Thursday, September 27, 2018

Five Important Criteria in Applying Pressure Gauges

Ashcroft pressure gauge
Process pressure gauge.
(Ashcroft)
Pressure gauges are installed in countless industrial and commercial applications around the world. From hygienic pharmaceutical process lines, to the most unpleasant and hostile areas in chemical, power, and food processing plants.

While there are millions of possible combinations of shapes, sizes, options and materials, pressure gauges all share the five  following application criteria, required for safe use and long product life.
Ashcroft diaphragm seal
Diaphragm seal.
(Ashcroft)


1 - Process Media Properties: Media that is corrosive, sludgy, or that can solidify is a potential problem for pressure gauges. In non-corrosive, non-clogging media applications, a direct connection without intermediate protection can be applied. For process media that could potentially clog or chemically affect the gauge's wetted parts, a diaphragm seal should be used.

2 - Process Media Temperature: Very hot media, such as steam or hot water, can elevate the gauge's internal temperature leading to failure or an unsafe condition. For high temperature applications, the use of a "pigtail siphon" or diaphragm seal is recommended. Siphons act as a heat sink and lower the exposure temperature. Diaphragm seals isolate the gauge from the higher temperatures.

Siphon
Pigtail siphon.
3 - Ambient Operating Temperature and Environment: It is important to know the ambient environmental rating for any process instrument. Elevated ambient temperatures, moisture, vibration, and corrosive atmospheres can all affect accuracy, calibration, and safety. Choose the proper housing and mechanism materials if oxidizing or reducing atmospheres exist, and consider the addition of ancillary devices, such as remote diaphragm seals to physically relocate the gauge away from the hostile area.

Snubber
Snubber
4 - Severe Pressure Fluctuations: In applications where dramatic line pulsations or strong over-pressure conditions are a possibility, the use of pressure restrictors, snubbers, or liquid-filled gauges will extend the service life of the pressure gauge.

5 - Mounting: Pressure gauges are standardly available with bottom (radial) and back connections. NPT (National Pipe Thread Taper) threaded connections are generally the standard. Many other process connections are available though, such as straight threads, metric threads, and specialized fittings. Make sure you know how the gauge is being connected. When mounting, pressure gauges should be almost always be mounted upright.

For more information about pressure gauges, contact Mead O'Brien by visiting https://meadobrien.com or by calling (800) 892-2769.