Chapter 6 Tightness testing and Purging Flashcards
(26 cards)
What is the NPM (no perceptible movement on the gauge during a tightness test?
0.25mbar on a water gauge, 0.2mbar on a digital gauge
What is the let-by test testing?
checks if the emergency control valve (ECV) or meter control valve is allowing gas to pass through even when it’s supposedly closed
As a domestic gas engineer what is the maximum installation volume you can work on?
0.035 meter cubed.
As a domestic gas engineer what is the maximum pressure in the system you can work on?
Anything below 2 bars.
When to test for Tightness test? (There are more than 3 answers)
- Completion of new pipework installations.
- After alteration of existing installations.
- New extensions to pipework.
- Prior to any work on existing pipework.
- Where there’s a known or suspected gas leak.
On a meter which is not zeroed, the 2 different reading shown on the U gauge is 21mbar and 18mbar, what is the correct pressure?
(21-18)/2 = 19.5mbar.
What is Maximum permissible pressure drop on a G4/U6 meter with pipework Diameter of 28mm?
4mbar
(2.5mbar for 35mm pipework)
What is the Maximum permissible pressure drop on a E6 Ultrasonic meter, or No meter with a pipework of 28mm?
8mbar
(4mbar for pipework 35mm)
At what pressure do we do the let-by test, and how long is test for?
7-10mbar for 1 minute.
During the let-by test, the pressure increased to 12mbar within the minute of the testing, what should you check?
The isolation valve, check by disconnecting the outlet union and apply LDF to the valve barrel or ball.
What is the maximum inlet pressure to medium pressure meter installation that our domestic gas engineers are allowed to work on?
2bar (medium pressure is up to 2 bar)
What is the maximum pipework diameter a domestic gas engineer is allowed to work on?
35mm (Anything above will be classified as commercial)
What is the maximum rated capacity through the primary meter a domestic gas engineer is allowed to work on?
16 m3/h (a U16 meter)
What is the maximum installation volume (IV) including any meter and its fittings a domestic gas engineer is allowed to work on?
0.035m3
Anything above this will be classified as commercial work.
What is the testing pressure for a low-pressure tightness test?
20mbar-21mbar
What is the testing pressure for a medium-pressure tightness test?
18mbar-19mbar
What is the equation for adding up total installation volume?
IVt = IVm + IVp + IVf
Installation volume Total = Meter IV + Pipe IV + Fitting IV
The pipe installation volume is 0.004 meter cubed, what is the fitting installation volume?
IVf = IVp * 0.1
IVf = 0.004 * 0.1 = 0.0004 m3
For medium pressure tightness test, how does the tightness test carried out when there is a meter inlet valve just before the meter inlet?
Same procedure as the low-pressure tightness testing process.
What needs to be sprayed with LDF following a tightness test?
ECV, Anaconda, Testing point, pressure regulator, meter connections.
What is the OFF-ON-ON-Spray process after a tightness test on a medium pressure system
Gauge off, ECV on, lever on. Spray.
What is the purge volume for a G4/U6/E6 meter with pipe diameter of 28mm or below.
0.01m3
What is the purge volume for a U6/G4/E6/U16/G10 meter with pipe diameter of 35mm?
1.5 times the IV (Installation volume)
The label on a G4 meter reads: Q = 6m3/h … V 2dm3, what is this V? How does this relate to purge volume?
V is badge volume, which is the internal volume of the gas meter. Purge volume of this meter will be 5 times the badge volume - 5 * 2 dm3 = 10 dm3 = 0.01m3
