Care must be taken to ensure a safe working environment when selecting and ordering a pressure gauge or thermometer. The following information can assist with the selection.
Casing Size
To suit the availability of space or reading from a distance. Choose from 50, 63, 80, 100, 120, 150 & 250 mm dia.
Casing Type
Choose from the bottom or back entry to suit the application. Case material: Stainless steel 304.
Mounting Flange
To suit the case size and type for mounting in a panel or against a surface. Choose from the front or rear flange.
For panel mounting ( front flange, rear entry ) choose from 3 hole flange or slim line front ring with u- bracket.
Wetted Parts
These parts must be compatible with the process media. Choose from Cu-alloy ( brass ) or stainless steel 316.
For media that will corrode the wetted parts or obstruct the pressure port, a diaphragm-type chemical seal should be selected.
Fitting Size and Positions
To facilitate correct positioning. Choose from 1/8″, 1/4″, 3/8″, or 1/2″ BSP or NPT at the bottom or rear of the case.
Working Pressure
Although pressure gauges will tolerate full-scale pressure for short periods, in general, the working pressure should not exceed 70% of the full-scale value of the pressure gauge. For thermometers, media pressure should not exceed 2500 kPa without the use of a suitable thermowell.
Media Temperatures
For pressure gauges, media temperature should not exceed 70°C. If so, choose from a syphon tube, cooling element, capillary assembly or diaphragm seal to isolate the gauge from media. For thermometers, select the temperature range double that of the media operating temperature.
Working Conditions
Adverse working conditions such as vibration, pulsation and shock loads, require the use of a dampening device.
Choose from glycerine/ silicone filling, a snubbing device or capillary assembly to remove the instrument from the cause.
Fitting Types
- BSP ( parallel ) thread seals using the seat at the end of the thread. It is advisable to use copper or another suitable sealing washer to ensure a good seal. (see diagram 1)
- BSPT / NPT ( taper ) thread seals using the mating of the thread. PTFE (Teflon) tape or any other suitable jointing material will ensure a good seal. (see diagram 2)
Installation
Always secure the instrument using a suitable wrench on the hexagon/square of the threaded connection.
Twisting the instrument by hand on the case can cause damage to the internals of the instrument. (see diagram 3)
For gauges with flanges to facilitate panel or surface mounting, please support gauge fitting with a suitable size wrench to counter the force of tightening the process fitting, this will prevent damaging the gauge internals.
Diagram 1
Diagram 2
Diagram 3
