Expansion vessel ruptured twice in 11mths (Tornado unvented indirect)

[globalste1]

Hi all

I’ve looked on here for quite a while and I’ve found one or two people who have had the same sort of problem, like this one
https://www.diynot.com/diy/threads/...nless-steel-tank-leaking.367499/#post-2793773
I have a Tornado 250ltr unvented indirect cyclinder, in June 2018 the bladder failed (Petry dish flowing giveaway) and this was replaced with a new expansion vessel and a new PRV and some other bits that I forget about.

In November 2019 the space above the cylinder flooded with water. The heating engineer claimed it was a cylinder failure, so I drained the water out with a pump (all 40litres of it) and then stuck a camera down and could see the expansion vessel had ruptured through the metal and was pumping water out. I would say the vessel was corroded as well as having ruptured.

this week, I noticed some moisture at the top of the jacket, I took the lid off and well... 2” of water at the bottom on top of the cylinder again!!! I drained the water with a syphon again and then stuck my camera down there. Almost the same thing again, But this time a large bulge in the expansion vessel along the neck. Photo below.

im getting the feeling I’m either getting poor expansion vessels from my plumbing company/fitter, or, there is something weird going on with the cylinder controlling it’s pressure maybe? I’d be really interested to hear if anyone has seen this before and what they would be looking at replacing/changing. I’m trying to avoid a new cylinder system as I can’t really afford the layout at the moment.

many thanks

 

[Servotech]

It's quite a problem with these expansion vessels isn't it.
During the manufacture of them Im told that the inner coating sprayed on to protect them dosen't always fully get into the seems hence they rust up in no time.
You could try a different manufacturer?
Making them out of copper would be the answer in my book because there is a royalty amongst metals and steel isn't a very noble metal.
You would never use steel fittings in a open vented system because they would rust up in no time so why make expansion vessels for unvented out of it?
Of course non of this is much use to you as it is a "trade problem", all I can do is wish you better luck with your next ex vessel.
servotech,

 

[Gasguru]

Water should never come into contact with the steel unless the membrane has failed...that's usually from lack of regular maintainance.
The air pressure should be checked and topped up at least yearly.....I do mine every 6 months.