Pre-Start Checklist for Machine Guarding and Lockout

Why the Pre-Start Checklist Exists

A pre-start checklist exists to catch failures before the operator reaches the controls. In mining environments, a missing bolt, a fatigued interlock, or a misapplied tag can turn a routine start into a serious incident. The checklist standardizes the inspection so that the same questions are asked every time, regardless of shift or crew.

The focus here is not on general safety philosophy. It is on the specific verification of machine guarding and lockout systems before equipment receives power. These systems form the first line of defense against contact with rotating shafts, crushing points, and high-energy storage. If they fail, subsequent controls may not save the operator.

Verify the Physical Guarding

The first step is a walkaround of the equipment. Look for guards on every exposed point of rotation or motion. This includes drive shafts, sprockets, belts, chains, hydraulic cylinders, and grinding or crushing surfaces.

Check each guard for integrity. A guard with a bent hinge, a missing fastener, or a gap larger than the design limit is not functioning. The gap matters. An operator can insert a hand or tool into a gap that is too large, even if the guard appears present.

Watch for damage caused by previous maintenance. Sometimes a guard is removed to access a component and then replaced incorrectly. The fasteners may be the wrong size, or the guard may sit at an angle that allows contact with moving parts. A guard must cover the hazard fully. It must not be propped up, taped in place, or held by a temporary fastener.

Check Interlocks and Safety Devices

Guarding is not only physical. It is also electrical. Many machines use safety interlocks that cut power when a guard is open. These interlocks are often made up of a switch, a sensor, and a control circuit.

Test each interlock. Open the guard and confirm that the machine will not start. Close the guard and confirm that the machine can start. If the machine can start with the guard open, the interlock is failed. This is a red flag.

Also check light curtains, presence sensors, and emergency stop buttons. Light curtains must be unobstructed and clean. A dirty sensor may not detect an operator entering the danger zone. Emergency stops must be clearly visible and accessible. A button that requires two hands to press is not an emergency stop. It is a control.

Red flags for interlocks include:

1. A switch that is taped to the closed position.
2. A sensor that is covered in dust or debris.
3. An emergency stop that is not red or is hidden behind a panel.
4. A control circuit that allows startup without a guard closure signal.

Apply Lockout and Tagout Correctly

Lockout and tagout isolate energy sources. This includes electrical, hydraulic, pneumatic, mechanical, and thermal energy. The purpose is to ensure that no one can accidentally restart the machine while maintenance or inspection is occurring.

Before startup, verify that all lockout devices are removed. This means checking every energy source. If a hydraulic accumulator is charged, it may release pressure even if the pump is off. If a mechanical component is under tension, it may move unexpectedly.

Each lock must have a unique tag that identifies the person who applied it. The tag must be legible. If the tag is faded, torn, or missing, the lock is not valid. A lock without a tag is a hazard. It may be applied by someone who is no longer on site, or it may be a leftover from a previous task.

Red flags for lockout include:

1. A lock with a tag that does not match the current crew.
2. A padlock that is damaged or has a broken shackle.
3. A tag that is attached to a guard instead of the energy isolation point.
4. Multiple locks on a single point with only one tag present.

Confirm Operational Safety Controls

Operational safety controls are the procedures and software settings that govern how the machine behaves. This includes speed limits, torque limits, and automatic shut-downs.

Check that the control panel displays no active safety faults. Some machines have diagnostic screens that show the status of safety circuits. If a fault is present, the machine may be in a degraded mode. It may run, but it will not stop if a guard is opened.

Review the operator interface. Confirm that the startup sequence requires confirmation. Some machines allow a simple button press to start. This can be dangerous if the operator is distracted or if a third party is nearby. A two-step confirmation, or a requirement to stand in a specific position, reduces the risk of accidental activation.

Also check that the machine is in the correct mode for the task. A mode that allows high speed is not appropriate for a task that requires precision or where personnel may be close to the machine. The mode selection must match the work plan.

Review Documentation and Training

The physical checks must match the documentation. Pull the equipment manual or the specific safety data sheet for the machine. Compare the installed guards to the diagrams. If a guard is missing, identify why. Was it removed for maintenance and not replaced? Was it damaged and awaiting repair?

Check the lockout log. It should list the energy sources, the isolation points, and the personnel involved. If the log is incomplete, the lockout procedure was not followed correctly. This indicates a training gap.

Confirm that the operator has completed training on the specific machine. Training is not just a signature on a form. It must include hands-on practice with the safety controls. The operator must know how to test the interlocks and how to apply and remove locks.

Red Flags and Stop-Work Conditions

Some conditions are too serious to document and continue. They require immediate stop-work.

1. A guard is missing or damaged.
2. An interlock is bypassed or taped closed.
3. A lockout device is missing or the tag is illegible.
4. An emergency stop does not function.
5. A safety fault is displayed on the control panel.
6. The machine cannot be verified as isolated before maintenance.

If any of these are present, stop. Do not attempt to fix the issue without proper authorization and tools. The risk of injury outweighs the schedule.

Table of Common Guarding Failures

Failure Type	Description	Corrective Action
Missing Guard	No physical barrier over a rotating part	Install correct guard from spare parts inventory
Broken Fastener	Guard bolt is stripped or missing	Replace fastener with correct grade and torque
Bypassed Interlock	Switch taped to closed position	Remove tape, repair switch, test circuit
Dirty Sensor	Light curtain covered in dust	Clean sensor, verify detection with hand test
Missing Tag	Lock applied without identification tag	Remove lock, re-apply with proper tag and ID
Wrong Guard	Guard installed over wrong component	Remove incorrect guard, install correct guard

Final Verification Before Power-Up

Once all checks are complete, perform a final verification. Walk the perimeter of the machine. Confirm that no personnel are in the danger zone. Confirm that all guards are closed and locked. Confirm that all locks are removed and tags are stored.

Then, perform a low-speed test run if the procedure allows. Observe the machine from a safe distance. Listen for unusual noise and watch for vibration. If anything seems wrong, stop immediately.

The checklist is not a formality. It is a verification tool. Each item must be checked, not just marked. A tick in a box without a physical check is a failure. The goal is to ensure that the machine is safe to operate and that the operator is protected from the hazards present in the machine itself.