Foxboro SRD991 Positioners Overheating?

[jlr899]

Replacing old Bailey control valve positioners with Foxboro-Eckardt SRD991 intelligent positioners on our waste heat boilers. Worked fantastic until the warmer ambient temps reach into the 90'S at which time they started to overheat and fail until they cool down. Foxboro stated temp rating at 80c (175f). Has anybody else out there had the same problem, and how did you correct it. As of right now we've tubed plant air into the housing to keep them operational, don't want to continue this due to the least bit of moisture will fry the electronics.
Thanks

 

[waross]

Throw out the electronics and go with a pneumatic positioner.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Fisher's (Emerson) Fieldvue series of positioners can operate at 125°C if you can use the remote feedback module, or up to 85°C for direct mounting. Is that extra 5°C enough?

How much heat are you receiving from ambient air, and how much is conducted via mountings or from direct radiation from the boiler plant? Can you provide local lagging to reduced radiant heat? Thermally isolating linkage or mounting?

You might want to post a link to this thread in forum698 - don't start a complete new thread on the same subject or a moderator will probably delete it in order to keep the place tidy and well-ordered.

 

[itsmoked]

Mount cardboard stand-ins in different positions, (especially under, the pipe (if horizontal). After a sufficient time period gun them with a temp gun, up close, and see if a different mounting position would provide a large operating temp improvement. Often drafts or convection can product large differences. Like 20F or more.

Otherwise, heat shields, insulating gaskets, like Scotty suggests or use a remote unit like Bill suggests.

Keith Cress
kcress -

http://www.flaminsystems.com