Pressure Test of Nitrogen Cylinders 1

[ak1965]

We have replaced the valves of some Nitrogen Cylinders.

What kind of pressure test we can carry out on these cylinders?

Can Pneumatic or Hydro Test be done on these cylinders?

Will it go as per ASME Section VIII Div 1 ?

If yes, how to create pressure inside the cylinders?

 

[metengr]

In replacing the valves did you alter the original design pressure of the cylinders? If not, a pressure test is not required just because you replaced in-kind valves - unless you believe corrosion or other service related conditions have resulted in loss of wall thickness.

 

[ak1965]

Thanks Metengr,

Your version sounds very logical....! HT may not be needed..!

However, I feel that sicne the valve is a threaded valve, does it not make mandatory to hydro test the cylinder & new valve as an assembly??


Just a lateral thought...!

 

[metengr]

No. I would visually inspect the threads on the cylinder and if no visual damage is observed (corrosion, galled threads, loss of threads), install the valve.

 

[unclesyd]

i agree with the above post there is no problem changing the valve. there is big caveat in the valve has to a duplicate of the one that was installed by the manufacturer. There can be no modification or altering of the valves.

If these cylinder are on damage, from the people that fill the cylinder with N2 it is there responsibility to test the cylinder at some interval. The last inspection information is stamped into the cylinder near the top. Take the latest date.

Do a little search on "Compressed gases' and you will find a lot of information on the treatment and testing of said cylinders. The DOT did regulated these cylinders.

 

[hacksaw]

why are you repairing a N2 cylinder?

 

[ak1965]

@ hacksaw

This is not a weld repair, we just replaced the valve with a new one. we did nothing on the tank body.

Tanks are in sound condition and well protected by coating.

 

[Jimmer12]

If you are referring to a nitrogen compressed gas cylinder, like a welding tank, then they are not governed by the ASME. They are governed by the DOT, and require hydrostatic testing every 5 years.

The last hydro test date will be stamped in the shoulder of the cylinder, indicating month/year (01/09 for jan 2009), with the test facilities registration # in the middle, and if they are a DOT 3AA series tank (which will be also stamped on the shoulder), then the hydro test pressure will be 5/3's the working pressure. So on a 2400psi cylinder you'd have a 4000psi test pressure, which will be performed in a water bath hydro test.

The water bath allows them to measure the expansion of the cylinder at max test pressure, then measure the contraction after the pressure is released. If there is more then 10% permanent expansion, the cylinder is condemned.

Jim