Manometers and test points
Connecting, zeroing and reading U-gauge and digital manometers.
This topic supports
- M03.2Connect and read a manometer to measure standing, working and operating pressures.
Draft: this lesson hasn't yet been technically reviewed.
A is how you see what the gas is doing. A reading is only useful if the gauge is right for the job, set up properly and connected to the right point.
Interactive artefact
Manometers on a test point
U-gauge and digital manometer on a test point: standing versus working pressure as appliances fire.
Will demonstrate
- Connecting a U-gauge and a digital manometer to a test point
- Reading standing pressure with appliances off
- Watching working pressure as appliances fire
Planned. This interactive will appear here when it's built.
Choosing and looking after a gauge
Any gauge must be suitably ranged, suitable for the gas and for the place it's used in, and calibrated as its manufacturer requires.
| Water (U-gauge) | Electronic | |
|---|---|---|
| Must read to | 0.5 mbar | 0.1 mbar |
| Calibration | Not needed, but keep it well maintained | At least every 12 months (or as the manufacturer says), with a certificate |
| Before use | Zero it | Zero it, use it within its temperature range, and let it settle to room temperature first, because electronic gauges can drift as the temperature changes |
A display that shows lots of decimal places isn't necessarily that accurate. Check the gauge and its tubing for leaks immediately before taking a reading. If you're in a place where there may be gas in the air, the gauge may need to be certified for hazardous areas (see 6.5).
Where the test points are
- The meter: use the meter installation's test point where it has one. Where there's no meter test point, BS 6891 requires one no more than 300 mm after the ECV or AECV.
- Each appliance: a test point at the appliance inlet, if the appliance doesn't have a suitable one of its own. It can be built into the isolation valve.
- Inside the appliance: test points on the gas valve for inlet and burner pressure, as the manufacturer's instructions show.
Taking a reading
- Zero the gauge, and connect it with suitable tubing.
- Open the (undo or remove its test screw), and connect the tube.
- Take the reading under the conditions the check calls for (all appliances off for standing pressure, for example, or at high load; see 3.3).
- Remove the gauge, close the test point, turn the gas back on if needed, and test the test point with leak detection fluid.
Sources: IGEM/UP/1B Ed. 4 4.1gauges BS 6891:2015 8.6test points CCN1 Issue 16 §10 PC 1–4, K&U 4measuring OP
Tutor notes
- Have learners connect both a U-gauge and an electronic gauge to the same test point and compare readings.
- Ask why an electronic gauge carried in from a cold van might read wrongly for the first few minutes.
- CCN1 §10 knowledge item 4 covers using an electronic gauge and its calibration.