The lockout sequence step by step

Lockout follows a fixed sequence. The order matters: each step depends on the one before it, and skipping or reversing steps creates gaps. Shutting a machine off at the disconnect while it is running under load can damage equipment and create an arc. Locking out before notifying operators can leave someone in a dangerous position. Starting work before verifying can leave a missed energy source live. This lesson walks through the sequence step by step, explaining what happens at each stage and why.

OSHA's 1910.147(d) lists six steps for applying energy control: preparation for shutdown, machine or equipment shutdown, isolation, application of lockout or tagout devices, control of stored energy, and verification of isolation. Paragraph (c)(9) adds that affected employees must be notified before controls are applied. Many programs present the sequence as eight steps, as below, by making notification and doing the work explicit.

Step 1: Prepare

Preparation starts before anyone touches the equipment. The authorized person:

• identifies the job and the equipment, including anything connected upstream or downstream;
• gets the current machine-specific procedure and reads it, checking that it matches the equipment as it is today;
• identifies every energy source, its type and magnitude, and its isolating device, using the procedure's energy source inventory;
• identifies stored energy and how it will be released or restrained;
• gathers the locks, tags, devices, blocks and test instruments needed;
• considers other hazards, such as confined spaces, hot work, working at heights or chemicals, that need separate permits or controls;
• decides whether this is an individual lockout or a group lockout (lesson 8).

If there is no procedure, or the procedure does not match the equipment, stop and get it resolved before going further. A procedure that lists one disconnect for a machine that now has two is worse than useless, because it creates false confidence.

Step 2: Notify affected persons

Tell the operators and anyone else working with or near the equipment that it is being shut down and locked out, why, and roughly for how long. This prevents surprises: an operator may be partway through a cycle, may have material in the machine, or may be about to restart it. In large areas, notification may include signs, barriers or a radio announcement. Notification also helps ensure no one is inside the machine or its danger zone when it is shut down.

Step 3: Shut down

Stop the equipment using its normal stopping procedure: the stop button, the operator controls or the shutdown sequence in the operating instructions. Bring moving parts to rest and complete or abort any process cycle safely. Using the normal stop first avoids two problems: interrupting a running process abruptly can create its own hazards, such as material jams, pressure spikes or product spills, and opening an electrical disconnect under heavy load can cause arcing and damage. The control system is the right tool for stopping; the isolating device is the right tool for keeping the equipment stopped.

Step 4: Isolate

Operate each energy-isolating device to the safe position: open the disconnect switch, switch off and isolate the breaker, close the valve, disconnect the plug, insert the blank. Isolate every source on the inventory, not just the main one. Make sure the device is fully in the off or closed position; a disconnect handle that looks open may not be if the linkage is broken. Where possible, visually confirm the isolation, for example by seeing the open blades of a visible-break disconnect or the closed position indicator on a valve.

Step 5: Apply locks and tags

Place your personal lock on each isolating device, using the correct lockout device where the isolating device does not accept a lock directly, and attach your tag. Each authorized person who will be exposed applies their own lock. For a group lockout, follow the group procedure (lesson 8). The lock must hold the device in the safe position so it cannot be operated. Check by trying to move the handle gently; it should not move.

Step 6: Control stored energy

Release, restrain or otherwise make safe all stored energy. Bleed trapped air and hydraulic pressure through bleed valves; lower raised parts to their rest position or block them; release spring tension; wait for flywheels and rotors to stop; allow hot parts to cool; discharge capacitors following the manufacturer's procedure; drain and vent lines. If stored energy could build up again, such as pressure from a leaking valve or heat from a reaction, keep checking it until the work is finished. Lesson 7 covers stored energy control in more detail.

Step 7: Verify

Before any work starts, verify that isolation has worked and the equipment is at a zero energy state. First make sure everyone is clear of the equipment. Then try to start it using the normal controls (the 'try' step), check gauges, and, for electrical work, have a qualified person test for the absence of voltage with a properly rated tester, testing the tester before and after. Return the controls to the off or neutral position after the try. Verification catches missed sources, failed isolating devices and mislabeled breakers. Lesson 7 is devoted to it.

Step 8: Do the work, keeping control

Only now does the servicing or maintenance start. Keep your key with you at all times. If the job changes, for example because you discover another energy source or need to work on a different part of the machine, stop and update the lockout before continuing. If you leave the area for a break, your lock stays on. If the job continues past your shift, follow the shift change procedure (lesson 8). If you need to energize the equipment temporarily for testing or positioning, follow the testing procedure in lesson 9, which requires clearing everyone and following specific steps.

Checking the sequence on the job

Experienced authorized persons talk through the steps as they go, and many workplaces use a checklist on the back of the procedure or placard. A quick self-check before starting work is: have I notified, isolated every source on the list, locked and tagged each one, controlled stored energy and verified? If the answer to any part is uncertain, go back. The few minutes this takes are the cheapest insurance in maintenance.

When the procedure does not fit

Sometimes the equipment in front of you does not match the procedure: there is an extra valve, a breaker is labeled differently, a disconnect has been moved. Do not improvise. Stop, tell your supervisor, and have the procedure corrected or a temporary procedure approved before continuing. Report the mismatch so the procedure can be updated. Many serious incidents start with an authorized person adapting a procedure on the spot because the job was urgent.

Communicating during the job

Lockout is also communication. A visible lock and tag at each isolation point tells others the equipment is out of service; a sign or barrier at the machine reinforces it. Many sites record active lockouts on a board or in a log at the control room, so that operators and supervisors know which equipment is unavailable and who to contact. When the work is finished, the same channels are used to tell people the equipment is back in service.