Pneumatic Proof testing
Pneumatic Proof testing
(OP)
I have 6000 psi 1/4" S.S Helium supply line for a test lab that was only hydrostat pressure tested to 6750 psi. The facility contractor should have been proof tested this to 1 and 1/2 times, or 9000 psi. The system is already installed in place and it is not feasible to perform another hydro. For a pneumatic proof test, in place of a hydrostat, I have seen test pressures anywhere from 10% to 25% over MEOP. I do not have a latest copy of ASME 31.1 or 31.3. Does anybody know what the test pressure should be and how long I should hold that pressure? And if only 110% is needed for a pneumatic test, do I really need to perform the proof test again?





RE: Pneumatic Proof testing
PER B31.3-1996 SECTION 345 THE TEST PRESSURE FOR A PNEUMATIC
TEST IS 110% OF THE DESIGN PRESSURE. ASSUMING YOUR SYSTEM HAS A DESIGN PRESSURE OF 6000PSIG 100Deg F THE TEST PRESSURE WOULD BE 6600PSIG.
SINCE IT WAS TESTED AT 6750PSIG A NEW TEST WOULD BE UNNECESSARY.
A HIGHER TEST PRESSURE MAY BE SPECIFICE BY THE DESIGN ENGINEER OF THE SYSTEM BUT B31.3 REQUIRES ONLY 110% FOR A PNEUMATIC TEST AND 150% FOR A HYDROSTATIC TEST OF THE DESIGN PRESSURE.
RE: Pneumatic Proof testing
RE: Pneumatic Proof testing
RE: Pneumatic Proof testing
RE: Pneumatic Proof testing
For hydrostatic tests there is a restriction per B31.3. For pipe systems at elevated temperatures the allowable stress at test temperature(St) and the allowable stress (S) at design temperature (Per Table A-1) should be ratioed and multiplied by 1.5 and the design pressure to determine the test pressure. St/S must not exceed 6.5.
RE: Pneumatic Proof testing
GTD
RE: Pneumatic Proof testing
If not specified properly the contractor may have installed seamed tubing, due to lower cost and may had to hydrotest the line at lower pressure due to a lower pressure rating of the seamed tubing.
This may be a wild idea, but experienced the installation of seamed tubing myself, while we expected seamless tubing.
It does not hurt to check the type and pressure rating of the installed tubing.
Krossview/OK
RE: Pneumatic Proof testing
You and i know it will hold more, but its not what we know, its about what we can prove on paper! And as for allowable maxes, sec I for all other section is 90% of yeild strengh ( 2% offset) at test pressures. also 137.1.4 at no time during the test shall and part of the piping system be subjected to a stress greater than that permited by 102.3.3(B) During pressure tests performed in accordance with 137 the circumferential (hoop) stress shall not exceed 90% of the yield strenght (2% offset) at test temp. blah blah. the sum of long stresses due to test pressures and live and dead loads at the time of test, excluding occasional loads, shall not exceed 90% of the yield at test temp.
anyways i hope that helps.
RE: Pneumatic Proof testing
1.2 for pnue.
1.5 for hydro.
RE: Pneumatic Proof testing
double check the Material data sheet.
RE: Pneumatic Proof testing
There are serious restrictions and limitations required by code when pnuematic testing . See for example Sect VIII div 2 par AD-151, AD-151.2, At-400, AT-410, AT-411.
Pneumatic testing has a much greater potential for catastrophe than hydrotest if pressure vessels are involved.
Be certain fo code limitations and make darn sure the test temperature is above any ductile limits of the weld zones.