If I understand correctly what you mean by electronically monitoring, it is very common. I have never seen a lockout used that wasn't monitored. Usually one of the contacts of the lockout relay are fed to the SCADA or DCS system.
Oh, and it is best to use a contact on the last deck for the SCADA indication so that if something happens and the whole lockout doesn't actually roll (it happens) then you won't see the expected result.
We don't have a SCADA but we are planning to get one.
Right now the lockout lights up an annunciator...which I guess in a way is electronic. Sometimes I realize the stupidity of my question after I read your answers...thanks.
davidbeach, I had never heard of that. Is this with the ElectroSwitch series 24 type or other? Which is the last deck? (closest to the handle or farthest away)
I would assume the farthest away on an electroswitch, as the coil is located near the handle.
On a HFA I would assume nearest the handle, as the coil is at the back end.
But a comment: I would also monitor the condition of the coil, to be sure the circuit is intact. This would be good to see that you have DC in the whole circuit (in case of a DC fuse blowing).
Pretty reliable yes. But when they don't (or when related switches like instrument transfer switches don't) the results can get really ugly. If you're really paranoid, you monitor both the first and last decks and alarm on discrepancy. Last deck would be furthest from the coil. Shafts break, shafts twist.
It was long that thought that they were so reliable that one was enough for any application. There have been some ugly incidents that resulted in an 86 that failed to roll meaning that breakers weren't tripped and breaker failure wasn't initiated. The 86 trip coil can be monitored just the same as a breaker trip coil can be monitored.
There have also been nuisance rolls of the LOR without it receiving a trip initiate. There is a Mfg Service advisory to address this, but they are not always followed.
It was long that thought that they were so reliable that one was enough for any application. There have been some ugly incidents that resulted in an 86 that failed to roll meaning that breakers weren't tripped and breaker failure wasn't initiated. The 86 trip coil can be monitored just the same as a breaker trip coil can be monitored.
I'm looking at this lockout circuit and notice they have the normally closed lock out contact in series with the coil. This contact is in series with another normally closed contact on this same manually operated switch. I guess this is normal practice in case the contact doesn't operate?
Lockout contacts usually come in pairs. I think this is more of a mechanical consideration. Think of two fixed contacts with terminals, and a center section that rotates with the shaft. The alternative would require a flexible conductor that would be subject to fatigue.
The contacts in series with the coil are to interrupt the current when the device operates, much the same as "a" contacts in series with the trip coil of a circuit breaker. Typical "operate" currents of some 86 devices are quite high. The 86 contacts are designed to handle interrupting this current.
We commonly use an indicator light in the lcokout relay trip circuit in much the same fashion as the indicator light in a circuit breaker coil trip circuit, i.e., a low-current indicating lamp paralleled across the trip contacts. Presence of voltage in the 86 trip circuit will keep this lamp illuminated.
Some modern protective relays perform a similar service. I'm thinking of GE's UR family which has output contact voltage and current monitoring. If you're using one of these devices, then the status of the voltage and current elements are available as data to be programmed for whatever purpose you might wish.
Simultaneously we use a contact from the 86 device as a digital input to our UR relay, giving us another piece of data for using programming the device as well as for recording in the event record.
