Open vented hot water. Explosion situations?

[charliechaplinspants]

Also a blocked vent pipe and cold feed pipe (ie due to freezing in the loft and being uninsulated) - can lead to CYLINDER IMPLOSION (when a tap isopened the pressure in the cylinder falls to BELOW ATSMOHPERIC PRESSURE and can cause the cylinder to deform.

How would that happen? if the cylinder is full and the vent has frozen and the cold feed to the cylinder, (is that the cold feed you meant)? is frozen, then you opened the hot water tap, wouldn`t the water in the cylinder just come out of tap until the top bit of cylinder was drained? How/why would it implode?

I am asking this question because I am interested to know why, not because I already think I know the answer because I don`t.( for my friends out there).

 

[seco services]

same as a primatic cylinder if you bung the system and open a draincock
the cylinder will implode

 

[Hugh Jaleak]

I have seen a cylinder shaped like an hourglass after the vent/cold feed froze. Whilst a cylinder will stand considerable external pressure, in the event of the vent/cold feed freezing, any hot draw off can cause a vacuum inside the cylinder and atmospheric pressure pushes the sides in.

Liken it to a plastic soft drinks bottle, drink out of it without allowing air to replace the liquid drunk, it implodes.

 

[charliechaplinspants]

Very interesting, thanks very much.

 

[Onetap]

With open vented hot water systems, what situations (s) can occur such as a fault(s) that could cause an explosion?.... I have heard there is a chance of it, but am not sure how? And would like to for obvious reasons? I know the cylinder has a vent pipe to take away steam if the boiler thermostat does fail?.... Anyone able to help me please?...

It cannot happen if the system is vented. It can happen if the open vent is blocked, for example ,

1) Open vent blocked by freezing. I have been told of an incident where this happened with a solid fuel boiler.

2) Incorrectly installed with no open vent. This happened on a fishing boat, the Fleur de Lys. The explosion sank the boat within minutes. The crew were fortunate to survive.


Old type immersion heater thermostats were prone to fail 'On' by the contacts weldig themselves together. There were 2 fatal accidents in recent years in which the cold water storage tank filled with boiling water and collapsed. I believe both tanks were incorrectly installed, a BS storage cistern should be able to tolerate boiling water for many hours. New thermostats now have an additional manual reset thermostat.

 

[doitall]

I have seen a cylinder shaped like an hourglass after the vent/cold feed froze. Whilst a cylinder will stand considerable external pressure, in the event of the vent/cold feed freezing, any hot draw off can cause a vacuum inside the cylinder and atmospheric pressure pushes the sides in.

Liken it to a plastic soft drinks bottle, drink out of it without allowing air to replace the liquid drunk, it implodes.

Just to add to this, assuming the cold feed and expansion is blocked, there's three ways the cylinder can implode.

A standard cylinder cannot, simply by opening a tap.

It's possible as the water cools.

It can if there's a secondary return, and water is drawn from the return leg.

It can if you attempt to drain the cylinder.

I've seen vents capped, and check valve fitted in the vent.

 

[BingoBongo]

I have seen a cylinder shaped like an hourglass after the vent/cold feed froze. Whilst a cylinder will stand considerable external pressure, in the event of the vent/cold feed freezing, any hot draw off can cause a vacuum inside the cylinder and atmospheric pressure pushes the sides in.

Liken it to a plastic soft drinks bottle, drink out of it without allowing air to replace the liquid drunk, it implodes.

i have also seen a bottom floor flat cyl being drained,syphon above flats and implode said cylinders

 

[namsag]

Secoservices....... Come on then spill the beans did you bung a primatic and find out the hard way

 

[seco services]

Secoservices....... Come on then spill the beans did you bung a primatic and find out the hard way

no come on namsag.

i think i read it on here someone did yrs ago

 

[namsag]

We had an apprentice do it and collapsed it completly what a mess.

Mr lazy here thought i would try it to change a rad valve , listening carefully as i took no more than quarter of a pint out ,thump , went an looked a fair size dent took bungs off and dent popped out. Lesson learnt