Selecting a Pressure Gauge    

For complete recommendations see the Ashcroft Pressure Gauge Manual

Range   The maximum operating pressure should not exceed 75% of the full-scale range.  The normal operating range should be in the middle half of the range whenever possible.

Dial Size   Select a dial size that is easily read at the normal reading distance once the gauge is installed.   

Pressure System Material   It is critical that the materials of the gauge’s pressure system are compatible with the fluid.   Typical tube and/or bellows construction includes:  Phosphor Bronze Bourdon Tube with Brass Socket, 316 SS Bourdon Tube with 316 SS Socket or Alloy Steel Socket.   Consult the Ashcroft Corrosion Data Guide for proper material selection*.  For applications where standard gauge materials or fluid characteristics are not compatible with the media, a diaphragm seal may be needed to protect the pressure instrument.

Accuracy   Pressure gauge accuracy is the difference (error) between the true value and the indication expressed on the pressure gauge as a percentage of span.    Gauge accuracy standards as determined by ASME B40.1

ASME B40.1 Typical Use Accuracy
Grade 3A Test Gauges +/-0.25% of span
Grade 2A Process Gauges +/-0.5% of span
Grade 1A Industrial Gauges +/-1.0% of span
Grade A Industrial Gauges +/-2-1-2% of span*
Grade B Commercial Gauges +/-3-2-3% of span*
 

* Accuracy expressed as +/-2-1-2% equals +/- 1% of the middle half of the range with +/-2% over the remaining half of the scale.  +/-3-2-3%  equals +/-2% over the middle half over the range and 3% over the remaining half.

 

Case   A wide variety of case materials and styles are available.  Determine how the gauge is to be installed and mounted.   Cases are available from Stainless Steel, Carbon Steel, Aluminum and Thermoplastics.  Mounting can be direct to the piping, of surface mounted to a wall or flush mounting in a panel.  

Window   Glass lens is standard in many gauge styles, while shatterproof glass or plastic lens are available for options.

Temperature   To assure long life and accuracy, pressure gauges should preferably be used at an ambient temperature between –20 and +150 deg F.  For complete information, review Section 2.0 of the Ashcroft Pressure Gauge Manual

Vibration    Whenever possible gauges should be located to minimize the effects of vibration.  Remote mounting via flexible tubing is a common practice.  Other methods to reduce wear associated with vibration include liquid filling and DuraPlus™ movements.  

*Note:  The corrosion guide is intended to be used as a general guide in the recommendation of materials for corrosive service.  It must be regarded as an indicator only and not as any guarantee for a specific service.