) director supervising the A/D operation must address known hazards associated with the operation and come up with methods to protect the employees from those hazards. The A/D director must consider each hazard, determine the appropriate means of addressing it, and oversee the implementation of that method.
Snagging
Suspension ropes and pendants must not be allowed to catch on the boom or jib connection pins or cotter pins (including keepers and locking pins). This could damage the cables or other components and result in injury.
Pendant cables are typically used in a latticed boom crane system to easily change the length of the boom suspension system without completely changing the rope on the drum when the boom length is increased or decreased. In many cases, the pendant cables hang alongside the boom and may get caught (snagged) on the pins, bolts, or keepers as the operator raises the boom.
If snagging occurs, the cables can be damaged, or the boom may rise then drop suddenly as a snagged cable releases from the pin. This can result in shock loading and damage to cables and components.
Counterweight strikes
Counterweights are usually large, heavy plates made of steel and/or concrete. The A/D process typically involves the installation and removal of counterweights.
During the installation/removal process, employees tend to be in close proximity to counterweights. If a counterweight sways as it’s being installed or removed, an employee can be struck by it or crushed between it and the crane.
The A/D director must address this aspect of the hazard, such as by taking steps to have the operator minimize the amount of sway and by positioning the employees to minimize their hazard exposure.
Additionally, after the counterweights are installed, the crane may have to swing to complete the boom assembly. The A/D director is required to address this aspect of the hazard as well, such as through the proper positioning of employees and enhancing their awareness of the counterweight swing zone so that they will avoid being struck or crushed.
Loss of backward stability
There are three points during the A/D process at which there is a heightened risk of loss of backward stability. These are:
- When swinging the upperworks,
- During travel, and
- When attaching or removing equipment components.
Therefore, before any of these occur, the A/D director is required to consider whether precautions need to be instituted to ensure that backward stability is maintained.
Working out of operator view
- Communication procedures should be established so that operators can know when crew members are out of their view and may be in danger from the equipment.
One common hazard is an operator swinging or moving the crane when assembly/disassembly (A/D) personnel are in a crush/caught-in-between zone and out of the operator’s view. An effective and practical means of preventing these accidents is through a communication procedure that provides key information to, and coordination between, the operator and these workers.
That’s why the operator must be informed when a crew member is going to a location in, on, under, or near the equipment or load that is out of view of the operator, and where the movement of the equipment could injure the worker.
When the operator knows that a crew member went to a hazardous location, the operator must not move any part of the equipment (or load) until the operator is informed via a prearranged system of communication that the crew member is in a safe position.
An example of such a system would be the use of a signal person who gives an all-clear signal to the operator once the signal person sees that the employee has exited the hazard area.
Another example would be where the employee in the hazard area is equipped with a portable air horn and, in accordance with a prearranged horn signal system, sounds an appropriate signal to the operator that the employee has exited the hazard area. To be effective, the prearranged signal system needs to be designed so that this all-clear signal could not be confused with a horn signal from some other employee for another purpose.
Boom hoist brake failure
- To avoid boom hoist brake failure, it’s important to accurately account for the loads that will be placed on the brake, including additional boom that may be added to the crane.
Boom hoist brake failure is a hazard that can be present during both assembly and disassembly, although it is more typically an assembly hazard. In many older cranes, the boom hoist brake mechanism has an external or internal mechanical brake band that operates by pressing against the hoist drum. As the configuration of the crane changes and, for example, more boom is added, this type of boom hoist brake may slip unless it has been adjusted to hold the extra weight.
The inability of an unadjusted brake to hold the increased load will not be evident until the additional boom section has been added and the operator attempts to rely on the brake in a subsequent phase of the operation. If the operator does not first raise the boom a small amount after the section has been added (with the crew clear of the boom) to test the brake, employees could be injured later in the process when the operator manipulates the boom and is unexpectedly unable to brake it.
In many cases, if the brake is insufficient, an adjustment to it will correct the problem. If it remains insufficient, the employer is required to use a boom hoist pawl, other locking device, backup braking device, or another method of preventing dangerous boom movement (such as blocking or using an assist crane to support the load) from a boom hoist brake failure.
The brake test needs to be performed before anyone relies on the brake. It needs to accurately account for the loads that will be placed on the brake.
Wind speed and weather
- The A/D must determine the maximum safe wind speed and account for other weather-based hazards under the specific conditions of the equipment and site.
The assembly/disassembly (A/D) director is required to address hazards caused by wind speed and weather to ensure that the safe A/D of the equipment is not compromised. Selecting any one particular speed as a maximum would be arbitrary because of the variety of factors involved.
For example:
- Different cranes and crane types vary with respect to the “sail” area they present.
- An assembly process involving use of an assist crane may require lower wind speeds than one in which no assist crane is used.
- A/D operations done “in the air” (that is, with the boom elevated in the air, without ground support for the boom) may require lower wind speeds than a boom assembled/disassembled on the ground.
The A/D director must determine the maximum safe wind speed under the circumstances.
Other weather conditions that can affect the safety of A/D include, for example, ice accumulation on crane components. Ice can both add to the weight of the components and make surfaces on which employees work slippery and dangerous. The A/D director must address weather conditions that affect the safety of the operation.
Working under the boom, jib, or other components
- If possible, workers should avoid removing pins while under the boom (or jib or similar components) because of the risk of collapse.
- If removing pins while under the boom can’t be avoided, the A/D director must implement procedures to minimize the time, exposure, and risks involved.
One hazard an employee may encounter is removing pins while under the boom (and jib or similar components). If the wrong pins are removed while employees are under the component, it can move or collapse.
Even when pins are removed in the correct order, there may be unexpected stresses in the component, such as stored kinetic energy, that may not be apparent until that energy is released upon the removal of the pin. This can result in unexpected movement of the component.
Removing pins while under the boom should be avoided when possible. There is an exception: where the employer demonstrates that site constraints require one or more employees to be under the boom, jib, or other components when pins (or similar devices) are being removed, the assembly/disassembly (A/D) director must implement procedures that minimize the risk of unintended dangerous movement and minimize the duration and extent of exposure under the boom.
Sample scenario for the exception
In this scenario, there is a boom that cannot be disassembled on the ground because of aboveground piping (as might be found, for example, in an oil refinery) that precludes lowering the boom to the ground. The boom must therefore be disassembled in the air, and the employees who remove the pins must perform that work from an aerial lift whose base is positioned on one side (the near side) of the boom.
To gain access to the pins on the far side, the aerial lift basket must move under the boom, since, due to lack of room, the aerial lift cannot be repositioned on the far side.
To minimize the risk of unintended dangerous movement while the pins are removed, the A/D director uses an assist crane that is rigged to support the boom section that is being detached, using particular care to ensure that the section end that is near the employee(s) removing the pins is well supported.
The duration and extent of exposure is minimized by removing the far side pins first, moving the aerial lift basket as soon as possible to the near side so that the employees are no longer under the boom, and then removing the near side pins.
Other hazards
- To minimize risks, employers should in most cases follow manufacturer limitations and procedures for the equipment.
- Cantilevered boom sections, shipping pins, pile driving equipment, and rigging all have specific requirements for safe use.
To minimize risks on the jobsite, employers in the construction industry using mobile cranes in the construction industry must address the following issues.
Cantilevered boom sections
A common mistake in assembly/disassembly is cantilevering too much boom. When this is done, structural failure can occur in components such as the mast/gantry, boom sections, and lifting lugs.
Employees may be struck by falling components from this type of failure. To prevent accidents from cantilevering too much boom during assembly/disassembly, the manufacturer’s limitations on cantilevering must not be exceeded.
If the manufacturer’s limitations are not available, the employer is required to have a registered professional engineer (RPE) determine the appropriate limitations, and to abide by those limitations. The RPE’s determination must be in writing to ensure that the assessment has been done.
Weight of components
As with any load to be lifted by a crane/derrick, the weight of the components must be available to the operator so that the operator can determine if the lift can be performed within the crane/derrick’s capacity. This requirement applies irrespective of whether the component is being hoisted by the crane being assembled/disassembled or by an assist crane.
Manufacturer prohibitions
Manufacturers’ prohibitions always take precedence. A prohibition specified by the manufacturer is a clear sign that if it is not heeded, a significant hazard would likely be created.
An employer would be able to choose to use either manufacturer assembly/disassembly procedures or the workplace’s own, as long as the procedures meet the requirements. However, in either case, the manufacturer prohibitions regarding assembly or disassembly would need to be met.
Shipping pins
Reusable shipping pins, straps, links, and similar equipment must be removed. Once removed, they must be stowed or otherwise stored so that they do not present a falling object hazard.
Being properly stowed might include being placed in a special hole or bracket designed to keep the item from being dislodged. Storage on the equipment could include placing them in an equipment box in the cab.
Pile driving
Equipment used in pile driving operations must not have a jib attached. The constant pounding of the pile driving hammer and the sometimes-rapid descent of the pile causes the boom to bounce.
If a jib were installed on the tip, as the boom bounces the jib could be thrown backward against its stops, which would likely cause structural damage to the boom. The damage could cause the boom to immediately fail or could diminish its capacity.
Rigging work
When rigging is used for assembly/disassembly, the employer must make sure that:
- The rigging work is done by a qualified rigger.
- Synthetic slings are protected from abrasive, sharp, or acute edges and from configurations that could cause a reduction of the sling’s rated capacity, such as distortion or localized compression. Note: Requirements for the protection of wire rope slings are contained in 1926.251(c)(9).
- When synthetic slings are used, the synthetic sling manufacturer’s instructions, limitations, specifications, and recommendations are followed.
Component selection and configuration
- Cranes and derricks should be assembled in accordance with manufacturer specifications, not in the order in which components arrive.
To determine the proper selection of components and proper configurations, employers should consult the manufacturer’s instructions, limitations, and specifications. Regarding component selection, hazards are associated with the use of components that the manufacturer neither intended nor planned for incorporation into the equipment. Such components could adversely affect the capacity and performance of the crane/derrick, make the manufacturer’s specifications (including the load chart) and instructions inapplicable, and adversely affect other components on the crane/derrick.
Similar hazards are posed by configuring the crane/derrick in a manner that does not accord with the manufacturer’s instructions, limitations, and specifications. This could occur when trucks carrying boom sections arrive out of sequence.
To save time, some employers assemble the sections in the order in which they arrive rather than waiting for the correct section. This results in a crane/derrick configured differently than intended by the manufacturer. Because the crane/derrick is designed and tested as a unit, the failure to configure the crane/derrick as the manufacturer had intended could present the same hazards as those described above for improper component selection.
There may be instances when the crane manufacturer no longer exists and the employer can no longer obtain the manufacturer’s instructions, limitations, and specifications regarding the selection of components and configuration of the equipment. In such cases, a registered professional engineer familiar with the type of equipment involved must approve, in writing, the component selection and configuration.
Section 1926.1434 allows cranes/derricks to be modified under certain circumstances. To the extent a crane/derrick is modified in accordance with this section, the employer cannot be required to follow the manufacturer’s original instructions, limitations, and specifications regarding component selection and configuration regarding those modifications. Instead, the employer is required to follow the component selection and configuration requirements approved according to 1926.1434.
Finally, the equipment must be inspected after assembly has been completed to ensure that the component selection and configuration are correct.
Outriggers and stabilizers
- Outriggers and stabilizers must be used according to manufacturer specifications; for example, they must either be fully extended or deployed as specified in the load chart.
Outriggers are designed to take all load off the tires. Stabilizers are designed to relieve some, but not all, of the sprung weight for the purpose of increasing the stability of the vehicle.
Any time outriggers or stabilizers are used, all of the following requirements must be met (except as otherwise indicated):
- The outriggers or stabilizers must be either fully extended or, if manufacturer procedures permit, deployed as specified in the load chart.
- The outriggers must be set to remove the equipment weight from the wheels, except for locomotive cranes. This provision does not apply to stabilizers.
- When outrigger floats are used, they must be attached to the outriggers. When stabilizer floats are used, they must be attached to the stabilizers.
- Each outrigger or stabilizer must be visible to the operator or to a signal person during extension and setting.
- Outrigger and stabilizer blocking must follow the Occupational Safety & Health Association (OSHA) requirements for blocking material: “The size, amount, condition and method of stacking the blocking must be sufficient to sustain the loads and maintain stability.” (1926.1404)
- Outrigger and stabilizer blocking must only be placed under the float/pad of the jack or, where the outrigger or stabilizer is designed without a jack, under the outer bearing surface of the extended outrigger or stabilizer beam.
- For locomotive cranes, when outriggers or stabilizers are used to handle loads, the manufacturer’s procedures must be followed. When loads are lifted without using outriggers or stabilizers, the manufacturer’s procedures must be met regarding truck wedges or screws.
Work area control
- Employees should be aware of the danger of being struck or crushed by the crane’s superstructure when it’s rotating.
- The site’s CE should coordinate work so that cranes working near each other do not collide.
The work area is the accessible areas in which the equipment’s rotating superstructure (whether permanently or temporarily mounted) poses a reasonably foreseeable risk of:
- Striking and injuring an employee, or
- Pinching/crushing an employee against another part of the equipment or another object.
Hazards of rotating superstructures
The rotation of a crane’s superstructure can cause serious injury and death to employees working near the crane. Specifically, there are two hazards employees need to be aware of:
- Being struck by the rotating superstructure, and
- Being crushed against another part of the crane or against another object by the rotating superstructure.
The employer is required to erect and maintain control lines, warning lines, railings, or similar barriers to mark the boundaries of the hazard areas. One type of barrier that is often used is attached directly to the crane and moves with the equipment.
There is an exception, and that is when the employer can demonstrate that it is feasible to erect such barriers on neither the ground nor the equipment. In that case, the hazard areas must be clearly marked by a combination of warning signs (such as “Danger — Swing/Crush Zone”) and high-visibility markings on the equipment that identify the hazard areas. In addition, the employer must train each employee to understand what these markings signify.
Cranes working near each other
If there are several cranes working near each other, and if any part of a crane/derrick is within the working radius of another crane/derrick, the controlling entity (CE) must institute a system to coordinate operations. If there is no CE, the employer (if there is only one employer operating the multiple pieces of equipment) or employers must devise and institute such a system.
Protecting employees in the hazard area
- A pre-arranged system of signals is a good way to communicate to a crane operator that an employee is out of sight in the swing hazard area.
There may be times when an employee must go into part of the crane’s swing hazard area that is out of sight of the crane operator. Before doing so, the crane operator must be informed that someone is entering the swing hazard area.
Once the crane operator has been informed that an employee is within the swing hazard area, the operator must not rotate the superstructure until the operator is informed, according to a pre-arranged system of communication, that the employee is in a safe position.
An example of such a communication system would be the use of a signal person who gives an all-clear signal to the operator once the signal person sees that the employee has exited the hazard area. Another example would be where the employee in the hazard area is equipped with a portable air horn and, in accordance with a pre-arranged horn signal system, sounds an appropriate signal to the operator that the employee has exited the hazard area.
To be effective, the pre-arranged signal system needs to be designed so that this all-clear signal could not be confused with a horn signal from some other employee for another purpose.
Keeping clear of the load
- To keep employees clear of the load, hoisting routes should minimize employee exposure, and employees should stay out of the fall zone unless their task requires them to be there.
The Occupational Safety & Health Association’s (OSHA) 29 CFR 1926 Subpart CC has specific requirements for keeping employees clear of the load:
- Where available, hoisting routes that minimize the exposure of employees to hoisted loads must be used, to the extent compatible with public safety.
- While the operator is not moving a suspended load, no employee must be within the fall zone, except for employees who are:
- Engaged in hooking, unhooking, or guiding a load;
- Engaged in the initial attachment of the load to a component or structure; or
- Operating a concrete hopper or concrete bucket.
OSHA defines “fall zone” as the area (including but not limited to the area directly beneath the load) in which it is reasonably foreseeable that partially or completely suspended materials could fall in the event of an accident. For example, if wind is causing the load to swing, the employer would need to consider the breadth of the swinging (or potential swinging) in determining the extent of the fall zone.
Another example is where a bundle of materials is suspended and some loose materials at the top of the bundle may slide off sideways. In such a case, those materials could foreseeably fall outside the area directly beneath the load.
Rigging and receiving the load
- Materials being hoisted must be rigged by a qualified rigger in a way that prevents unintentional displacement and uses hooks with self-closing latches (or their equivalent).
When employees are engaged in hooking, unhooking, or guiding the load, or in the initial connection of a load to a component or structure, and are within the fall zone, all of the following criteria must be met:
- The materials being hoisted must be rigged to prevent unintentional displacement.
- Hooks with self-closing latches or their equivalent must be used.
- Exception: “J” hooks are permitted to be used for setting wooden trusses. This exception is designed to allow the truss to be unhooked without the need for an employee to go out on the truss. This avoids the additional exposure to fall hazards that would otherwise occur from going out on the truss to release a latched hook.
- The materials must be rigged by a qualified rigger.
When a load is being landed, only employees needed to receive a load are permitted to be within the fall zone. An employee receiving a load will typically need to be within the fall zone when the load is being landed because that is the time when the load needs to be guided to a specific landing point.
Tilt-up or tilt-down operation
- During a tilt-up or tilt-down operation, only employees essential to the operation can be in the fall zone, and no one can be directly under the load.
In tilt-up and tilt-down operations, one end of a component, such as a precast panel, is either:
- Raised, tilting the component up, usually from a horizontal position (often on the ground) to a vertical position; or
- Lowered, tilting the component down, usually from a vertical position to a horizontal position on the ground or other surface.
Note: These requirements do not apply when receiving a load; they only apply during tilt-up and tilt-down operations.
During a tilt-up or tilt-down operation:
- No employee can be directly under the load.
- Only employees essential to the operation are permitted in the fall zone (but not directly under the load).
An employee is considered “essential to the operation” if the employee is conducting one of the following operations and the employer can demonstrate that it’s infeasible to perform that operation from outside the fall zone:
- Physically guiding the load;
- Closely monitoring and giving instructions regarding the load’s movement; or
- Detaching the load from or attaching it to another component or structure (such as, but not limited to, making an initial connection or installing bracing).
Signs, signals, and markings
- When equipment is left unattended, barricades or caution lines and must be used to keep employees from entering the fall zone.
- Equipment that’s out of service must be clearly tagged as such.
The requirements for signs, signals, and markings in the Occupational Safety & Health Association’s (OSHA) 29 CFR 1926 Subpart CC include the following.
Leaving the equipment unattended — Barricades/Caution lines and notices
When the equipment is left unattended, barricades or caution lines and notices must be erected to prevent all employees from entering the fall zone. No employees are permitted in the fall zone when the equipment is unattended, including those who are:
- Engaged in hooking, unhooking, or guiding a load;
- Engaged in the initial attachment of the load to a component or structure; or
- Operating a concrete hopper or concrete bucket.
Out of service — Tag-out
When the employer has taken the equipment out of service, a tag must be placed in the cab stating that the equipment is out of service and is not to be used. When the employer has taken a crane function(s) out of service, a tag must be placed in a conspicuous position stating that the function is out of service and is not to be used.
If there is a warning (tag-out or maintenance/do not operate) sign on:
- The equipment,
- The starting control, or
- Any other switch or control,
then the operator must not activate the switch or start the equipment until the sign has been removed by a person authorized to remove it, or until the operator has verified that:
- No one is servicing, working on, or otherwise in a dangerous position on the machine; and
- The equipment has been repaired and is working properly.
Fall protection
- Employees who might be exposed to fall hazards must be trained in fall protection requirements, including the use of installed fall protection such as guardrails and personal fall protection such as body belts.
A study of crane-related fatalities in the U.S. construction industry found that 2 percent of the fatalities resulted from falls. Falls from cranes, particularly when the operator is entering or leaving the crane, also cause numerous non-fatal injuries to construction workers.
Training
Employers must train each employee who may be exposed to fall hazards while on, or hoisted by, equipment covered by the Occupational Safety & Health Association’s (OSHA) 29 CFR 1926 Subpart CC. The training must consist of:
- The fall protection requirements listed below, and
- The applicable fall protection requirements in Subpart M — Fall Protection (1926.500 and 1926.502).
Types of fall protection
“Fall protection equipment” is defined as “guardrail systems, safety net systems, personal fall arrest systems, positioning device systems, or fall restraint systems.” (1926.760)
“Fall restraint system” is defined as “a fall protection system that prevents the user from falling any distance. The system is comprised of either a body belt or body harness, along with an anchorage, connectors and other necessary equipment. The other components typically include a lanyard and may also include a lifeline and other devices.” (1926.751)
The types of fall protection required for cranes are the same fall protection equipment required under other OSHA standards.
Personal fall arrest equipment and use
Personal fall arrest system components must be used in personal fall arrest and fall restraint systems and must conform to the criteria in 1926.502(d), except that 1926.502(d)(15) does not apply to components used in personal fall arrest and fall restraint systems. Either body belts or body harnesses must be used in personal fall arrest and fall restraint systems.
There is a required use exception, namely that operators do not need to be tied off when moving to and from their crane cabs.
Fall protection is also not required for employees on decks, since that equipment is typically designed so that employees are not exposed to a fall hazard.
Installation and maintenance of fall protection
- Equipment manufactured after November 8, 2011, must meet fall protection standards including boom walkways and safe access between the ground and operator workstations.
The following information is for crane manufacturers and for employers. Employees should also be aware of these requirements.
- Boom walkways. Equipment manufactured after November 8, 2011, with lattice booms must be equipped with walkways on the boom(s) if the vertical profile of the boom (from cord centerline to cord centerline) is 6 or more feet.
- Steps, handholds, ladders, grab rails, guardrails, and railings. The employer must maintain in good condition originally equipped steps, handholds, ladders, and guardrails/railings/grab rails. Equipment manufactured after November 8, 2011, must be equipped so as to provide safe access and egress between the ground and the operator workstation(s), including the forward and rear positions, by the use of steps, handholds, ladders, and guardrails/railings/grab rails.
Existing equipment manufactured before November 8, 2011, does not have to be retrofitted with new steps, handholds, and railings simply because the existing design may vary from what is required in Subpart CC.
Non-assembly/Disassembly work vs. assembly/disassembly work
- For point-to-point movements during non-assembly/disassembly work, employees need fall protection under the conditions listed in Table B.
- During assembly/disassembly, fall protection is required when working near an unprotected edge more than 15 feet up (with some exceptions).
For non-assembly/disassembly work, employees must use provided fall protection equipment when they are on a walking/working surface with an unprotected side or edge more than 6 feet above a lower level when moving point-to-point (when the employee is in the process of going to or from a workstation).
The following table describes point-to-point movements requiring fall protection.
Table B — Point-to-point movements requiring fall protectionOn non-lattice booms (whether horizontal or not horizontal) | Non-lattice booms generally present more hazards (than lattice booms) to workers who must walk them to reach other work areas, devices, and equipment. Non-lattice booms are typically extensible booms, and the surface is usually oily from the hydraulic mechanisms. |
On lattice booms that are not horizontal | An employee may need to move point-to-point on a lattice boom to inspect a part that may need repair, or to make the repair. In many cases, the boom may not be horizontal, since space limitations can make it difficult to lower the boom to perform the work. Since the boom would be elevated, there would usually be a point on the boom above the level of the worker’s feet to attach a lanyard. |
On horizontal lattice booms where the fall distance is 15 feet or more | The 15-foot minimum distance is used because a personal fall arrest system tied off at the level of the employee’s feet, with a lanyard long enough to allow the employee the range of movement necessary for this work, might not prevent the employee from falling to the next lower level. |
Employees must also use fall protection equipment when they are on a walking/working surface with an unprotected side or edge more than 6 feet above a lower level and not moving point-to-point. For example, if an employee is stationary at a workstation on any part of the equipment (including the boom, of any type), the employee needs fall protection, except when the employee is:
- At or near draw works when the equipment is running,
- In the cab, or
- On the deck.
Assembly/Disassembly work
For assembly/disassembly (A/D) work, employees must use provided fall protection equipment when they are on a walking/working surface with an unprotected side or edge more than 15 feet above a lower level, except when the employee is
- At or near draw works (e.g., rotating drums and sheaves) when the equipment is running;
- In the cab; or
- On the deck.
Monorail hoists enforcement policies
- OSHA excludes monorail hoists from the Subpart CC requirements as long as other OSHA requirements are met.
The Occupational Safety & Health Association (OSHA) has a new enforcement policy that excludes monorail hoists from the requirements of Subpart CC — Cranes and Derricks in Construction, as long as employers meet other OSHA requirements.
The following is from an OSHA Memorandum issued June 30, 2017.
“The scope of Cranes and Derricks in Construction (the cranes standard, 29 CFR Part 1926, subpart CC) includes a functional definition for the equipment covered. The standard applies to ‘power-operated equipment, when used in construction, that can hoist, lower, and horizontally move a suspended load.’ (29 CFR 1926.1400[a]). Monorail hoists are not explicitly excluded from the scope of the rule, and OSHA has issued several letters of interpretation confirming the crane standard’s coverage of specific monorail hoists in certain construction operations.
“As a number of stakeholders have pointed out, the standard is not a perfect fit for monorail hoists, and OSHA intends to consider rulemaking options to address this issue. The purpose of this memorandum is to announce a temporary enforcement policy pending the resolution of that rulemaking process.
“Most monorail hoist systems have a completely fixed monorail (I-beam). When used in construction, these hoisting systems are typically mounted on equipment such as work vehicles, trailers, and scaffolding systems. The monorails can be extended and contracted in only a fixed horizontal direction to hoist materials and can only hoist them as high as the monorail. Some examples of materials commonly lifted and placed by monorail hoists during construction are precast concrete components (septic tanks, storm drain and sewer conduits, vaults, etc.); storage tanks (propane, oil, etc.); mechanical components (engines, commercial generators, etc.); trade specific components (electrical transformers, industrial spooled materials, sewer lids, etc.); and temporary storage units.
“Monorail hoists present unique issues. Many monorail hoist manufacturers do not design their systems to meet any particular criteria recommended in consensus standards, though the designs of their hoisting mechanisms most resemble those of overhead hoists covered by ASME 830.172015 (Cranes and Monorails (With Underhung Trolley or Bridge)).
“Stakeholders have pointed out that a number of the provisions of the crane standard add very little protection when these monorail hoists are used. For example, the stakeholders have told OSHA that because these monorails are fixed such that they do not angle up or down, the equipment does not warrant the elevated level of protections from power-line contact required by the crane standard. They also note that monorails cannot boom out significantly beyond the wheelbase of a vehicle or the base of its supporting structure, and thus the hoisting equipment does not pose the dangerous cantilevering and stability hazards that are addressed by requirements of the crane standard.
“Furthermore, they assert that there is no need for specific protections from hazards posed by booming out loads, boom free fall, equipment swing radius, or any crane-related hazards that would necessitate the use of devices like level indicators, boom/jib stops, boom/jib limiting devices, boom length/radius indicators, and drum hoist rotation indicators.
“Finally, stakeholders have pointed out that the loads handled by monorail hoists are not heavy enough to trigger the need for a load weighing device or the use of load charts to prevent overloading and tipping the hosting equipment.
“However, it is clear that monorail and overhead hoist systems present recognized workplace hazards, including those addressed by 29 CFR 1926.554 (Overhead hoists), ASME B30. l 7, and various manufacturers’ recommendations. For the reasons discussed above, and until the application of the cranes standard to monorail hoists is revisited through rulemaking, OSHA intends to exercise its enforcement discretion by not citing employers for failing to achieve full compliance with the cranes standard when monorail hoists are used, if the following conditions are met to protect employees:
- Compliance with 29 CFR 1926.554 (Overhead hoists). OSHA notes that its Overhead Hoist standard requires the use of outriggers and other supports whenever prescribed by the manufacturer.
- Operators of this equipment are trained in accordance with 29 CFR 1926.21.
- The employer has determined that each operator is qualified to safely operate that hoisting system per 29 CFR 1926.20(b)(4).
- When monorail hoists are mounted on equipment such as work vehicles, utility trailers, scaffolding systems (including mast climbing), and various other mobile or stationary support systems, the employer must also comply with all other OSHA construction requirements that are applicable to each supporting vehicle, equipment, and structure.
“Should an employer operating such equipment fail to comply fully with all of the requirements described, the requirements of the crane standard would apply.”
Scaffolding in general industry and construction
- All employers who use scaffolds in construction work or production processes must comply with OSHA’s scaffolding standard, 29 CFR 1926 Subpart L.
- The standard specifies how employers must minimize employee risk by providing properly constructed scaffolds, fall protection, and training.
The Occupational Safety & Health Association’s (OSHA) 29 CFR Subpart L standard sets performance-based criteria to protect employees from scaffold-related hazards such as falls, falling objects, structural instability, electrocution, and overloading. It also addresses training and various types of scaffolds, as well as falling object protection, ladders, weather conditions, aerial lifts, and stilts.
Scope/Who must comply
All employers performing construction work with scaffolds and general industry employers who use scaffolds in their production processes must comply. OSHA regulates scaffolding at 29 CFR 1926 Subpart L, 1926.450 through 1926.454 — Scaffolding.
Basic requirements
OSHA’s scaffolding standard has several key provisions that employers must follow:
- Protect each employee more than 10 feet above a lower level from falls using guardrails or a fall arrest system, except those on single-point and two-point adjustable suspension scaffolds. Each employee on a single-point and two-point adjustable suspended scaffold must be protected by both a personal fall arrest system and a guardrail.
- Ensure that the height of the top rail for scaffolds manufactured and placed in service after January 1, 2000, is between 38 and 45 inches. For scaffolds manufactured and placed in service before January 1, 2000, the height of the top rail can be between 36 and 45 inches.
- Make sure that cross bracing used as a top rail is between 38 and 48 inches above the work platform.
- Install mid rails approximately halfway between the top rail and the platform surface. When a crosspoint of cross bracing is used as a mid-rail, it must be between 20 and 30 inches above the work platform.
- Ensure that support scaffold footings are level and capable of supporting the loaded scaffold. The legs, poles, frames, and uprights must bear on baseplates and mud sills.
- Fully plank or deck supported scaffold platforms.
- Restrain supported scaffolds (with a height-to-base of more than 4:1) from tipping by guying, tying, bracing, or the equivalent.
- Ensure that scaffolds and scaffold components support at least four times the maximum intended load. Suspension scaffold rigging must support at least six times the intended load.
- Train each employee who works on a scaffold on the hazards and the procedures to control the hazards.
- Make sure a competent person inspects the scaffold and scaffold components for visible defects before each work shift (and after any occurrence that could affect structural integrity).
- Have a qualified person design and load scaffolds in accordance with the design.
- Have a registered professional engineer design specific types of scaffolds.
- When erecting and dismantling supported scaffolds, a competent person must determine the feasibility of providing a safe means of access and fall protection for these operations.
Training
All employees must be trained by a qualified person to recognize the hazards associated with the type of scaffold being used and how to control or minimize those hazards. The training must include the following:
- Fall hazards,
- Falling object hazards,
- Electrical hazards,
- Proper use of the scaffold, and
- Handling of materials.
Requirements for specific types of people
- OSHA defines a competent person as someone who can identify hazards in the relevant working conditions and has authorization to correct them and requires a competent person to be in charge of training and inspection.
- OSHA defines a qualified person as someone with a recognized degree/certification or equivalent demonstrated experience and requires a qualified person to perform certain design and training duties.
- Certain types of especially hazardous scaffolds and components must be designed by a registered professional engineer.
While “competent” and “qualified” ideally apply to everyone in a workplace, the Occupational Safety & Health Association (OSHA) specifies particular definitions for these adjectives and assigns different scaffolding responsibilities to each.
Competent person requirements
OSHA defines a competent person as “one who is capable of identifying existing and predictable hazards in the surroundings or working conditions, which are unsanitary, hazardous to employees, and who has authorization to take prompt corrective measures to eliminate them.” (1926.32)
The scaffolding standard requires a competent person to perform the following duties under these circumstances:
- In general:
- Select and direct employees who erect, dismantle, move, or alter scaffolds.
- Determine if it is safe for employees to work on or from a scaffold during storms or high winds and to ensure that a personal fall arrest system or wind screens protect these employees.
- Note: Windscreens should not be used unless the scaffold is secured against the anticipated wind forces imposed.
- For training:
- Train employees involved in erecting, disassembling, moving, operating, repairing, maintaining, or inspecting scaffolds to recognize associated work hazards.
- For inspections:
- Inspect scaffolds and scaffold components for visible defects before each work shift and after any occurrence that could affect the structural integrity, and authorize prompt corrective actions.
- Inspect ropes on suspended scaffolds prior to each work shift and after every occurrence that could affect the structural integrity, and authorize prompt corrective actions.
- Inspect manila or plastic (or other synthetic) rope being used for top rails or mid rails.
- For suspension scaffolds:
- Evaluate direct connections to support the load.
- Evaluate the need to secure two-point and multi-point scaffolds to prevent swaying.
- For erectors and dismantlers:
- Determine the feasibility and safety of providing fall protection and access.
- Train erectors and dismantlers to recognize associated work hazards.
- For scaffold components:
- Determine if a scaffold will be structurally sound when intermixing components from different manufacturers.
- Determine if galvanic action has affected the capacity when using components of dissimilar metals.
Qualified person requirements
OSHA defines a qualified person as “one who by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training, and experience has successfully demonstrated the ability to solve or resolve problems related to the subject matter, the work, or the project.” (1926.32)
The standard requires a qualified person to perform the following duties in these circumstances:
- In general:
- Design scaffolds and load them in accordance with the design.
- For training:
- Train employees working on the scaffolds to recognize the associated hazards and understand procedures to control or minimize those hazards.
- For suspension scaffolds:
- Design the rigging for single-point adjustable suspension scaffolds.
- Design platforms on two-point adjustable suspension types that are less than 36 inches wide to prevent instability.
- Make swaged attachments or spliced eyes on wire suspension ropes.
- For components and design:
- Design scaffold components and direct their construction in accordance with the design.
Registered professional engineer requirements
The standard requires a registered professional engineer to perform the following duties in these circumstances:
- For suspension scaffolds:
- Design the direct connections of masons’ multi-point adjustable suspension scaffolds.
- To design:
- Scaffolds that are to be moved when employees are on them.
- Pole scaffolds over 60 feet high.
- Tube and coupler scaffolds over 125 feet high.
- Fabricated frame scaffolds over 125 feet high above their baseplates.
- Brackets on fabricated frame scaffolds used to support cantilevered loads in addition to workers.
- Outrigger scaffolds and scaffold components.
Capacity and platform requirements
- Each scaffold and component must be able to support its own weight plus at least four times the maximum intended load.
- Scaffold platforms must be as free as possible of gaps between planking and must include fall protection on any platforms narrower than 18 inches.
Each scaffold and scaffold component must support without failure its own weight and at least four times the maximum intended load applied or transmitted to it.
A qualified person must design the scaffolds, which are loaded in accordance with that design.
Scaffolds and scaffold components must not be loaded in excess of their maximum intended loads or rated capacities, whichever is less.
Load-carrying timber members should be construction-grade lumber of a minimum of 1,500 lb-f/in2.
Platform construction
Scaffold planking must be able to support, without failure, its own weight and at least four times the intended load.
Solid sawn wood, fabricated planks, and fabricated platforms may be used as scaffold planks following recommendations by the manufacturer or a lumber grading association or inspection agency.
Each scaffold platform and walkway must be at least 18 inches wide. When the work area is less than 18 inches wide, guardrails and/or personal fall arrest systems must be used.
Each platform must be planked and decked as fully as possible. The space between the platform and uprights cannot be more than 1 inch wide.
When side brackets or odd-shaped structures result in a wider opening between the platform and the uprights, this space must not exceed 9 inches.
Tables showing maximum permissible spans, rated load capacity, and nominal thickness are in Appendix A of the standard.
Platform safety procedures
The platform must not deflect more than 1/60 of the span when loaded.
The standard prohibits work on platforms cluttered with debris.
Employers are required to protect each employee on a scaffold more than 10 feet above a lower level from falling to that lower level.
To ensure adequate protection, guardrails must be installed along all open sides and ends before releasing the scaffold is released for use by employees, other than the erection and dismantling crews.
Guardrails are not required, however, when:
- The front end of all platforms are less than 14 inches from the face of the work.
- Outrigger scaffolds are 3 inches or less from the front edge.
- Employees are plastering and lathing 18 inches or less from the front edge.
Steel or plastic banding must not be used as a top rail or a mid-rail.
Supported scaffolds
- Supported scaffolds are platforms supported by legs or other rigid support.
- Scaffolds with a height-to-base-width ratio of more than 4:1 must be restrained by guying, tying, bracing, or similar, placed as required.
Supported scaffolds are platforms supported by legs, outrigger beams, brackets, poles, uprights, posts, frames, or similar rigid support.
The structural members, poles, legs, posts, frames, and uprights must be plumb and braced to prevent swaying and displacement.
Supported scaffolds with a height-to-base-width ratio of more than 4:1 must be restrained by guying, tying, bracing, or an equivalent means.
To prevent tipping, either the manufacturers’ recommendation or the following placements must be used for guys, ties, and braces:
- Guys, ties, or braces should be installed at the closest horizontal member to the 4:1 height and repeated vertically, with the top restraint no further than the 4:1 height from the top.
- Vertically — guys, ties, and braces should be installed every 20 feet or less for scaffolds less than 3 feet wide, and every 26 feet or less for scaffolds more than 3 feet wide.
- Horizontally — guys, ties, and braces should be installed at each end and at intervals not to exceed 30 feet from one end.
To ensure a firm foundation, supported scaffolds’ poles, legs, posts, frames, and uprights must bear on baseplates and mud sills or other adequate foundation.
Forklifts can support platforms only when the entire platform is attached to the fork and the forklift does not move horizontally when workers are on the platform.
Front-end loaders and similar equipment can support scaffold platforms only when they have been specifically designed by the manufacturer for such use.
There may be times when employers need to increase the height of employees on the supported scaffold. On a large-area scaffold, stilts may be used. When a guardrail system is used, the guardrail height must be increased in height corresponding to the height of the stilts.
The manufacturer must approve any alterations to the stilts.
Note: A large-area scaffold consists of a pole, tube, and coupler systems, or a fabricated frame scaffold erected over substantially the entire work area.
Suspension scaffolds
- Suspension scaffolds consist of one or more platforms suspended from an overhead structure.
- Proper support, secure connections, and fall protection are all especially vital when suspension scaffolds are being used.
A suspension scaffold contains one or more platforms suspended by ropes or other non-rigid means from an overhead structure. Examples of suspension scaffolds include:
- Single-point
- Multi-point
- Multi-level
- Two-point
- Adjustable
| - Boatswains’ chair
- Catenary
- Chimney hoist
- Continuous run
- Elevator false car
| - Go-devils
- Interior hung
- Masons’
- Stone setters’
|
Some of the requirements for all types of suspension scaffolds:
- Employers must ensure that all employees are trained to recognize the hazards associated with the type of scaffold being used.
- All support devices must rest on surfaces capable of supporting at least four times the load imposed on them by the scaffold when operating at the rated load of the hoist, or at least 1.5 times the load imposed on them by the scaffold at the stall capacity of the hoist, whichever is greater.
- A competent person must evaluate all direct connections prior to use to confirm that the supporting surfaces are able to support the imposed load.
- All suspension scaffolds must be tied or otherwise secured to prevent them from swaying, as determined by a competent person.
- Guardrails, a personal fall arrest system, or both must protect each employee who is more than 10 feet above a lower level from falling.
- A competent person must inspect ropes for defects prior to each work shift and after every occurrence that could affect a rope’s integrity.
- When scaffold platforms are more than 24 inches above or below a point of access, ladders, ramps, walkways, or similar surfaces must be used.
- When using direct access, the surface must not be more than 24 inches above or 14 inches horizontally from the surface.
- When lanyards are connected to horizontal lifelines or structural members on single-point or two-point adjustable scaffolds, the scaffold must have additional independent support lines equal in number and strength to the suspension lines and have automatic locking devices.
- Emergency escape and rescue devices must not be used as working platforms, unless designed to function as suspension scaffolds and emergency systems.
- No materials or devices may be used to increase the working height on a suspension scaffold. This includes ladders, boxes, and barrels.
Components and situations
- Counterweights, outrigger beams, tiebacks, suspension ropes, and scaffold hoists are all components of suspension scaffold systems that must be chosen and installed according to requirements to function safely and correctly.
- Welding can be done from suspension scaffolds with careful attention to both fall safety and electrical safety.
The various components of suspension scaffold systems include counterweights, outrigger beams, tiebacks, suspension ropes, and scaffold hoists. These all must be installed, inspected, maintained, and used in compliance with regulations in order to minimize hazards.
Counterweights
Counterweights used to balance adjustable suspension scaffolds must be able to resist at least four times the tipping moment imposed by the scaffold operating at either the rated load of the hoist, or 1.5 times (minimum) the tipping moment imposed by the scaffold operating at the stall load of the hoist, whichever is greater.
Only those items specifically designed as counterweights must be used.
Counterweights used for suspended scaffolds must be made of materials that cannot be easily dislocated. Flowable material, such as sand or water, cannot be used.
Counterweights must be secured by mechanical means to the outrigger beams.
Vertical lifelines must not be fastened to counterweights.
Outrigger beams and tiebacks
Outrigger beams (thrustouts) are the structural members of a suspension or outrigger scaffold that provide support. They must be placed perpendicular to their bearing support.
Tiebacks must be secured to a structurally sound anchorage on the building or structure. Sound anchorages do not include standpipes, vents, other piping systems, or electrical conduit.
A single tieback must be installed perpendicular to the face of the building or structure. Two tiebacks installed at opposing angles are required when a perpendicular tieback cannot be installed.
Suspension ropes
The suspension ropes must be long enough to allow the scaffold to be lowered to the level below without the rope passing through the hoist, or the end of the rope configured to prevent the end from passing through the hoist.
The standard prohibits using repaired wire.
Drum hoists must contain no less than four wraps of the rope at the lowest point.
Employers must replace wire rope when any of the following conditions exist:
- Kinks;
- Six randomly broken wires in one rope lay, or three broken wires in one strand in one lay;
- Loss of one-third of the original diameter of the outside wires;
- Heat damage;
- Evidence that the secondary brake has engaged the rope; or
- Any other physical damage that impairs the function and strength of the rope.
Suspension ropes supporting adjustable suspension scaffolds must be a diameter large enough to provide sufficient surface area for the functioning of brake and hoist mechanisms.
Suspension ropes must be shielded from heat-producing processes.
Scaffold hoists
Requirements for scaffold hoists include the following:
- Power-operated hoists used to raise or lower a suspended scaffold must be tested and listed by a qualified testing laboratory.
- The stall load of any scaffold hoist must not exceed three times its rated load.
- The stall load is the load at which the prime-mover (motor or engine) of a power-operated hoist stalls, or at which the power to the prime-mover is automatically disconnected.
- Gasoline-power-operated hoists or equipment are not permitted.
- Drum hoists must contain at least four wraps of suspension rope at the lowest point of scaffold travel.
- Gears and brakes must be enclosed.
- When a hoist makes an instantaneous change in momentum or an accelerated overspeed, an automatic braking and locking device must engage, in addition to the operating brake.
- Manually operated hoists used to raise or lower a suspended scaffold must be tested and listed by a qualified testing laboratory.
- These hoists require a positive crank force to descend.
Welding from suspension scaffolds
Welding can be done from suspended scaffolds when:
- A grounding conductor is connected from the scaffold to the structure and is at least the size of the welding lead.
- The grounding conductor is not attached in series with the welding process or the work piece.
- An insulating material covers the suspension wire rope and extends at least 4 feet above the hoist.
- Insulated protective covers cover the hoist.
- The tail line is guided, retained, or both so that it does not become grounded.
- Each suspension rope is attached to an insulated thimble.
- Each suspension rope and any other independent lines are insulated from grounding.
Scaffold access
- When scaffold platforms are more than 2 feet above or below a point of access, employers must provide access, which can include ladders, stair towers, ramps, walkways, or integral prefabricated frames.
Employers must provide access when the scaffold platforms are more than 2 feet above or below a point of access.
Direct access is acceptable when the scaffold is not more than 14 inches horizontally and not more than 24 inches vertically from the other surfaces.
The standard prohibits the use of cross braces as a means of access.
Several types of access are permitted:
- Ladders, such as portable, hook-on, attachable, and stairway;
- Stair towers;
- Ramps and walkways; and
- Integral prefabricated frames.
Employees erecting and dismantling supported scaffolding must have a safe means of access provided after a competent person has determined the feasibility and analyzed the site conditions.
Clearance distances between scaffolds and power lines
- The required clearance distances between scaffolds and power lines depend on the lines’ voltage and whether they are insulated or not.
The standard requires specific clearance distances. The following table lists these distances:
Insulated lines voltage | Minimum distance | Alternatives |
---|
Less than 300 volts | 3 feet | |
300 volts to 50 kV | 10 feet | |
More than 50 kV | 10 feet plus 0.4 inches for each 1 kV over 50 kV | 2 times the length of the line insulator, but never less than 10 feet |
Uninsulated lines voltage | Minimum distance | Alternatives |
---|
Less than 50 kV | 10 feet | |
More than 50 kV | 10 feet plus 0.4 inches for each 1 kV over 50 kV | 2 times the length of the line insulator, but never less than 10 feet |
Fall protection
- For most types of scaffold, the required fall protection is a personal fall arrest system, guardrails, or both.
- To protect workers from falling objects, employers should install protective equipment such as toeboards and nets and have workers wear hard hats.
Fall protection includes guardrail systems and personal fall arrest systems. Personal fall arrest systems include harnesses, components of the harness/belt (such as D-rings), snap hooks, lifelines, and anchorage points.
Vertical or horizontal lifelines may be used.
Lifelines must be independent of support lines and suspension ropes and not attached to the same anchorage point as the support or suspension ropes.
When working from an aerial lift, users should attach the fall arrest system to the boom or basket.
Fall protection for specific types of scaffold
The following chart illustrates the type of fall protection required for specific scaffolds:
Type of scaffold | Fall protection required |
---|
Aerial lifts | Personal fall arrest system |
Boatswain’s chair | Personal fall arrest system |
Catenary scaffold | Personal fall arrest system |
Crawling board (chicken ladder) | Personal fall arrest system, or a guardrail system, or by a three quarter-inch diameter grabline or equivalent handhold securely fastened beside each crawling board |
Float scaffold | Personal fall arrest system |
Ladder jack scaffold | Personal fall arrest system |
Needle beam scaffold | Personal fall arrest system |
Self-contained scaffold | Both a personal adjustable scaffold arrest system and a guardrail system |
Single-point and two-point suspension scaffolds | Both a personal fall arrest system and a guardrail system |
Supported scaffold | Personal fall arrest system or guardrail system |
All other scaffolds not specified above | Personal fall arrest system or guardrail system that meets the required criteria |
Protection from overhead falling objects
To protect employees from falling hand tools, debris, and other small objects, employers should install toeboards, screens, guardrail systems, debris nets, catch platforms, canopy structures, or barricades. In addition, employees must wear hard hats.