checking safety devices on gas hob and oven

[g60rge]

hi, im working towards my acs and have a query,

if im checking safety devices on a gas hob/cooker,

letby/tightness

lid shut off

check controls are working and not letting by or stiff/loose

check stability device/hose connections etc

i check the fsd by lighting the oven and watching it light on low flame, once the phial has heated up it allows the main burner to light (30 secs). Shut the gas off, wait for the click (time it) turn back on, should start off on low flame again.

check the flame returns to bypass after temp is satisfied

check the seals with a sheet of paper

now ive found nothing in my notes to suggest checking ffd shut off on hobs and cookers and doing the tightness test to ensure gas isnt being passed to the burners which worries me.

thinking about it, if the gas supply was interrupted and then reinstated, but the ffd shut the gas off, how is the appliance reset? as ive never seen one with a reset button. if they dont, then what happens?

thanks in advance

 

[Hobo128]

So why do you need to work out a purge volume ?

 

[Hobo128]

well if installation is up to 28mm it would be 0.01m3

So why do you need to work out a purge volume ?
I mean cant you just purge 0.01m3 through everytime if the pipe work is not greater that 28mm. Dont forget im doing my acs soon and need explanation.

 

[GrahamM]

So why do you need to work out a purge volume ?
I mean cant you just purge 0.01m3 through everytime if the pipe work is not greater that 28mm. Dont forget im doing my acs soon and need explanation.

Correct. The standard purge volume for a G4/U6 meter with 28mm pipe is 0.01m³ as Syty states.
Only if bigger meter or greater than 28mm pipe does this change.

 

[kirkgas]

Just to change the subject because this thread is so fresh and im doing my acs too,
When purging existing pipework say after a service or something do you have to work out a purge volume to purge it or can you just purge 0.01 m3 of gas through. I understand that you have to work out purge volumes to check its within your limits.

check your notes and get your head round this you seem to be mixing a couple of things up
depending on meter and/or pipe size you only need to purge 0.01m3, if above 28mm or U16 meter there is a calculation to do, but a purge calculation isnt done to see if it is within limints of your work scope, the calculation is to work out how much gas to purge and whether you purge to air with no ignition or constant ignition
the calculation to decide whether you cvan work on it is IV (Installation Volume) and if over 0.035m3 isnt domestic

 

[kirkgas]

if the gas pipe has been opened, i would do a purge calculation and follow the correct procedure to remove explosive mixtures!

i wouldnt do a purge calculation until i had done a visual inspection to see what meter and pipes were fitted, as you dont need to calculate every install

 

[kirkgas]

But what if you cant see the pipe work and you dont know how many fittings or how much 22mm pipe runs though the ceiling? Are you only doing purge volume caculations to check if you are allowed to purge it with out igniting. I am confused. Alot of the time you can see the pipework and you cant go ripping floor boards up.

you never need to know how many fittings are on an install to work out purge volume, its down to meter and/or pipe size, if you cant see all the pipework you need to work on a best endeavour, say 28mm pipe disappears under the floor and 8m away 22mm pipe appears up as you dont know where it drops down simply take it as 28mm all the way, the reality is it wont make much difference, remember we are nearly talking about IV and PV in the same thread, max IV for domestic ticket is 0.035m3 (approx 90m x 22mm pipe with an E6 meter, so you will never go over in a domestic as you wont get any gas out of the pipe if the appliance is 90m away from the meter, if there is any 35mm pipe or a U16 meter you need to work out IV before you start, (o.035m3 max for domestic) if you can work on it you need to work out PV so you need PV of the meter and then calculate pipe lengths (again if you cant see all the pipe or where it reduces assume larger size) once you add up all the pipe volumes, add 10% for fittings (thats why you dont need to know how many there are) then multiply answer by 1.5 lastly add PV of meter, if under 0.02m3 purge to vented area, if over 0.02m3 you need to light it as soon as you start purging

 

[dancinplumba]

nice one kirkgas, lots of helpful information, and a lot of typing

 

[mutley racers]

So, on a U6 meter, you have to purge times the badge capacity which is 0.355 and this has to be burned. Do you just use a lighter at the hob? As you are not able to use electricity?

 

[mutley racers]

So when you guys say turn the gas off and wait for the click, do you mean just turn the gas off on the tap? Not like on the isolation valve like any other appliance? Am sure you wouldnt disconnect it from the bayonet fitting. Or would you?

 

[mutley racers]

ok, I have looked in my Viper and gas book and it says that for a U6 meter with 28mm pipe, you purge 0.01m3. And you do not need to light it. Which on the dial, is just between increment 3 and 4. But, if on my acs assessment, i lit the gas at the cooker, would it be allowed? As, it is recommended to in both my viper and Corgi to light. If so, what do i use to light it? A lighter or bit of paper?

Thanks for all the help guys

 

[Hobo128]

you never need to know how many fittings are on an install to work out purge volume, its down to meter and/or pipe size, if you cant see all the pipework you need to work on a best endeavour, say 28mm pipe disappears under the floor and 8m away 22mm pipe appears up as you dont know where it drops down simply take it as 28mm all the way, the reality is it wont make much difference, remember we are nearly talking about IV and PV in the same thread, max IV for domestic ticket is 0.035m3 (approx 90m x 22mm pipe with an E6 meter, so you will never go over in a domestic as you wont get any gas out of the pipe if the appliance is 90m away from the meter, if there is any 35mm pipe or a U16 meter you need to work out IV before you start, (o.035m3 max for domestic) if you can work on it you need to work out PV so you need PV of the meter and then calculate pipe lengths (again if you cant see all the pipe or where it reduces assume larger size) once you add up all the pipe volumes, add 10% for fittings (thats why you dont need to know how many there are) then multiply answer by 1.5 lastly add PV of meter, if under 0.02m3 purge to vented area, if over 0.02m3 you need to light it as soon as you start purging

Thanks pal thats cleared it up for me.

 

[sparra1100]

out of all the things in gas /acs ect this is the one thing that scares me the most just carnt get my head round the amount of gas that comes out by doing it by the book ive done it that way and it took ages to clear an was scared incase anyone came in and switched something on or the fridge fired up or the fone went ect as you carnt turn everything off in a house especaily a freezer full of frozen food, had this discusion on here loads of times, i understand why they do it but dont agree with it, if you smell the slightest amount of gas wen in a house transco tell you to turn the gas off and open all doors windows etc so why is it ok to let that amount of gas into a room i still use my sniffer on my anton till it goes to high to purge i no thats not the "correct"way but just carnt do it the other way

 

[kirkgas]

out of all the things in gas /acs ect this is the one thing that scares me the most just carnt get my head round the amount of gas that comes out by doing it by the book ive done it that way and it took ages to clear an was scared incase anyone came in and switched something on or the fridge fired up or the fone went ect as you carnt turn everything off in a house especaily a freezer full of frozen food, had this discusion on here loads of times, i understand why they do it but dont agree with it, if you smell the slightest amount of gas wen in a house transco tell you to turn the gas off and open all doors windows etc so why is it ok to let that amount of gas into a room i still use my sniffer on my anton till it goes to high to purge i no thats not the "correct"way but just carnt do it the other way

why are you scared? you are purging to ventilated area and the gas cant explode till it is between 5-15% volume, you are only purging 0.01m3 gas so if 0.01m3 is 5-15% of the room volume and likely to explode what size will the room be? and that would also mean you had shut the window to stop the gas escaping, on a hob or cooker, 20-30 secs will purge the correct volume it just isnt going to be a problem,

 

[heliotrope]

out of all the things in gas /acs ect this is the one thing that scares me the most just carnt get my head round the amount of gas that comes out by doing it by the book ive done it that way and it took ages to clear an was scared incase anyone came in and switched something on or the fridge fired up or the fone went ect as you carnt turn everything off in a house especaily a freezer full of frozen food, had this discusion on here loads of times, i understand why they do it but dont agree with it, if you smell the slightest amount of gas wen in a house transco tell you to turn the gas off and open all doors windows etc so why is it ok to let that amount of gas into a room i still use my sniffer on my anton till it goes to high to purge i no thats not the "correct"way but just carnt do it the other way

If you 'carnt' be doing the purging by the book and if you 'carnt'
be doing it the "correct" way I would wonder if you are competent
to be doing gas work at all.

Are you registered with Gas Safe Register as a GSR installer?

 

[sparra1100]

why are you scared? you are purging to ventilated area and the gas cant explode till it is between 5-15% volume, you are only purging 0.01m3 gas so if 0.01m3 is 5-15% of the room volume and likely to explode what size will the room be? and that would also mean you had shut the window to stop the gas escaping, on a hob or cooker, 20-30 secs will purge the correct volume it just isnt going to be a problem,

get all that kirkgas mate dont disagree and dont no why, it just does, 20 or 30 secs i do that anyway no loads of gas safe people and dont no anyone who purges by the book all say the same as me