Module 6 Tightness Testing and Direct Purging Flashcards
When would you do a tightness test? (exclude appliances from this answer)
5 situations
1) Pipe work – new / modified
2) Gas leaks / pressure loss
3) Routine testing
4) Before purging
5) Closure of a valve e.g. ECV
When would you do a tightness test?
(only answers related to appliances)
1) After connecting
2) Connected but isolated
3) Connected, not isolated, turned off
When do you purge a system?
4 situations
1) Pipe work – new / modified
2) Loss of pressure
3) Suspect air in system
4) When installation is to be taken out of service
For a U-gauge what is the
1) smallest unit that can be measured
2) perceptible difference
1) 0.5mb
2) 0.25mb
Can you use washing up liquid as LDF?
No, it is corrosive
What are the maximum gas rates for the following meters?
i) E6
ii) U6/G4
iii) U16/E10
i) 6m3/h
ii) 6m3/h
iii) 6m3 – 16m3/h
For pipe diameters up to 28mm what is the pass criteria (in mbar) for the following meters:
i) E6
ii) U6/G4
iii) U16/E10
i) 8 mbar
ii) 4 mbar
iii) 1 mbar
What can happen it you knock or tilt a token or Quantum meter?
Locks out to prevent fraud. ESP will have to come and reset it
What does a let by test measure?
Gas passing the isolation valve – U-gauge reading will rise
Describe the three stage of tightness testing (include mbar and times)
1) Let-by test (10mbar / 1 minute)
2) Temperature stabilisation (20mbar / 2 minutes)
3) Tightness test (20mbar / 2 minutes)
Let by test
Test pressure is x - y mbar
7 - 10 mbar
Stabilisation and Tightness test
Test pressure is x - y mbar
20 - 21 mbar
If the installation fails the let-by test what steps must you take?
1) Close ECV, remove anaconda and test valve with LDF
2) If ECV fails LDF test you need to phone the ESP
What is the purge volume of installations where the pipe work is <=28mm + a G4 meter
0.01m3
If you are purging to air what four things should you do?
1) Extinguish all sources of ignition
2) Don’t turn electrical switches on or off
3) Open doors and windows
4) Inform customer
If the purge volume is >0.02m3 should you purge to air for flame?
Flame
Once you have purged the system what should you do?
1) If you have loosened a fitting to purge the system retighten and ensure it does not leak
2) Make sure all appliances work.
Following a gas escape what is an allowable pressure drop when doing a tightness test?
No perceptible movement
Name five situations when there should be no perceptible movement when doing a tightness test
1) Gas escape / smell
2) Installation isolated by ESP
3) New installation
4) All appliances isolated
5) Let by test
Above which pressure will a regulator lock up?
23 mbar
Tightness test – reading is within the permissible drop however there is a slight smell of gas.
Passed of failed test?
Failed
Does the picture show a tightness test for a new or existing installation?
Existing installation
Why?
Control valves on
Appliances off
Does the picture show a tightness test for a new or existing installation?
New Installation
Why?
All taps off or appliances disconnected
Test repeated with taps open , cooker lids up
What is the picture of?
Medium pressure valve
Name 4 components on the medium pressure valve
The picture is of a medium pressure installation – what is the yellow valve called?
Test Valve
If an installation for a house operates at a pressure greater than 21mbar, max rating >16m3/hr or the installation volume >0.035m3 should the gas testing conform to:
a) IGE/UP/1B
b) IGE/UP/1
c) IGE/UP1A
d) All of the above
e) Either b or c
b or c since the installation is commercial or industrial
The formula for calculating installation volumes is Mv + Pv + Fv
What do the symbols Mv, Pv and Tv mean
Mv – Meter Volume
Pv – pipework volume
Fv – Fittings volume
What is the gas volume for a G4 type meter?
a) 0.0024m3
b) 0.008m3
c) 0.025m3
b) 0.008m3
Using the attached figures to help what is the internal volume of the following installation:
U6 meter
11m x 35mm, 4m x 22m, 7.5m x 15mm
Fittings not know so add 10% of Pv
When calculating the internal volume of an installation and the fittings volume is not know what do you do?
Add 10% of the Pv
Reason for purging?
Ensure that an installation is left in a safe condition and ready for use
The formulae for calculating purge volume is Mpv+Ppv+Fpv
Explain each part
Mpv – meter purge volume
Ppv – pipework purge volume, found by Pv x 1.5
Fpv - fittings purge volume = Ppv x 0.1
Using the attached figures calculate the purge volume for the following installation:
U6 meter, 9m of 35mm copper, 6m of 22mm and 6m of 15mm copper
= 0.01 +[(9 X 0.00084 + 6 X 0.00032 + 6 X 0.00014) X (1.5)] + (Ppv X 0.1)m3
= 0.02548 + (Ppv X 0.1)
= 0.02548 + 0.001548
= 0.027028 m3
If the purge volume is >0.02m3 the gas should be purge to a flame. If a suitable appliance does not exist what should you do?
Temporarily install a burner
