• Different types of energy are associated with different forms of motion and different kinds of hazard.
• Energy becomes hazardous whenever it builds to or is released in an amount that could cause injury.

Energy is the power for doing work. There are different types of energy, but all are associated with motion. All types of energy exist in two basic forms: potential energy and kinetic energy.

• Potential energy is stored energy that can be drawn upon to do work. Potential energy can be viewed as motion waiting to happen based on an object’s position, such as the energy found in elevated, suspended, compressed, or coiled materials. When the lockout/tagout standard refers to “stored energy,” it is referring to potential energy.
• Kinetic energy is energy that an object has because of its motion. Kinetic energy in the workplace is present in any moving objects, such as released loads, uncoiling springs, and moving machinery.

Potential energy can be transformed into kinetic energy. For example, tensioned objects such as suspended loads have potential energy — energy that has the opportunity for motion. Releasing the load converts potential energy to kinetic energy, causing the load to drop.

Types of energy

• Chemical energy is the energy stored in chemical bonds and released in chemical reactions. Common sources of chemical energy in industry include:
  • Liquids such as gasoline, diesel, benzene, acids, and caustics;
  • Gases such as propane, natural gas, and methane; and
  • Solids such as fertilizer, wet and dry cell batteries, and combustible dust.
• Electrical energy involves the flow of charged particles through electrical circuits. Common sources of electrical energy include:
  • Alternating current (AC) and direct current (DC);
  • Equipment and conductors at household and industrial voltages;
  • Photovoltaic systems, motors, and hybrid vehicles; and
  • Circuit breakers, transformers, capacitors, and inverters.
• Gravitational energy is the energy objects have due to Earth’s gravity. Any raised object is a source of gravitational energy, including:
  • Hoisted vehicles,
  • Raised dumpster lids,
  • Objects supported by a crane, and
  • Elevated dump-truck beds.
• Hydraulic energy is the energy transmitted by pressurized fluids. Common sources of hydraulic energy include the hoses, pumps, valves, actuators, and reservoirs found on:
  • Forklifts,
  • Vehicle hoists,
  • Power press equipment, and
  • Injection molding machines.
• Mechanical energy is the combined kinetic and potential energy of mechanical systems. Common sources of mechanical energy include:
  • A wind turbine rotating in the breeze,
  • A paddle wheel rotating with flowing water,
  • Moving vehicles and mobile equipment,
  • A compressed spring, and
  • High-volume sound waves.
• Pneumatic energy is the energy transmitted in systems of pressurized air. Common pressurized air or gas systems include the pipes, pumps, valves, actuators, and pressure vessels found in:
  • Coating and pesticide sprayers,
  • Air compressors, and
  • Tank and pipe purging systems.
• Stored energy is energy that remains in a machine or system after the main power source has been disconnected unless otherwise drained, released, or relieved. Stored energy may include springs, fluids under pressure, electrical capacitor charge, and chemicals or steam.
• Radiation involves the movement of waves or particles through space or another medium. Sources of radiation include:
  • Visible light, infrared light, and ultraviolet light;
  • Non-ionizing radiation, such as lasers, radio frequency (RF), and microwaves (MW); and
  • Ionizing radiation, such as computed tomography (CT) and X-rays.
• Thermal energy is the kinetic energy of moving particles. Common sources of thermal energy include:
  • Hot water,
  • Heated oil,
  • Steam, and
  • Liquid nitrogen.

Energy transformation

Energy is often converted from one type to another to make it more useful. For instance:

• Chemical energy stored within a fuel such as natural gas is released as thermal energy when it is burned at a power plant.
• This thermal energy can be used to heat water within a boiler to create steam, which expands to rotate a turbine, generating electricity.
• The electrical energy is then distributed along power lines to businesses where the electricity can be used to power an air compressor.
• The compressor’s electric motor forces ambient air into a pressure vessel, confining large amounts of air into a small space for future use.
• This stored air is pneumatic potential energy that can be used later. During an electrical power failure, an air-powered tool can still be used if sufficient potential pneumatic energy (compressed air) remains in the air compressor’s pressure vessel.

The machinery and equipment that make energy conversions such as these have multiple sources of hazardous energy that must be addressed before authorized workers perform servicing and maintenance activities.

How energy becomes hazardous

Energy becomes hazardous when it builds to a dangerous level or is released in a quantity that could injure a worker. Hazardous energy is never far from those who need to service or maintain equipment. Simply turning the power off does not make equipment safe! It is critical that employees who service or repair equipment know both how hazardous energy could harm them and how to control it.