ACS Tightness Testing & Purging 2 — Questions and Answers
Question 1: What is the primary purpose of purging a gas installation?
- To increase the operating pressure in the pipework
- To remove air and replace it with fuel gas (Correct answer)
- To clean debris from the internal pipework surfaces
- To test the pressure integrity of the installation
Correct answer: To remove air and replace it with fuel gas
Purging displaces air (or inert gas) from the pipework and replaces it with fuel gas to allow appliances to operate safely and reliably.
Question 2: Which UK Gas Industry standard primarily covers tightness testing and purging of domestic natural gas installations?
- IGE/UP/2
- IGEM/UP/1B (Correct answer)
- BS 6891
- COSHH Regulations 2002
Correct answer: IGEM/UP/1B
IGEM/UP/1B is the Gas Industry standard specifically covering tightness testing and purging of domestic-sized natural gas installations.
Question 3: When purging gas into a room, what is the essential safety requirement?
- The room must be completely sealed to contain the gas
- The room must be well ventilated with doors and windows open (Correct answer)
- All ignition sources must be active to burn off the gas immediately
- Purging into a room is never permitted under any circumstances
Correct answer: The room must be well ventilated with doors and windows open
The room must be well ventilated so that gas released during purging is sufficiently diluted to prevent the formation of an ignitable mixture.
Question 4: What must be confirmed before attempting to light an appliance after purging?
- That the gas meter has recorded consumption during the purging process
- That the smell of gas has completely disappeared from the room
- That gas is flowing freely and consistently at the appliance burner (Correct answer)
- That at least 30 minutes have passed since purging was completed
Correct answer: That gas is flowing freely and consistently at the appliance burner
Gas must be flowing freely at the burner before ignition is attempted to ensure successful and safe lighting of the appliance.
Question 5: If a gas supply has been interrupted and then restored, in what order should appliances be purged and re-lit?
- Largest appliances first, then progressively smaller ones
- All appliances simultaneously to minimise purging time
- One appliance at a time, starting with the one nearest the meter (Correct answer)
- Any order, as the gas pressure equalises automatically throughout the system
Correct answer: One appliance at a time, starting with the one nearest the meter
Appliances should be purged and re-lit one at a time, starting with the appliance nearest the meter, to ensure a controlled and safe purging process.
Question 6: What action should be taken if a new installation fails a tightness test before purging?
- Proceed with purging and retest the installation afterwards
- Locate and repair the fault before any further testing or purging (Correct answer)
- Report the failure to the gas transporter and leave the site
- Increase the test pressure and repeat the tightness test immediately
Correct answer: Locate and repair the fault before any further testing or purging
Any fault must be located and repaired before proceeding, as introducing gas into a leaking system would create an immediately dangerous situation.
Question 7: When purging through an appliance burner rather than a dedicated purge point, what must the gas engineer ensure first?
- The appliance isolation valve is closed and the burner tap is open
- The appliance burner tap is open and the appliance is ready for ignition (Correct answer)
- All other appliances in the property are also being purged at the same time
- The appliance has been fully disconnected from the gas supply during purging
Correct answer: The appliance burner tap is open and the appliance is ready for ignition
The burner tap must be open so gas can flow through and displace the air within the appliance, ready for immediate ignition once purging is complete.
ACS Tightness Testing & Purging 2
What is the primary purpose of purging a gas installation?