Modifications after Hydrostatic/Pneumatic Test
Modifications after Hydrostatic/Pneumatic Test
(OP)
We have a piping system being built in accordance with B31.3. Due to the layout, we must remove a flanged spool to get our test apparatus in. After we test the piping and replace the spool do we need to retest the two flanged joints? We have similar cases with union joints.
My thinking is that we could consider it a minor addition to replace the spool and waive retesting based on 345.2.6 (with the owner's approval, of course).
Is this common industry practice? We don't have any welds to make the golden weld and we did not design in any test ports for the leak test. The fluid service category is M, but since M345 states that 345 applies in it's entirety I would think we could still do this.
Any thoughts are appreciated.
My thinking is that we could consider it a minor addition to replace the spool and waive retesting based on 345.2.6 (with the owner's approval, of course).
Is this common industry practice? We don't have any welds to make the golden weld and we did not design in any test ports for the leak test. The fluid service category is M, but since M345 states that 345 applies in it's entirety I would think we could still do this.
Any thoughts are appreciated.





RE: Modifications after Hydrostatic/Pneumatic Test
RE: Modifications after Hydrostatic/Pneumatic Test
jt
RE: Modifications after Hydrostatic/Pneumatic Test
jte - The spool has not been hydrotested for code compliance. We need to break into the system to get our apparatus in to do the code test (it is actually pneumatic). So we will have two flanged joints that are not tested. In fact, there are additional joints that are disassembled and realigned for the test set-up so we will have multiple untested joints.
I realize this is not the best practice, but unless it is a code violation I can't get anything done about it.
The plant is not yet in service so this would not be maintenance (which is exempt from B31.3).
RE: Modifications after Hydrostatic/Pneumatic Test
Remember - for a code pressure test, you're hydrotesting the welds and gross structural integrity of the pipe and fittings, not the bolted flanged connections.
jt
RE: Modifications after Hydrostatic/Pneumatic Test
I must humbly disagree with your interpretation of the code test. You are not testing gross structural integrity, but rather checking for leaks. 345.1 states that “Prior to initial operation … each piping system shall be tested to ensure tightness…” Also, you are required to check everything, not just welds and fittings. 345.2.2 (a) states that “… all joints and connections shall be examined for leaks.” At least this is my interpretation.
Thanks again for your thoughts.
RE: Modifications after Hydrostatic/Pneumatic Test
Yep, only equivalent to around 30 lbs of TNT (unless I ran the numbers wrong). Min distance for personnel should be 155' and at that perimeter you can expect glass windows to fail. At a bit below 100' you can expect eardrums to rupture; ~50' you can expect lung damage.
jt
RE: Modifications after Hydrostatic/Pneumatic Test
I don't have ASME PCC-2 and a copy isn't available at our library, but here is the equation I always use based on adiabatic expansion:
E = (k)/(k-1) * (PV) * [1 - (P/atm)^((k-1)/(k))]
Where:
P = test pressure (Pa)
V = volume (m³)
k = ratio of specific heats (1.4)
atm = atmospheric pressure (101325 Pa)
1 kg TNT = 4184 kJ
Running those numbers I get less than half a pound of TNT.