The Press That Cycled While Someone Was Inside
A maintenance technician reached inside a stamping press to clear a jam. His partner was supposed to hold the e-stop button. The partner got distracted, released the button, and the press cycled. The technician’s hand was seriously injured. The root cause was not a careless operator. It was a missing lockout. The e-stop was held by a person, not locked by a device. A person’s attention is not an energy isolation. The press should have been locked out at the energy source — not stopped by a finger on a button.
Lockout/Tagout (LOTO) is the most fundamental safety procedure in a plant. It is also the most bypassed. Here is how to do it right.
What LOTO Actually Is
LOTO is the practice of physically locking the energy isolation device (the disconnect switch, the valve, the circuit breaker) so nobody can turn the machine on while someone is working on it. Each worker places their own personal padlock on the isolation device. The machine cannot be restarted until every padlock is removed. This is not a suggestion — it is a regulatory requirement in most jurisdictions (OSHA 29 CFR 1910.147 in the US).
The key idea: the worker’s life is on their own lock. No one else can remove it. A single “group lock” where the supervisor holds the key is not LOTO — it is a wish.
The Six-Step LOTO Procedure
- Prepare: Identify all energy sources (electrical, pneumatic, hydraulic, mechanical, gravitational). Know what feeds the machine.
- Shut down: Operate the normal shutdown procedure. Stop the machine.
- Isolate: Turn off the disconnect, close the valve, engage the mechanical block. Physically separate the energy source from the machine.
- Lock and tag: Place your personal padlock on the isolation device. Attach a tag with your name and date. If multiple workers, each places their own lock.
- Release stored energy: Bleed the air, release the hydraulic pressure, lower the raised load, discharge the capacitors. Verify zero energy.
- Verify: Try to start the machine (press the start button). It should not start. This confirms the isolation works.
The LOTO rule: You do not work on a machine that is merely “off.” You work on a machine that is locked out, with stored energy released, and verified off by pressing the start button. The press that cycled was stopped but not locked. A finger on an e-stop is not isolation.
Stored Energy: The Forgotten Step
Turning off the power does not make the machine safe. Energy is still stored in:
- Pneumatics: The air in the line can still move a cylinder. Bleed it.
- Hydraulics: Pressure in the accumulator can still lift a press. Release it.
- Gravity: A raised arm or a suspended load can fall. Block it.
- Electrical capacitors: High-voltage capacitors hold a lethal charge for minutes after power-off. Discharge them.
- Mechanical springs: A compressed spring can release energy. Block it.
The most common LOTO violation is skipping step 5. The power is off, but the air pressure still drives the cylinder when the valve leaks. Bleed, block, discharge — then work.
Group Lockout: Many Locks, One Hasp
When a team works on a machine, they use a group lockout hasp — a multi-lock clamp on the isolation device. Each worker puts their own padlock on the hasp. The machine stays off until the last lock is removed. No one removes another worker’s lock (except in an emergency, with a documented procedure). This is the only safe way to share a lockout.
Audit LOTO, Do Not Trust It
LOTO procedures look good on paper and fail in practice. Audit them: walk the plant and watch a maintenance task. Do the workers lock out? Do they bleed stored energy? Do they verify? The press incident was a single audit finding waiting to happen — the e-stop was being used as a lockout. Find these before an incident does.
A LOTO Readiness Checklist
- Has every machine been inventoried with its energy sources?
- Does each isolation device accept a padlock (hasp or lockable disconnect)?
- Are personal padlocks assigned to every worker (not shared)?
- Is there a written LOTO procedure for each machine?
- Is stored energy identified and bled before work?
- Is there a group hasp for multi-worker tasks?
- Is the “verify start” step in the procedure?
- Is there a rule that no one removes another worker’s lock?
- Has LOTO been trained and documented?
- Is there an annual audit of LOTO compliance?
The Bottom Line
The press that cycled while someone was inside was not an accident waiting to happen. It was a LOTO violation made real. Lock the energy source, bleed the stored energy, verify the start button does nothing, and wear your own personal padlock. The worker who goes home at the end of the shift is the one who locked the machine — not the one who trusted a colleague’s finger on a button.
