Safety when pressure testing

[JSU]

Could someone go through the necisary precautions that need to be kept when dealing with pressure/leak testing?

[chilly1]

Wear safety glasses and gloves. Never test over 100 psi when first pressurizing a system. Always use a dry inert gas. Never test with an air compressor or oxygen. If there is a leak use soap and water to find it if you dont have an electronic tester.Relieve system of anypressure prior to welding or removing parts from the system. Wokr safe!

[JSU]

iam saying lets say I have a reciever. I want to pressure test it to 350psi. I would first charge to 100psi then charge to 350psi? how do I know it wont rupture? cvs

[Redwolf]

You'll know it won't rupture at a lower pressure after it ruptured at a higher pressure :)

[chilly1]

Don't pressure test to 350 psi. Pressure test under water at the systems operating pressure plus 50% then set the system up with a cutout or pressure relief at 40% over pressure then you will not have to worry ever.
By testing under water if it does rupture the water will slow the projectiles to safer velocities, use a long hose and stay behind an armored shield...

[Redwolf]

Thank god I've met you :lol:

[chilly1]

There is not a need to pressurize to 350psi unless you are in a hurry and are certian the components can take it,,, If you are donig a final leak test pressureize to 100 psi and let it stand overnight, That is what I do for a final to make sure there is no leaks.

[gkiing]

On my compressor (tecumseh) it says DO NOT FIELD TEST PRESSURES ABOVE 150PSI in red printing..

Also if you test 350psi and you havent tested it before that has the potential for somethig to really make a bang.

[JSU]

350psi is about 225psi + 50% on a high side. So things on the low side only need 100psi?

[HawainPanda]

hmmm, sorry, just had to ask, wat does high side and low side mean? sorry for asking on your thread JSU

chilly1, how good are the electric testers? seems to me, it would be alot faster than spraying but are they accurate?

[JSU]

high side equals discharge before expansion valve low side equals suction side acter expansion valve.

[HawainPanda]

okey, thx jsu

[chilly1]

hmmm, sorry, just had to ask, wat does high side and low side mean? sorry for asking on your thread JSU

chilly1, how good are the electric testers? seems to me, it would be alot faster than spraying but are they accurate?

I have never had an electronic leak tester I trusted. The help find the leaks but can you be sure there are none , no not at all. The only way to be sure is to pressurize to 100 psi nitrogen for a day or so and if teh pressure does not drop then you can be sure it does not leak.

[JSU]

What about the diferance in temperature? doesnt that have an effect on the pressure in the system?

[gkiing]

I believe that since nitrogen has a very low boiling point (-172c) that a change in temperature would not mean a very significant change in pressure. However, when pressure testing with propane (r290, which I don't reccomend unless you have nothing else, even r22 is better) the pressures will often jump around 10psi or so between the temp differences of day/night. The unit im working on now I tested at 100psi with propane and at night it went down to 89psi, then back up to 101 the next day. I then had it properly tested when i got my dry N2, and the pressures didn't change at night or the next day.

[saratoga]

What about the diferance in temperature? doesnt that have an effect on the pressure in the system?

Does the Ideal gas law well enough at the pressures we're dealing with? I know it devates under extremes, but I'm not sure when it becomes significant. Most likely you could use it to correct for gas expansion.

P1 * T2 / T1 == P2 where P is pressure, and T is temp.

[gkiing]

yes, boyle's law and beer's law can be used to calculate the pressure/temperature change.