gas pipe sizing

[Inverness]

revising for my gas, trying to understand pipe sizing.

I've got the spec college book and I'm trying to get my head round the gas pipe sizing from the books from class. we don't start it until march but I'm wanting to get a head start as theres lot to study and I'm a slow learner.

I'm struggling with understanding the maximum pressure loss from the meter at any point of use is 1mb. can someone explain this in a easier way if they can.

also from the diagram i have with meter A to the first tee B is pipe length 3 meters long and states it has two elbows? overall equivalent length is 4meters. as the elbows at as 0.5 x 2.

i can't work out where the 2 elbows are? cause from B - C is a fire.

i hope this isn't too much for some ones advice.

 

[Orlando5007]

Re: revising for my gas, trying to understand pipe sizing.

Maximum pressure loss from meter to each appliance is 1mbar

Lets say house Has a boiler
The maximum pressure loss from the meter to the boiler can only be 1mbar (the pressure is lost when the pipe is too small or theres too many bends)

 

[Orlando5007]

Re: revising for my gas, trying to understand pipe sizing.

Have you got a picture of the diagram?

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

a---------------b------------------d
|
|
|
c

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

if you can imagine below the b is the pipe work for c

 

[Orlando5007]

Re: revising for my gas, trying to understand pipe sizing.

Just send a picture

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

View attachment gas sizing example.pdf

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

a-b i don't understand why it says there is 2 elbows? i lost.

 

[Orlando5007]

Re: revising for my gas, trying to understand pipe sizing.

It basically wants you to imagine that between point b and c theres bends

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

what about the 1mb maximum drop from the meter?

 

[Orlando5007]

Re: revising for my gas, trying to understand pipe sizing.

Let me get home ill work it out for u tonight

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

thank you.

 

[Inverness]

Re: revising for my gas, trying to understand pipe sizing.

can you explain about the pressure loss. i can find out the amount of gas required from the table but where it becomes a struggle to understand is when it talks about the maximum pressure loss at 1mb

 

[Dotty]

Re: revising for my gas, trying to understand pipe sizing.

I've moved this to the arms because we don't discuss gas in open forum but at the same time we want to encourage and help you with your learning.

What the exercise is trying to do is get you to size each section of pipework so no section has a drop greater than 1mbar. I aim for 0.5 max but that's me.

The exercise shows you leg a-b, b-c and b-d with the appliance load on each leg. Because the diagram would be complicated by showing each bend and tee you're just told how many there are.

So, work out your size using m3/hr for leg b-c. Same again for b-d. Add your two loads together in m3/hr and work out your pipe size for a-b.

And then Bob's your aunt's live in lover.

 

[Inverness]

[MENTION][MENTION][MENTION]

[PHP][ATTACH]26787.vB[/ATTACH]

[/PHP][/MENTION][/MENTION][/MENTION]can someone find the answers for my pipe sizing

 

[Inverness]

View attachment 26788

 

[Inverness]

 

[Inverness]

 

[Inverness]

the table below is where I've got my answers from.

 

[ShaunCorbs]

what do you get ?

 

[Inverness]

 

[Inverness]

 

[Inverness]

its a rough table.

 

[Inverness]

hi shaun I've posted my answers. its quite rough.
thanks for your time.

 

[Inverness]

is the layout letters correct for the a-b and so on? and the size of pipe that is required for the amount of gas provide for each appliance. if its wrong I'm never going to get it.

 

[ShaunCorbs]

at a rough look your off how many elbows for the sections of pipe?

esp for a load of about 56kw

 

[Inverness]

I've included my bends and tees in the my overall pipe length.

 

[ShaunCorbs]

I've included my bends and tees in the my overall pipe length.

no so i can work it out 🙂 unless your drawing is right?

 

[Inverness]

Instead of writing how length of pipe answer then equivalent length i just added my answer total.

 

[Inverness]

my drawing is exactly for what you see for the amount of bends and tees.

 

[ShaunCorbs]

my drawing is exactly for what you see for the amount of bends and tees.

ok also D-E 8.7 m3 of gas???????

 

[Inverness]

a-b, 2m length pipe, tee 0.5, overall pipe size 2.5m

 

[ShaunCorbs]

think this will help you more bud

[DLMURL]http://copperplumbing.org.uk/sites/default/files/content_attachments/domestic-gas-planning-and-sizing_0.pdf[/DLMURL]

and give us 10 will work it out

 

[Inverness]

i assumed from d-e 8.7 m3 of gas required to feed appliance f, appliance h and appliance j. all added to 4.7m3 of gas.

 

[Inverness]

ok thanks. ill haver a read of this and once i think I've got it ill ask you guys>

 

[ShaunCorbs]

i assumed from d-e 8.7 m3 of gas required to feed appliance f, appliance h and appliance j. all added to 4.7m3 of gas.

you put 8.7 and not 4.7???????

 

[Inverness]

yes thats what i mean.

 

[Dotty]

Don't fret too much Invy, everyone struggles with this at first but once you've got it it's a doddle.

 

[Inverness]

thanks that means a lot. I've been trying to do this allay but still don't get it.

 

[Dotty]

I've also merged both your threads to avoid confusion.

 

[Inverness]

thank you. shaun has put me into the right direction so hopefully reading this is the proper way of understanding it.
when you do gas pipe sizing does everyone do this table to work out the size of pipe?

 

[ShaunCorbs]

thank you. shaun has put me into the right direction so hopefully reading this is the proper way of understanding it.
when you do gas pipe sizing does everyone do this table to work out the size of pipe?

ive got a mears calcs but if i have to back to the books

 

[ShaunCorbs]

A - B 5.7m3 2m : 2m , 1.5m = 3.5m, 35mm

B - C 1.0m3 1m : 1m , 0.0m = 1.0m, 15mm

B - D 4.7m3 4m : 4m , 0.5m = 4.5m, 35mm

D - E 4.7m3 2m : 2m , 0.5m = 2.5m, 35mm (will be ok in 28mm)

E - F 1.0m3 1m : 1m , 0.0m = 1.0m, 15mm

E - G 3.7m3 2m : 2m , 0.5m = 2.5m, 28mm

G - H 1.0m3 2m : 2m , 0.0m = 2.0m, 15mm

G - J 3.2m3 5m : 5m , 0.0m = 5.0m, 28mm

not 1000% as all ive got at home is a ft3h mears calc 😀

 

[Inverness]

 

[ShaunCorbs]

looks fine mate starting to get the hang of it ?

 

[Inverness]

its down too you mate.ill do more and let you see.

would it be good practice to have the actual pressure loss at 0.5 instead of being close at 1.0.?

 

[ShaunCorbs]

its down too you mate.ill do more and let you see.

would it be good practice to have the actual pressure loss at 0.5 instead of being close at 1.0.?

in theory yes but then you start going big for example 22mm for a gas fire (7kw) etc

but depending on site conditions running 28mm to as close as you could to the boiler wouldn't hurt

most manufacturers allow 1.5mb at the gas valve test point anyway, and you will find you will have a little wiggle room as the figures arnt that accurate etc (people state different for pressure loss on elbows etc) and im sure you could get it lower by doing some formed bends

 

[Inverness]

Hi Shaun how do you get the progressive drop on the last appliance?

 

[ShaunCorbs]

Hi Shaun how do you get the progressive drop on the last appliance?

add (col 9)

1-2, 2-4 and 4-6 if you mean cooker

1-2 and 2-3 if you mean gas fire

1-2, 2-4 and 4-5 if you mean boiler

 

[Inverness]

 

[Inverness]

here is some more gas sizing practise attempts.
I've think I've manage to grasp it now.

the main pipe run c-d to find out its progressive pressure drop you add the actual pressure drop from previous b-c progressive drop ?

 

[ShaunCorbs]

for the progressive pressure drop of lets say F



A-B + B-D + D-F = progressive pressure drop of F etc

 

[Inverness]

for each appliance to find out its progressive pressure loss you need to add all sections of pipe that feeds that appliance so by finding out f you have to plus all the actual pressure drop together ab- bd- df.

but what about pipe work that isn't feeding any appliances??

 

[ShaunCorbs]

for each appliance to find out its progressive pressure loss you need to add all sections of pipe that feeds that appliance so by finding out f you have to plus all the actual pressure drop together ab- bd- df.

but what about pipe work that isn't feeding any appliances??

yes and what do you mean like A-B and B-D ? just add upto that point

like you want to know the ppl of D

its A-B + B-D = ppl of D

 

[AlexGas]

View attachment 26896

Try to do your calculations using latest BS figures for pressure loss of fittings. See if you get the same result.

 

[Inverness]

Isn't the copper institutions bs figures?

 

[AlexGas]

Isn't the copper institutions bs figures?

Can you see the figures in my previous post?

 

[Inverness]

I have the bpec Gas saftey manual so I'll start and do more practice attempts with these pressure loss figures it even goes up to 35 mm.
Thanks again.
It takes time to understand it and the books are written in such away that it's designed to be taught by a teacher. But who needs a teacher when there is you guys.lol
I know it's early but I don't begin my gas until March next year so I'm studying for it now so when the teacher starts explaining things I'll no what he is talking about and I'll be able to explain it in a easier format to my friends in the class too.
My boss is gas safe but we don't to a lot just commissions boilers and sometimes re-rout gas pipe to suit new boilers. But with the plumbing forum I'm teaching my boss new things too.

 

[AlexGas]

All the best, hope it goes well for you.

 

[Inverness]

I can see the figures in your last post. But I thought .5 for each elbow and tee .3 for formed bend?

 

[Inverness]

I didn't know there is pin point figures from the bs6891 2015

 

[Inverness]

On the gastite website there is detailed pipe pressure losses for even couplings. Is this what you do for precise measurements?

 

[AlexGas]

I didn't know there is pin point figures from the bs6891 2015

It was new to me too. That's the latest British Standard.

 

[Inverness]

The book we have been given from college said this is all we need to know to pass. When did it come out?

 

[spanner]

Maximum allowance from meter to appliance 1mbar. From the meter work out the consumption rate of a a meter of pipe up to the maximum of 35mm diameter. The larger pipe bore the more retained.
Then reduce the sizing slightly further down the run. And not forgetting to + 0.5 of resistance for each and every fitting then adding in to actual length.