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A panel already has two emergency stops - for two diesel engines powering an alternator and hydraulic pumps- and requires a third for the actual control system. The original two are legacy, the latest is new (don't ask).
My gut feeling is that more than one emergency stop mushroom in a single location is dangerous, if they affect different systems- in a panic, the operator can't know which is the right one to push. On the other hand, it's not obvious that killing the whole power system is necessarily the safest thing to do. For example, if someone is trapped in the machinery, the machinery has to be made "safe", but killing the alternator power would kill all but the emergency lights, and the machine operates mainly at night. And killing the hydraulic power might lead to uncontrolled movement of the machinery as it falls back to the no- pressure position.
Has anyone had to treat emergency stops where a panel controls different systems with conflicting requirements?
My gut feeling is that more than one emergency stop mushroom in a single location is dangerous, if they affect different systems- in a panic, the operator can't know which is the right one to push. On the other hand, it's not obvious that killing the whole power system is necessarily the safest thing to do. For example, if someone is trapped in the machinery, the machinery has to be made "safe", but killing the alternator power would kill all but the emergency lights, and the machine operates mainly at night. And killing the hydraulic power might lead to uncontrolled movement of the machinery as it falls back to the no- pressure position.
Has anyone had to treat emergency stops where a panel controls different systems with conflicting requirements?