Gas Pipe Sizing and Regulations (UK)

[friartuck]

Hi anyone

Has anybody got any explanation for the way our gas regs are written?

Just to explain, In the UK we have several squillion regs just to confuse everyone. Quite often one set contradicts another and they dont always make sense. Logic seems to have been forgotten.

If for example you have to size a gas supply from a meter to an appliance (boiler, gas fire, etc) you have a starting pressure which is set by the gas supplier (Transco). This is nominally 21mBar or about 8.3" WG. The regs than allow you a pressure drop of 1mBar (bugger all)...excuse my terminilogy.

Now this is bad enough when you are sizing a main that runs 20-30metres, but we also have an addedd problem. and that is Building Regulations.

Now just to explain, when a boiler house is refurbished or a new system is installed, all significant plant items need to be metered. (generally items above 50kW)

This means that we have meters all over the place.

The added problem then is that the meters have relatively high pressure drops (a diaphragm meter can have a 2 or 3mB PD)

We are then left in a quandary. We have to install over sized meters (turbine generally) which become less accurate when they operate at low duties. And we have to massively over size the pipework as well to ensure that the overall PD does not exceed 1mB.

Its also too costly to install boosters.

Anyone got any ideas of how to get round this problem.

(PS, the gas regs are currently being re-written but they don't seem to be concerned about this problem...they won't allow a 3mB overall PD for instance)

seems like the same old story of 'the useless, ignorant and impractical' in charge of the camp, with common sense left outside in the cold.

Sorry about moaning but there must be something that can be done!!!!!

Any suggestions?

Friar Tuck of Sherwood

 

[ChasBean1]

I agree with you, FriarTuck. The gas regs should be concerned with pipe gauge, the right installation and bracing, the right pipe dope and the right safety features... Pressure drop? Shouldn't be their jurisdiction, unless there's a related safety issue. The main question is what is the minimum gas pressure for the equipment and can this be met with the given piping and meter size, at design flow. If calcs show the gas supply can meet the equipment criteria under this condition, install that piping and that meter, and if you have to, demonstrate < 1 mB pressure drop during the summer...

 

[imok2]

I believe that the only solution is for more common sense to get involved in the regulation process,if you can't fight them then dilute them with common sense. I know this sounds simplistic but you and your fellow engineers may have to get involved.