The following is a simple systematic procedure to follow for all lock-out and tag-out situations. Complex site or equipment specific procedures should be created for activities in all workplaces. Upon receiving authorization to shut down equipment for maintenance, the first priority is to obtain a written checklist. This checklist will ensure that all policies and procedures are followed in the proper order, the correct Personal Protective Equipment and other precautions are taken, and it will ensure that no steps have been missed.
The first step is to prepare for shut down by identifying what types of energy will be involved (i.e. electric, hydraulic, pneumatic or pressure) as well as identifying other possible hazards such as chemical or temperature exposure. Be especially mindful of potential energies that have been built up or stored as this type of energy may have devastating results when released. Keep in mind that there may be more that one source and type of energy that powers a machine.
The second step is to shut down the equipment using the normal stopping procedure for the equipment that is to be serviced. This may be as simple as turning off a switch, or it may involve following a shut down procedure depending on the complexity of the machine. If this is the case, then you must follow the shut down procedure accurately to prevent accidents.
Step 3: Isolate And Disconnect Energy Sources
The third step involves the careful isolation of the energy sources that feed the system. This is accomplished by throwing main disconnects and breakers, closing valves, disconnecting or capping any other energy sources such as hydraulic or pneumatic systems, and pressure vessels. Always disconnect electrical power from the source, do not just rely on pulling fuses.
Step 4: Apply Locks, Tags And Other Warnings
The fourth step involves applying locks, tags, or other lock-out devices (see next section) to all disconnect switches, valves, plugs, and all other energy-isolating devices and take the key with you. This will ensure that the equipment is not accidentally re-energized while the equipment is being serviced. Although locks are considered to be the best protection, tags should also be used in conjunction with the locks to provide important information regarding the lock-out. Tags must display your name, department, and notification that removal of a tag is strictly prohibited.
Step 5: Relieve Potential Energy
The fifth and final step involves controlling any stored energy that may be present throughout the system. Potential energy is one of the most dangerous forms of energy because it can strike quickly and without warning, it is therefore imperative that the control of stored energy is verified and monitored continuously until the work has been completed, or the hazard no longer exists. The following are additional methods of controlling stored energy:
- Relieve, block or disconnect any energy that still may be present or that may feed the system.
- Make sure that all parts have stopped moving; learn to identify types of motion.
- Release any pressure in lines or pipes that may be trapped.
- Blank pipes.
- Discharge static or built up electrical charges by attaching ground wires.
- Block and firmly support any elevated equipment.
- Block any machine parts that may collapse, fall or drift.
- Check that all spring-loaded parts are adequately blocked.
Step 6: Double Check the Lock-out Or Tag-out
Always take the time to verify that the lock-out procedure is complete before working on equipment. This simple double check will help to ensure your safety, as well as that of your co-workers.
- Notify all affected employees that the lock-out is complete and the work is beginning.
- Check to make sure that the lock-out area is clear of personnel.
- Make sure that all locks and tags are firmly in place.
- Always test to make sure that the proper systems have been locked out.
- Test the equipment by pressing the start buttons, and then return them to the off position.
- Test electrical panels for live wires or circuits using an approved tester.
- Ensure that only authorized personnel will be working on the machinery.
- Make sure any required permits have been filled out in full, correctly, and signed.
- Check the lock-out status periodically to prevent accidental start up of the equipment.