1. Size the range around the working pressure
A common rule of thumb is to pick a range where normal operating pressure sits near the middle of the scale — roughly between a quarter and three-quarters of full scale. Under steady pressure the working point should not exceed about 75% of full scale; under pulsating pressure keep it nearer 65%. A gauge that spends its life at the top of the dial work-hardens the Bourdon tube and drifts early; one that reads at the bottom of the dial gives poor resolution.
2. Match the accuracy class to the job
| Use | Typical accuracy |
|---|---|
| General plant indication and utilities | ±1.6% to ±2.5% of span |
| Process control and quality-relevant readings | ±1.0% of span |
| Test and reference gauges | ±0.25% to ±0.5% of span |
Buying more accuracy than the process tolerance needs adds cost without benefit — and a high-accuracy gauge on a vibrating line will not hold that accuracy anyway.
3. Choose wetted materials for the medium
- Brass / bronze — air, water, non-corrosive oils. The economical default.
- Stainless steel — corrosive media, steam, outdoor and washdown areas, food and pharma environments.
- Monel, Hastelloy and other alloys — chlorides, acids and other aggressive chemistry.
Also check the case and window: a stainless case with a safety glass or polycarbonate window pays for itself outdoors.
4. Use a diaphragm seal when the media is difficult
Slurries, viscous fluids, crystallising media and anything that clogs an impulse line should be isolated with a diaphragm seal. Two points matter: the fill fluid must suit the process temperature and any food or pharma requirement, and the seal must be filled and assembled correctly, since a seal system is calibrated as one assembly with its gauge.
5. Deal with vibration and pulsation
- Glycerine or silicone filling damps pointer flutter and protects the movement.
- Snubbers or restrictor screws smooth pressure spikes from pumps and compressors.
- Remote mounting with a capillary or a panel-mounted gauge keeps the instrument off the vibrating line entirely.
6. Install it so it can be maintained
- Fit an isolation valve so the gauge can be removed without a shutdown.
- Use a siphon (pigtail) on steam so hot vapour never reaches the element.
- Support the gauge, not the tubing — never let a heavy gauge hang on its process connection.
- Leave the dial readable from where the operator stands, at eye level where possible.
- Never over-tighten on the case; tighten on the hex flat of the socket only.
Quick selection checklist
- Working and maximum pressure, plus expected spikes
- Medium, temperature and whether the line is prone to clogging
- Required accuracy against process tolerance
- Dial size and mounting style for readability
- Connection size and thread standard
- Environment: outdoor, corrosive, vibration, washdown
- Whether calibration certification is required at supply