natural gas 2" pipe 10 psi 1

[PNA]

we have a customer that has a 2" diameter sch 40 pipe at 10 psi, it runs well over 100' with lots of elbows, etc.

then it is stepped down to 1-1/4" diameter reducer to a pressure regulator, to drop the 10 psi down to 7" wc (which we recommend doing it in 2 stages) and the outlet is 1-1/4" to stepped up to 2" diameter

we need 3000 cubic feet per hour at 7" wc in order to have enough btu's to heat up our furnace

we originally had a 3" diameter tee down to 2" diamter manifold (short section, less than 5')

this was removed by the gas fitter, and replaced with a 2" diameter tee

what happens is we fire 1 burner, then afterwards we fire the other 2 burners.

we get a huge drop in temperature in the furnace when that happens

is it lack of supply?

 

[PNA]

As far as what was there before the furnace was installed? I have no idea what chart, actual pressure, etc. Visible piping twists and turns like crazy, then goes through a roof and disappears somewhere...

 

[PNA]

One thing i have learned over the years, is that "SHOULD WORK" doesnt explain to my bosses why it doesnt work.

 

[BigInch]

Regardless of what upstream pressure the chart uses (not sure, but probably in the 1' WC or so area), what sounds more important here is the number of fittings. "Turing like crazy and going through the roof" to me implies using nothing less than an equivalent length factor of 1.5, at least until you an get a count on those fittings.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[PNA]

Agreed!

Would that not be up to the contractor doing the supply piping to calculate?

 

[zdas04]

I recently raised the gas pressure in my house from 7 inWC to 9 inWC and doubled gas flow. Really, it was twice as much flow to the on-demand water heater and we went from under performing to over performing (i.e., couldn't support 2 showers when water temp was below 60F to being able to support 3 showers at 40F water temp). I couldn't believe it (the gas company did it based on charts in their truck) so I did the calcs myself and got a very similar number. That was a big change in flow for a very small change in pressure. Without a pressure assumption, those charts are much worse than worthless.

The fittings and pipe routing would be a big deal at MUCH higher flow rate or flowing a higher density fluid, for this problem it isn't in the round-off error.

David

 

[PNA]

was that on a 1/2" or 3/4" supply?

 

[zdas04]

1-inch to the water heater. The header is 1-1/4.

David

 

[PNA]

Wow! Mine is 3/4 from the meter

 

[BigInch]

Then what's the problem?

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[PNA]

Main issue, is the customer wants they're furnace running properly, we provided detailed info on what was required for utilities and the contractor is doing a lot of finger pointing. So commissioning delays may have penalties.

 

[PNA]

If i can provide eng info contrary to what the contractor is claiming will work, i will do so. End of story.

 

[BigInch]

You'll need a verified drawing of the piping and fittings and at the least the ambient temperature, inlet flowrate & pressure where you specified delivery conditions, the regulator inlet and outlet pressures and the burner specs to verify your specified delivery conditions and accurately determine pressure losses to argue authoratively with the contractor and convince the owner. Only then will you reach "end of story".

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[PNA]

I understand that and hopefully a resolution will come sooner than later, and all the info will eventually be "found" out

Paul

 

[racookpe1978]

Track the whole line down: "Up and into the roof" won't convince somebody if they go looking. I'm suspicious of anything you haven't looked at yourself.

Sounds like dollars are at stake, and you need to be sure of what that line looks like. Are you sure that "delivery presure" isn't expected to be "at the ;property line" and not at the "pipe entrance"/

 

[PNA]

that is a big concern, and yes you are correct, $$$$$ are involved.

if i was the contractor, and i knew i had to replace the whole length of supply back to wherever it goes, and neglected to quote that or do that prior to installation? that would get messy

 

[katmar]

The length and complexity of the line before the regulator is irrelevant if the pressure is 10 psig at the regulator when the furnace is running. Only if this pressure drops significantly when the furnace runs is there any likelihood of a problem here. But maybe check the calibration of the pressure gauge.

If your drawings showed a 3" line from the regulator to the manifold then you have every right to insist on it being fixed. And while the line is isolated to make this change, do a quick check for debris.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[PNA]

i dont think a 3" line is going to happen

 

[PNA]

a few years ago i specified a 3" connection on a 3" manifold, to supply 5,000,000 btu's of natural gas, it worked beautifully