Pipe sizing calculation question

[Blumper]

Hello chaps, was hoping one or more of you can clarify a question re the above. When sizing pipework for an installation, I know that the Kw per appliance and the total Kw is used in the calculation,(plus the bearing in mind for future appliances etc) but in the case of a gas hob, for example a large Rangemaster with a wok burner and 4 additional burners, is the total Kw (converted to m3 of course) for all burners included in the calculation ? I ask because I am aware that in the case of gas rating a hob, only three burners are lit for the calculation on account of the fact that it is unlikely that all will be used at once. I have a sneaking feeling I might have overlooked an obvious, but I'd rather be sure.......... thanks loads...

oh and one other thing..........if you were to do a let-by & tightness test on a meter that had two rusted elbows on the upstream pipework, but both appear mechanically sound and tested satisfactorily....would you NCS that ? I know that signs of impinging corrosion is an AR, but would you 'flag' them anyway ? Have read the unsafe situations manual but would still appreciate your thoughts.........thanks loads again

 

[justalex81]

you must calculate all appliances at their maximum kw rating.

regarding the elbows, they'd have to be seriously corroded and have a lot of pitting to be dangerous.

 

[Hardy1]

appliances maximum kw rating must be used, and also if showing serious signs of corrosion i would AR .

 

[kirkgas]

you are confusing appliance gas rating with meter rating, when calculating/checking an appliance you must have it on full rate, if you are measuring the working pressure of the meter you use 3 rings of a hob, the other thing to consider is the meter training notes which look at diversity factor, and makes allowances for multi appliances being used intermittently to calculate "average" consumption when deciding what meter is required

 

[justalex81]

he's calculating the size of the gas pipe needed not the size of the meter.

 

[kirkgas]

he's calculating the size of the gas pipe needed not the size of the meter.

i appreciate that, but as well as calculating pipe sizes he MUST confirm that any alterations he makes do not exceed the safe limit of the meter

 

[ADM360]

With referance to the corroded elbows up stream of the meter. I would say that it was you call as to saftey of them!! as you've asked the question, I would guess you are concerned about them. Two options - write out a warning notice AR, cap off gas and inform gas carrier!! or tell the customer what you've found and that you have to issue a notice and cap off, and let them ring the carrier saying " done a meter reading and thought the meter looked a bit rusty, is this ok?" saves you paper work and capping off!!

 

[kirkgas]

With referance to the corroded elbows up stream of the meter. I would say that it was you call as to saftey of them!! as you've asked the question, I would guess you are concerned about them. Two options - write out a warning notice AR, cap off gas and inform gas carrier!! or tell the customer what you've found and that you have to issue a notice and cap off, and let them ring the carrier saying " done a meter reading and thought the meter looked a bit rusty, is this ok?" saves you paper work and capping off!!

if you say its AR they you wont be capping the gas supply

 

[Halesowen1]

Dont know how you would get on here, if you think it is AR how can you turn off the gas and advise the customer not to use?? As the problem may be before the Valve. I would say contact supplier.

 

[Halesowen1]

In my handbook it says AR for any corrosive damage to the meter, regulator or any installation pipework.
But as I said above, this is only going to work if the elbows are after the ECV.

 

[Blumper]

Thanks fellas, one and all. Its all clear in the head now, cheers too kirkgas for the reminder re 3 burners for working pressure at the meter test, that's what confused the issue........... re the elbows, I'm working alongside an GS engineer and I thought they should have been NCS at least, rusty but not yet 'corroded'. So much personal interpretation in this game.......!!

 

[GrahamM]

You will come across external meters and pipework with surface rust/corrosion. Metallic pipework/fittings/meters when exposed to moist atmospheres will corrode to some degree. This does not warrant following up unless you believe the corrosion is becoming extensive enough to affect the integrity of the material.

Just like older boilers, the internal casing may be showing signs of corrosion. As long as not severe, all I do is note on paperwork that it is something to keep an eye on for future visits. That's all.

 

[Blumper]

Cheers Graham, exactly what is being done.