Tightness Testing & Purging Flashcards
7 cards from real ACS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Tightness Testing & Purging flashcards as text
What is the purpose of a let-by test on a gas installation?
Answer: To check for leakage past the closed Emergency Control Valve (ECV)
A let-by test checks whether the Emergency Control Valve (ECV) is sealing correctly or allowing gas to pass when in the closed position.
How is a let-by test correctly performed on a domestic gas installation?
Answer: Close the ECV and check for a pressure rise on the downstream side using a manometer
With the ECV closed, a manometer connected downstream will show a pressure rise if gas is passing through (letting by), indicating a faulty valve.
During a let-by test, what does a pressure rise on the downstream side of the closed ECV indicate?
Answer: The ECV is allowing gas to pass through when in the closed position
A pressure rise downstream of the closed ECV indicates the valve is not sealing properly and is allowing gas to pass through, known as letting by.
At what stage of checking a gas installation should the let-by test be performed?
Answer: As the first check, before the tightness test
The let-by test is performed first to confirm the ECV seals correctly, which is the essential foundation for all subsequent tightness testing.
If a let-by test reveals that the Emergency Control Valve (ECV) is faulty, what is the correct action?
Answer: Notify the gas transporter, as the ECV is their responsibility to repair
The ECV is the property of the gas transporter (network operator), so any defect must be reported to them for repair — it is not the installer's responsibility.
Under the Gas Industry Unsafe Situations Procedure (GIUSP), what classification applies to an unlocated gas escape discovered during a tightness test?
Answer: Immediately Dangerous (ID)
An unlocated gas escape is classified as Immediately Dangerous (ID) because the source of the escape cannot be made safe and poses an immediate risk of fire or explosion.
What action must a gas engineer take when an Immediately Dangerous (ID) situation is identified during tightness testing?
Answer: Turn off the gas supply and prevent the consumer from using the installation
For an ID situation, the gas supply must be turned off and the consumer must be prevented from using the installation to eliminate the immediate danger.