ASME B31.3 Hydrostatic Test pressure for valve

[Chap123]

Hello guys,

Im checking process of piping system mounted on a skid.

It is LPG transloading Package.Our client performed hydrotest for 1 hour at 240 psi with valves in open open position on piping.

Im confused does it meet ASMEB31.3 requirements.

What is the maximum hydrostatic test pressure for valves according to ASME B31.3?

We are using 300# fange class rating and min hydrostatic test pressure of that class is 1110 psi.

My question is why client used 240 psi for valves in open position? Any provision im ASME B31.3 advice anything on that?

 

[Dhurjati Sen]

Dear Chap,

Check if the pressure test that was carried out was for the skid that includes the piping as well as the valves.

The valves need to be pressure tested separately. API 598 comes in handy.

DHURJATI SEN

 

[mk3223]

It sounds that the valves, tested at 240psi, was separate items from your skid piping. is it correct?

If the valves outside the skid, your client may determine the test pressure of the whole system as B31.3 compliance, which may be lower than the skid test pressure of CL300.

 

[LittleInch]

"does it meet ASMEB31.3 requirements". I don't know - you haven't given us any real information such as the design pressure and temperature.

~ B31.3 is normally to test at 1.5 x MOP. If 240 psi is 1.5 X MOP then the answer is yes.

I'll give you fully open is not normal, usually you open valves half way.

"What is the maximum hydrostatic test pressure for valves according to ASME B31.3?"
B 31.3 doesn't have a test pressure specific for valves. All items within a piping system exposed to pressure need to be suitably rated to meet the Design pressure / MOP.

"We are using 300# flange class rating and min hydrostatic test pressure of that class is 1110 psi." err no. Class 300 flanges are one thing, the bit between the flanges can be rated to anything. However normally class 300 valves will be designed to handle pressures up to the relevant class 300 temperature pressure rating as specified in the relevant valve design code.

"Why has client used 240 psi?" I don't know for sure, but my guess is because the Design pressure MOP of the system is 160 psi and therefore the test pressure only needs to be 240 psi.

Your client appears to have used class 300 valves where class 150 valves could be used, but that's their problem presumably.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Chap123]

The spools are fabricated and hydrotested per the line list.

Once that’s complete they install the snappy joe valves and do an additional leak test on the spool to 240 psig because the snappy joe pressure rating is not as high.

Should not be a leak test as per pressure rating of the spool?

 

[LittleInch]

what's the design pressure / MOP of the spool?

Just because you have certain items which have a higher maximum rating, doesn't mean you need to test the entire system to that pressure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GD2]

Chap123,
In a piping system, the system will be made of many piping elements in addition to the pipe.
The hydrotest pressure is determined by the weakest component/element in the system. So you need to make a list of all the piping elements and it's design pressures.
Once done, the test pressure = 1.5 x Design Pressure (of the weakest element) x Stress Ratio (ST/S), where ST is the basic allowable stress at test temp, S is the basic allowable stress at design temp. ST/S = 1, if the design temp is below the test temp.
Both ST and S can be found in Table A-1 of B31.3. B31.3 limits the stress ratio to 6.5.

Hope it helps.



Ganga D. Deka, P. Eng
Canada