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New Valve Feedback Signal Woes
Replaced a Jordan MV-1020 with an RCV SEVA-200. Feedback 4-20 gives constant 100% open indication at HMI regardless of valve position.

Replaced a Jordan MV-1020 with an RCV SEVA-200. Feedback 4-20 gives constant 100% open indication at HMI regardless of valve position. Two identical valves were replaced and both act the same way (yes, I broke both of them). My predecessor had replaced other valves with an older model (non-SEVA)of RCV valve with success.

I have connected my Fluke process meter to both the valve output signal and have simulated a feedback signal to the PLC with valid indications for both tests. The selector switch is at position 3 for 4-20 signals. I have verified polarity and in a fit of frustration have tried reversing the signal wires (my plant has unique properties. Depending on which contractor did an installation black may be - or +).

Any pointers for where to look next?

By W.L. Mostia on 16 March, 2018 - 11:53 am
2 out of 2 members thought this post was helpful...

Did you read the 4-20mA signal from the RCV SEVA 200? It appears that the RCV SEVA-200 has an active (4-wire) 4-20 mA output rather than the 2-wire sensor signal from a transmitter that your HMI typically expects. I believe that it is also grounded at the RCV SEVA- 200, which would require an isolated input at your control system.

William (Bill) L. Mostia, Jr. PE
ISA Fellow, FS Eng. (TUV Rheinland)
WLM Engineering Co.

Sorry for such a late reply...

It turned out to be that the SEVA didn't require loop power. Once I re-wired without our power supply in the loop all worked well.