gas pipe sizing

[tddo]

Hello, i want to power a 180kw lpg burner. My pipe runs 25m between the first stage (1.5 bar output) and second stage (0.5-1.5bar working cond). I am confused as to why all the charts online are about 15 times less pressure (probably for the seconds stage) generally below 0.5bar usually see even less like 0.03 bar. I am confuused. What copper pipe size do i need for this? The pipe runs in an outside area.

 

[1503-44]

Because that's way too much pressure. You're going to burn down the forest.
Its a Natural gas flow of around 0.15 cubic feet per second. 9 ft2 a minute.
You should only need 2 psi (0.13 bar) to move that 25m in a 1" pipe.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[MortenA]

@tddo, you say "LPG" so i assume that is from a bottle/ tank (although 180kW is a bit much for a bottle so most likely a tank)?

You should not do any fixed installations yourself IMO get a certified plumber to do this Any hoses you can buy in fixed lenght. The regulator and hose comes with fixed length hoses but may vary in design from country to country even within EU.

--- Best regards, Morten Andersen

 

[tddo]

Its from a big tank yes. So i should just put the first and second stage pressure regulators right at the output of the tank and then go 25m straight for the burner at really low pressure with pipe size according to the charts (1 1/2 in)?
In the other case if i want to move the gas at 1.5 bar what pipe should i use? Doesnt that pressure guarrantee better capacity for the burner?
remember I want 600.000 BTU/h

 

[MortenA]

I cant help you, i just think that you should put safety first and get a professional to do this!

--- Best regards, Morten Andersen

 

[PEDARRIN2]

Look at IFGC or NFPA 58.

If the charts don't work, then you need to use the equation in IFGC, Chapter 4 or applicable equation in NFPA 58.

You need to look at your fuel load for your burner. KW is not a fuel unit of flow.

1.5 bar seems a bit high to use downstream of first regulator.

You put the first regulator at the tank, size the pipe based on the flow/length/pressure using the charts. Put the second regulator at the at the equipment. Size the pipe the same way.

 

[LittleInch]

tddo,

Please check you numbers AND units as they don't seem to make any sense to me.

Burner pressure is usually about 35mbarg.

Not sure why you are reducing pressure to 1.5barg d/s the tank??

Usually you just reduce to working pressure (~35-40 mbarg ) and then run in that size to the burner if its relatively close, which yours is (25m)

Find out what 180kW /(that's a decent sized burner) means in terms of gas flow in LPG for your unit (depends on efficiency) then probably work on a max velocity of about 7 to 10m/sec is my quick and simple way of figuring out your pipe size.

At those sort of sizes, even a few mm difference in ID can make a big difference in pressure drop / velocity.

Or just stick in a 2" pipe and be done with it. It's only 25m of the stuff.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[tddo]

Thank you for the responses, we only do gasinstallations in small boilers and we put 2 regulators side by side as instructed by specs and all suppliers. Its a two step pressure drop. I have never done such an installation and wanted to know the difference between my options. The installers I talked to do it like this : first reduction in pressure -> run the pipe -> second reduction. And it seemed odd to me to run a huge pipe with that pressure, and therefore posted in a couple of forums. From what I nderstand, i will look into the specs of my first regulator, see how low it can go and run the accoding pipe, then reduce the pressure to 30mbar or whatever is needed for my burner - yes its a big one for for a very badly maintained air boiler .
In any case, will those people essentially providing way way more fuel than necessary have any problems in the future?

 

[LittleInch]

"In any case, will those people essentially providing way way more fuel than necessary have any problems in the future?"

Eh?

Your system will only use the fuel you burn. The only downside to a bigger pipe than strictly required is a few dollars.

Also your regulators are in series, not "side by side" which implies a redundant system or maybe two different sized regulators both feeding the same pipe??

Is that what you are talking about? - A sketch of your system always helps.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

California gas plumbing Code

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/12/fuel-gas-piping#12

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[FacEngrPE]

You do not say if your installation is portable or fixed.
If fixed please see the local building or fuel gas code example, then if required by your jurisdiction obtain a construction permit or better hire a licensed plumber or gas fitter who will take care of any required permits and inspections.

If portable, it may not be subject to your building code - you should verify.
Portable installations may use flexible hose sold for this sort of application rather than pipe. Your pressure at the using equipment is unusually high for fixed appliances, but is not uncommon for industrial torches. Supply pressure to a torch needs to be adjusted so that the fuel consumption is approximately the rated BTU input, then the air supply needs to be adjusted so that the flame burns cleanly. This should be explained in the torch instructions.

 

[georgeverghese]

Assuming this 180kW burner references lower heating value, and with LPG lower heating value at 85MJ/sm3, we get a mass rate of 14kg/hr, volume rate=7.6sm3/hr

Downstream of the 150kpag regulator, use 1/2inch pipe (or tubing if you must, not preferred usually), with velocity at 26fps and pressure drop of 1.5psi/100ft
Downstream of the 50kpag or 35mbar pressure regulator, switch out to 3/4inch pipe or tube, with velocity of 26fps, pressure drop = 0.34psi/100ft - velocity and pressure drop are for the 35mbar case. For the 50kpag case, velocity = 18fps,pressure drop = 0.26psi/100ft
Check with burner vendor what the lpg supply pressure should be. Setting a wrong supply pressure can lead to flameout or flashback or flame lick or poor turndown performance.