Broken Pressure Guage

[Farenheit251]

I've been running some high temps and apparently a plug on top of the guage has blown out. I could probably get a new plug off an old TM skeleton of a friend or distributor and refill w/ glycerine but I am not sure if there is something else wrong. Doesn't seem like water should be entering the guage and pouring out the top. Would the glycerine and a plug stop it or is the guage toast?

 

[Shawn Forsythe]

The gauge is "toast", as you put it.

The only reason the plug would dislodge, and fluid would exit is if the bourdon tube is burst or leaking.

The Bourdon Tube is a coiled or curved piece of flattened copper tubing inside the gauge. The external pressure is guided into the tube and causes it to flex, resulting in a change in curvature of the tube. These curvature changes are linked to the dial indicator for a number readout. If the tube leaks, there is nothing you can do but replace the gauge.

The viscous glycerine fill dampens the movement of the mechanism to reduce needle vibration for easier reading, and to prolong the life of the movement.

 

[Shawn Forsythe]

Steve,

That is not a relief valve, per se. It is the fill plug for the glycerine fill. However, gauges do have an airspace in the top of the gauge. It is this airspace, on a sealed gauge that can expand or contract with altitude differences between the manufacturer and the end user. This plug also serves as a means to vent this differential.

It is for this reason that the fill plug is popped off the gauge upon installation to equalize outside pressure, with that of the internal airspace inside the gauge. In most cases you can simply replace the plug and be done with it. However, on vacuum gauges and in some cases on pressure gauges, you might want to snip the "tit" on the plug to permit a small venting hole so external barometric changes don't effect the accuracy of the gauge due to a differential between the outside, and the inside of the gauge.

 

[glenboy]

same thing happend to me on the job so i got a higher psi guage and no prob