Nitrile or Viton o-rings for heat exchanger?

Keith-i

Keith-i

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The o-rings for my heat exchanger are ridiculously expensive for what they are (£20 ea) so I have been looking for aftermarket alternatives. I can get the required sizes but there is a choice between Nitrile and Viton. Does anyone know which is most appropriate or would be most typically used?
 
I've been using the el'cheapo ones, sure it's nitrile for the last 5-6yrs, no issues, replaced them once when I took the h/e appart again for cleaning.

V.
 
Either will do I have standard nitrile.

It's would not be possible for the temperature in a heat exchanger to get much above 100 degrees C without causing other damage.

My fresh water thermostat is set at 92 degrees C so the only time that temperature could go much above that is if the raw water flow stops
 
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Thanks for the input. On the basis it seems that either is suitable I shan’t fret too much about which I get.
 
tbh the only chance of any liquid going over 100C in my boat is if something's horribly wrong and a leaking o-ring is going to be the least of my problems.
By all means go for viton, don't think they're that expensive tbh!

PS. sorry replied first and then saw Roger's reply... saying the same thing
 
Viton are based upon PTFE and are generally more chemically resistant (except to refrigerants), and wil ltolrate higher temperatures. Nitrile is used extenisvely on refrigeration compressors to > 100oC, but the seals can become brittle after a few years service.

It does sound like the OP is experiencing MAT for his O rings (Marine Added Tax). If you can measure the ID or OD and cross section diameter list them kn here ansd I wil attempt to size it. If the ring is flattened list the CSD in both planes, it si generally the average of the two.
 
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superheat6k said:
It does sound like the OP is experiencing MAT for his O rings (Marine Added Tax). If you can measure the ID or OD and cross section diameter list them kn here ansd I wil attempt to size
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For the sake of a few extra pence Viton sounds the better option. Fortunately the sizes are quoted in the official parts list as 118x3.55 and 135x4. I have found them both from uk suppliers.
 
3.55 will be interesting to source!
I assume that's mm, I think you generally get half mill sectional dia sizes in o-rings, maybe wrong but that's what I can get down here.
I'd go for the closest and due to the price difference I'd buy a set for either size, so 3.5 and 4.0mm dia.
I'd even buy the larger dia (in section) at a slightly smaller dia overall so that you have to stretch it to fit therefore reducing the sectional dia a bit, but I think that's at splitting hair territory.
Sorry if I sound like a cowboy, but half a mill in dia at these sizes is practically nothing as I guess it sits in a notch created by the casing on two sides and the core on the inner side. Then "lid" comes and bolts on top and squeezes the lot. Slightly larger wont create problems, slightly less may not seal, much larger will not fit properly and be a pain to put everything together.
Of course if it goes in a groove in the core which then slides in the housing (v.much doubt it!) then accuracy would be quite important.

V.
 
Vas, you're right the 0.05mm accuracy seems absurd. However it is a listed size on one of the UK suppliers I found so I may as well get the correct one! Indeed, it sits in a groove so slightly oversized would not be a problem.
 
I spoke to bowman heat exchangers when I was rebuilding my heat exchanger and they quited an imperial size for the O rings so the 3.55mm could be 9/64 inch.
 
3.53 is a standard CSD for imperial range O rings. The one described above is BS247 is 117 ID or BS 248 is 120 ID. At that diameter the 117 will stretch slightly to sit in the groove.

This explains about the various materials and sizes ...

O Ring Catalogue.pdf
 
thanks Trevor,
but opening a 112 page PDF on o-rings it's completely demoralising :rolleyes:
I did save it though on the appropriate folder :)

V.
 
vas said:
thanks Trevor,
but opening a 112 page PDF on o-rings it's completely demoralising :rolleyes:
I did save it though on the appropriate folder :)

V.
Click to expand...
Well not much else to do in locked down Britain for many presently, so a good afternoon's read I thought. :)

I've plenty of other broadly similar tomes.
 
I've placed an order with a company called Polymax that seem to supply a vast range and types of o-rings. I went for Viton and they work out 1/4 of the price compared to the marine supply. The 3.55 dia was listed under their metric variety.
 
In actual fact neither material is particularly suitable for immersion in hot water, with Viton being the least suitable of the two.

Ideally you should seek out EPDM for higher temperature capabilities [to 150c] and very good in water /steam environments.

Try Simply bearings EPDM O Rings: EPDM Rubber O Rings & Seals

Hope that is useful.
 
Scarron said:
In actual fact neither material is particularly suitable for immersion in hot water, with Viton being the least suitable of the two.

Ideally you should seek out EPDM for higher temperature capabilities [to 150c] and very good in water /steam environments.

Try Simply bearings EPDM O Rings: EPDM Rubber O Rings & Seals

Hope that is useful.
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Trouble with EPDM is its remarkably poor resistance to hydrocarbons. Shoe soles are made from it and in a couple of minutes standing in oil they begin to go sticky. Even the grease that most people will use on assembly will have a bad effect on it.

In the past Viton was very much more expensive than nitrile and hence rarely used other than for gasoline but it seems there is now not a lot of difference between them.
 
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