Pneumatic Leak Test (when the design temperature is greater than the test temperature) 5

[FrancoBr]

During my work last week, I was asked about the possibility to change the hydrostatic leak test for pneumatic leak test.
The line condition is:
Fluid: Steam
Temperature: 650°F
Design Pressure: 275 Psig

At first the test was specified in accor with ASME B31.3 Hydrostatic leak test
345.4.2 Test Pressure
PT = 1.5 PRr

result: PT= 1.8P

If I want to change for pneumatic test, the ASME recommend in para.345.5.4 shall not exceed the lesser of (a) 1.33 times the design pressure.

If I change for pneumatic leak test, I will not get to represent the effect of temperature. This way I wont put my system in real conditions during the test.

So my question is:
In work conditions that I have high design temperature, I shouldn't do the pneumatic leak test?

Thank's in advance

 

[pennpiper]

You wrote:
"So my question is: In work conditions that I have high design temperature, I shouldn't do the pneumatic leak test?"

My answer is NO!!!

prognosis: Lead or Lag

 

[FrancoBr]

Pennpiper

Thank's for answer. I kept the hydrostatic due to security. But in cases where hydrostatic is not possible, how we do?

 

[pennpiper]

Define why hydrotesting is not possible.

prognosis: Lead or Lag

 

[MJCronin]

One of the common questions MBA managers use to "test" the young, inexperienced engineering staff is the old pneumatic test question.

Please do not fall into this trap......

You should keep in mind that ALL PIPING INSTALLERS WOULD MUCH RATHER PNEUMATICALLY TEST THAN HYDROSTATICLY TEST ! !PNEUMATIC TESTING IS QUICKER, MORE SIMPLE AND CHEAPER FOR THE INSTALLER.

This is especially true if the PIPING INSTALLER HAS YOUR BOSS, THE MBA....ON HIS SIDE ASSIGNING ALL RESPONSIBILITY TO YOU ! !

Google "pneumatic testing" piping, vessels and "accidents"....... read the many articles, heed the advice

....use the image searches also !

This issue has been brought up many times on these fora...... have you searched for other threads on this topic ?

 

[FrancoBr]

Hello, MJCronin.
Thank's for your answer.
I hadn't searched for other threads on this topics. Is my first time on forum.
I will look for the same topics. Agree with you the boss always prefers the pneumatic test independent of the case, with us assigning all responsibility.

Pennpiper.
You're right, always is possible use hydrostatic test. The piping installer said me that the circuit of test is too big for use hydrostatic and will be more complicate do the test.

I kept the hydrostatic.
thank guys

 

[moltenmetal]

Hydrostatic testing is always safer and should be done first if there are not good reasons to preclude it. Good reasons would include a process or associated equipment which is so water- or other nonhazardous liquid-sensitive that a liquid-filled test cannot be done without damage. A steam system would, in my opinion, very rarely qualify.

Hydrostatic testing is sometimes followed by gas leakage testing, where the hydrostatic test greatly reduces the risk of failure under the lower pressure pneumatic leak test.

We do routinely pneumatically test systems which are of very limited product of pressure times volume (the product being stored energy which might be released during a failure), and of a physical configuration that makes filling with water (and complete emptying afterward) very difficult. Complete filling is necessary to make a hydrostatic test safe AND sensitive.