Level Control Valve Malfunction on Offshore Platform

Oh dear. I don't know about these valves, but I have had plenty of experience with salt water and electronics. The fact that your valve malfunctioned from the water exposure could mean that its electronics was exposed. Can you disassemble it enough to inspect the circuit board and connectors? Hopefully it's a coated board, but given the failure, perhaps not.

A fresh-water rinse, with immediate aggressive drying may help. But be careful, we don't want the drying temp to get over 70C and perhaps melt some plastic someplace. A hot-air gun is useful. As far as connectors go, sometimes reseating them after cleaning with silicon grease can help. I know that sounds scary, silicon grease? But it displaces the salt-ion moisture and then upon closure the connector contacts should wipe their way to clean metal despite the grease. It's worked for me in mid-ocean. Desperate times can call for desperate measures.

First: If the positioner is contaminated with water and oil, your instrument air is crappy. At the very first opportunity, put coalescing filters on everything that consumes air. You need a refrigerant dryer in your air system, just after the storage tank.

It's not salt water in the unit, it's fresh water condensed from the atmosphere. When you compress air, it compresses the humidity too, and the relative humidity becomes greater than 100%. That's why you get gallons of water when you drain the receiver, which should be done either daily or (better) automatically.

There is a chance that you have rainwater coming down the conduit. In your environment that would likely have some salt in it, from spray on the platform. It can only get in if the conduit entry is not sealed. If that's the case you are violating the explosionproof rating of the housing. Masoneilan usually puts in a sealed conduit plug with a pigtail for external wiring connection. Your installation guys may have thrown that away.

Blow off the circuit board with (dry) compressed air. If there are any tracks of corrosion clean them with a Q-tip and rubbing alcohol. The rubbing alcohol dries quickly and is not conductive nor corrosive. Inspect the pcb connectors and clean them gently but as thoroughly as possible. They should be gold-plated to resist corrosion, but the gold is very thin and you can scrub it off. A miraculous product called CorrosionX should be sprayed on the connectors to prevent further corrosion. Available at marine supply houses everywhere.

Remove the spool valve and clean it with long Q-tip and alcohol. It should have no oil or grit in it. The spool should move freely and show no scratches on its surface.

Get used to doing this. If the air is bad as I think it is, every pneumatic instrument on the platform is next.