Hi Gurus

Why do Citroen use nitrogen in the spheres? Secondly I have a sphere represuriser thingy and just need to get the gas which i'll source from BOC, is any grade of Nitrogen OK and how smaller bottle can I realistically get

//Chris

Hi Chris

As it 'post no 1' I had better welcome you to the club, Welcome, having done that, to your question. I would conclude nitrogen is used because in it's pure form it is non reactive, so cant damage anything, I would imagine that air would work just as well. I take it that when you mention 'BOC' that you are in the UK, in view of the price of replacement spheres, I wouldn't have thought that it would be cost effective to recharge your own, unless you intend to do it on a commercial basis. But then again, if you are an XM owner.....

Peter.N.

I believe that Nitrogen is used because, with its relatively large atomic structure, there is less diffusion through the diaphragm membrane. Although nitrogen doesn't support combustion, I don't think that's the reason it's specified as there's nothing in the sphere to combust.

Derek

Nitrogen is also one of the cheapest gasses available as it is a by product of oxygen production. Formula 1 teams use it in their tyres as it is more stable than air under temperature changes (and of course it is non combustible).

John

Hi,

BOC can supply you with 2 sizes of bottle. The cost for the smaller one is:

monthly rental £4.55 / refill £13.15 (ex VAT)

You can't buy the bottles outright - though it is slightly cheaper to pay the rental charge 1, 3 or 5 years in advance! If you're only using it for your spheres the gas will last until hell freezes over.

You can find your local depot by calling BOC on 0800 111 333. There's no restriction on supplying the gas - they just need an account application completed before you take it away.

Presumably you already have Valprex valves on your spheres?

Roy

At that price it's cheaper to replace all your spheres every three years!

Derek

Yes 1st post but I lurked a while

Thanks for your replies.

Yes I have the Valprex valves and the tool to pump them up and yes I'm in the UK

My XM has 7 spheres at £20-25 each so £140-175

get a bottle for 1 month every year (if needed), and I know they accept full bottles back as i used to do it with Argoshield welding gas, so that will cost about £60 over three years and I have 3 Hydractive Cits at the moment

And as a lot of the cheaper spheres i've had from GSF or Eurocarparts seem to arrive partially flat and up to 4 year old from the build date, I usually get regassed from the likes of Pleaides etc.

So £175 per car £525 for all of them every three years so I could save £465 doing it myself, and I've found there is usually some attention required around the 2-3 year range

Thanks Chris

Hi Chris,

Good call - it really is the ultimate method in my opinion. Easy to top up without removing the spheres from the car so you can check them more regularly.

In addition to the financial savings you're going to prevent the needless waste of all those spheres. As long as you check them within 3 years the spheres will last forever.

Welcome to Club-XM.

Roy

Ah well, that's different!

Peter.N.

Hi Guys.

Considering sphere replacement on the new toy and I'm quite interested in the replace v. regas issue.

First thing that I'm curious about is the internal diaphragm ---- does it never give out ? It must be under stress one way or the other.

Is the regassing tool absolutely Citroen specific or just a suitable pressure pump using an approprate adaptor ? Are all spheres capable of being re gassed ?

Any thoughts or info most welcome. If I simply buy exchange, who do we all go to, or avoid ?

Mike.

A very interesting thread on FCF at the moment about this very subject. Martin from Pleiades has posted some info and I see that Peter has invited him over here as well

Your location is not far from Coventry so why not pop into Leek Motors in Coventry (ring first 02476 220 714 )and ask Nigel Leek to check all your spheres and regass or replace as necessary What peace of mind that will bring!
p.s. the centre spheres are a bit of cow to get at and that applies especially to the anti-sink sphere ( if yours are fitted with them)
I had 4 spheres cheked,charged and guaranteed for under £120 about 18 months ago.
The centre spheres - which really control the softness - will be more costly to remove and that job ran to just over £200.
You could even go to Westroen in Manchester who would quote you for a full check and change. Both are very good and I have used both companies in the past.
Both are Citroen orientated and know what they are doing.

As far as I understand, the choice of Nitrogen was made primarily for being physically highly comprimable which gives elasticity in small volumes and under high pressures.

Hi all, another reason for nitrogen is that with pure dry nitrogen you have less risk of oxygen in present and that helps conserve the rubber of the diaphragms in the spheres.

Believe it or not there is a risk of combustion where you have a compressed gas and an oil together, especially with oxygen present in the gas!