Commercial gas pipe sizing

[Tranx]

Hello,

I'm currently working on a project to install a CHP engine at a hotel and installing a couple of new boilers. The total installed capacity will be 440kW. We need to run a new gas supply pipe around the outside of the building, it'll be about 90 meters and 18 elbows, so a long run! Before we get too far I need to work out whether we will be able to supply this volume of gas to the appliances with 50mm steel or if we'll have to get it all welded up in a larger bore.

I'd really appreciate it if someone could point me in the right direction to pipe sizing guidelines so I can calculate what we'll need to use?

It'd be great if someone could also comment on the possibility of using PE buried underground, and whether this would be beneficial.

Thanks in advance,
Jimmy

 

[Riley]

We will not give gas advice unless you are Gas Safe. If you aren't then your gas engineer will be able to work this out for you

 

[Tranx]

Can I please ask why that is? I simply want a formula that will allow me to calculate the required bore, therefore allowing me to determine whether or not a welded pipe would be required and hence whether it would be worth it or not to continue with this project. Welded pipe is very expensive!

 

[joni os]

Arrange for gas supply and meter closer to point of usage. Volume and distance best at service mains pressure.

 

[Tranx]

Thanks for the reply, but we've already looked into this option and unfortunately it is not a possibility.

 

[ShaunCorbs]

You haven't a hope in hell 50mm will be able to cope

May I ask who is installing the boilers ?

Also what's the op/mop ??

 

[Riley]

We won't give the details as you're clearly not gas safe. We will not offer any info pertaining to gas installation advice to unqualified persons. Read the forum rules.

 

[ShaunCorbs]

Now now lads (think he knows he needs to be)

Tranx where's the project maybe a commercial engy is close to you ??

Also pe vs steel there about the same cost only difference is install time

 

[Riley]

Just saying as people get indignant when we say no and the reason why is obvious

 

[SimonG]

Somebody not read the rules?

If you are gas safe, get your post count over ten and apply for the private gas safe section.

 

[Scott_D]

Welded pipe is very expensive!

So are CHP engines and commercial boilers, if someone is designing the system they would calculate the pipe sizes required

 

[Tranx]

You haven't a hope in hell 50mm will be able to cope

May I ask who is installing the boilers ?

Also what's the op/mop ??

Can I ask how you calculated that 50mm will be too small?

If the project goes ahead we will have local plumbers install the boilers and bring in a commercial gas engineer to do the gas supply.

 

[Tranx]

So are CHP engines and commercial boilers, if someone is designing the system they would calculate the pipe sizes required

Yeah, we're trying to design the system now and would like information on how to calculate the required pipe size. We had a commercial gas engineer come out who said he thinks it'll have to be over 2", but he wasn't 100% sure, and said he wasn't qualified to weld.

 

[rpm]

You can`t design what you don`t understand and there lies the problem, you will not get the answer you seek from this gas safe minded forum so please give it a rest now.

 

[Tranx]

Now now lads (think he knows he needs to be)

Tranx where's the project maybe a commercial engy is close to you ??

Also pe vs steel there about the same cost only difference is install time

Thanks for the reply. We were led to believe that buried PE would be significantly cheaper than welded steel, due to the type of run it would have to be welded on site, which adds to the cost then there's the nitrogen purging & so on...

 

[Tranx]

You can`t design what you don`t understand and there lies the problem, you will not get the answer you seek from this gas safe minded forum so please give it a rest now.

I'll happily admit to a lack of knowledge, but what makes you think I don't understand what I need to do? I'm trying to calculate the required pipe diameter that will allow me to move enough gas ~40m^3 to supply 440kW of appliances, 90m from the meter to final destination. I need to ensure pressure drop across the run is minimal, and will allow the continued supply of 40m^3 gas.

All I want is a simple equation that will allow me to calculate this.

Otherwise I'll have to take it back to basic fluid mechanics & have to do lots of research into pipe roughness, calorific values, specific densities, the effects of pressure on pipe wall friction and velocities, the bloody Darcy-Weisbach formula, etc etc...

Surely there's a simple formula to calculate as accurately as reasonably practicable the required diameter? I can't imagine day to day plumbers having to do this every time they size a pipe.

 

[Tranx]

You haven't a hope in hell 50mm will be able to cope

May I ask who is installing the boilers ?

Also what's the op/mop ??

We will have to have a new gas meter installed anyway if the job goes ahead as the current one will be undersized. Can you shed some light on typical meter operating pressures? I understand that standard domestic is 21 mbar, the current meter on site just says <75mbar. What's likely to be the standard operating pressure of that meter? Can we go to higher pressures? and does that bring in more complications? I would guess the usual way is to keep pressures past the meter low and to increase pipe diameter?

Cheers.

 

[Scott_D]

You will need someone with commercial gas for the appliances
A local plumber can't do it

 

[Scott_D]

You will need someone with commercial gas for the appliances
A local plumber can't do it

 

[ShaunCorbs]

Right ok

Plumbers can't install the boilers or flues needs to be a commercial gas engy (as need to make sure safety devices and installed to current regs)

Regarding steel pipe with a distance of that length using 50mm will give you a pressure loss of around 8mbar with a low pressure system <75mbar (normally running around 21-35mbar op) which your only allowed a max of 1 mbar

So you can see your well off

Tbh you would be best to contact the services of a commercial gas safe engy in the designing stages will make the job run a lot smoother in the end

Any other questions please ask

 

[ShaunCorbs]

We will have to have a new gas meter installed anyway if the job goes ahead as the current one will be undersized. Can you shed some light on typical meter operating pressures? I understand that standard domestic is 21 mbar, the current meter on site just says <75mbar. What's likely to be the standard operating pressure of that meter? Can we go to higher pressures? and does that bring in more complications? I would guess the usual way is to keep pressures past the meter low and to increase pipe diameter?

Cheers.

You would have to speak to the network provider see what they can supply

If you go with steel tube get a commercial engy to work out what he requires, and get him to install it with a coded welder

 

[joni os]

Otherwise I'll have to take it back to basic fluid mechanics & have to do lots of research into pipe roughness, calorific values, specific densities, the effects of pressure on pipe wall friction and velocities, the bloody Darcy-Weisbach formula, etc etc...

Surely there's a simple formula to calculate as accurately as reasonably practicable the required diameter? I can't imagine day to day plumbers having to do this every time they size a pipe.

The "Pole Formula" is a simplified version of Darcy's but underestimates pressure drop as diameter of pipes decreases.
Boilers, even if domestic, will require fitting by commercial gas fitters because of meter and volume of gas in system.
Why is the option of bringing meter closer to plant not available.

 

[Riley]

Dear lord

 

[SimonG]

Dear lord

He'll be along in a bit

 

[rpm]

, the bloody Darcy-Weisbach formula, etc etc...

:hand:

 

[rpm]

, the bloody Darcy-Weisbach formula, etc etc...

:hand:

 

[Rickster123]

I'm closing this thread because I'm a "day to day plumber".

No gas advice given here.