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Sensitivity Test as per 31.3

Sensitivity Test as per 31.3

Sensitivity Test as per 31.3

(OP)
I have a cryogenic pipe which should be pneumatically tested instead of hydro-tested.
the exclusion zone of the pneumatic test is quite high and in case of energy release it will cause a damage to the surrounding facilities.
as per ASME 31.3 guidance we should go for sensitivity test as per pressure vessel code V article 10.

the sensitivity test to be done at 25% of the design pressure which seems not sufficient measure to detect the leak.
some people advised to go for GOLDEN Weld better than sensitivity test.

Please advice.
Regards,

RE: Sensitivity Test as per 31.3

(OP)
I will provide more details if required!

RE: Sensitivity Test as per 31.3

You're doing a leak test, not a strength test.

Independent events are seldomly independent.

RE: Sensitivity Test as per 31.3

First off - why can't you hydro test it? There are many ways of dewatering and drying pipes - methanol, vacuum, dry / warm air blow through etc. air testing could easily introduce water unless you're really careful and at some point I asusme you would dry the pipe before introduction of your very cold liquid. Drain and vent points are very common on pipiing simply for filling and draining test water.

Second - you need to discuss all of this with the certifying / safety authority to make sure they are happy with whatever you come up with. There's no point in spending lots of time trying to do it another way if they won't accept it.

Any pressure will deteck leaks if you go round phsically testing with soap sprays - a bit basic, but it works. They won't get you a strength test.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: Sensitivity Test as per 31.3

tabuaisha,
I have been working on LNG projects for the past 8 years and we have successfully pneumatically tested hundreds of kilometres of cryogenic pipework.
If these piping systems failed we would have probably destroyed plenty of "surrounding facilities" but they still have to be tested.
If all required quality systems are in place from start to finish and have been complied with then you should have no concerns,
Cheers,
DD

RE: Sensitivity Test as per 31.3

In the USA NFPA 59A requires all methane lines to be radiographed or UT inspected in addition to leak testing. Pressure testing is required per 345. As such, the sensitive leak test per 345.9 could be performed subject to all of the added NDE specified therein, analysis and the Owner/Operator approval. As per DekDee we have pneumatically tested the cryogenic natural gas lines, all of which are 304L SS. I don't consider the carbon steel at -50 F "cryogenic"

You will need to review with the Jurisdiction and Owner.

RE: Sensitivity Test as per 31.3

There has been at least one incident in China resulting in several deaths during pneumatic testing of LNG plant piping. It should be everybody in the industry's concern.

Independent events are seldomly independent.

RE: Sensitivity Test as per 31.3

(OP)
Thank you for your esteemed replies.
As BigInch said there is a high safety concern about performing pneumatic testing. there is a fear of the released energy which might affect the existing facilities as well.
in addition in this LNG plant we have a lesson learned in using hydrotest in the cryogenic pipe. The 100% dryness Could not be guaranteed and a damage happened in the cryogenic heat exchangers.
I tried to summerise the code recommendation as following which is similar to what "weldstan" stated above but how relyable is that? That is my concern.

in ASME B 31.3 para 345.1
(Required Leak Test)
(c) Where the owner considers both hydrostatic and pneumatic leak testing impracticable, the alternative specified in para. 345.9 may be used if both of the following conditions apply:
"(2) a pneumatic test would present an undue hazard of possible release of energy stored in the system,"
345.9 Alternative Leak Test
345.9.3 Test Method. The system shall be subjected to a sensitive leak test in accordance with para.345.8.
345.8 Sensitive Leak Test
The test shall be in accordance with the Gas and Bubble Test method specified in the BPV Code, Section V, Article 10, or by another method demonstrated to have equal sensitivity.
Sensitivity of the test shall be not less than 10−3 atm•ml/sec under test conditions.
(a) The test pressure shall be at least the lesser of 105 kPa (15 psi) gage or 25% of the design pressure.
(b) The pressure shall be gradually increased until a gage pressure the lesser of one-half the test pressure or
170 kPa (25 psi) is attained, at which time a preliminary check shall be made. Then the pressure shall be gradually increased in steps until the test pressure is reached, the pressure being held long enough at each step to equalize piping strains.

ARTICLE 10 - LEAK TESTING
APPENDIX I — BUBBLE TEST — DIRECT PRESSURE TECHNIQUE
I-1000 INTRODUCTION
I-1010 SCOPE
The objective of the direct pressure technique of bubble leak testing is to locate leaks in a pressurized component by the application of a solution or by immersion in liquid that will form bubbles as leakage gas passes through it.
......

RE: Sensitivity Test as per 31.3

(OP)
the test media will be Nitrogen.

RE: Sensitivity Test as per 31.3

Big Inch,
I am currently working in Malaysia and I have previously worked in Thailand, China and the Phillipines.
Based on my exposure to safety standards and practices in these countries I would be extremely wary of going anywhere near a pneumatic test being performed in these countries.
However, IMHO if a piping system has been fabricated correctly, installed correctly and tested correctly there is no significant danger involved with pneumatic testing.
Cheers,
DD

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