Mep-831a Oil Pressure switches keep breaking.

[AfghanVeteran2010]

Hello all,

Today I broke my third Nason SM-2B-15F oil pressure switch. All the switches end up leaking where the plastic mates up with the brass end. Has anyone else had their switches die on the regular?

 

[Chainbreaker]

Have you been able to take apart any of the failed switches? I'm wondering how the plastic portion is retained in place? Is it screwed into the brass portion or is it a slip fit relying on the sealant to mechanically secure it or is the sealant only there to seal threads? If it were threaded in place to the brass portion and possible to take it apart w/o breaking, I would try another sealant, perhaps JB Weld it in place.

Looking at the MFG's website the SM series switches are rated for: Maximum Operating Pressure 250 PSI (17 Bar) Proof Pressure 750 PSI (51 Bar)

Perhaps there was a bad lot of switches produced...

 

[AfghanVeteran2010]

You hit it right on the head, its retained by screwing in to the base. Ill try some different thread sealant. Thank you Chainbreaker.

 

[Chainbreaker]

That's what the SS brain trust of active members is for. I don't have an 831 (would like to though) but sometimes it helps to look at the problem from another angle. Once you figure out what sealant works best you will have yourself a few repaired spares on hand!

 

[Guyfang]

That's strange. Never, ever, saw one of these switches leak. Only saw them fail to open and close. So many different pieces of equipment used these type switchs, we never even looked at them. Just changed them. I had no idea they screwed together. Good call Chainbreaker!

 

[Farmitall]

Is it possible to fit a thin round or flat O ring in the bottom of that without obstructing the action of the switch?

 

[Demoh]

That's strange. Never, ever, saw one of these switches leak. Only saw them fail to open and close. So many different pieces of equipment used these type switchs, we never even looked at them. Just changed them. I had no idea they screwed together. Good call Chainbreaker!

I have one that failed and the failure mode was leaking out of that little allen set screw. This was a set that had some hours on it. Thought I put a bad one in to replace that one but for a reason much too long to post here.

And great news about them being screwed together indeed. I may do an actual failure analysis on it and see if my suspicions are confirmed. (broken diaphragm)