Tightness Testing Flashcards
Basic requirements to test gas ECV and pipework & purging
When performing a Let-by test what pressure should it be set at and for how long do you time it?
Let-by is between 7-10mbars and you time it for 1 minute
What is the purpose of a let-by test?
To test the ECV isn’t leaking.
What does it mean if the Let-by test fails?
Means gas is leaking through the ECV
i.e. a rise in pressure during let-by
What is stabilisation pressure set at and for how long do you stabilise?
Stabilisation is set at 20-21mbars for 1 minute
What does the final stage of a tightness test comprise of once let-by and stabilisation has been done and what are you testing?
It comprises of a ‘Final Test’ at 20-21mbar for 2 minutes
Testing tightness of the installtion
i.e. no leaks in pipework or appliances
Can new pipework have a permisable drop in pressure?
For new pipework, no permissable drop in pressure is allowed.
What is normal operating pressure for a domestic property?
21mbar
What pipework diameter can a domestic gas engineer work up to?
35mm
What meters can a domestic gas engineer work on?
Up to maximum U16 or G10 which are the largest meters we can work on and anything below these meter types
so…
U6,G4, E6
What is the maximum pressure (in Bar) a domestic gas engineer is allowed to work on?
Up to 2bar
or
2bar is 2,000mbar
What is the maximum installation volume a gas engineer can work on?
An Installation volume not exceeding 0.035cm2
When should a tightness test be performed?
- New Installations
- Alterations to, or use of existing installations
- New extensions to existing pipework
- Prior to any work on existing installations
- Where there is a known or suspected gas escape
- Where there is a complete loss of pressure upstream of the ECV
- Routine testing of existing installations.
- Immediately before purging
The human eye cannot detect perceptible movement less than what on a u-gauge and what on an electronic gauge?
- 25mbar on a u-gauge
- 2mbar on an electronic gauge
The size of a permissible drop depends on what?
Size of meter and pipework installation volume
What is an AECV and what is an MIV?
AECV = Additional Emergency Control Valve
MIV = Meter Inlet Valve
Let-by test fails if the pressure what?
Rises
Why do you need to do a stabilisation test?
A stabilisation test is done because the gas pressure in a pipe needs time to stabilise due to temperture fluxuations.
When are permissable pressure drops allowed?
Pressure drops are allowed on…
- Existing installations as long as they are within the allowed permisible pressures and there is no smell of gas.
If the final stage of a tightness test fails and the pressure drops what does this indicate?
Indicates there is a leak in the installation or appliances.
When doing a tightness test and there is a very small pressure loss on an existing installation what should you do?
Refer to the permissible pressure loss chart
If it is an existing installation,
and the pressure loss is within
‘permissible pressure loss chart parameters’
and there is no smell of gas
then this would be a pass.
When doing a tightness test and there is a very small pressure loss on a new installation what should you do?
If a new installation then no pressure drop is allowed
Firstly you would need to establish if it is the pipework or an appliance that is leaking?
- Turn off appliances at appliance isolation valve.
- Test for tightness again, if there is still a leak it means the pipework is leaking.
- Find the leak and repair.
What are the permissable pressure drops for existing installations for pipework less than or eq. to 28mm?
Ultrasonic Meter
6m3/h or less (E6 meter) or no meter = 8mbar
Diaphragm Meter:
6m3/h or less (U6 or G4 meter) = 4mbar
Diaphragm Meter:
More than 6m3/h but up to & including 16m3/h (U16/G10 meter) = 1mbar
What are the permissable pressure drops for existing installations for pipe diameter more than 28mm or less than 35mm?
Ultrasonic Meter
6m3/h or less (E6 meter) or no meter = 4mbar
Diaphragm Meter:
6m3/h or less (U6 or G4 meter) = 2.5mbar
Diaphragm Meter:
More than 6m3/h but up to & including 16m3/h (U16/G10 meter) = 1mbar
If an installation being tested does not have a meter
i.e. a flat with a remote meter, then what size pipe on the permissible pressure loss chart should this be based on?
It should always be based on the 28mm or less permissible pressure loss chart.
Basically you can have a higher pressure drop for a flat with no meter (means you would be testing the main meter that supplys that flat) there will always be a larger pressure drop from a shared meter hence a higher tolerence.
If Let-by fails what action should you take?
- Isolate ECV
- Fit Earth Bonding Leads
- Disconect ECV anaconder
- Spray LDF into ECV valve
- If ECV is leaking reconnect anaconder
- Call the Gas Supplier
What are the 8 visual checks that need to be done on a meter before doing a tightness test?
- Check ECV falls to correct position and doesnt spin round.
- Check anaconda is not damaged, twisted, corroided.
- Check there is an on/off label on the anaconda.
- Check Regulator is not damaged/ tampered with.
- Check meter is secure.
- Check earth bonding is 600mm from upsteam pipe to first tee.
- Check label present on front of meter
- Check other there are no other isolation valves.
How do you test if pipework or appliances are leaking, and if the pipework is leaking, what would you do?
Test by turning off the appliances at the isolation points, then doing a tightness test, this will establish if there is a leak in the pipework or the appliances.
If the pipework is leaking then you have to find the leak and repair it
Pressure loss in pipework is not allowed
What pressure is supplied to the gas meter?
75mbar
Gas being supplied directly to the meter is at 75mbar what device on the meter reduces the pressure down and to what pressure is it reduced to?
The regulator reduces the proessure to 21mbar
Before performing a tightness test what should you discuss with the customer?
Advise customer
- What you are doing
- Ask customer if any issues
- There will be a smell of gas
- No smoking
- All appliances will be turned off
If doing a tightness test and the cooker installed in the property is a standalone cooker with a lid what must you do before performing the tightness test and why?
You must shut the lid because the lid has an SSOV valve fitted if the lid is left open the gas is still supplied to the appliance
