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Dropping Gas Pressure


#1

Hi! I’m from the Philippines, and there’s probably 1 in 1,000 jewelry makers here who uses oxy-lpg for their torches so this community is my best bet to ask questions and get answers.

I bought a set of smith little torch with regulators included and another pair of regulators last Dec 2018 from Rio Grande. Since I had to have them shipped here to the Philippines, I was only able to try them recently. My question is, is it normal for the pressures drop from 8 psi to 5 psi when I open the valves of the torch? By the way, the regulators are single stage.

Also, I have messaged Rio Grande 4 times, but I get no reply.


#2

Rio follows this discussion, they should reply…Rob


#3

Thanks, Rob! I finally got a reply. The tech guy from Rio Grande said that it’s normal for the pressure to drop a little (I hope 8 psi to 5 psi is little) when I open the torch valves. I just need to adjust the pressure if I find that the flame is insufficient.


#4

Dropping pressure in fluid dynamics is a well known phenomenon. Take two sheets of paper approx. 1" apart and blow in between. The flowing air results in a pressure drop, and the sheets will move towards each other because of the constant ambient pressure.
We use this effect for our water jet vacuum pumps, formula 1 racing cars are pulled to the ground caused by the high speed air flow underneath and planes are flying because the higher speed of air along the upper surface of the wings.
More of this you’ll find online, e.g.: en.wikipedia.org/wiki/Darcy-Weisbach_equation :wink:
Your practical approach might be to adjust your pressure with the torch burning.
Sandor


#5

Thank you, Sandor! It’s clear now.

Chad