E-stop Circuit Wiring

[mike k]

I am working on a project where the engineer designed an E-stop system to drop out all the circuits within a room of the building. The building is a military facility and used for testing & calibration of special equipment. There are several different voltages AC & DC within the space(s). Each space (room) has E-stop buttons a predetermined location around the perimeter of the room. All the circuits that enter the room are (branch circuits & Panel board feeder circuits) and controlled by mechanically held contactors. I have now way of knowing what type of equipment or the final use of this facility. This is do to the sensitive nature of the equipment which is to be installed by their personal after our scope of work has been completed. The problem I have is the E-stop circuit has a key rest (sounds good) it also has an interposing relay (good so far) which basically opens up after the E-stop has been depressed and closes (energizes) after the key reset and the relay holds itself in; but if the control circuit (voltage) is lost there the relay will open but there is no way to drop out or ?unlatch? the mechanically held contactors because of no (Voltage). Is this a proper design? What concerns should I pose to the customer & engineer? Are there any specific violations or compliance issues with this design?

 

[petersonra]

Re: E-stop Circuit Wiring

presumably the engineer knows what he is doing. since they have not given you any additional information to work from, I'd be inclined to follow the drawings.

 

[iwire]

Re: E-stop Circuit Wiring

Originally posted by petersonra:
presumably the engineer knows what he is doing.

Maybe the 'engineer' is just an out of state laborer 'playing' engineer for a day.

It does not take any skill to draw lines on paper.

 

[iwire]

Re: E-stop Circuit Wiring

Mike, my joking around with Bob not withstanding I do suggest you voice your concerns on paper.

I would do it with an RFI (Request for information) which would go to the engineer through the general contractor and would be available to the customer also.

It is a simple thing to make a supervision circuit for this control power. It might be worth while to suggest this

Considering this is apparently a safety system IMO your concerns are valid and you should CYA.

 

[kiloamp7]

Re: E-stop Circuit Wiring

There are frequently many different things to consider depending on the scenarios involved. But sometimes a "safety circuit" can be made more "failsafe" by using an electrically-held contactor.

 

[charlie tuna]

Re: E-stop Circuit Wiring

we once wired a lock system for a top security military group---they monitored and recorded all voice communication between airplanes. it was actually the commanding officer that caught the error-------------if everyone on the base got inside the security barrier ---- there was no way to get out!!!!! they had us put a key switch in and the commanding officer had the key on a chain around his neck!!!

 

[petersonra]

Re: E-stop Circuit Wiring

what you might see as a safety circuit might not really be a safety circuit. with the limited info you have, it would be difficult to make a determination at your level as to just what the purpose of the circuitry is.

one would probably never wire a machine estop circuit this way, but if there is no movement, thus far less danger to humans, it might well be perfectly appropriate.

just because it has red mushroom head buttons does not mean it is really a safety circuit.

 

[iwire]

Re: E-stop Circuit Wiring

Originally posted by petersonra:
what you might see as a safety circuit might not really be a safety circuit. with the limited info you have, it would be difficult to make a determination at your level as to just what the purpose of the circuitry is.

His 'level'?

 

[petersonra]

Re: E-stop Circuit Wiring

Originally posted by iwire:
His 'level'? :roll:

It's a high security area. They may not want him to know what they are doing or why.

[ June 25, 2005, 09:15 AM: Message edited by: petersonra ]

 

[iwire]

Re: E-stop Circuit Wiring

Originally posted by petersonra:
It's a high security area. They may not want him to know what they are doing or why.

Fair enough, I would still send the engineer an request for information through the GC to cover my @*^. They could send it back to me simply saying that info is not available to me and I would still be on record asking the question.