OFN or NOT?

A few years back i had a conversation with a technical engineer who was into his refrigerants. He suggested that the molecular size of R410a (or at least its components) was smaller than a molecule of OFN. He advised using helium to pressure test rather than OFN as it would find any leaks. I have asked equipment manufacturers, BOC, and other people and have not had a straight answer from anyone, the most common answer being, well we have always used OFN and not had any problems.

SO, was the techi correct, but the need to use helium to small to worry about?

For info i am currently employed by a large Japanese manufacturer and get the same vague answers everyone else have given. Am i flogging a dead horse?

Thanks

No, you're not flogging a dead 'un.

By and large he was correct. But times change and so do practices.

At one time it was commonplace to do all testing with the refrigerant in use on the equipment but that is now not allowed. (at least in the UK)

OFN is cheap and relatively portable that is why it is favoured on sites as an initial test. You can use the same stuff direct to atmosphere for purging too.

It is true that most Fluorocarbons have a smaller molecular structure that Nitrogen but it doesn?t always follow that they will leak where Nitrogen will not. Nitrogen will identify problem leaks at site ? a further test with the charge added is always a good idea when the charge is added to make sure.

Helium used for testing joints in refrigeration gear is high purity and expensive ?it?s not the stuff you put in balloons!

The advantage with helium is that its molecular structure allows fugitive leaks to show up rapidly where other substances may leak very slowly. This helps to identify microscopic porous material. For this reason Helium is in use in controlled factory production, where a high degree of leak tightness is needed particularly on welded joints.

Hermetic compressor cases are a good point in question. In these instances the technique of testing is different and opposite to the one you would use at site. The helium is on the outside of the item being tested and is drawn in by negative pressure if there is a leak.

A typical technique goes like this; the item to be tested, with a vacuum pump attached, is placed in a sealed chamber which is then pressurised with a small amount of Helium on the outside of the item. The exhaust of the Vacuum pump is taken through a mass spectrometer that analyses the helium content that would enter the item being tested if it had a leak. The same technique is used in manufacture of absorption equipment, particularly as the shells are subject to vacuum pressure in use.

This is the ultimate in leakage testing, though not really suitable for site use, because it is an expensive process all round.

Some of the Japanese manufacturers that I know of use a variation of this on thier production lines.

Hope this helps.
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Rolls-Royce V-8 (1905)

Hy Dad,

We have dscussed the subject in the past.

It is advised to use OFN with some Helium ,about 10%.

The results are very good and every little leak is found quick and easy.

Chemi :)

Hi Chemi,

Sounds good only one problem :(

I already carry:- 2x404 2x22 1x134,408,409 2 ofn 1oxy 1acy 1 reclaim plus tools and parts. I must be getting near to my GVWand thats without me getting inAnd then add another bottle of helium :eek: :eek:

What happened to the good old days of carrying R12/R502 and that done everything :rolleyes:

Regards

Fatboy

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QWhat happened to the good old days of carrying R12/R502 and that done everything

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Hi Raymond

You can get Helium in small bottles.


Funny you mention it cause just yesterday, I got a contract from an old Hotel. all the fridges and freezers run on R-12 and R-502 :D

Need to replace two compressors.
Any suggestions? ;)

Chemi ;)

Hi Chemi,

I am also doing a lot of hotels at the moment and wat i am finding is the only time they see an engineer is when it's too late and they have blow the compressor.

First thing i would do although i am sure you have done it already is have a GOOD look at the units and list everything that need or will need doing shortly. door seals, fan motors, condensers, compressors, driers, gas and labour.Go through the lot and then see if it's worth repairing them. I know it's good for service business going back because the old units keep breaking down but at the end of they day would it just be worth replacing he units.

Personally i would normally use 409 on the fridges and 408 on the freezers but obviously it depends what compressor you get. These small units there is no way to flush the systems if they have burnt out so i dont like converting to poe unless the compessor has to be a poe

Regards

Raymond

Hi Raymond.

Absolutely right. These hotel people are funny.
The first thing I do when I get there' is looking at whats cooking for lunch and what time, the girls are having coffee ;)

It is impossible to get 408 and 409 over here. Don't know why.

R12 and R502 are easy to get though and so are new compressors for these refrigerants.

Door seals are hard to find so special ones have to be ordered.

Chemi :)

If You used 100% Helium and you were rubbish at Brazing, everybody on site would be talking like fools.

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Originally Posted by chemi-cool

Hi Raymond.

Absolutely right. These hotel people are funny.
The first thing I do when I get there' is looking at whats cooking for lunch and what time, the girls are having coffee ;)

It is impossible to get 408 and 409 over here. Don't know why.

R12 and R502 are easy to get though and so are new compressors for these refrigerants.

Door seals are hard to find so special ones have to be ordered.

Chemi :)

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Hmm

some kind of export business Opportunity exists here..;-)

cheers

richard

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Originally Posted by rbartlett

Hmm

some kind of export business Opportunity exists here..;-)

cheers

richard

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If you easily can get ***** 12 then the market for replacements maybe are rather limited.

Jan Steen

Hi....I am a new guy to this site ...last week I was chatting to a citb guy who told me that when he mentioned the above to a prominent Japanese manufacturer he was told..."we do not want you to look for very minor leaks in our systems too hard"...was this said tongue in cheek I wonder??...I look forward to reading the site on a regular basis....regards Superheatman.

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I look forward to reading the site on a regular basis....

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Hi Superheatman,
Welcome, I hope you will consider posting once in a while ;)

Chemi :)

It is an offence under the eviromental protection act to knowingly put a leaking system onto the market. Any engineer installing such equipment would also be breaking the law.

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Originally Posted by Superheatman

Hi....I am a new guy to this site ...last week I was chatting to a citb guy who told me that when he mentioned the above to a prominent Japanese manufacturer he was told..."we do not want you to look for very minor leaks in our systems too hard"...was this said tongue in cheek I wonder??...I look forward to reading the site on a regular basis....regards Superheatman.

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Very much tongue in cheeck, I'm afraid......

Everyone knows that the Japanese are renowned for their sense of humour.
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vaporizer wholesaler