Gas Safe ACS - Accredited Certification Scheme Tightness Testing and Purging Questions and Answers

Question 1

An engineer is performing a tightness test on an existing domestic Natural Gas installation with a U6/G4 meter and 22mm pipework.
If there is no smell of gas, what is the maximum permissible pressure drop over the two-minute test period according to IGEM/UP/1B?

Accepted Answer

4 mbar.

Answer

0 mbar, as no pressure drop is ever acceptable.

Answer

2 mbar, provided all appliances are disconnected first.

Answer

8 mbar, but only if the meter is an E6 type.

Question 2

What is the primary purpose of purging a new gas installation pipework before commissioning any appliances?

Accepted Answer

To displace air with fuel gas, ensuring a safe, non-explosive mixture is present at the appliance burners.

Answer

To clean the pipework of any water or debris left over from the installation process.

Answer

To conduct a high-pressure strength test on all the pipework joints and fittings.

Answer

To verify the correct operation of the gas meter's measurement index.

Question 3

Which of the following describes the correct sequence of tests when recommissioning a domestic gas installation at the meter, according to IGEM/UP/1B?

Accepted Answer

Let-by test, Tightness test, Purge.

Answer

Tightness test, Purge, Let-by test.

Answer

Purge, Let-by test, Tightness test.

Answer

Strength test, Let-by test, Tightness test.

Question 4

An engineer performs a tightness test on an existing installation and records a pressure drop of 7 mbar over 2 minutes, which is outside the permissible limit. The leak cannot be immediately located or repaired. What is the correct immediate action required under the Gas Industry Unsafe Situations Procedure (GIUSP)?

Accepted Answer

Turn off the gas supply at the Emergency Control Valve, attach an 'Immediately Dangerous' warning notice, and inform the responsible person that it must not be used.

Answer

Advise the customer to call the National Gas Emergency Service and then leave the property.

Answer

Leave the gas supply on but issue an 'At Risk' warning notice to the homeowner.

Answer

Re-test the installation at a higher pressure to make the leak more obvious.

Question 5

According to IGEM/UP/1B, when must the gas from a direct purge be ignited at an open burner rather than being vented to the atmosphere?

Accepted Answer

When the installation volume (IV) is 0.02m³ or greater.

Answer

Only when purging commercial or industrial installations.

Answer

Whenever the pipework diameter exceeds 22mm.

Answer

In all circumstances to ensure complete removal of air.

Question 6

During a tightness test on a domestic Natural Gas installation, what are the specified test pressure and duration for the main tightness test phase, following the initial 1-minute stabilisation?

Accepted Answer

20 mbar for a duration of 2 minutes.

Answer

10 mbar for a duration of 5 minutes.

Answer

50 mbar for a duration of 1 minute.

Answer

20 mbar for a duration of 1 minute.

An engineer is performing a tightness test on an existing domestic Natural Gas installation with a U6/G4 meter and 22mm pipework.If there is no smell of gas, what is the maximum permissible pressure drop over the two-minute test period according to IGEM/UP/1B?

An engineer is performing a tightness test on an existing domestic Natural Gas installation with a U6/G4 meter and 22mm pipework.
If there is no smell of gas, what is the maximum permissible pressure drop over the two-minute test period according to IGEM/UP/1B?