Spheres and failure modes

[thorter]

I had a quick look for any sphere photos, but all I found were these two. I am pretty sure they were genuine OEM parts. You can see inside surface rippling that the splits may have followed (would expect non original to be similar), and also the area heated by the welding. The second photo is a cylinder stopper made from the threaded part, and you can see the lip that is inside once the sphere has been formed.

T

[white exec]

Interesting to compare the base welds on these:

split sphere, as above

genuine Citroen sphere (Acc)

genuine Citroen sphere (Acc)

If you look closely, the weld on the split sphere is narrow, does not cover the 'shelf' of the damper insert, and does not extend very far up the sphere wall.
It looks as if that weld has just opened up, allowing the sphere wall to peel away.
The unwelded edge of the wall is clearly visible.

All the Citroen spheres I have here are finished to the same standard as the last two photos.

[aerodynamica]

Wow! Exploded sphere! I've certainly heard of this before - about 15 years ago Darrin from citroen classics in staines had this same failure on his 1966 ID19B. It was caused by the same reason: pressure regulator cut out valve sticks and the hp pump continues to feed pressure until something goes..... it's a known problem on early Ds using the alloy body pressure regulator but I've never heard of the event on any cast body units (every citroen since 1967). But the failure here isn't as strange as you think, the accumulator sphere is the largest cross sectional area of any line pressure part between the pump and the system and so that sectional area will be subject to the highest force and no surprise it fails here. This has nothing to do with the sphere being flat or having the spikes on the top part by the way. It's funny, on the ID19, the accumulator aims down to the ground and Darrin told me about the hole it made on the ground!