Nitrogen Leak Test Procedure

Helium leak checking does a much better job of identifying where a leak exists for vacuum chambers.

I suspect that nitrogen is used for some leak testing in some application somewhere just because of the abundance of this gas available and thus its low cost. But you give us nothing to even make a speculation about how one uses this ubiquitous gas.

By searching on internet I came to know this:

- Nitrogen/Helium mixture(99% Nitrogen/ 1% Helium) is used for some rare cases.

- otherwise only Nitrogen is used for all other situations.

I found nowhere that Helium could be used individually.

Thanks,

OK, if you don't want us to help you that's fine. Don't answer any requests. Just go away, baffled.

:|

I know nothing about the practicalities of leak testing, but I like to be informed. I understand that the oxygen content of air would make it undesirable in some contexts, so my first guess would have been nitrogen. What makes helium preferable, since it is a lot more expensive?

Helium is the smallest atom/molecule. If one has any leakage path into your vacuum chamber these little guys will find it. So if you cannot pump down your chamber to the vacuum numbers predicted, a combination of a roughing and turbo pump feeding a mass spectrometer optimized to look for helium atoms pumps down the chamber. A small stream of helium is then gently and slowly blown over suspected leak points of the chamber. If the spectrometer reads a spike in helium one now knows where a leak exists that needs some repair. Removing the helium stream and waiting for the pumps to clear out the helium inside the chamber will now allow for other possible leak points to be tested. Typically very little helium is used in this test but obviously this will change on the outside surface area of the chamber and the number of leaks present.

Where nitrogen leak test is applicable/required? When specified.

- How to perform this leak test ? With pressurized Nitrogen.

The total lack of knowledge and understanding on your part makes one hesitant to arm you with any pressurized gas, nor the knowledge of how it is used.

If you can't find the answers by searching, you don't need to know.

Since you've begun the education, one also needs to determine if the test is a test of "effusion", or "permeation" of the gas.

Another detail omitted by the OP.

Are we testing plumbing or a membrane?

I'll fade away now, as I have to watch the birds eat their breakfast now.

Thanks for answering my first question. Second question is regarding Nitrogen leak test procedure.if performing leak test on process piping joints (flanges,valves,nozzles),should I proceed one pipeline as a whole,or in segments,what would be the best practice. Thanks,

The best practice is to look at your system and then establish a test plan with consideration of the test requirements of any standard applicable.

First, there is more about pressure testing than can be said in a few brief comments.

Nitrogen is a common test medium because of economy and not many undesirable reactions with subsequent process substances. (That must be checked, though.) Nitrogen is commercially available in cylinders of about 2300 psi. You may need an outlet pressure regulator to keep your piping from being over-pressurized (or at least a well monitored pressure gauge).

Progressive testing by sections is a good idea; some leaks may be found before pressurizing the whole piping system.

Bit of reading here for you.

· ASME B31.1. Section 137.5.5

· ASME B31.3. Section 345.5

· ASME VIII Div 1. Section UG-76 & UW-100.

· ASME PCC-2 Repair of Pressure Equipment and Piping

· AS 1210 Pressure Vessels. Section 5.11.

· AS/NZS 3788:2006 pressure equipment - In service inspection. Section 16

· AS 4037 Pressure Equipment - Examination and Testing. Section 18.

· AS 4041 Pressure Piping. Section 6.8 and U.

· AS 4458 Pressure Equipment - Manufacture. Section 20.

The The most important thing about nitrogen/pneumatic testing is the stored energy and safety distance.

The stored energy for the pneumatic test is calculated on the test pressure and volume

Using AS/NZS 3788:2006 pressure equipment - In service inspection Section 16.2

Good lucky.

Check the web for a freak incident in Brazil, a tank was blown off its foundation bolts and ended up 4 stories up.

If you are testing process piping, except for vacuum piping, the most frequent method of testing is the good old soap and water test. A solution of about 10-25% liquid dish washing soap in water in a spray bottle or other suitable container, such as a lab wash bottle, is filled and the solution placed on the fittings and/or piping. Any bubbles indicate a leak. Nitrogen is one of the least expensive compressed gases so no attempt is made to recover it. Being relatively inert it seldom reacts with other chemicals. Cheap, easy, and readily available solves the problem.

If this is being done in the low temps of winter and the solution freezes, add a little ethylene glycol (anti-freeze) to the solution. Add until the solution no longer freezes.

Good Luck, Old Salt

Nitogen and helium testing are used to detect leaks in the flanged joints.

(tighteness verification)

It is a very sensitive test and is used when the product is flammable, corrosive or poisonous.

Usually it used in refineries and petrochemical during the pre-commissioning and commisionig phase..

The flange joint must be seal with adhesive tape. And drill a small hole to enter the sensor of the equipment used to detect nitrogen or helium.

WP

Generally, one does not use nitrogen in leak testing of surface condensers that operate in a vacuum on the condensate side. One uses pure helium. Helium is emitted from a small tube around the area(s) where the leak is expected, and then detected on a mass spectrometer connected to the vacuum exhausting system, or other convenient point. In this way, the locale of the leak is ascertained, and can then be isolated further, and the problem corrected. You will no great success using nitrogen, in such a configuration, as nitrogen is already leaking through as fast as it can.

If you are referring to a pressurized test of a vessel to assure sealing, then that is a completely different scenario. That is typically a hydrostatic test, and as the name implies, one applies pressure of a gas that is inert to the situation (nitrogen), and observes pressure over time. To pass the test, vessel must not leak down more than a specified % of applied pressure in the specified time.