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Anonymous Poster #1

Why Helium Leak Test is Required for Hydrogen Services?

02/25/2016 7:03 AM

Hi 2 all,

i was going throught internet for helium leak test for hydrogen service

whether its compulsory to use for hydrogen service

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#1

Re: Why Helium leak test is required for hydrogen services

02/25/2016 7:15 AM

Think about it. Think about it carefully. If the equipment is under test and some part fails the test due to a leak, what would be the preferable fluid that leaks:

  • Hydrogen, which is flammable, or
  • Helium, which is not flammable

eh?

https://en.wikipedia.org/wiki/Hindenburg_disaster

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#2

Re: Why Helium leak test is required for hydrogen services

02/25/2016 7:37 AM

Molecular size is important too. I think helium is smaller than H2 (stable hydrogen). Plus, I think helium is easy to detect with handheld devices.

Drew K

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#3
In reply to #2

Re: Why Helium leak test is required for hydrogen services

02/25/2016 12:54 PM

Hydrogen is very easy to detect with small handheld devices.

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#6
In reply to #3

Re: Why Helium leak test is required for hydrogen services

02/26/2016 2:57 AM

About 20 years ago I was giving a verbal test to someone who wanted to use LPG in an lunchwagon and needed to pass the test.

The final question that I asked was "After connecting the tank(of LPG) how would you determine if the connection was not leaking?"

Due to what I thought was a language barrier he couldn't answer, so I repeated the question using slightly simpler wording.

His answer: "Use a match?" He obviously failed, and that's why there were no further questions.

BTW at that time my daughters about 5 and 9 years old would come out with their bubble soap whenever I connected a new tank to the gas barbecue grille we had.

Not being snarky, just that your reply brought up a long forgotten memory.

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#8
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Re: Why Helium leak test is required for hydrogen services

02/26/2016 12:42 PM

Well, no snarkiness taken as my post was intended to be tongue-in-cheek.

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#10
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Re: Why Helium leak test is required for hydrogen services

02/26/2016 1:17 PM

I figured that, just that your reply brought back an old memory.

Humor appreciated.

Casper

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#4

Re: Why Helium leak test is required for hydrogen services

02/25/2016 2:32 PM

(from memory) I believe it depends on the industry and application, some still allow flammable process gasses to be use for blow downs in piping systems (eg-natural gas).

HOWEVER this has caused a number of near misses and deadly explosions and I am not aware of any industries or systems where hydrogen is compulsory over an inert substitute such as helium (perhaps if the system was a fully closed loop system).

Perhaps some very specialised systems allow hydrogen leak testing, but you would need to check the standards regarding this and they should clearly indicate such and describe how it is to be done safely in the event inert gas leakage .

What's the application exactly?

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#7
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Re: Why Helium leak test is required for hydrogen services

02/26/2016 3:02 AM

I would also cite the wide range over which hydrogen flashes (4-98%?)as well as the fact that a hydrogen flame is almost invisible.

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#11
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Re: Why Helium leak test is required for hydrogen services

02/26/2016 1:49 PM

I believe it was 4% LEL and 96% UEL.

We had to do testing with silver-zinc battery housings (pressure vessels) to make sure we had a good nitrogen purge of the evolved hydrogen and oxygen. Used O2 sensors from MSA and flammable gas sensors from Crowcon Detection Inst.

We used hydrogen when we were characterizing the purge system. The safety people were going all bonkers over this. The irony was on the other side of the high bay, there was a welding room with oxygen acetylene tanks. Way more dangerous than the hydrogen. But as soon as you request use of hydrogen, all you get are "oh, the humanity" knee-jerk reactions. We had to have our company fire marshall present for all tests.

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#5

Re: Why Helium leak test is required for hydrogen services

02/25/2016 11:01 PM

Helium--

The Helium leak test, The leak detection method uses helium (the lightest inert gas) as a tracer gas and detects it in concentrations as small as one part in 10 million. The helium is selected primarily because it penetrates small leaks readily, is inert and will not react with the test piece and also has a natural low quantity in air making detection less complicated. It is possible to detect leaks as small as 5.10-10 pa m3/s in vacuum mode and modern digital machines can detect 5.10-10 pa m3/s in sniffing mode.

  • Usually a vacuum inside the object is created with an external pump connected to the instrument.
  • Alternatively helium can be injected inside the product while the product itself is enclosed in a vacuum chamber connected to the instrument. In this case Burst and leakage tests can be combined in one operation.
  • Hydrogen--The Hydrogen sensor, The object is filled with a mixture of 5% hydrogen/ 95% nitrogen, (below 5.7% hydrogen is non-flammable (ISO-10156). This is called typically a sniffing test. The handprobe connected to the microelectronic hydrogen sensors is used to check the object. An audiosignal increases in proximity of a leak. Detection of leaks go down to 5x10-7 cubic centimeters per second [1]. Compared to the helium test: hydrogen is cheaper than helium, no need for a vacuum, the instrument could be cheaper but is not as sensitive as a helium leak detector so will not find smaller leaks.
  • HeliumDetects smaller leaks, more sensitive, inert gas, can detect 1 part in
  • Hydrogen-Cheaper than Helium, no need for vacuum, can be used in small concentrations below the LEL for H2, won't find smaller leaks, not as sensitive, instrumentation cheaper,
  • etc.https://en.wikipedia.org/wiki/Hydrogen_leak_testing
  • Which to use is up to the customer, the standard writer, the compliance organization and the builder. Contact them and find out from them why it is done either way. Don't waste your time with a bunch of autonomous creatures that call themselves engineers or "fans of engineering". Find out from the sources why it is done the way they want it to be done.
  • First place to start is to spend some more time to Google subjects more relevant to the testing processes.
  • Good Luck, Old Salt
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#9

Re: Why Helium Leak Test is Required for Hydrogen Services?

02/26/2016 12:58 PM

We never did helium tests for hydrogen. I've seen helium tests for silane but that is much worse than hydrogen. If you're indoors it might be a different animal but outdoors that seems like overkill. Test with nitrogen and soapy water for flanges and other equipment that was gotten into and be done with it.

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