250VDC solenoid valve circuit continuity verification 1

[dbp8518]

I am modifying the solenoid valve circuit from "deenrgize to actuate" to "energize to actuate" logic of a feed water regulatin valve at a nuclear station. I need to add some sort of low current device to monitor the circuit continuity to assure that the solenoid will operate when logic demands it to operate. Due to real-estate on the control panel my concept to add neon lamps in the circuit is not viable. Does any one have other possible solution?

 

[ScottyUK]

Is the "de-energise to actuate" part of a fail-safe design? Why change the design if so?

In principle you could bleed a low current, well below the operating level of the solenoid, through the coil and monitor for continuity that way.


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[dbp8518]

Yes it was original fail-safe design which is being modified due to single point vulneribity concerns.

 

[OperaHouse]

I'm confused. If you don't have the space for a pilot light, what kind of monitoring do you want. Can't get more minimal than that! I would prefer a current monitoring system like using a LED in series or solid state relay to operate some monitor. In either case a zener should be used in parallel with the current monitoring device to maintain operation in case the monitor fails.

 

[buzzp]

I am sure you will analyze, thoroughly, what you are doing. If not, please do. In any case, a similar concept is used with "Lock Out Relays" to prove coil integrity. They are also energize to operate devices. Electroswitch makes these relays. They have an LED indicator with a suitable output for a PLC or whatever. You should be familiar with these working at a nuke station.

I looked at making something a while back and can't recall any details without my file at work. Ill try to check and see if I came up with anything creative.