Gas Pipe Sizing Calculations

[princegoose]

I need to add a cooker supply and have been trying to work out the sizing of the pipe but have come unstuck as can't see anything over 30 meters in 'THE' chart. Have checked Corgi, Viper and old text books with no luck.

All lengths include allowance for pipe and fittings (copper).

A-B = 7.5 Meters
B-C = 5 Meters
B-D = 28.5 Meters

B = TEE
C = BOILER @ 2.6 m3/h
D = COOKER @ 1.04 m3/h

Using the chart, so far, A-B needs to be 28mm, B-C needs to be 22mm but as the theoretical pressure loss over the B-D is 0.33mbar I haven't a clue what to do as multiplying it by 3 gives 85.5 Meters which there isn't an option for.

What can I reference?

Does anyone know? Other than saying ''just use 28mm for a few extra meters son''.

Thanks

 

[AlexGas]

The CORGI book is one way to work out the pipe sizing. Try Progressive Pressure Drop calculation here:
http://www.ukcopperboard.co.uk/lite...ion-Tips/Domestic-gas-planning-and-sizing.pdf

 

[princegoose]

Hi, thanks.

Where in the corgi book does it show you how to calculate the size, other than having to use the table/chart?

 

[AlexGas]

Page 107

 

[princegoose]

Thanks Alex.

I've already tried that. The problem I'm having is that the table doesn't go above 30 Meter lengths. As the last length of pipe I have is 28.5 Meters long when I multiply it by 3 (to get the pressure loss (0.33mbar) relevant to the length) it becomes 85.5 Meters long. I'm sure there's a formula to work this out. Or is there another chart out there which goes longer than 30 meters?

 

[AlexGas]

It is very tight! If you ran your 28mm for extra 13m pass the T (the rest in 22) - the cooker run Pressure Drop will be 1.19 mbar. Not ideal. You might get away with it though, there's plenty of discharge on your last 22mm length. I'd give the Gas Safe a call.

 

[AlexGas]

Get your head around the Progressive Pressure Drop calculation at http://www.ukcopperboard.co.uk/liter...and-sizing.pdf

See Table 2. Your drops will be different.

 

[princegoose]

Ahhhh, I gotcha, thanks, I'll have a good look at it this evening.

Thanks mate.

 

[AlexGas]

Here it is:
A-B 3.64m3/h Total Length 7.5m Chart Length 30 in 28mm
To get the Pressure Loss – divide your Total Length by Chart Length.
7.5m/30m=0.25mbar A-B Pressure Loss is 0.25mbar, You see what I’m saying – it’s not 0.33mbar! You've got more money to play with.
Now you have to do the rest…
As I say - ran 28mm for another 13m and see what you get. It's just above 1mba (NCS). Talk to GS.

Hope it helps.

 

[Simon F]

I had heard of 50m pipe sizing charts but never seen one until recently when I bought the John Reginald combi book, it has a 50m chart.

 

[AlexGas]

OK, let’s start again. Using the table above:

A-B 3.64m3/h Total Length 7.5m Chart Length 40m in 28mm Pressure Loss is 0.1875mbar
B-D 1.04m3/h Total Length 28.5m Chart Length 50m in 22mm Pressure Loss is 0.57mbar
Now we are talking!
According to this – you can have the B-D run to the cooker in 22mm – all 28.5m in 22.
Result! I must admit I haven't seen the table with length of pipe being 40 and 50m before. Never had to run it that far. I’m saving that. Thanks again to Simon.

Hope you are good to go now, princegoose.

 

[AlexGas]

I was wondering why we couldn't have the next discharge figure for 40m, cos there was plenty of discharge at 30m. And I couldn't see anything in the BS to tell us - we can't use figures for runs more than 30m for our calculations. You learn something every day!

 

[princegoose]

Bloody hell guys, thanks. TBH I wouldn't have worked it out myself, so saved me a lot of hassle.

So

A-B 28mm
B-C 22mm
B-D 22mm

?

 

[AlexGas]

Yes, you really need to understand how we came to it though. How do you know I’m not talking rubbish here? I can print a book too. Trust but check!

You can have your current BS 6891:2005+A2:2008

Installation of low pressure gas pipework of up to 35 mm (R1¼) in domestic premises (2nd family gas) — Specification

Here:
[DLMURL]http://www2.warwick.ac.uk/services/estates/projects/ed/edtechnical/gasservices/gas.pdf[/DLMURL]

Thanks to good people of Warwick.

 

[princegoose]

Ay, I'll go over it and ring GS to make sure.

Thanks

 

[mutley racers]

Nice Simon, I have that book but didn't notice the chart went up to 50m. What do you think of the book by the way?

Thanks for the BS link Alex. Am going to have a quick looksy at that