Verification by the authorized employee that the previous steps of the procedure have effectively isolated the machine or equipment must be done prior to starting the servicing or maintenance work. The authorized employees need to verify that:
- the machine or equipment has been turned off or shut down properly;
- all the energy-isolating devices were identified, located, and operated as needed;
- the LOTO devices have been attached to the energy-isolating devices; and
- the stored energy has been rendered safe.
The authorized employee(s) also need to verify that, by performing these steps, they have EFFECTIVELY isolated ALL the hazardous energy associated with their servicing and/or maintenance activities such that they cannot be injured by hazardous energy sources while performing the servicing and/or maintenance activities. These potentially life-saving steps are intended to assure the employee that the machine or equipment is isolated from the energy source, that the residual energy has been dissipated or blocked, and that injury could NOT result from the inadvertent activation of the operating controls.
BOTH visual inspections and physical tests are important elements of verification of de-energization. Visual inspection techniques are critically important as authorized employees can visually confirm that switches, valves, breakers, etc., have been properly moved to and secured in the OFF or SAFE position. Visual inspection can also verify whether or not LOTO and other protective devices have been applied to the energy-isolating devices in a manner that would prevent the unsafe movement of the isolation device. Finally, a visual inspection can be used to verify that isolation has taken place by determining that ALL motion has stopped and that ALL coasting parts, such as flywheels, grinding wheels, saw blades, etc., have come to rest. However, in the majority of situations, visual inspection techniques must be accompanied by physical tests to ensure that the steps taken to isolate hazardous energy have worked successfully to isolate the energy from the machine or piece of equipment.
OSHA emphasizes that in order to ascertain whether hazardous energy has been effectively isolated reliably, the authorized employee(s) generally will need to use a combination of visual inspection techniques and other detection methods. Depending upon the measures necessary to detect the presence of hazardous energy, visual inspection techniques generally will need to be performed in conjunction with the use of a test instrument (e.g., voltmeter; combustible gas indicator) and/or a deliberate attempt to start up machines or equipment. Indeed, in most cases, it is only through the use of a test instrument or a deliberate attempt to start up a machine that the authorized employee will be able to ascertain whether the steps are taken to isolate hazardous energy (which were checked through visual inspection techniques) actually worked to isolate the energy from the machine. The appropriate combination of verification methods will depend upon the types of machinery or equipment involved, the complexity of the system, and other factors.
For example, visual verification that a disconnect switch is in the open or off position, even in conjunction with the operation of the equipment’s control(s), is NOT a reliable indication that an electric circuit has been de-energized when employees will be working on or near exposed electrical parts (PLEASE see my most recent posts Verifying ZES is DIFFERENT for electrical workers!). It is possible to interrupt a portion of the circuit so that the equipment will not operate even though the rest of the circuit is still alive. Therefore, a qualified electrical worker must use test equipment to verify de-energization by testing the electric circuit elements and equipment parts to which employees will be exposed. A test is also required to check for any voltage even though specific parts of a circuit have been de-energized and presumed safe. Under certain conditions, it is possible to feed circuits from the load side (e.g., back-feed; short circuit) or to have induced voltage. See §1910.333(b)(2)(iv) on electrical safety-related work practices for further details.