Module 6 Tightness Testing and Direct Purging

Question 1

When would you do a tightness test? (exclude appliances from this answer)
5 situations

Answer 1

1) Pipe work – new / modified
2) Gas leaks / pressure loss
3) Routine testing
4) Before purging
5) Closure of a valve e.g. ECV

Question 2

When would you do a tightness test?

(only answers related to appliances)

Answer 2

1) After connecting
2) Connected but isolated
3) Connected, not isolated, turned off

Question 3

When do you purge a system?
4 situations

Answer 3

1) Pipe work – new / modified
2) Loss of pressure
3) Suspect air in system
4) When installation is to be taken out of service

Question 4

For a U-gauge what is the

1) smallest unit that can be measured
2) perceptible difference

Answer 4

1) 0.5mb
2) 0.25mb

Question 5

Can you use washing up liquid as LDF?

Answer 5

No, it is corrosive

Question 6

What are the maximum gas rates for the following meters?

i) E6
ii) U6/G4
iii) U16/E10

Answer 6

i) 6m³/h
ii) 6m³/h
iii) 6m³ – 16m³/h

Question 7

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

Answer 7

i) 8 mbar
ii) 4 mbar
iii) 1 mbar

Question 8

What can happen it you knock or tilt a token or Quantum meter?

Answer 8

Locks out to prevent fraud. ESP will have to come and reset it

Question 9

What does a let by test measure?

Answer 9

Gas passing the isolation valve – U-gauge reading will rise

Question 10

Describe the three stage of tightness testing (include mbar and times)

Answer 10

1) Let-by test (10mbar / 1 minute)
2) Temperature stabilisation (20mbar / 2 minutes)
3) Tightness test (20mbar / 2 minutes)

Question 11

Let by test

Test pressure is x - y mbar

Answer 11

7 - 10 mbar

Question 12

Stabilisation and Tightness test

Test pressure is x - y mbar

Answer 12

20 - 21 mbar

Question 13

If the installation fails the let-by test what steps must you take?

Answer 13

1) Close ECV, remove anaconda and test valve with LDF
2) If ECV fails LDF test you need to phone the ESP

Question 14

What is the purge volume of installations where the pipe work is <=28mm + a G4 meter

Answer 14

0.01m³

Question 15

If you are purging to air what four things should you do?

Answer 15

1) Extinguish all sources of ignition
2) Don’t turn electrical switches on or off
3) Open doors and windows
4) Inform customer

Question 16

If the purge volume is >0.02m³ should you purge to air for flame?

Answer 16

Flame

Question 17

Once you have purged the system what should you do?

Answer 17

1) If you have loosened a fitting to purge the system retighten and ensure it does not leak
2) Make sure all appliances work.

Question 18

Following a gas escape what is an allowable pressure drop when doing a tightness test?

Answer 18

No perceptible movement

Question 19

Name five situations when there should be no perceptible movement when doing a tightness test

Answer 19

1) Gas escape / smell
2) Installation isolated by ESP
3) New installation
4) All appliances isolated
5) Let by test

Question 20

Above which pressure will a regulator lock up?

Answer 20

23 mbar

Question 21

Tightness test – reading is within the permissible drop however there is a slight smell of gas.

Passed of failed test?

Answer 21

Failed

Question 22

Does the picture show a tightness test for a new or existing installation?

Answer 22

Existing installation

Why?
Control valves on
Appliances off

Question 23

Does the picture show a tightness test for a new or existing installation?

Answer 23

New Installation

Why?

All taps off or appliances disconnected

Test repeated with taps open , cooker lids up

Question 24

What is the picture of?

Answer 24

Medium pressure valve

Question 25

Name 4 components on the medium pressure valve

Answer 25

Question 26

The picture is of a medium pressure installation – what is the yellow valve called?

Answer 26

Test Valve

Question 27

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

Answer 27

b or c since the installation is commercial or industrial

Question 28

The formula for calculating installation volumes is Mv + Pv + Fv

What do the symbols Mv, Pv and Tv mean

Answer 28

Mv – Meter Volume
Pv – pipework volume
Fv – Fittings volume

Question 29

What is the gas volume for a G4 type meter?

a) 0.0024m³
b) 0.008m³
c) 0.025m³

Answer 29

b) 0.008m³

Question 30

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

Answer 30

Question 31

When calculating the internal volume of an installation and the fittings volume is not know what do you do?

Answer 31

Add 10% of the Pv

Question 32

Reason for purging?

Answer 32

Ensure that an installation is left in a safe condition and ready for use

Question 33

The formulae for calculating purge volume is Mpv+Ppv+Fpv

Explain each part

Answer 33

Mpv – meter purge volume
Ppv – pipework purge volume, found by Pv x 1.5
Fpv - fittings purge volume = Ppv x 0.1

Question 34

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

Answer 34

= 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

Question 35

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?

Answer 35

Temporarily install a burner