Setup Key Switch Muted on a 250-Ton Press
In a toolroom supporting a stamping plant, a 250-ton straight-side mechanical press is being set with a new progressive die weighing 1.9 t. The die hangs from the crane on two 1.5 t swivel hoist rings threaded into M16 holes in the upper shoe; a third lifting point is a tapped hole in the punch holder. The light curtain has been muted with the setup key switch so the setter can jog the ram while watching the stock lifters. For blocking, the setter placed a 100 mm length of hardwood between the upper and lower shoes. While reaching in to clear a slug at station two, the setter's sleeve catches on a stripper bolt. The ram is at top dead centre but the flywheel is still coasting down. No one is hurt. The plant has a written lockout/tagout procedure, rated die safety blocks in the crib, and a pre-start checklist that was not filled in.
1. Identify the highest-risk condition in this setup and list, in order, the immediate actions required before any further work on the press.
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Highest risk: a person reaching into the die space while stored energy remains (coasting flywheel plus a gravity-loaded ram) and with blocking that is not rated for the load. The hardwood block is being used as a safety block; wood can crush or split and is not designed for a 1.9 t die.
Immediate actions, in order:
- Stop the job and remove the setter from the point of operation.
- Lock out the press main disconnect and the light-curtain mute circuit; apply personal locks and tags.
- Wait for the flywheel to come to a complete stop before any further entry - top dead centre is not a safe state while the flywheel is rotating.
- Lower the ram onto rated die safety blocks, or install them on the die posts, sized for the upper-die weight with a margin.
- Clear the slug with a hook, air blast or brass tool - never a hand.
- Inspect the sleeve and report the near miss before restart.
2. Evaluate which engineering and administrative controls failed, and specify the corrections you would implement.
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Engineering failures: the mute key switch allowed the presence-sensing device to be bypassed with no hold-to-run or reduced-speed safeguard; no rated die safety blocks were in use; lifting was planned with three points of unknown capacity and unknown thread engagement - the M16 holes in a hardened shoe may have only a few usable threads. Administrative failures: the pre-start checklist was not completed, there was no spotter, and the setup procedure allowed reaching in.
Corrections:
- Replace the simple mute with a setup mode that requires hold-to-run at reduced speed (inch or single stroke) plus an enabling device.
- Add rated die safety blocks to the setup kit and make their use mandatory before any entry into the die space.
- Verify lifting points by calculation and use a certified lifting assessment; require a spotter.
- Add a second-person verification step and revise the setup procedure, then retrain the crew.
3. The supervisor says the setup key switch makes the task safe. How do you respond, and what documentation would you create?
Read the worked answer
Respond with the principle: a key switch only defeats the light curtain. It does not remove stored energy, does not support the ram, and does not protect against a control failure or a coasting flywheel. Entry into the die space requires energy isolation and physical blocking sized for the load.
Documentation to create:
- A near-miss report with a factual, non-punitive description so the next near miss is reported too.
- An updated hazard assessment covering the setup task, not just production running.
- A corrective-action log with owner and due date for the mute circuit, blocking and lifting issues.
- An audit of the setup crew within the week to confirm the new procedure is being followed.