Commercial Gas

[Lavafox]

Hey guys, I'm a plumbing/heating apprentice and one of the assignments my instructor gave me was quite a headscratcher, I need some formulas and calculations here. Here's the scenario.

Discribe how to install gas pipework from meter to appliances. Total kW on appliances is 316 kW. (Yes that's 316 kW, we do commercial gas for restaurants ect) Work out what pipe size is required from the meter.

The appliances are: Range cooker, oven, 2 x frier, steamer. Which brings the total heat input to 316kW.

There are 6 elbows in run to the appliances, and 5 tees (all fitted with gate valves and are connected to the appliaces via flexies)


Now, I know how to actually cut, thread, join the pipe, but I can't actually do the calculations as my instructor is usually doing them.

Oh and the pipe we use is grade black low carbon steel, even though it's painted red!

Any thoughts, formulas would be well appreciated.

 

[monoxide62]

You should have all the info required @ the assesment centre (IGE/UP/1)

316kw? , are you sure?

Without length of pipe runs , appliance input etc etc it's an impossible question to answer.

The steel used would be medium grade (blue) , the 'red paint' is red oxide , some suppliers will have the steel already painted other won't , yellow orca will be the final colour coat.

 

[monoxide62]

all fitted with gate valves

 

[Lavafox]

You should have all the info required @ the assesment centre (IGE/UP/1)

316kw? , are you sure?

Without length of pipe runs , appliance input etc etc it's an impossible question to answer.

The steel used would be medium grade (blue) , the 'red paint' is red oxide , some suppliers will have the steel already painted other won't , yellow orca will be the final colour coat.

We've already completed the job. We used inch and a half pipe (40mm) This is not actually an assessment, it's homework, if you will. Ideally I'm suppose to be concentrating on installing domestic boilers and such, but because we do so much commercial work, my instructor is pushing me to learn more.

The total kW of the appliances is 316, as I mentioned. So if we devide 316 by 5 (total appliances) that gives us 63 kW, per appliance (roughly)

My question is, how did he find out what size pipe to use? The answer is: to supply 5 appliances with a heat input of 316kw you a pipe size of 40mm (inch and a half)

 

[onlyfitidealboilers]

First of all you may need a chart. pipesizing?

 

[Biggles..]

First job is to convert kw to m3/hr.This will give you total load to the first branch

You then need your pipe length and fittings, from there you would use

View media item 14237
You need to the smallest pipe that will allow the m3/hr to pass for your length of pipe.

That's about it really,little bit more to it,but roughly that's it.

 

[Biggles..]

Oh and if your run between mmeter and first appliance is more than 5meters ,if you've used DN40 then your pipe will be too small.

Elbows are .5m equivalent length.

 

[gasafengineer]

My question is, how did he find out what size pipe to use? The answer is: to supply 5 appliances with a heat input of 316kw you a pipe size of 40mm (inch and a half)

To convert KW to M3 = KW X .094........... 316 KW would require 29.7 M3 , if net heat input specified multiply x 1.1.

 

[Lavafox]

First job is to convert kw to m3/hr.This will give you total load to the first branch

You then need your pipe length and fittings, from there you would use

View media item 14237
You need to the smallest pipe that will allow the m3/hr to pass for your length of pipe.

That's about it really,little bit more to it,but roughly that's it.

Thank you dude, you're a goddamn lifesaver! If you wouldn't mind though, since I'm such a knobhead, explain how to use this chart?

 

[onlyfitidealboilers]

Say your all the appliances added upto 20m/h ³ the pipe before the first T needs to be able to carry 20m/h ³ then say a cooker was 3m/h ³ the pipe needs to be able to carry that!

I aint to good at explaining tho!

easy tho

 

[Lavafox]

Say your all the appliances added upto 20m/h ³ the pipe before the first T needs to be able to carry 20m/h ³ then say a cooker was 3m/h ³ the pipe needs to be able to carry that!

I aint to good at explaining tho!

easy tho

This might just be slightly too advanced for me, since i've only been doing this apprenticeship for 1 year and I'm already doing commercial gas calculations

Unless someone would be willing to simplify this for me, for example what m/h³ is, and for example why do we times by .094 (what is this number?) and once you get the m/h³ which in this case is 29,7 m/h³ <-- what does that actually give you? is that a pipe size?

Oh boy I must be a disgrace to the whole plumbing community

 

[Agile]

Unless someone would be willing to simplify this for me, for example what m/h³ is, and for example why do we times by .094 (what is this number?) and once you get the m/h³ which in this case is 29,7 m/h³ <-- what does that actually give you? is that a pipe size?

m/h³ ------ That means metres per cubic hour!

But I cannot explain what a cubic hour is!

I also wonder what a 63 kW oven looks like unless its a large bus sized bread oven!

The ventilation system must be very good to remove 316 kW of heat.

 

[monoxide62]

Say your all the appliances added upto 20m/h ³ the pipe before the first T needs to be able to carry 20m/h ³ then say a cooker was 3m/h ³ the pipe needs to be able to carry that!

I aint to good at explaining tho!

easy tho

This might just be slightly too advanced for me, since i've only been doing this apprenticeship for 1 year and I'm already doing commercial gas calculations

Unless someone would be willing to simplify this for me, for example what m/h³ is, and for example why do we times by .094 (what is this number?) and once you get the m/h³ which in this case is 29,7 m/h³ <-- what does that actually give you? is that a pipe size?

Oh boy I must be a disgrace to the whole plumbing community

29.7 m3/h is the total ammount of gas that those appliances would consume if all running together.

0.94 is just a conversion factor ie: 1kw/h would consume .094 cubic meters an hour of gas (m3/h) (dependant on CV)

Once the total KW of all appliances have been calculated they are then converted to M3/h , from this figure we can work out pipe sizing from chart taking pressure loss into account , if working out the pressure loss on an existing installation then other factrs regards pressure loss are taken into account ie: effective length in refference to maximum length (flow discharge chart).