sphere shelf life

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sphere shelf life

Post by RobC » Thu Nov 09, 2006 11:58 am

hello, wonder if anyone can advise...:

if a brand new sphere has been 'on the shelf' for 3 years is it still worth buying, or will it have deteriorated?

ta muchly
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Post by docchevron » Thu Nov 09, 2006 12:00 pm

If it's a genuine sphere, maybe I'd get it if it was cheap.
If it's an AMTEX sphere I'd walk away, it'll be flatter than the ones you'll wana replace!

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Post by RobC » Thu Nov 09, 2006 12:11 pm

thanks for the tip! the ones i'm thinking of are genuine cit ones.

further to this, anyone heard of "IFHS" as a sphere manufacturer? if so any experiences good or bad?

:)
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Post by docchevron » Thu Nov 09, 2006 12:20 pm

RobC wrote:thanks for the tip! the ones i'm thinking of are genuine cit ones.

further to this, anyone heard of "IFHS" as a sphere manufacturer? if so any experiences good or bad?

:)
I wouldn't worry too much about the age then, but I'd get them pressure tested / re-gassed before fitting.

I seem to remember I had a BX a while back with IFHS spheres but I got the impression they were just recon cit units?? They seemed ok to me, unlike the rest of the car......

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Post by Way2go » Thu Nov 09, 2006 1:21 pm

docchevron1472 wrote:If it's a genuine sphere, maybe I'd get it if it was cheap.
If it's an AMTEX sphere I'd walk away, it'll be flatter than the ones you'll wana replace!

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Chris G
Curious statement about the Amtex sphere Doc, do you consider they have short lifetimes or is that only if they are not in use?

Also this talk of re-gassing, my original spheres on the car did not have valves on the back - so if regassing is an option can this be done through the LHM port then? :?
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Post by docchevron » Thu Nov 09, 2006 1:51 pm

Way2go wrote:Curious statement about the Amtex sphere Doc, do you consider they have short lifetimes or is that only if they are not in use?

Also this talk of re-gassing, my original spheres on the car did not have valves on the back - so if regassing is an option can this be done through the LHM port then? :?
Amtex spheres have only a single membrane. They come with a 2 year gaurentee and seem to be designed to last 2 years and 1 day!
If you regas an Amtex every year they last reasonably well but genuine spheres are triple membrane and so long as they are kept gassed will last indefinitley.

On the back of a sphere that hasn't been gassed you'll see a little bung (flat head bit sticks out). When you need to re-gas then this bung is removed with mole grips or similar and then a valve is fitted before recharging.

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Post by Way2go » Thu Nov 09, 2006 1:59 pm

Thanks for that Doc, the regassing mystery has puzzled me for a while.

Is regassing worthwhile over replacement? How long can the life of a sphere be extended to by regassing?
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Post by docchevron » Thu Nov 09, 2006 2:04 pm

Depends really.

If the sphere is an Amtex unit, re-gas every 12 months (maybe two years if your lucky!) you might get 7-10 years out of them so long as the membrane hasn't failed.

I've known genuine spheres to last over 25 years with regular gassing (every three years or so).

So long as it's gassed before it goes totally flat they usually go on.

I got pi$$ed off with Amtex spheres (I bought several sets that were 2 years old from the shelf!) so dont bother anymore.

Genuine spheres are not cheap but again, if they are kept gassed they will outlive an Amtex by years making the initial price difference null and void!

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Post by Way2go » Thu Nov 09, 2006 2:19 pm

What cost for re-gassing & who does it?

First time is presumably higher cost due valve fitments?
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Post by docchevron » Thu Nov 09, 2006 2:33 pm

Any decent independant citroen garage should have the necessaries in stock!

Can't comment on other garages but Bristol 2CV's dont charge more for fitting valves. Since the guys there are lovely they dont make any money out of me (it's all cost price), which is bad business practice on their part since I'm their biggest customer!!

Cant remember what they charge for a re-gas but I'll be having lunch with them tomorrow so will enquire!

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Post by sleepy0905 » Thu Nov 09, 2006 4:49 pm

I bought some from GSF last year and they were 4 years old from the date stamp on them they had to go back they were totally flat.
So they do have a shelf life and as already said anything over 3 years is too old I was told by citroen they had to be no more than 12 months otherwise it isnt worth changing them.
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Post by ellevie » Thu Nov 09, 2006 5:10 pm

It might be worth compiling a list of garages who can test or test&regas spheres. So far we have
2CV
Westroen
Pleiades.
I don't know of anyone down on the south coast who does them. I also know that Rignall Garage (Louis Barbour) doesn't. Interestingly, they said that they would not trust any spheres that had been on the shelf for more than 2 years (they get theirs from GSF). I've asked a number of experts about the shelf life of spheres but the answers are not consistent. I suppose the only way is to test spheres as they come off the shelf, but not many people have the kit to test them. I don't suppose vendors would be too happy about testing them, especially if it turns out that they don't last very long on the shelf.
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Post by jeremy » Thu Nov 09, 2006 5:27 pm

I fitted a new accumulator (Al-Ko) from Euro Car Parts - and it failed after 12 months ( got a face full of LHM!). I think it was about 4 months old when I purchaed it.

The other 4 spheres from the same source which I must have fitted 5 years ago now are fine, as is the new accumulator (different make)

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Post by ellevie » Thu Nov 09, 2006 6:25 pm

Here's an interesting theory from the FrenchCarForum,
noz on the FCF wrote:When the sphere is on the shelf the diaphragm inside is completely pressed flat against the inside surface of the steel sphere. The diaphagm only occupies the lower half of the sphere, the top have being bare steel. The pressurised gas is pushing against all of the surfaces inside the sphere equally. The bottom part of the diaphragm has a hard plastic disc attached just where it passes over the orifice in the threaded part of the neck. The diaphragms are made of nitrile rubber compounds. At a molecular level the gas molecules will eventually pass through the diaphragm material just like a ballon which deflates after a while. However, this would only be the case if there was air on the other side of the diaphragm. When the sphere is on the shelf and the diaphragm is pressed against the inside steel surface then the migration of molecules is halted at the steel/rubber interface. Whilst it is not impossible for the gas molecules to pass through the steel this would take 10 orders of magnitude longer than through the rubber (due to the relative permeability of both materials). In which case the gas molecules may migrate through the rubber but they can't get any further than the steel surface. The only part of the diaphragm with contact to the outside air is the part above the orifice. At this point the diaphragm is thicker and capped with a hard plastic disc.

The only other part of the sphere which has the potential to leak is at the filler plug. Beneath the plug top there's a groove containing an o-ring. Its the o-ring which does the sealing.

When the sphere is in use the outside of the diaphragm is now no longer pressed against the inside steel surface of the sphere. The interface is now between the rubber and the LHM fluid. In this case the migrating molecules of gas passing through the diaphragm are able to escape into the fluid and be carried away back to the reservoir finally escaping to the atmosphere.

Overall my opinion is that the on-shelf sphere life is much greater than suggested above and previous writings on the same subject. The escape route for the gas is extremely limited. However, in use, the gas pressure will reduce as fast as the molecules can find their way though the molecular structure of the rubber.

I am not suggesting however that the pressure should not be checked before fitting the spheres to your vehicle. That simply constitutes good engineering practice.
David

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Post by jeremy » Thu Nov 09, 2006 6:57 pm

Presumably this means that spheres don't last as long on a car with anti-sink as they do on one without - as they will be in the same state as when on the shelf whenever the suspension is lowered.