NIST GCR 01-814
A Guide to the EU Machinery Directive
- The emergency stop device must:
- middot; have controls that are identifiable, clearly visible, and quickly accessible;
- stop the dangerous process as quickly as possible (without creating additional hazards); and
- where necessary, trigger safeguard movements.
- Once the emergency stop control has been actuated, the emergency stop order must be maintained until it is specifically overridden, or reactivated. It must be impossible to engage the device without triggering a stop command. Disengaging the device must not restart the machinery.
- When machinery or parts of machinery work together in complex installations, the stop controls and the emergency stop must stop the machinery and all equipment upstream and/or downstream if continued operation can be dangerous.
e. Mode Selection
- The control mode selected must have priority over all the others, except the emergency stop device.
- Where there are several control or operating modes, there should be a mode selector which can be locked into each position. The operator should be able to make a choice based on unequivocal action on the control device.
- If the machine must operate with neutralized protection devices (such as when one must work inside the machine), then the mode selector must simultaneously
- disable the automatic control mode,
- permit movements only by controls requiring sustained action,
- permit the operation of dangerous moving parts in enhanced safety conditions (such as reduced speed) while preventing hazards from linked sequences, i.e., machinery should only be operable on a step-by-step basis, and
- prevent any dangerous movement by acting voluntarily or involuntarily on the machine's internal sensors.
- A person adjusting the machinery must be able to control operation of the parts he is working on and have a clear view of the mechanisms he is controlling.
f. Failure of the Power Supply
Note: The manufacturer of machinery is not responsible for defects in the electrical system of the site or establishment that will house the machine. The manufacturer should, however, provide for protection against electrical failures that will cause sudden start-up by making the machine's control circuit electrically separate from the one of the place of use. The manufacturer is cautioned as well to take preventive measures against all risks associated with failure in the power supply system.
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