I can't get this dang SPG open.

[psiborg1812]

Hey everyone, I'm sure this has been asked before, but i cannot for the life of me unscrew the faceplate from one of my SPG's housings. I've tried a strap wrench, soaking it in hot water, and the largest pair of vise grips i own just slip off. The actual gauge is corroded as heck so I am trying to swap out the bad gauge for a good gauge. Any suggestions on how to budge the sucker?

Thanks!

 

[Peter_C]

Say what? The front of the gauge doesn't come off. If you are talking about the hose connection with the stem inside, you could try soaking it in vinegar.

 

[psiborg1812]

Yes it does. The clear face part of the SPG housing unscrews so that you can remove the gauge from the housing. Most are older than dirt and stuck closed.

 

[fisheater]

Yes it does. The clear face part of the SPG housing unscrews so that you can remove the gauge from the housing. Most are older than dirt and stuck closed.

Photos would help.

When I think "SPG," I'm thinking of something like this:



The clear faceplate isn't designed to be removed.

 

[Fishpie]

Chanellocks and a vice as a last resort (the threaded stem of the gauge will prevent it from slipping in the vice).
A few days of WD or PB anti seize may help.

What gauge is it? Some that look like they unscrew are actually pressed on.

 

[steveharriss]

We need to see a picture. Whilst there are HP gauges with bayonet rings I've yet to see the feature on an SPG which by it's very name is designed to be immersed in a liquid. What would you gain by removing the glass anyway. AFAIK the bourdon tube is sealed to the inlet stem so you're going to pay as much for the works as you would a brand new gauge and there would then be doubts abouts it's 'waterproofness' surely?

http://www.wika.co.uk/upload/Download_TB_PM_Pressure_Gauge_Window_Rings_en_us_17206.pdf

 

[Fishpie]

I've opened pressure gauges for several reasons.
To reattach the dial to the body.....the little screws that hold it come loose quite frequently.
To reattach the needle.
To reposition the needle that has been bumped to the wrong side of the stop pin.
Reposition needle that doesn't read zero. Only do this if you have a puller and it's only a couple of hundred psi off or 20 BAR as it will effect the accuracy at the other end of the scale.
.....Leaks can be washed out and dried but a permanent cure is 50/50 even with relubing the o rings and op plug.
.....It's also possible to re calibrate by fiddling with the quadrant and spring (a bit like putting a new line on a recoil pull start of a small engine....but much smaller and fiddly).


It's usually better just to buy a new gauge in most instances.

 

[steveharriss]

So have I; but on a submersible pressure gauge? Never.



This is one with a bayonet ring with an adjustable pointer

 

[miketsp]

I had one that stuck so I wanted to open it to see why. I also went crazy trying to unscrew the face-plate ring. In the end I gave up and took a hacksaw to the body. Surprise - although the face-plate ring looked like it was on a thread and should have just unscrewed, it was actually welded (or very well glued with a sealant) to the body. I couldn't separate even small segments.

For the record, it was sticking because the pinion gear that turned the pointer had worn teeth but just at one position. If I had been able to open the face-plate it would have been a simple repair. Just bend the quadrant a little to operate on a different part of the pinion. It would have worked like new.

 

[Couv]

As Fishpie said, on some gauges you can unscrew the faceplate, but some you cannot. If the faceplate is clear, i.e. no metal bezel you should be able to see an o-ring under it. If you cannot see an o-ring, then the faceplate is probably pressed on.

Likewise, some gauges with a metal bezel will unscrew, some don't.

BTW the corrosion probably indicates a small leak, so if you're able to recalibrate the gauge, don't forget to replace the seals.

"If at first you don't succeed, use a bigger hammer."

Good luck, please keep us posted.