# Gas pipe sizing

#### bster

Is there an actual calculation I can use to find out the correct pipe size for a 40meter run. I’ve tried the charts\wizards but they only give flow rates upto a max of 30meters. and you cant guess by deducting the flow for a 10meter run because it is not a constant difference (you know what i mean).

Got a chart up to 50m if you want to email me.

The flow rate that gives a 1.0 mb drop over 40 metres will be the same as the flow rate that gives a 0.5 mb drop over 20 metres, or a 0.25 mb drop over 10 metres, for any given pipe size.

But if 40m of 22mm pipe had a discharge of 2m³/hr, how would you apply that to say 50m.

Easy....
calculate the pressure drop over the max length given in your table, then re-calculate for the rest of the actual length using the 'dropped' value. OK - it probably won't be 100% accurate but it will be within 5%, I believe.

croydoncorgi said:
Easy....
calculate the pressure drop over the max length given in your table, then re-calculate for the rest of the actual length using the 'dropped' value. OK - it probably won't be 100% accurate but it will be within 5%, I believe.

Using that method would give you a pressure drop of 1.25m/bar which is correct, but can you estimate the discharge using the same method or is there a sneaky way of multiplying length x pipe size x pressure.

for example, 50 m of 22mm will discharge 1.78m³/hr whereas 40m will discharge 2m³/hr.

There must be a formular I think.

thats it a fomula would be nice.

i've worked it out know by seperating the runs into sections (there are 3 appliance), so the 40meters became 10m,10m and 20m sections (done properly using a gas sizing example and breaking the sections as appliance are being teed off).

28mm pipe for the 40m run to a 3.8m\hr appliance and a .2m/hr heater (21m run) and 1m/hr hob (7m run).

= 28mm pipe from meter for 40 meters to 3.8m/hr appliance and 15mm pipe at the 10meter tee for .2m/hr appliance and 15mm pipe for the hob teed at 30meters off the 28mm pipe.

But the 28mm wouldn't be large enough with those rates.

i,ve worked it out and it was well under

I'll post the breakdowns if u want to check (and probably show me up!).

bster said:
i,ve worked it out and it was well under

I'll post the breakdowns if u want to check (and probably show me up!).

Ok, if you email it I can return the chart.

just read your post and i'd already copied some figures from word so i may as well paste them on now i'm here.

here goes

a-b = 4.9m\hr@10m = 28mm(meter - first tee)
b-c = 0.2m/hr@22m = 15mm(first tee - 1st appliance)
b-d = 4.7m/hr@20m = 28mm(first tee - second tee)
d-e = 1.0m/ht@6m = 15mm(second tee - second appliance)
d-f = 3.7m/hr@15m = 28mm(second tee - third appliance)

note: all lengths are the total equivelent (inc bends,tees,elbows) lengths. I have taken the pipe sizes from the BS chart, but i have not calculated the allowable pressure drop, in this case .33mb per appliance.

bster said:
just read your post and i'd already copied some figures from word so i may as well paste them on now i'm here.

here goes

a-b = 4.9m\hr@10m = 28mm(meter - first tee)
b-c = 0.2m/hr@22m = 15mm(first tee - 1st appliance)
b-d = 4.7m/hr@20m = 28mm(first tee - second tee)
d-e = 1.0m/ht@6m = 15mm(second tee - second appliance)
d-f = 3.7m/hr@15m = 28mm(second tee - third appliance)

i love diggin holes - i used to be a gardener and then an archaeologist (i'm not joking) .

dew you speel rongely on porpus

i divvent spell rongly bonny lad that's ow i speek ask DIA

marra

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