There are two types of energy. Kinetic energy is the force caused by the motion of an object. A spinning wheel is an example of kinetic energy. A spring under tension is an example of potential energy. Garbage compactors and gravel crushers are also examples.
Potential energy can also be the potential energy from suspended parts or springs.
To keep equipment from being energized during repairs or maintenance, it can often be locked out . A lock, either combination or key, is then placed over the energy isolating device. This lock remains over the energy source until servicing or maintenance is completed. A piece of machinery is tagged out when the machine is turned off and a tag with a written warning is attached to the disconnect switch, circuit breaker or valve or other energy isolating device. The purpose of the tag is to assure that the equipment will not be operated until the tag has been removed.