Purging Flashcards
To purge gas supply after certain actions to eliminate air from the system
Why do we need to purge?
Why - - >
We need to remove all the air in the pipework
If we have a mixture of 5%-15% gas in air remains in the pipes this could cause an explosion
New, test, exist, loss, air
When do we need to purge?
We need to purge…
- New installations and New Extensions
- After a tightness test
- Any alterations to existing pipework
- Complete loss of pressure upstream of ECV
- Whereever there is a possibility of air in the pipework
Clue: Pipework size, meter size, Metric/imperial meter
What is the purge volume for the varying types of pipework, and meter sizes, for metric and imperial meters?
- Its based on the meter and pipework size.
- Pipework less than or equal to 28mm with a U6, G4 or E6 meter
purge volume is 0.01m3 metric meter or 0.035ft3 if an imperial
meter which is 3.5 segments on an imperial meter. - Pipework more than 28mm but less than or equal to 35mm is 1.5 x the Installation Volume,
Clue: Customer, area ventilation, appliances
What should you do before purging?
- Extinguish any sources of ignition advise the customer
- Make sure all appliances are turned off & open doors and windows
- Turn off gas appliances
Appliances, Area Ventilation, ignite flame whilst purging Y/N, Pipework/Meter Size, other appliances,
How do you purge installations less than 0.02m3, step by step, starting from informing the customer?
- Ensure gas appliances tuned off
- Ensure customer made aware and no sources of ignition
- Open Doors and Windows
- Note the dial / number on the meter before purging starts
- Purge from the furthest point i.e. appliance, or gas isolation valve, you dont have to ignite the flame if installation is less than 0.02m3
- Purge until smell of gas or stable flame then turn off gas.
- Go back to meter, check 0.01m3 or 0.035ft3 of gas has been purged if meter is U6, G4 or E6 meter with pipework equal to or less than 28mm. If meter is U6, G4, E6 or U16/G10 and pipework is above 28mm or equal to or less than 35mm then purge volume 1.5 x the installation volume, if not enough purged then go back and purge more until enough has been purged.
- Note the final meter number.
- Once purged go to each appliance and run appliace until a stable flame is acheived.
Calculate IV
How do you know if an installation is less than 0.02m3?
Its based on installation volume.
(total lenght of gas pipework in a house including what will be added & the meter size + 10% for fittings).
- Pipe dia. (specific fig. ref chart) x lenght of pipe = SUB TOTAL.
- SUB TOTAL x 10% for fittings
- Add the 10% & TOTAL together
- Add meter size (specific fig. ref chart) to TOTAL = FINAL TOTAL
- FINAL TOTAL is either under 0.02 or over it this is the
installation volume.
PV
When can you purge into the atmosphere?
Purge into the atmosphere when the installtion volume is less than or equal to 0.02m3
Purge volume, if pipework is eq. to or less than 28mm with a U6 meter or equivilent size meter the purge volume is always 0.01m3, however, if the pipework is greater than 28mm or eq. to or less than 35mm what is the purge volume?
It is 1.5 x the installation volume
(Calulate the installation total volume with fittings at 10% and meter size then multiply by 1.5 to = Purge Volume).
What is IV?
What is PV?
IV = Installation Volume
PV = Purge Volume
For an intstalltion volume over 28mm pipe, to calculate purge volume what figure do you need to multiply by?
You multiply the total installation volume by 1.5
When purging, if an imperial meter, you need to purge 0.35ft3, what does this equate to in revolutions on an old imperial meter?
0.35ft3 is 3.5 resolutions of the dial on the meter.
When purging, using a metric meter and the purge volume is 0.01m3 (means installation is eq. to or less than 28mm pipe & small meter)
and the meter says 0.080 what would the meter read after 0.01m3 had been purged?
The meter would read 0.090m3 after 0.01m3 has been purged.
test, new, air, pressure
When do you need to purge?
Purge..
- After a tightness test.
- New installation or new extensions
- Alterations to or re-use of existing installations
- Complete loss of pressure upstream of the ECV or installation pressure
- Where there is a possibility of air being present in the installtion
If the purge volume is above 0.02m2 what must you do when purging?
You must ignite the flame
After purging, what must you do to other appliances in the property?
You must switch them on and run them until a stable flame is achieved make sure they are working correctly.
You dont want angry customers coming back to you after you have left the premises saying something isnt working!!!
where, combustion, air flow, issues, stability, picture
After working in any property and after a purge under IGEM rules (26.9’s) we have to do a visual inspection of other appliances in the property to make sure they are safe.
Example if you are working on a boiler and in the same room there is a cooker, you need to do a visual risk assessment on the cooker - this is a legal requirement.
Question is: What are the minimum visual checks?
If working on an appliance in the same room as another appliance then visual checks should be…
- Location - make sure installed in accordance with legal req’s
- Flueing - make sure visual ok, and positioned correctly, meets with legal req’s
- Ventilation - meets with legal ventilation req’s
- Signs of distress - not damaged, or danagerous in anyway
- Stable/Secure - is it secure?
- Flame picture - check the flame is within spec.
Appliances, Testing, Air in Pipework
When do you need to do a visual risk assessment?
You do a visual risk assessment when…
- An appliance is encountered whilst working on another appliance
- An appliance is encountered during a tightness test
- An appliance is encountered when purging the system of air & relighting following work elsewhere on the installation
