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chemi-cool
27-08-2004, 09:47 AM
I have just heard from a friend that Helium is used for detecting the smallest leaks in a system.
The system evacuates and filled with Helium up to 15psi and the leak is detected with th regular electronic leak detector.

Any comments?

Chemi

Peter Croxall
27-08-2004, 10:14 AM
Hi Chemi,
Are you sure that it is an electronic leak detector and not an ultrasonic leak detector? :confused:

donhoban
27-08-2004, 11:16 AM
Helium was used more by manufacturers previously because the detector was hugely expensive, however I believe cheaper detectors have become available in the last few years.

Helium doesn't detect smaller holes, however it does show leaks more quickly than standard leak tests, and that's why it was advantageous to manufacturers of coils who could process their production more cost effectively

chemi-cool
27-08-2004, 01:06 PM
Hi donhoban.

Isn't the molecule of Helium smaller, allow the gas to come out in smaller holes then refrigerants?

Peter, I haven't a clue but ultrasonic detector is very uncommon with fridgy's.

Chemi

donhoban
27-08-2004, 02:26 PM
Isn't the molecule of Helium smaller, allow the gas to come out in smaller holes then refrigerants?


As I understand it, bearing in mind, I'm an engineer,not a phyisicist or chemist - molecular size of helium is about 10-10m or 0.0000000001 meters

Say we assume the leak is 1/1000 of a mm across - we'd still potentially fit 1000 molecules of helium across the gap at any one time!

So really, unless we start dealing with monster molecules, I don't think the relative size difference between helium and refrigerant is important.

I could of course be wrong :)

chemi-cool
27-08-2004, 02:38 PM
Hi donhoban.
From what I've heard, this is why Helium is being used.

I dont see any other reason.

Chemi :)

Argus
27-08-2004, 02:57 PM
Helium has been used for many years in certain production methods where a high degree of system tightness is demanded. Typically it could be used for measuring the porosity of high end spec castings.

The ?detector? as such is a mass spectrometer. Despite its very high level of efficiency it is also potentially the most expensive because of the equipment needed.

I saw it used by Carrier many years ago in Syracuse where they were testing Absorption system unishells. The whole machine would be wrapped in a plastic ?tent? and a measured amount of helium admitted to it. A vacuum pump would then draw a vacuum on the inside of the system and the exhaust of the pump would be directed through a mass spectrometer.

Not a technique for your average site??.
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Andy
27-08-2004, 03:16 PM
Hi :)
we use nitrogen with 10% Helium for strenght/leak testing HFC refrigeration systems. This in my experience is the only way to ensure that an HFC plant is gas tight.
Add the nitrogen, add the helium, get the soapy water out and watch the leaks appear. :o
Kind Regards. Andy.

chemi-cool
27-08-2004, 03:20 PM
Thanks Andy.

Thats the kind of answer I was looking for.


Chemi :)

donhoban
27-08-2004, 03:31 PM
Thats the kind of answer I was looking for.


I'm sorry I failed you Chemi :rolleyes:

chemi-cool
27-08-2004, 03:43 PM
I'm sorry I failed you Chemi

You certainly didn't!
The whole thing came up when I had a discussion with a local manufacturer about better ways to locate leaks in systems in new units.

He mentioned the Helium test as Argus described and I was sure I will find more practical answers here.

Andy is a very practical person and I like his answers.

Chemi

donhoban
27-08-2004, 04:20 PM
No worries, I'm only yanking your chain :)

I must admit though as far as site installs, I'm with Andy, soapy water is the only way!

chemi-cool
27-08-2004, 04:27 PM
You know, as all as those electronic gadgets are concern, I think I'm one of these who always use the soapy water.

Never let me down.

Chemi

Mark
27-08-2004, 05:25 PM
Hi :)

Yes i agree,to clarify leaks good old soapy water ;)

For the last 4 years ive been using a electronic javac Tekmate they can really aid leak detection,Ive found alot of leaks with this unit .Mostly in large supermarkets ;)
The sensitivity of the leak detector can sometimes be misleading :eek: ,but allows leak detection of most refrigerants including HFCs :)

Best regards Mark :)

Peter_1
27-08-2004, 09:17 PM
Leak check a Copeland: they pull each compressor in a vacuum.

Then, the compressor goes in a sort of small iron chamber (+/- 3 ft high and 2 ft diameter) and they add a light helium pressure in that chamber.

The vacuum hoses are still connected to the running vacuum pump. At the outlet of the vacuum pump, they have a very sensitive mass spectrometer which can detect the smallest amount of helium.

They said there that they use helium because it can escape the easiest of all gasses through very small leaks and it's with the proper electronics easy and accurate detectable.


Each compressor has always leaks through the gaskets (the gaskets are made of some sort of paper and has a capillarity), you could see on the computer of the mass spectrometer a rise in the graph as soon they added helium but then the graph flattened - but they know for each compressor the 'standard leakage'
As soon as a compressor goes beyond this 'standard leak' it goes out the line to search for the leak. This test last only some minutes.

Then it goes to the final drying: vacuum for a longer time with a DC current through the windings to heat up the internal of the compressor.

Same technique for vacuum chambers (+/- 2 m diameter) where they evaporate aluminum on a foil to make capacitors.
To test the seal/gasket, they pull a the vacuum chamber in vacuum and at the outlet of the vacuum pump a mass spectrometer.
They then go round the sealing with a flexible which is exhausting a very small amount of helium.

We did once the same test there in that factory: mass spectrometer at the outlet of our standard pump which we had installed with long hoses 15 m further away, sprayed with the helium and in no time we had the leak. We also saw 'leaks' around the gaskets.

Peter_1
27-08-2004, 09:24 PM
Hi donhoban.

Isn't the molecule of Helium smaller, allow the gas to come out in smaller holes then refrigerants?

Peter, I haven't a clue but ultrasonic detector is very uncommon with fridgy's.

Chemi

I have an ultrasonic but it's only usable to search for leaks in gaskets around the doors.
You must almost hear and know where the ***** leak is to find it with an ultrasonic.

Latte
06-09-2004, 06:34 PM
Surely if we start using Helium for leak detection we are going to all start talking like Joe Pasquale :eek: :D

Regards

Raymond

RogGoetsch
06-09-2004, 07:43 PM
...but ultrasonic detector is very uncommon with fridgy's.

True, but I recommend it as a very valuable tool under some conditions. I finally broke down and bought one a few years ago when a leak was driving me crazy. They had come down to about $200. Mine uses earphones and supplies a hiss in the hearing range proportional to what the detector is receiving, with a sensitivity adjustment.

They are excellent when a system is out of gas, since that usually means a large leak which overwhelms most halide detectors. Of course the oil often shows such a leak, or you can find it quickly by pressurizing with nitrogen and listening for the hiss, but when this fails, the best feature of the ultrasonic detector is that you can use it directionally.

You need to pressurize with nitrogen if the system is empty and shutdown fans and adjacent equipment to eliminate background ultrasonics but then you can home in on the source very quickly, in many cases. With a thumb on the sensitivity adjustment, you track the noise right to the source. Last time, I found a leak in the interior of an evaporator coil in minutes, which was losing about 2 ounces per day. (Pressurized to 100 psi first.)

For very small leaks and on rooftops where there is too much background ultrasonic noise (wind, traffic) it is not effective.

Rog

botrous
06-01-2005, 09:29 PM
Never heard about this helium technic , but from 2 days i watched a show on discovery about Boing the aircraft manufacturer and they use ammonia gaz to test the (wings) fuel tanks for leak , they fill the wing with ammonia gaz then coat the wings with a yellow paint , where ever there is leak , blue prints will appear

Lc_shi
07-01-2005, 01:31 AM
I kown there are some big companys apply Helium leak detector in their production line. It's said that more precision could be achieved and thus the time to make -up charge be to 8 years(for home use split ones).
In our plant, there still use nitrogen +soapy water+keeping presure 24hr method. It still works for small volume production. I think it's no good for mass production.
My opinion is the better tech bring better quality ,but "fit for use " is more practical in some situation.

Daddy Cool
07-01-2005, 01:13 PM
Hi Chemi,

have you looked at the thread titled "OFN or Not?" similar subject.

botrous
07-01-2005, 01:40 PM
The more the technology advances the more tests needed , the more atmospher polluted the more tests needed .
Unfortunably high tec technics are still very expensive to use by small and medium companies . . . the goverments should support the price of such testing materials in order to develope their countries industries and their contribution in the atmospher clearness preservation

chemi-cool
07-01-2005, 01:42 PM
Hi Daddy cool.

No I didn't but I couldn't find it either, can you post the address so I can have a look?

Thanks

Chemi :)

Daddy Cool
07-01-2005, 02:25 PM
Hi Chemi, :)

i think this is the correct one, you will have to excuse me if not, i'm on some spaced out medication at the moment and not really on this planet. good luck.

http://www.refrigeration-engineer.com/forums/showthread.php?t=2158

chemi-cool
07-01-2005, 08:05 PM
Hi Daddy cool,

What medication? Can I have some? :D

The use of OFN as I see it, is from two main reasons: One, the price.
Two, If you keep a small flow through a system while soldering, the pipes remain clean (no oxidation) inside, so it saves time and money on cleaning the pipe work.

Get Better,

Chemi :)

Tejbir Singh
08-01-2005, 01:11 PM
hi Chemi,

Try using Coloured liquid soap with OFN and you will be able to find smallest of leaks clearly this is the best method we use to find smallest of leaks.

Tejbir Singh

chemi-cool
08-01-2005, 04:24 PM
Hi Tejbir.

How do you mean, standard liquid soap which comes green or yellow? Or adding a bit of food colour or what?

Does the bobbles come out different?

Chemi :)

botrous
08-01-2005, 06:10 PM
What do u mean Chemy by "food colors " never heard about this and want to learn more , can you please describe how it's used ? when to use it ? and the proportion you need ?
Thanks in advance

Tejbir Singh
09-01-2005, 08:39 AM
Hi Tejbir.

How do you mean, standard liquid soap which comes green or yellow? Or adding a bit of food colour or what?

Does the bobbles come out different?

Chemi :)

Hi Chemi

colour is not important, since the soap is sticky it stay even on vertical place say near pump end gaskets or near seal in open type compressors and leakage even of pin head bubles will create a whitish or light colour bubles which will accunlate at the site of leakage very effective and pin pointing, try this.

Tejbir Singh

Abe
09-01-2005, 10:23 AM
I still dont understand..........perhaps if you dont mind Tejbir, explaining a bit more
Thx

botrous
09-01-2005, 02:00 PM
Ayub i think that Tejbir means that colors will appear on soap , like if a soap bible is exposed to light , you can see colors in it

Tejbir Singh
09-01-2005, 03:05 PM
I still dont understand..........perhaps if you dont mind Tejbir, explaining a bit more
Thx

hi Aiyub

take any liquid soap apply it to the site where you want to check for the leak, if there is any leak even if its very small
you will see it in the form of white foam since the small bubles get trapped in highly viscous liquid soap. but remember to remove the soap with plenty of water since any trace will cause corrsion.

I hope this explaines the process try it once and you will get fond of this method.

Tejbir Singh

Abe
09-01-2005, 08:43 PM
So whats this all about food colouring and all that ??? :rolleyes:
All it is is a bit of Fairy liquid!!! :D
Been using that for yonks............. :)

Boutros..............yes, those colours are the light spectrum !!!! :eek:

chemi-cool
09-01-2005, 08:53 PM
I guess that this is it, fairy liquid or any other soap and the colour is the bottle.

Chemi :)

botrous
11-01-2005, 10:36 PM
Hehe , So that what was all about , Fairy soap lolololol , light spectrum , what about new technics
???

Abe
11-01-2005, 10:48 PM
Nothing techie about fairy Boutros
Fairy is a famous brand washing up liquid in UK

And Chem youre wrong..............colour is not colour of bottle.
It is the translucent, effervescent colours of the rainbow when you blow Fairy bubbles!!!

And I forgot to add.............its so safe and good on your hands as well!!!

:)

FreezerGeezer
12-01-2005, 08:23 AM
Actually, food colouring does have a part to play in supermarket leak detection. :p
I always used to bung a bottle of red food colouring into a bucket of water when trying to find water leaks on the cabinets. That way, I could see where the water was coming from amongst all the other water that had already leaked & not been cleaned up! :D
I nicked the idea from geologists, who dye cave streams then search for the dyed water in the surrounding streams & rivers to find where the cave water system comes out.

THERMOACC
12-01-2005, 07:14 PM
I like the idea with using food colouring to find water leaks on cabinets....wish i thought of that a few months ago!! I think i`ll start carrying some in the car for the next time :)

botrous
12-01-2005, 09:43 PM
Aiyub , i know that fary is very famous , it's famous here as well .
I am intersted in this food colors things , if someone have more information please post it

Abe
12-01-2005, 10:00 PM
Im intrested in this colour thing as well now
The only thing I can think of is either,
Curry powder...........madras
Ayurvedi

Put us out of our misery Tejbir!!

botrous
14-01-2005, 12:12 AM
I am thinking what about concentrated "essence" that's used for coloring and falavoring bevereges , i gonna buy some and test it on 10 L of water and see how the color concentration will be

FreezerGeezer
14-01-2005, 09:06 AM
I used to get the permission of the Manager to help myself to a couple of bottles of red (Cochineal) food dye from the bakery section. You know, the stuff our mums/wives use to colour icing sugar. It worked a treat! :D
And if the manager wouldn't let me have some, I'd buy it. It was only 70p or so, from memory.

botrous
14-01-2005, 11:24 PM
I've seen the price of the food color in the market , here each 10 ml costs about 1.5 USD

Servicefrigo
15-01-2005, 10:58 AM
How about the new UV methodes forr a leak detection.Its a litlle expensive,but have avantage also .Personal I think it-s a very good methode.How about this?

chemi-cool
15-01-2005, 11:34 AM
How much It will cost if the plant has 1 ton of refrigerant?

Chemi :)

Servicefrigo
22-01-2005, 06:53 PM
Sory I did*t now how big is a supermarket ( 1 tone refrigerant :eek: ) In that case the things are change !

botrous
23-01-2005, 08:15 PM
Sory I did*t now how big is a supermarket ( 1 tone refrigerant ) In that case the things are change !

ServiceFrigo 1 Ton of refrigeration = 12000Btu/h

As for why we say 1 ton of refrigeration . . . .
From where this came . . .
A ton (1000Kg) of ice at 0C needs 24 hours to melt at 0C so the ammout of Btu's needed is 288000 Btus that makes 12000 Btu/h , that's where the naming (is i can say it for using a name) ton of refrigeration came .
So one ton of refrigeration is the ammount of heat needed per hour to melt 1000Kg of ice at 0C in an 0C invernomment (surrounding tempreture) :cool:

Servicefrigo
24-01-2005, 06:39 AM
Dear Botrus
I understend 1 tone refrigerant !as I say before that meens 1000 kg.R22 , R134A,or otheers.

botrous
24-01-2005, 04:07 PM
Ah sorry Servicefrigo , i read refrigerant ; refrigeration ..... excuse me

Jan-Willem
07-03-2005, 08:34 PM
Hi Chemy,

We often use a mixture of helium and nitrogen to ensure a 100% leaktighness test. Helium molecules are the most smallest and therefor perfect to find the smallest leaks.

Normally this test can't be performed by an ordinary refrigeration contractor because of the huge investments with has to be done for buying a mass spectrometer. We are outsourcing the test to a NDI (Non Destructive Investigating) contractor.

Before filling up the installation you've to tape all flanges, connections and tubing in order to concentrate the leaked out mixture in the right place. Be aware that a helium conterminated enviorement can destroy your test!!

Our procedure as following,

Nitrogen pressure test in 3 stages at 1 bar, 5 bar and 10 bar.
Nitrogen pressure test up to MAWP (Maximum Allowable Working Pressure)
Release Nitrogen
Tape off all flanges etc.
Add mixture for huge installations and 100% helium for the smaller ones. Up to 1 bar.
Apply for at least 1 hour stand time before leaktightness test.
Find leaks with mass spectrometer (Do not use the testrod of the spectrometer for making holes in the tape)

Good Luck

Peter_1
07-03-2005, 09:48 PM
What about PED regulations which states much higher testing pressures (+/- 25 bars on high side in most occasions)

Derek
08-03-2005, 01:53 PM
PED = Design and Manufacture

Proof Test with Nitrogen or Argon (cheap and no environmental issues)
Leak Test at max operating pressure (limit pressure al la PED) with helium as it gives a quantifiable result if done in a chamber.

PSSR (UK) = Operation and Maintenace

Leak Test with helium and portable mass spectrometer (16K) again gives a quantifiable result if elak is above background levels (10e-6 m.bar.lt.sec-1).

Washing Up liquid = corrosive salts and water will fill small porosities under capilary action and give false results but thats in the molecular leak rate zone.

Nitrogen Under water = corrosion risk and water will fill small porosities under capilary action and give false results but thats in the molecular leak rate zone.

Snoop or leak Detection Fluid = Not corrosive and viscious so pretty relaible for laminar leaks.

Ultrasonic = Excellent in plant rooms not good for low pressure slow leaks and won't pick up oil signature from temperature/vibration activated leaks. No quantifibale display!

Capacitive hand helds pick up every thing from cleaning solvents to bad breath but give users 'confidence' frequent 'ghost leaks' in plant rooms. No quantifibale display!

Beta source detectors relaible but radiation hazard means hassels at end of the warranty period. Gives ppm and mass per year.

IR Sensors good but bulky usually wall mounted and access by tubes making it slow to respond. Displays in ppm not mass per year.

New HFC legislation

This will mandate leak detection hand held for inspection.

Just the rantings of a few years trying to find Nirvana and missing it..... :)