Hydraulic Pressure Gauge Leaking Glycerin

[CTRLyourself]

Quick (amateur, I know nothing about hydraulic gauges) Question:

I have been shipped 5 hydraulic stainless steel pressure gauges from GDG.
2 of them have leaked a small amount of glycerin that was inside them. There is still more than 50% glycerin inside the gauge.

1. Will the loss of fluid affect the accuracy of the gauges?
2. Why did it leak? it appears to have come out the bottom. There is a small grub screw in the base of the valve where it connects to the pressure line. Should this grub screw have been screwed in or out for transit? And what position should it be in when fitted? It appears to leak glycerin when I screw it out slightly, but it is hard to tell.

Many thanks in advance.

 

[Compositepro]

The purpose of the glycerin is to damp vibration of the needle in a high vibration environment. The gauge accuracy is not affected by it leaking out. The casing should have a vent plug that must be oriented to the top so that the pressure in the case is at ambient pressure. You can add more glycerine there. The "grub screw" is probably a restrictive orifice used as a pressure snubber to prevent pressure pulses from moving the needle very rapidly. The orifice will tend to trap hydraulic fluid in the gauge, which will slowly leak out. It should be screwed all the way in to seat the screw so that flow is only through the orifice. It is unscrewed when cleaning is needed.

Some gauges do not have a vent but have a flexible diaphragm in the case (like the plastic face plate). The case should not be completely filled with glycerine. High pressure gauges are not much affected by a few psi of case pressure.

 

[MikeHalloran]

Conversely, low pressure gages ARE affected by presence of confined glycerin. The rubber sbipping plug should be removed from the case, or pierced, e.g. with a hot needle.


Mike Halloran
Pembroke Pines, FL, USA