Blog posts tagged with 'capillary tubing'

On high vibration industrial applications, reading a pressure gauge can often be frustrating or in some cases down right impossible without the proper configuration on the gauge.  Very often, the end user may experience:

• The indicating needle shaking back forth making it difficult to get an actual reading
• The indicating falling off its access from the vibration
• Damage or short longevity of the gauge due to constant wear and tear of the pressure gauge internals

There are a few options that can be used to help legibility of the pressure gauge:

1. Liquid Filling – Liquid filling the gauge with either a glycerin or silicone is easily the most popular solution and least expensive.  The viscosity of glycerin or silicone makes it a thicker fluid than something water.  With the case filled with glycerin, the needle has a harder time from shaking back forth from the vibration.  This in turn steadies the needle and allows for accurate reading.  In addition to help steady the needle, the glycerin also acts as a lubricant for the internals of the pressure gauge allowing for a longer life out in the field.
2. Dampening Movement – Getting a pressure gauge with a dampening movement is the next best option especially for those who do not like liquid filling and prefer a dry gauge.  A silicone dampener is put on the internals of the pressure gauge near the axis of the pointer.  This steadies the pointer and allows for the same outcome as if the gauge was liquid filled.  Typically a dampening movement needs to be special requested though
3. Capillary Tubing with Diaphragm Seal – As an option for extreme vibrating applications where liquid filling and/or dampening movements aren’t enough, the pressure gauge is often mounted to a capillary tube and diaphragm seal filled system.  The diaphragm seal is mounted at the process connection.  Capillary tubing (often 5 feet in length) is connected to the diaphragm seal and on the other end of the tubing is the pressure gauge.  The pressure gauge is then typically mounted to a wall or panel away from the vibration and a proper reading can be seen.  The diaphragm seal, capillary, and gauge assembly is filled with a fluid (often silicone), to allow for an accurate reading.

For a complete list of our liquid filled gauge options, take a look at our mechanical gauges product page.

For differential pressure applications with caustic or thick medias, mounting a differential pressure gauge directly to the process can be detrimental to the integrity of the gauge.  The wetted material of the gauge may corrode away or the differential gauge could potentially become clogged.

A solution to this problem would be to isolate the wetted parts of a differential gauge by mounting diaphragm seals made of a compatible metal or plastic to the inlet and outlet sides of the differential gauge.  However, unlike a standard pressure gauge with one port, you cannot mount a diaphragm seal directly to the differential gauge because the ports of the gauge are typically too close together to accommodate the size of the diaphragm seal.

A solution to this is to install capillary tubing in between the gauge and the diaphragm seal.  This allows for flexibility during installation, safety from high temperatures or vibration, and room for the diaphragm seals to fit on the gauge.  The entire assembly is a filled system just like a standard gauge mounted on a diaphragm seal.  The air is evacuated from the assembly and replaced with a fluid (usually silicone or glycerin).
For more information on differential gauges and/or mounting instruments to diaphragm seals, contact us.