Commsioning - Hydrostatic Vs. Pneumatic Testing 3

[Ollie42]

We manufacture pressure vessels and execute 3 integrity/release tests ahead of shipping the units.

1. Hydrostatic Testing 1,43 x design pressure (30 min)
2. Vaccum Test (Pull Down to full vacuum)
3. Helium Leak Testing (8 Bars Helium)

At commisioning the customer executes a leak test using either air or nitrogen, as media for testing. (Pneumatic Testing)

Pneumatic testing should be done at a lower pressure level, given the viscosity and surface tension of air is much lower for air/N2 than water, to simulate the same leak detection level as for the factory hydrostatic test already executed.

At what level of pressure should one accept this pneumatic leak test to take place, considering the factory hydrostatic test has been executed at 1,43 x design pressure ?

Best Regards Ole

 

[r6155]

And the code is?

Regards

 

[0707]

All the tests you mention are regulated by the codes.

Tell me the code I will tell you my opinion.

luis

 

[moltenmetal]

Once a hydrotest has been completed, a confirmatory pneumatic test done with air or other inert gas, at no more than 1.1x MAWP is a fairly low hazard additional activity- unless new modifications have been made. But with all tests, the test must be designed and executed properly.

It is also important not to confuse leakage tests with pressure integrity tests.

Others are correct: you need to identify the code to know for sure.

 

[SnTMan]

Presumably it is the bolted joints that are of interest. If so I'd ordinarily find 25 psig sufficient. A post-construction Code would seem to apply.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

With ASME VIII pressure leak test shall be performed prior to Hydrostatic Test.
Pressure-leak test shall not be at a pressure exceeding 25% of the Design Pressure.

Regards

 

[SnTMan]

r6155, VIII, 1? If so, can you cite please?

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

@ SnTMan
ASME VIII Div. 1 UG-99 .If you do the leak test after the hydraulic test and detect a leak it may need to be repaired by welding, then you have to repeat the hydraulic test.

ASME V: see leak test for the 25% of design pressure

Regards

 

[Ollie42]

Code is PED

 

[0707]

"Pressure Equipment Directive PED 2014/68/EU
Commission's Working Group "Pressure"
Guideline related to: Annex I sections 3.2.2 and 7.4

Question If the hydrostatic pressure test required by Annex I section 3.2.2 is
replaced by a pneumatic pressure test because filling with water is
harmful or impractical, what value has to be used for the pressure test?


Answer Either the values given in Annex I section 7.4 are to be used for the pneumatic
pressure test or the manufacturer has to achieve an equivalent level of safety
using other appropriate means.See PED Guideline H-02.


Reason

Note 1 Whether the test is pneumatic or hydrostatic, when the value of the pressure
deviates from the value of Annex 1 section 7.4, additional measures must be
applied to verify the pressure containment aspect including tightness (see PED
Guideline E-03).

Note 2 Attention is drawn to the fact that pneumatic testing can be highly dangerous.
Reference should be made to the appropriate national authorities for regulation
or guidance on the procedures to be followed."

https://www.weka-manager-ce.de/wp-c...68-eu-other-essential-safety-requirements.pdf

luis

 

[XL83NL]

Code is PED

Wrong, that's incorrect. The PED isnt and can never be a design code.

What is your design code?

Huub
- You never get what you expect, you only get what you inspect.

 

[SnTMan]

We are off the track here. This is a post construction activity.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Ollie42]

Design Code EN 13445

 

[Ollie42]

Let me update my question......or rephrase

Plate Heat Exchanger with design pressure 16 Bar.
This unit will be tested in the following way at our facility.

Test Test Pressure Tracer Medium
Factory tests Hydrostatic Pressure/Mechanical Test 22.8 Bar Water
Factory tests Vacuum 1.00E-05 Pa Air
Factory tests Leak 8 Bar Helium



The customer requests to make field test at same level as the hydrostatic test (22.8 Bar) , however using Nitrogen or Dry Air as tracer gas.

Customer Field Tests Leak 22.8 Bar Air
Customer Field Tests Leak 22.8 Bar N2


We are 100% sure the units has the required mechanical strength for the 23 Bars from the hydrostatic test , however both viscosity and
surface tension are forces that will prevent water from escaping through even a very small hole,
forces that do not prevent dry air/nitrogen from escaping through the same size hole.

Therefore we need to compare our Helium leak test to the customer pneumatic test.
Pneumatic testing with Nitrogen or dry air as tracer gas, at 22.8 Bar, versus a Helium leak test at 8 Bar ?

Therefore can we consider the 8 Bar Helium test being superior in level of leak detection, to the 23 Bar Dry Air / Nitrogen. ?

Are there any kind of co-relation in terms of factors or numbers, testing Helium vs. (Dry Air / Nitrogen) for the pressure?

 

[0707]

XL83NL

Don´t be annoyed!

"The Pressure Equipment Directive (PED) is a European legislation aimed at removing the technical barriers to trade relating to the supply of pressure equipment throughout Europe.

It is based on Essential Safety Requirements (ESRs) that govern design, manufacturing, inspection & testing.

Pressure vessels made for US companies follow ASME
while those destined for Europe are governed by PED.

The latter is mandatory for the European Union. The documentation requirements for PED are a bit more stringent. There are also different costs associated with the various PED categories & modules depending on volume, pressure & hazardous/non-hazardous gas / fluid.

There are no major technical differences between the two system requirements for material testing.

But while the two system designs are slightly different, they both provide “good engineering” practices assuring the production of sound pressure equipment."

Ollie42

"Pneumatic tests are potentially more dangerous than hydrostatic because of the higher level of potential energy.

Pneumatic tests may be performed only when at least one of the following conditions exists:

 When pressure systems are so designed that they cannot be filled with water.

 When pressure systems are to be used in services where traces of the testing medium cannot be tolerated.

Using a pneumatic test instead of hydrostatic requires approval by the pressure systems program manager. In addition to a justification, a piping schematic for pneumatic pressure test is required.

To find leaks, a low pressure (30-50 PSI) air test is just as effective as high pressure (150 PSI) water test."

luis

 

[James Zilinger]

where are you all getting the calculation for this, example if i Have a Pneumatic test pressure of 125 psi what would be the equivalent Hydrostatic test? what is the formula for this?

thanks in advance

 

[Dhurjati Sen]

@0707

A pink star for you sir.

Why? Apart from being an expert, you are a nice guy.

Warm regards.

DHURJATI SEN

 

[DriveMeNuts]

Upon successfully completing the Hydro pressure test, the vessel is deemed to have adequate structural integrity. Therefore there is no issue with conducting a pneumatic leak test at or below MAWP.
However, your proposal of pneumatically pressurising the vessel above MAWP, up to hydrotest pressure where the vessel is potentially on the cusp of exploding, and then climbing over this potential pneumatic bomb to observe for leaks is insane and phenomenally dangerous.

 

[r6155]

Be careful. Pneumatic pressure test is to verify structural integrity. Leak test is not a pressure test.
Please see my comment on 31Aug 20.

Regards

 

[FacEngrPE]

Pneumatic proof testing is highly discouraged by ASME PCC-2
Equations have been published in Mandatory Appendix 501-II and III relating volume and pressure to the safe distance - with respect to the rupture blast pressure, and equivalent mass of TNT explosive.

The equations are built into this calculator.

https://www.piping-world.com/safe-distance-and-stored-energy-calculator-pneumatic-test

As many commenters above state, Pneumatic proof tests are not "safe". Keep people far away.