Hydrotesting of pipeline

what is called air content determination while pressurization of water in pipeline hydrotesting?
why it is necessary to determine while pressurization?
what happen if we won’t do???

Air determination, we never heard before.
Just known test temperature record and pressure test for hydrotest.
Pneumatic test may use dried air, nitrogen or argen.

Hello @BINH_VT.

You may confuse his question.
Is it necessary to extract internal air of pipeline during raising pressure?

Yes, internal air should remove to keep stable during pressurization and at holding pressure. It also prevent drop down pressure during test.

That is what?
Why dont ask how to remove trapped air during test?

Yes, the question should be cleared.
Trapped gas may unstablize pressure test due to air compresses alot more than water.

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It is required leak test for valves, E&I equipment when cleaning internal pressure.

sir, my question is during hydrotesting of pipeline,as per the itp we have to found air content determination using some formulas.and the value should be less than or equal to 0.02%.we aware trapping of air will leads to unstable of pressure.my questio why should we find these values and why it should be less than 0.2?

Please specify test medium?

we are using water…

This requirement may specific in project spec.
I am not sure this requirement from where in your spec, but you also find out in ASME B31.12 or ASME B31.8 which standard application.


which standard u read this tolerance 0.02%.

Entrained Air
4.4.1 Field DV/DP
Before the test section is under full test pressure, a field value of DV/DP
should be obtained. This value of DV/DP can be compared with the
theoretical value of DV/DP calculated under section 3.5 (completed during
pre-test calculations). A field value of DV/DP that is smaller than the
theoretical DV/DP indicates an incorrect pressure reading, incorrect
DV/DP calculation, or incorrect measurement of the volume under test. A
field value of DV/DP that is greater than the theoretical DV/DP indicates
the presence of entrapped air or other gas in the pipe section.
4.4.2 Obtaining Field DV/DP
During initial pressurization, the test section should be pressurized to
approximately 50 psi and allowed to stabilize. Take an accurate pressure
reading. Then bleed approximately 10 psi and allow the test section to
stabilize. Take another accurate pressure reading. Carefully, measure the
volume of the fluid that was bled and convert this to gallons if necessary.
Take the volume bled and divide this number by the difference in the
pressure readings. This is the field value of DV/DP.
CSLC-MFD 12-03-03
4.4.3 Acceptable DV/DP
The CSLC provided hydrotest calculation spreadsheet determines the
acceptable DV/DP range that corresponds to a volume of air that is 1% by
volume of the test section. Results that fall outside the range when
calculated by the spreadsheet indicate the existence of a significant
volume of air in the test section. (A common sign for significant entrained
air will be difficulty in initial pressurization.) In these cases, it is
recommended that the test section be bled of air at a high point or the line
be refilled, then re-check the field DV/DP.