Air test instead of hydrotest
Air test instead of hydrotest
(OP)
hi dear friends,
in one of our projects, contractor requested to do Air test instead of hydrotest for Reactor and Regenerator. consultant replied shop hydrotest is acceptable but proper nozzle to be provided for drain the water.
which one is correct???
Thanks a lot
in one of our projects, contractor requested to do Air test instead of hydrotest for Reactor and Regenerator. consultant replied shop hydrotest is acceptable but proper nozzle to be provided for drain the water.
which one is correct???
Thanks a lot





RE: Air test instead of hydrotest
For pressure vessels either is acceptable. Pneumatic (air or other gas) tests are often specified when moisture or residual water is a problem.
Regards,
RLS
RE: Air test instead of hydrotest
RE: Air test instead of hydrotest
Post-construction hydrotests may be difficult to impossible due to several reasons including dealing with water contaminated by the residual process fluid, structural stability, foundation, etc.
jt
RE: Air test instead of hydrotest
RE: Air test instead of hydrotest
See Appendix A
http
RE: Air test instead of hydrotest
Can you explain your comment with regards to cryogenic service with a bit more detail. I do not understand the negative impact of a hydrotest (at reasonably warm temperatures for the purpose of the test) on a vessel in cryo service.
jt
RE: Air test instead of hydrotest
for R&R, normally the vessels are refractory lined.You do not want to test using water as it will damage the refractory lining.In this instance, pneumatic test should be specified.Be aware that during the pneumetic test the stored energy due to the compressability of the air used for the test is much higher and thus more damgerous than with water. For this reason, I have seen R&R specified with 100%RT, and the closing weld is done under more stringent conditions and nde tested thoroughly ("golden weld") in order to eliminate the need for further testing.
John
RE: Air test instead of hydrotest
What if it fails? There is a lot of energy that must be bled off (explode out) in compressed air.
Water, on the other hand, is non-compressible, so as soon as the failure occurs and a little water drains out, the water pressure immediately drops very low.
RE: Air test instead of hydrotest
Here is another one where an engineer what if himself, almost out of a job.
We needed a new 24" line in the piperack for natural gas. The mechanical engineer looked at the existing supports and said they would not hold the weight of an additional new 24" line full of water. NOW WHAT.
The conservative engineer specified that we uninstall the line (cut it into about 8 pieces) and lower it back on the ground rewelded it back, xray 10% and test it with water,then cut it up, put it back in the rack and weld it up and then do a 100% xray on the new welds. I tried to get him fired, it cost $200,000 vs a air test that would have run about $5000. Oh to top it off the line fed a cryogenic unit so it took 2 days to dry the line with N2 to a -80F dew point.
RE: Air test instead of hydrotest
Similar to your 24" line saga...A long 24" flare line with all new 15'+/- supports. Project engineering & management supported a pneumatic test to save money on the support system. The plan was to take all the necessary and appropriate safey measures during the test. Just before testing, some nervous nelly in the facility's management had enough stroke and trumped the projects plan. It took a lot of cranes to support that line. The couldn't be dumped and had to be transported (via truck) to another location.
Arg...
RE: Air test instead of hydrotest
http:/
see 4.5
Pneumatic test if you must,minimum risk in all cases,distance or shields.
RE: Air test instead of hydrotest
Seems to miss the point. The testing of a new Reactor (which is a pressure vessel) and designed probably to high pressure and high temperature, requires conformance to ASME VIII, UG 99. The pneumatic test is a leak test only, that's way the hydrostatic test is required in the fabrication of pressure vessels, refer below:
UG-99 STANDARD HYDROSTATIC TEST
(a) A hydrostatic test shall be conducted on all
vessels after:
The alternatives are for special conditions only, testing on site, large vessel and no water around, residual water reacting with the process, etc..
Cheers,
gr2vessels
RE: Air test instead of hydrotest
Hello again and I do not agree with you.
UG-100(2)"not readily dried". That is all one needs and according to the first post,may be the case depending on service. You may also exceed 1.1 MAWP if calculated for.
Check the Interps.,UW-50,and last paragraph/first column of the Forward.
RE: Air test instead of hydrotest
I am quite familiar with an accident at a shop where an inadequately trained,yet qualified individual,lost his life.
Enough said for test procedures and qualifications, which were in place, but not strictly followed. I vowed since that time, never again would I defend the use of a pneumatic in lieu of a hydro.
I knew that people are fallible, but now, it takes more than just words in a Code book to convince me that a pneumatic test in lieu of a hydro is acceptable. Unless you know for certain, and are familiar with the safety concious environment within the shop, and are present around those who will be conducting the test, don't readily allow for pneumatic testing in lieu of a hydrotest.
There are three kinds of people in this world; those who can count and those who can't.
RE: Air test instead of hydrotest
So the line AS INSTALLED had no pressure test, just 100% x-ray. What was the point of all that preceeding activity? Could have just x-rayed he whole thing in the rack :)
Regards,
Mike
RE: Air test instead of hydrotest
RE: Air test instead of hydrotest
I've looked at a lot of accidents involving static testing and in every case either the test design was shoddy or the execution didn't follow the design. I don't think that there is a third reason for "accidents" during static testing.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Air test instead of hydrotest
Thank you
RE: Air test instead of hydrotest
it was really a good discussion.
RE: Air test instead of hydrotest
Yep, hydrostatic testing is a lot safer than pneumatic testing, keep telling yourself that.
David
RE: Air test instead of hydrotest
Hydrotest is a great deal safer
Failure of pneumatic test can be catastrophic both to surrounding equipment and personnel
Hydrotest has stress relieving benefits
100% xray may not show porosity in welds - believe me, I've been caught out with this
As professional engineers, we all need to consider our actions, and asking for advice from others if key. There is a consequence however....when we ask for advice, sometimes it may not be the answer we want to hear, but we should be professional enough to assess and analysis the advice given.
Pneumatic or hydrotest?? My vote goes with hydrotest for 99% of the time. If everything else has been exhausted, maybe a pneumatic.....now about classifying the workmanship as a "golden weld"? This then becomes wholly driven by procedures and checks through the manufacture....ideal conditions, best welder, best ndt, non critical system (low pressure, water etc). If the duty is non critical, then a non tested closure weld may - depending on insurance requirements - be acceptable.
Regards,
nambutler
RE: Air test instead of hydrotest
RE: Air test instead of hydrotest
Usually it is a general practise that all the pressure vessels will be hydro tested in the field at the time of comissioning. Hydro test will be a better option.
Regards,
Aravind Sujay
RE: Air test instead of hydrotest
RE: Air test instead of hydrotest
Please Review ASME PCC 2 2006
RE: Air test instead of hydrotest
A fundamental point seems to be missing from the discussion - the purpose of a pressure test.
Why specificaly can't the OP's pressure vessel be hydrotested during fabrication? A reactor vessel isn't fabricated with a refractory lining, so why can't it be hydro'd before the lining goes in? IMO The extra benefits and confidence afforded by a hydrotest, definitely outweighs the short term concerns of drying the vessel out.
A pneumatic test wont get you the benefits (notch blunting, shake down, integrity testing etc) of a hydrotest and has substantially more danger involved - remember, we're testing an untested vessel for it's integrity - the potential stored energy can not be overlooked.
Australia's pressure vessel code includes an appendix to calculate the pneumatic stored energy and the the recommended exclusion zone required for a pneumatic test. If you post up the dimensions, I'll run the numbers. For kicks I sometimes work out the equivalent kg of TNT that a pneumatic test represents - it helps put things in perspective.
If in building a vessel I know that I must do a pneumatic pressure test (and that's rare), apart from many controls during the test, I also specify that the vessel is extensively NDE'd during fabrication. This helps increase the confidence level that there isn't a defect lurking that might cause the vessel to fail.
On the topic of testing and rerating lines, let me ask you this question. Using round numbers, say you have a pipe with 100psi DP, hydrotested to 150psi. Now the process dept need it rerated to 125psi but don't want to get the line wet - so hydrotesting is out. A 1.1DP pneumatic test is still within the original hydrotested envelope... would there be any benefit in a pneumatic test? Do you give the line carteblanche approval to operate at the new condition without any pressure test? Additional NDE??
RE: Air test instead of hydrotest
ASME PCC-2–2006, page 139 -141
Article 5.1, Appendix II
Stored Energy Calculations for Pneumatic Pressure Test
Article 5.1, Appendix III
Safe Distance Calculations for Pneumatic Pressure Test
Article 5.1, Appendix IV
Risk Evaluation Considerations for Pneumatic Pressure Test
Article 5.2
Repairs and Alterations Without Pressure Testing
RE: Air test instead of hydrotest
ASME PCC-2–2006, page 139 -141:
Article 5.1, Appendix II
Stored Energy Calculations for Pneumatic Pressure Test
Article 5.1, Appendix III
Safe Distance Calculations for Pneumatic Pressure Test
Article 5.1, Appendix IV
Risk Evaluation Considerations for Pneumatic Pressure Test
Article 5.2
Repairs and Alterations Without Pressure Testing