ACS Pipework & Meters 2 — Questions and Answers
Question 1: What is the correct procedure for locating a gas leak using a leak detection fluid?
- Apply the fluid to all joints and look for gas bubbles, then turn on the gas fully for a pressure test
- Pressurise the installation and apply the fluid to each joint and connection, observing for bubble formation that indicates a leak (Correct answer)
- Turn off all appliances, then apply fluid while gas is flowing to check each joint
- Apply the fluid externally to the gas meter only
Correct answer: Pressurise the installation and apply the fluid to each joint and connection, observing for bubble formation that indicates a leak
Leak detection fluid (or electronic detector) is applied to pressurised joints while gas is flowing; bubbles indicate a leak at that point — a systematic approach from meter to appliance is used.
Question 2: What is a 'gas pressure governor' and where is it typically located?
- A device that increases gas pressure for high-demand appliances
- A device that reduces and regulates the gas pressure from the distribution mains to the correct operating pressure for domestic appliances, typically located in or adjacent to the meter box (Correct answer)
- A valve that stops gas flowing if the appliance overheats
- A device installed on the boiler to control the output temperature
Correct answer: A device that reduces and regulates the gas pressure from the distribution mains to the correct operating pressure for domestic appliances, typically located in or adjacent to the meter box
The gas pressure governor (regulator) reduces the relatively high distribution network pressure to approximately 21 mbar for domestic use, maintaining a consistent supply pressure regardless of network fluctuations.
Question 3: What is the permitted working pressure for a domestic low-pressure gas installation in Great Britain?
- 7 mbar
- 21 mbar (Correct answer)
- 50 mbar
- 100 mbar
Correct answer: 21 mbar
Domestic gas in Great Britain is supplied at a nominal working pressure of 21 mbar; appliances are designed to operate at this pressure, and significant deviations indicate a fault in the supply.
Question 4: What does a U-gauge (U-tube manometer) measure in gas engineering?
- The flow rate of gas through the pipework
- Gas pressure in millibars by comparing the height difference of water columns in a U-shaped tube (Correct answer)
- The carbon monoxide concentration in the flue gases
- The temperature of the gas supply
Correct answer: Gas pressure in millibars by comparing the height difference of water columns in a U-shaped tube
A U-gauge uses the hydrostatic pressure of a water column to measure low gas pressures in millibars — a simple and reliable instrument for checking standing and working pressure.
Question 5: What precaution must be taken before soldering copper gas pipework joints inside an occupied building?
- No special precautions are required for copper joints
- Isolate and purge the gas from the pipe section to be soldered, ensure adequate ventilation, use a fire blanket behind the joint, and have a fire extinguisher present (Correct answer)
- Notify the gas transporter 24 hours in advance
- Only solder joints after 6 PM when demand is low
Correct answer: Isolate and purge the gas from the pipe section to be soldered, ensure adequate ventilation, use a fire blanket behind the joint, and have a fire extinguisher present
Soldering (hot work) in a building requires gas isolation and purging to prevent ignition of residual gas, fire protection, and adequate ventilation — soldering on a live gas pipe is extremely dangerous.
Question 6: What does the term 'dead leg' mean in gas pipework?
- A pipe that has been correctly terminated with an end cap
- A section of gas pipework that terminates in an unused capped-off fitting, with no appliance connected, which retains dead gas in the line (Correct answer)
- A damaged pipe that must be replaced
- A pipe that runs vertically downward from the meter
Correct answer: A section of gas pipework that terminates in an unused capped-off fitting, with no appliance connected, which retains dead gas in the line
A dead leg is a capped pipe run left in the installation from a previous appliance — it retains gas in the unused section and represents an unnecessary length of pressurised pipe that should ideally be removed.
ACS Pipework & Meters 2
What is the correct procedure for locating a gas leak using a leak detection fluid?