DS/D Special - failed two piece accumulator sphere

UFO

Citroën Tragic
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Fellow Frogger
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Gerringong, NSW, Australia
I've had a fun day - well no, I haven't really, but in reality what happened today was fortunate both in location and time.

Here's the story...

A couple of years ago while UFO was being repainted etc, I decided that it would go back together with rebuilt spheres all around. I had a full set of old spheres with removable dampers that were rejuvenated by a couple of friends in CCCNSW. I had the new diaphragms and they did the hard work. Splitting, cleaning, painting etc and regassing. Great. They could not do the two piece accumulator I had as it is smaller and the clamps would not grip the collar etc. So, I went to level 2 and sent the sphere off to Richo.

NOW at this point I stress that what happened today was NOT Richo's fault in any way.

Richo did a wonderful job on rebuilding the sphere even to providing a new correct diaphragm (Desmopan). It came back to me within about 10 days. As UFO still had a good new style welded accumulator sphere on it, I decided to leave fitting the rebuilt one until a later time when I was "looking at it". That time came about 12 months later (late 2011/early 2012) when I was putting a new mounting gasket on the fuel pump.

Anyway - all went well.

In the meantime I read various stories about two piece accumulators going bang but decided that I would still proceed.

A couple of weekends ago I took UFO to Bundanoon and back (about 160km return) with four adults inside and it performed very well. Last weekend I did a pre Cit In oil change and checked underneath and all looked fine.

Today, due to some car arrangements here revolving around a still failing Xsara clutch, I decided to take UFO to work (35km each way) and leave the C4 for little UFO to go to Sydney and the C5 for Mrs UFO to do stuff she needed to do in Wollongong.

I set off for work and went around the Kiama bends with aplomb then up the hill before dropping down to Bombo beach on the Princes Hwy. It is three lanes here to allow northbound Kiama traffic to enter and usually as some dive right WAY too quickly I often move to the rightmost lane. I noted that there was a Police VW paddy wagon also coming on from Kiama. The cops accelerated up the middle lane and shot through and at that point I heard BANG, CLANG, CLUNK. Perhaps the people in cars nearby also heard it and no doubt with windows down they would also have heard a fair chunk of my vocabulary!

I thought the car had popped a conrod and had smashed the side of the block, so while manouvering into the left lane I tapped the brakes and also felt the weight of the steering. Oh shite! I know what happened.

I was able to pull to the side of the highway but on a bridge - fortunately with a bike and breakdown lane. As I pulled up there was whitish mist/smoke from under the bonnet. I had only the gears and park brake to pull up on.

2013-03-20 09.12.59.jpg 2013-03-20 09.13.18.jpg 2013-03-20 09.13.37.jpg 2013-03-20 10.24.28.jpg

Anyway, sure as eggs, the gas end of the accumulator sphere had blown off so it looked like. It's still sitting somewhere near Kiama Cemetery (perhaps Maryann is keeping it for me :disappr:) Fortunately nothing seemed to have hit anyone else nor surprisingly I could not see a large LHM stain on the road. However if it rains in the next few days I will be extra cautious going down that hill and into the left hand bend at the end!

Straight onto NRMA (I have Premium coverage on UFO) and told them where I was (eventually no BOMBO not BONDI) and about 80 minutes later the flat bed turned up. Giving the NRMA there dues, I asked them not to bother with a roadside guy as he would just look at it and tell me it's broken. I asked for an "all up" with a low angle tray. The NRMA person on the phone first made sure I was safe and not blocking traffic and could stay out of traffic's way - good move.

A while later I saw this black Hoondie I45 pull up in front of me with people taking pics out the window. Oh bugger! It was four of my staff on their way to a job in Nowra and they saw me and decided to a/ Stop and have a laugh at my expense and b/ Check if I was ok. They actually went into Kiama to do a U turn and come back. After a suitable amount of ribbing and chuckling from them, I gave them some travel advice and sent them on their way.... :wink2:

The flat bed turned up and did a sterling job of getting UFO on the truck - no scrapes at all. He delivered me and the car back home and helped me push it onto our (thankfully) almost flat driveway. Turns out he was the same bloke who brought the Xsara home a few weeks ago! :D

I called my boss and declared a flexi day so that I could get the spare (welded) sphere I had onto the car before the sun came overhead in the driveway.

After some time and cursing I got the regulator off, removed what was left of the old sphere, tested the spare and refitted the reg with sphere on and got the pipes back in place. Mutter, grumble, curse, swear etc. Of course I put all new seals on too. Pipe and sphere.
D accu sphere 3.jpg D accu sphere 4.jpg D accu sphere 1.jpg D accu sphere 2.jpg

I finished reattaching everything prior to starting the car and then let it bleed back to the tank for some time - until the froth and bubble stopped, did a few tighten and loosens of the bleeder valve then got brave and let her lift up to operating and then full height. All was good. I also topped up the LHM tank and only lost about 1 1/2 litres.

I have attached pics of the remnants of the sphere - aka our new door bell, and also pics of the subframe. I'm not sure if the dents I can see and feel are from today or a prior occasion, but there is a large indent the shape of the back of the sphere plus a smaller indent that would be the nitrogen screw (word?). The thread on the upper part of the sphere has blown off (the now C shaped section) and that was obviously the week point. The regulator had been ticking over at normal intervals prior - so it was not a failed diaphragm.

Anyway, out of all this, my recommendation is to never run a two piece regulator sphere. Use a modern welded accumulator sphere instead - please.

As to the timing - it is fortunate it happened today, as the next trip for UFO is to be to Griffith for Cit In. Who knows what may have happened had it popped going up Jamberoo or Macquarie passes on Thursday next week?
 
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Are you sure it was the sphere ..... You don't have a regulator problem I hope.... The replacement will go "BANG" in much the same manner :eek:

seeya,
Shane L.
 
The regulator is performing normally - as far as I can tell. Cycle time is about 50 seconds at idle, car comes up on idle in normal time and descends to flat in the typical time.
 
Anyway, out of all this, my recommendation is to never run a two piece regulator sphere. Use a modern welded accumulator sphere instead - please.

Craig,
There is NOTHING to prove or suspect the two piece accumulator sphere is to blame for anything.
Logic and experience tell me the sphere has failed because the regulator did not close off and bypass at 2450psi as t should.
Hence the pressure from the regulator exceeded the capability of the sphere to hold it. Probably burst around 6000+ psi.

Your accumulator needs to be serviced to be sure that this will not happen again. A welded sphere is not the cure.
It is unfortunate that this has happened, when was the last time you had your regulator checked or rebuilt?

Please only make recommendations where you are qualified to do so, to do otherwise is only likely to raise alarm unnecessarily.
Prior consulting with an authority and applying logic is a far safer course of action.

richo
The sphere was rebuilt on 5th March 2010.
I still have the images in my file of its condition at the time of receipt.
 
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The regulator is performing normally - as far as I can tell. Cycle time is about 50 seconds at idle, car comes up on idle in normal time and descends to flat in the typical time.

Please Craig, what you have quoted above has NOTHING to do with the regulator condition. It has only to do with the cars ability to operate at system pressure and its ability to lose pressure under operating conditions.
Please, have your regulator dismantled, checked, cleaned, resealed and tested.

richo
 
If you do change to the later style accumulator, don't bother regassing them using the threaded factory plug as they will foul on the crossmember in a D. They are often treated as a throwaway item. The only issue with them may be that they only come as 62 Bar and some models were meant to have a lower pressure accumulator. (EDIT: You could probably use a Xantia/XM Hydractive regulator sphere in a pinch as they do not have a damper either. The pressures are different depending on appliction though.)

How many times do you think that accumulator had been rebuilt over the years? As you have the fragments, a metallurgist would be able to inspect them and give an opinion as to whether it was a fatigue failure or an overload failure. Having the regulator checked and/or overhauled would probably be less involved than the forensics.

Yes, the time and location can make all the difference between a lucky save and a terrible crash! Reminds me of when the CX blew the heater core with instant loss of visibiity. Luckily, I knew the road (Harbour Bridge / Gore Hill Freeway) and it was 2am, so nothing to get in the way once I'd missed the overpass supports. Rather lucky really.
 
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I've had a fun day - well no, I haven't really,

.....Anyway, out of all this, my recommendation is to never run a two piece regulator sphere. Use a modern welded accumulator sphere instead - please.


Wise words, and when the welded units die - throw them. Small price to pay for reliability.:2cents:
 
Please Craig, what you have quoted above has NOTHING to do with the regulator condition. It has only to do with the cars ability to operate at system pressure and its ability to lose pressure under operating conditions.
Please, have your regulator dismantled, checked, cleaned, resealed and tested.

richo
About 10 years ago my accumulator exploded;fortunately it was on a ds21hyd. so the only damage was to the front crossmember as on this model the accumulator is mounted on the side of the gearbox. Replaced the sphere and no problems. The fact is that the ageing process of split spheres makes this a not unlikely occurance. Forget checking the regulator;just put a spare sphere and lhm in the boot.Andy.
 
I have had exactly the same problem, with the difference that the top did not come off completely. We were out on a run through the northern hills headed towards Kinglake on a winding dirt road. There was a bang and a lot of hissing and white vapour. Investigation found that most of the Diaphragm was on the outside of the sphere pushed through a crack no more than a millimetre wide. We had no alternative other than to keep driving and try to limp home with a flat car. The quickest route was to continue to Kinglake and then head down Mount Slide towards Yarra Glen. Great fun when all you have for stopping power is a hand brake. This device received quite a pounding. To cut a long story short we eventually got home and rolled slowly down our hill and into our driveway. I gave one last tug on the handbrake lever to come to the final stop. The damned thing came off in my hand. It had cracked completely through where the ratchet slide passes.
There was nothing wrong with the regulator. The two piece sphere had suffered from fatigue and just plain let go. I fitted a welded CX type sphere and never again was there any trouble.
 
About 10 years ago my accumulator exploded;fortunately it was on a ds21hyd. so the only damage was to the front crossmember as on this model the accumulator is mounted on the side of the gearbox. Replaced the sphere and no problems. The fact is that the ageing process of split spheres makes this a not unlikely occurance. Forget checking the regulator;just put a spare sphere and lhm in the boot.Andy.

FYI, the probability of a piece of foreign material preventing the spool valve in the regulator operating correctly and shutting off is likely.
It could be dislodged with the sudden release of pressure and the valve returning. That piece of material would be small and is probably now innocently residing in the reservoir filter, or still in the regulator.

I will suggest very few owners consider the servicing of their regulator (until something goes wrong), or even know anyone who has the capacity to check one correctly.
The regulators are probably older than the spheres attached to them in the majority of cases.

Correct maintenance, or rather the lack of it is the usual cause of component failure.

Fitting one piece welded spheres usually has the owner simply removing the regulator and replacing, fatiguing the pipework in the process. Every time you move those pipes they fatigue a little more. Eventually they succumb.

I agree that these spheres age, however, I'm yet to evidence a suspension sphere failing in this way, far more potential for failure, if you adopt your analogy.

richo
 
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The early LHS regulators were known to fail at the boss for the HP pipe outlet.
The shocks imposed on an accumulator sphere when the gas pressure is low or non existent can result in metal fatigue. The two piece spheres are very thin at the point at which Craigs and mine failed. Examining mine after the event showed that the break was crystalised in its metal structure and this is evidence of fatigue. Fitting reconditioned spheres is risky in that the operating conditions in the previous installation are often an unknown. People are known to run a car that has a constantly rapid cycling of the pressure regulator. This is not good for the sphere and the associated pipe work it is certainly harmful to early cast aluminium regulators. It is more likely to have failed due to this reason than to have had a piece of foreign matter lodged in the spool valve. However I do not discount this as a possibility given the neglect of the systems by certain past owners. I am sure that today given the precious nature of the cars and the care lavished on them, that neglect is now a thing of the past, especially among us Aussie Frog tragics. The consequences of previous neglect will from time to time come to the surface, causing us much consternation.
 
I had a similar experience with a one piece welded accumulator sphere. In my case excess pressure caused the O ring of the filler plug to fail, loud bang and hissing, creating a fine mist of hydraulic fluid. Replaced with another one piece sphere, without removing the regulator only to have the same result (slow learner). Removed the regulator and discovered on inspection that a small piece of O ring had jammed the central control valve. This I repaired and then put the regulator with a two piece accumulator back in the car. All is now working fine.

I guess that we (I) expect too much of our hydraulic systems, assuming that because a component has been working fine for 40 years, it will continue to do so indefinately. Perhaps we need to adopt the aircraft maintenance approach, replacing/repairing items at set intervals whether they need it or not.

Cheers
Richard
 
Another source of foreign matter in spool valves and check valves originates when people undo and replace pipe unions and insist on reusing the pipe seal to save time, probably because they do not have a new seal on hand. Where these seals work against the exposed threads in the bore of the union abrasion occurs and when the seal is removed there is often a small strand of rubber material that can break off and get into the pipe work. Where it ends up could be any where. Hopefully it gets trapped in the filter, but if it is on the High Pressure side of the component it will end up in that component.
The moral is -------Be Scrupulously Clean and Use New Pipe Seals. They are cheap and available readily on Ebay.
That said I must confess that I have been guilty of the former approach!! ------Bad Gerry!
 
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Turn the seals around ... the first time anyway! It's a bit like extending underwear use - front/back and inside out.

Even using a new seal doesn't remove the bits of old seal left in the pipe port, so, yes, it's a matter of good practice ensuring you removed all of an old seal first.
 
I'm with Richo here. Yes, old 2 piece spheres can be/are fatigued, but just because you have a welded sphere doen't mean you've solved the problem. When Dad ran & repaired citroens we saw only one exploded sphere between the late 60's and late 80's. But Dad threw away lots of spheres that had obviously been abused - unscrewed using cold chisels, the sides flattened in vices, deep cuts caused by stilsons. While welded spheres don't show that obvious abuse, how many times have they been dropped on concrete floors, or even thrown across a workshop? If you want to increase your comfort level with a 2 piece shere it is easy enough to get it crack tested or even X-rayed.
And as Richo rightly points out, the sphere is just one part of a complex high pressure system, lets look beyond the bit that broke & see if there is another issue, the sphere might simply be the bit that exploded this time.
 
Has anyone ever had a suspension sphere split? I have never seen this happen. They are a lot more robust than the accumulator sphere!
 
The accumulator sphere cops a lot more pressure and lot more shock loading than the suspension spheres. Brake accumulators on a DS are the same size as accumulator spheres and they don't cause trouble. They are to an extent insulated from the drama experienced by the accumulator sphere. I dismantled the two brake accumulators on my 1959 DS19 a few years ago to check them. They still held good pressure and the diaphragms and inside surfaces were fine. So I put them back together and regassed them.

Roger
 
<snipped>However I do not discount this as a possibility given the neglect of the systems by certain past owners. I am sure that today given the precious nature of the cars and the care lavished on them, that neglect is now a thing of the past, especially among us Aussie Frog tragics. The consequences of previous neglect will from time to time come to the surface, causing us much consternation.

If only that were the case.
The root problem I see is ignoring the workshop manuals, best workshop practise and the understanding of the nature of the engineering. This is usually, unfortunately, by owners who cannot afford or do not prioritise the funds necessary to do the work effectively or have it performed by the very few people who can.

Most of the owners working on their own cars or helping others unfortunately often perpetuate the poor work methods by demonstrating that not checking and maintaining correctly can result in a few more miles traveled and time saved. It is only the cars quality engineering which allows this continuing neglect and abuse.
 
One thing to take from this story is, if you drive a real Cit, pay special attention to the maintenance and adjustment of the handbrake. It is your last line of defence. If this had happened on the CX I should have had brakes via the front brake accumulator, as long as it to has been maintained of course. On my first CX we used to have queues at the petrol station, I used to let the CX roll down but when we went straight to rear suspension pressure for the brakes I knew I had a dead brake accumulator. Confirmed and rectified soon after.
 
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