Hydraulic plumbing question

[OneQuartLow]

Acquired a discard aerospace hydraulic test mule. (My 1/2T pickup was very unhappy.) One part is a temp gauge and probe.

The center piece is the high-pressure housing that threads into the plumbing. The right is the probe, and the left is the probe retainer.

The probe has a small amount of play - maybe .010 - inside the housing. Do I need to fill the gap with oil or similar to better conduct temp to the probe? (vs. error temp from the wire & fitting) What's the normal method for a doubly-walled piece like this?

I'll be using it for temps around boiling (homebrewing). High pressure isn't necessary but accuracy and response time are important.

Thanks,
David

 

[Rick in PA]

Just some thoughts here (I'm no temperature probe expert). Seems like some sort of fluid to couple the probe with the housing would be a good idea to minimize response time. Probably a good idea to use something non-toxic if it's going to be used around food. Possibly cooking oil? Maybe add an o-ring to keep the oil in the housing. Good luck with your new find.

 

[OneQuartLow]

Thanks Rick.

Now I'm thinking the design is as it is to better isolate the bimetal portion from the threaded end and external temps. (Note the slender probe waist.) If I add oil it'll conduct external sources more efficiently (bad). It'd also add mass & could slow response as much as it helps. Suppose I can try it with & without oil & see what happens.

Of course, if anyone has experience with this stuff please speak up.

Edit: Criminy, sometimes I'm slow. I have loads of thermal grease from systems work that'll stay in place just fine at 200F without walking to the threaded area.

[ April 13, 2003, 01:53 AM: Message edited by: OneQuartLow ]

 

[labman]

Where you are adapting something to a use far from its original, you need to look at the new requirements. The original housing likely was to enable replacing the probe without shutting the system down. It may have also been to keep the hydrolic pressure from crushing a standard probe. It looks like the probe and housing are both copper. If copper is no problem in your system, I would look at how to seal the probe in without the housing. That would give the fastest response. Perhaps drill a close fitting hole in a pipe plug, and seal the probe to it with epoxy or something your system won't attack.

Depending on the trouble you want to go to, you may be able to buy a probe that is threaded to screw in directly.

 

[Jay]

I don't know what the project is but I doubt you'd get very fast response times with this unit since it looks like it has a fair amount of mass. You are right about your original assumption that the air gap between the housing and probe will slow response time.

If I were measuring the temp of a fluid (an electrically non-conductive fluid) I'd spend 50 cents on a thermistor and make my own housing and just hang the thermistor in the fluid stream. That would give you infinitely better response time.

[ April 16, 2003, 12:41 PM: Message edited by: Jay ]