Expansion vessel failure

[danlightbulb]

Assuming it was just condensation in there, and the air completely vanished over time, then how can I get all that condensation out? Any water in the dry side of the vessel will be reducing its effective capacity? The shrader valve is at the top of the vessel, so when the pressure is gone it won't drain that way?

 

[terryplumb]

Fill the system ,bleed air from all rads including the one used as a makeshift EV ,fill to 1 bar.
And run c/ heating. See how you get on .

I give up !

 

[danlightbulb]

I give up !

Terry Im appreciating the help but Im trying to follow instructions from both yourself and John here. John says I should empty the vessel again which Ive now done.

@Johntheo5 Ive pressed the EV valve down and emptied all the air again. The air pressure came out first, no water came out but the system pressure dropped to zero. So I topped up the system back to 1 bar and depressed the valve again. A little bit of water came out which I collected in a small cup. Then I kept the valve depressed and basically a few droplets are coming out which I can soak up with some paper towel.

If I keep the valve down now, the system is at 1 bar but only a droplet is coming from the EV valve every few seconds.

If I press the valve down hard, Im getting a steady stream of a couple droplets a second, it doesn't seem to be slowing down.

 

[Johntheo5]

Very good, if the diaphragm is OK then it will be hard up against the schrader valve and absolutely nothing should come out of the open schrader valve NOT ONE MORE DROP EVEN
I would increase the filling pressure to 2bar let the schrader valve shut for say 5/10 minutes then reopen, if you get even a tiny amount of water from it, then the diaphragm is perforated.

 

[danlightbulb]

Very good, if the diaphragm is OK then it will be hard up against the schrader valve and absolutely nothing should come out of the open schrader valve NOT ONE MORE DROP EVEN
I would increase the filling pressure to 2bar let the schrader valve shut for say 5/10 minutes then reopen, if you get even a tiny amount of water from it, then the diaphragm is perforated.

Ok system is now at 2 bar and I will wait 10 minutes.

 

[Johntheo5]

Actually you don't have wait 10 minutes because the diaphragm will be hard up, just keep the schrader valve open and collect the droplets, if any, for a few minutes. Remember that when the system is hot that the air end vol is only 2 or 3 litres and a even a pin holed diaphragm allowing a drop every few seconds/minutes will waterlog the air end in very short order

 

[danlightbulb]

just keep the schrader valve open and collect the droplets

Cant do that unless I stand there with a tissue and a screwdriver holding the valve down - I don't have an open ended screw on/clip on schrader hose.

Anyway, Ive rechecked it, it seems nothing is coming out any more.

Will start refilling.

 

[Johntheo5]

Very good and well done.

 

[Johntheo5]

Start refilling after you have pre charged to 0.75bar.

 

[danlightbulb]

Ok EV is pumped to 0.8 bar. Valve cap put back on.

Drain valve closed and hose disconnected.

System filled to 1 bar, all upstairs rads reopened, temporary EV rad filled and bled.

 

[Johntheo5]

is there any way you can disconnect the filling line, if the system over pressurizes again then can definitely rule this out as a suspect

 

[danlightbulb]

is there any way you can disconnect the filling line, if the system over pressurizes again then can definitely rule this out as a suspect

I can, its an integral filling loop with a key insert thing. Will do it now.

 

[danlightbulb]

Ok system running and up to temp on boiler setting 2. Pressure very stable, climbed to just over 1 bar.

Will switch off now and let it settle before checking if any radiators need bleeding.

I've also tied a bag over the prv outlet to check for any drips.

 

[kidgreen61]

Has anyone considered that the flexi pipe connecting EV to hydroblock might be blocked ?

 

[Johntheo5]

A possibility I suppose originally but pressure just now on heat up seems normal, if flexi hose was still blocked the pressure would rise very rapidly.
The biggest puzzle to me is the amount of water that was spraying out of the schrader valve, I (still) find it hard to fathom as my very very rough calcs shows that only a few ml of water should condense out of the air when compressed.
The very comphrehensive tests seemed to rule out any pin hole in the diaphragm but of course (and hopefully not) the diaphragm would/could seal off the schrader valve with 2bar at the water end & 0bar at air end and water couldn't come out of the schrader valve even with a pin holed diaphragm.
Time will tell.