Beware of the pressure release valve

[steelaway]

Suddenly I was getting lots of water in my engine bilge.

After a quick inspection I found the insulation on my calorifier had split - and water was seeping out.

I can only imagine that the pressure release valve has failed and the hot water has over pressurised the calorifier - Now I need a new one at - HOW MUCH!!

I know you really should give the valve a pull now again, but mine is deep down at the bottom of the tank - I forgot - I wont forget again!!

 

Every one ------ check your over pressure release valve

 

Alex

[blackrose]

I'm assuming you have a non-return valve somewhere on the cold feed pipe near the calorifier? In effect this turns your calorifier into a pressure vessel because the hot water can't back up the cold pipe in the event of PRV failure. In this case you can also fit a hot water expansion tank either between the NRV and calorifier, or in the hot water outlet pipe from the calorifier. This means that you aren't solely relying on the PRV.

Edited September 5, 2011 by blackrose

[Boat&Bikes]

Can someone explain please? pressure relief valve?

 

Ian

[MtB]

Suddenly I was getting lots of water in my engine bilge.

After a quick inspection I found the insulation on my calorifier had split - and water was seeping out.

I can only imagine that the pressure release valve has failed and the hot water has over pressurised the calorifier - Now I need a new one at - HOW MUCH!!

I know you really should give the valve a pull now again, but mine is deep down at the bottom of the tank - I forgot - I wont forget again!!

 

Every one ------ check your over pressure release valve

 

Alex

 

 

Best never to assume anything where plumbing is concerned. I doubt it was a failed PRV, they are designed NOT to fail-dangerous.

 

I suspect the problem is one widely unrecognised in the boating world. Metal fatigue. Pressurised copper calorifiers work harden then stress-fracture in an unacceptably short timescale when connected to a pump which cycles on and off like in a boat. I've seen this many, many times as a plumber in domestic houses and several times already in boats.

 

The problem regularly occurs in domestic installations and most copper mains pressure hot water cylinders have now split and been replaced with stainless steel cylinders. Production of copper mains pressure cylinders has stopped and stainless steel is now used virtually exclusively for domestic calorifiers.

 

I predict the same will happen in the boat calorifier business eventually once the problem is widely recognised.

[blackrose]

Can someone explain please? pressure relief valve?

 

Ian

 

If you have a calorifier there will be a big button usually at one end, which automatically releases pressure once a certain pressure is reached. It can be manually operated by twisting it clockwise. Sometimes limescale can form inside the valve and cause it to stick, often with the consequences described above.

[MtB]

Can someone explain please? pressure relief valve?

 

Ian

 

A valve connected to the calorifier which opens and lets water out (to reduce the pressure) should the pressure inside the calorifier rise to the opening pressure, often (but not always) 3.0 Bar.

 

Did that make sense??!

[blackrose]

Best never to assume anything where plumbing is concerned. I doubt it was a failed PRV, they are designed NOT to fail-dangerous.

 

I suspect the problem is one widely unrecognised in the boating world. Metal fatigue. Pressurised copper calorifiers work harden then stress-fracture in an unacceptably short timescale when connected to a pump which cycles on and off like in a boat. I've seen this many, many times as a plumber in domestic houses and several times already in boats.

 

The problem regularly occurs in domestic installations and most copper mains pressure hot water cylinders have now split and been replaced with stainless steel cylinders. Production of copper mains pressure cylinders has stopped and stainless steel is now used virtually exclusively for domestic calorifiers.

 

I predict the same will happen in the boat calorifier business eventually once the problem is widely recognised.

 

Yes, the calorifiers that most of us use aren't very good quality. I've seen a few leaking ones on boats and these weren't caused by faulty PRVs. Trouble is that quality stainless ones are expensive.

[Boat&Bikes]

Red button valve at top on mine which given a slight turn lets a little pressure release sound then?

 

Ian

[alan_fincher]

Sometimes limescale can form inside the valve and cause it to stick, often with the consequences described above.

Isn't the more usual problem with lime-scale that it gets stuck in a partly opened valve, that will then not seat properly, so it continues to dribble, (or worse).

 

It's hard for me to see how lime-scale can stop a valve that needs 3 bar (or so) before it opens, from actually doing so ?

 

Note - I'm not disputing that calorifiers fail, but is it necessarily due to a PRV being unable to open ?

 

EDITED: to acknowledge that others have already said that a PRV ought to fail "safe", which I had missed......

Edited September 5, 2011 by alan_fincher

[steelaway]

Best never to assume anything where plumbing is concerned. I doubt it was a failed PRV, they are designed NOT to fail-dangerous.

 

I suspect the problem is one widely unrecognised in the boating world. Metal fatigue. Pressurised copper calorifiers work harden then stress-fracture in an unacceptably short timescale when connected to a pump which cycles on and off like in a boat. I've seen this many, many times as a plumber in domestic houses and several times already in boats.

 

The problem regularly occurs in domestic installations and most copper mains pressure hot water cylinders have now split and been replaced with stainless steel cylinders. Production of copper mains pressure cylinders has stopped and stainless steel is now used virtually exclusively for domestic calorifiers.

 

I predict the same will happen in the boat calorifier business eventually once the problem is widely recognised.

 

Hi

 

Thanks for that but is has definitely over pressured - there is a large bulge on the side.

 

See--------Presure release valve

 

Alex

 

Isn't the more usual problem with lime-scale that it gets stuck in a partly opened valve, that will then not seat properly, so it continues to dribble, (or worse).

 

It's hard for me to see how lime-scale can stop a valve that needs 3 bar (or so) before it opens, from actually doing so ?

 

Note - I'm not disputing that calorifiers fail, but is it necessarily due to a PRV being unable to open ?

 

EDITED: to acknowledge that others have already said that a PRV ought to fail "safe", which I had missed......

 

 

 

I know what you a saying but I cant think what else it could be.

If it had blown after the severe winter I would have blamed freezing

 

Alex

[nb Innisfree]

Two positions it can be installed

 

[Ark Right]

Best never to assume anything where plumbing is concerned. I doubt it was a failed PRV, they are designed NOT to fail-dangerous.

Mike, I read your posts and respect in the main your comments.

Can you explain "not failing dangerous"

Then can you please tell me that you fully understand a boats water system, with respect to copper tanks failing.

Please correct me on the following :-

A boats calorifier is pressurised by the boats water pump ( to around 2-2.5 bar depending on the pump ) to a closed system.

Heat is then applied to the hot water system via the engine, heater or fire which raises the pressure in the

system to the most vulnerable part, the calorifier, which is "protected" by a PRV. The PRV sticks, limescale etc and BOOM

The valve called a PRV is actually an SRV (safety relief valve) and should only deploy in the worst scenario.

Systems should be in place to protect equipment as a first defence, not a last resort.

An expansion vessel in the hot supply line will take up the stresses from the increase in pressure due to thermal expansion and protect the calorifier.

Cheers A

Edited September 5, 2011 by Ark Right

[smileypete]

Every one ------ check your over pressure release valve

What pressure is printed on the cap of the relief valve?

 

Also what make is the calorifier out of interest?

 

ETA: Is it possible the calorifier got partly frozen over winter?

 

cheers,

Pete.

Edited September 5, 2011 by smileypete

[nb Innisfree]

[/color]

[/color]

Mike, I read your posts and respect in the main your comments.

Can you explain "not failing dangerous"

Then can you please tell me that you fully understand a boats water system, with respect to copper tanks failing.

Please correct me on the following :-

A boats calorifier is pressurised by the boats water pump ( to around 2-2.5 bar depending on the pump ) to a closed system.

Heat is then applied to the hot water system via the engine, heater or fire which raises the pressure in the

system to the most vulnerable part, the calorifier, which is "protected" by a PRV. The PRV sticks, limescale etc and BOOM

The valve called a PRV is actually an SRV (safety relief valve) and should only deploy in the worst scenario.

Systems should be in place to protect equipment as a first defence, not a last resort.

An expansion vessel in the hot supply line will take up the stresses from the increase in pressure due to thermal expansion and protect the calorifier.

Cheers A

 

An expansion vessel can only work as a safety feature for a while, it's there to prevent PRV weeping, eventually pressure can still increase to above the safety limit, PRV should protect the calorifier even if EV isn't fitted.

[Mike Jordan]

Ive had a similar problem in the past when a very expensive PRV failed to open. The valves are now cheap and easily available, if fitting a calorifier now, I think I would fit two valves to reduce the risk, they are cheaper than the tank!

Mike

[MtB]

[/color]

[/color]

Mike, I read your posts and respect in the main your comments.

 

Thank you!

 

Can you explain "not failing dangerous"

 

They are designed to be 'fail-safe'. I e. be open (safe) as opposed to jamming shut (dangerous) if anything in the valve breaks or fails.

 

In reality they sometimes DO fail to open when tested, as the neoprene seal sticks the the seat occasionally. This can lead to a 3 bar PRV not opening until, say, 3.5 bar or 4 bar is reached.

 

Then can you please tell me that you fully understand a boats water system, with respect to copper tanks failing.

 

I can't tell you that! I will never claim to 'fully understand' anything! One is always learning, even in subjects in which others might think or say you are expert.

 

I CAN tell you however that I hold the qualification required (under the Building Regulations section G3) to install and service domestic mains pressure unvented hot water storage systems. These appear to me to be identical to boat systems, but much larger.

 

Please correct me on the following :-

A boats calorifier is pressurised by the boats water pump ( to around 2-2.5 bar depending on the pump ) to a closed system.

Heat is then applied to the hot water system via the engine, heater or fire which raises the pressure in the

system to the most vulnerable part, the calorifier, which is "protected" by a PRV. The PRV sticks, limescale etc and BOOM

The valve called a PRV is actually an SRV (safety relief valve) and should only deploy in the worst scenario.

 

This is not what is supposed to happen. There is supposed to be an expansion vessel to accommodate and smooth out the pressure fluctuations which otherwise occur with heating. Even if the vessel is missing and the PRV is also jammed closed or missing, there will be no boom. Just a gentle split and spill of the contents all over the floor.

 

UNLESS the water in the cyl has been heated to above 100 degrees C (possible due to the higher pressure) in which case reduction to atmospheric pressure will result in all the water instantaneously turning to steam which WILL be a BOOM. And a very dangerous boom too.

 

 

Systems should be in place to protect equipment as a first defence, not a last resort.

An expansion vessel in the hot supply line will take up the stresses from the increase in pressure due to thermal expansion and protect the calorifier.

 

Correct!

 

Mike

[steelaway]

What pressure is printed on the cap of the relief valve?

 

Also what make is the calorifier out of interest?

 

ETA: Is it possible the calorifier got partly frozen over winter?

 

cheers,

Pete.

 

 

 

Hi

 

The PRV is set at 2.5 bar, I can't remember the name of the calorifier and the label on the thing has disappeared.

It might have frozen during the winter but why has it taken till September to show itself?.

 

Thanks for all the input guys.

 

Alex

[Proper Job]

Hi

 

The PRV is set at 2.5 bar, I can't remember the name of the calorifier and the label on the thing has disappeared.

It might have frozen during the winter but why has it taken till September to show itself?.

 

Thanks for all the input guys.

 

Alex

Ha..........

 

That's boats for you....

 

They wait until you're least expecting it.

 

[nb Innisfree]

If no EV is fitted hydraulic expansion will result in PRV opening earlier due to it's opening pressure being reached earlier than if an EV is fitted, in normal operating conditions EV prevents PRV venting and weeping which is for the better.

[ditchcrawler]

Hi

 

The PRV is set at 2.5 bar, I can't remember the name of the calorifier and the label on the thing has disappeared.

It might have frozen during the winter but why has it taken till September to show itself?.

 

Thanks for all the input guys.

 

Alex

It frightened because it knows winter is not far away

[Bobbybass]

It frightened because it knows winter is not far away

 

Many of the pound shops are selling..'water leak detectors'..for..guess what...a pound !!

Little round..self contained..look like smoke detectors.

I bought a few of these...they take a 9 volt battery...2 for a pound.

I have these under the bed.( no..I'm not incontinent !!( ..in cupboards ..under the loo out pipe..etc..anywhere I may get a leak...

They have contacts on the bottom...and it starts to shriek if there is any moisture between them. I also soldered an extension lead to one...and at the other end...I have two short brass rods that go into a choc-bar contact block. This is cable tied into my rear bilge. If the water level starts to rise..it warns me just before my bilge pump starts to go. Handy last week when I came down the Wigan flight...and got the rear under some leaky gates.

 

Great early warnings...for £1.50 including battery.

 

bob

Edited September 6, 2011 by Bobbybass

[smileypete]

Ha..........

 

That's boats for you....

 

They wait until you're least expecting it.

They wait until you can *just* afford it.

 

cheers,

Pete.

[steelaway]

They wait until you can *just* afford it.

 

cheers,

Pete.

 

 

 

The total cost of replacement has come to £675, now we will see what Saga Insurance have to say about it.

 

After speaking to 3 company's about a new calorifier I found Sure Cal to be the most helpful, professional and a very competitive price.

 

Alex

Edited September 6, 2011 by steelaway

[steelaway]

Suddenly I was getting lots of water in my engine bilge.

After a quick inspection I found the insulation on my calorifier had split - and water was seeping out.

I can only imagine that the pressure release valve has failed and the hot water has over pressurised the calorifier - Now I need a new one at - HOW MUCH!!

I know you really should give the valve a pull now again, but mine is deep down at the bottom of the tank - I forgot - I wont forget again!!

 

Every one ------ check your over pressure release valve

 

Alex

 

 

 

 

Well it's bad news from Saga.

They wont cover the claim for the calorifier insisting that the PVR failure is - 'wear and tear'.

The policy seems to exclude all water damage - 'unless by sudden accidental incursion into another vessel'.

I have objected to this and I have asked if my boat would be covered by this policy, if the water leak from the calorifier caused the boat to sink above the engine - its seems from this reply, it wouldn't

 

Alex

[Keeping Up]

Well it's bad news from Saga.

They wont cover the claim for the calorifier insisting that the PVR failure is - 'wear and tear'.

The policy seems to exclude all water damage - 'unless by sudden accidental incursion into another vessel'.

I have objected to this and I have asked if my boat would be covered by this policy, if the water leak from the calorifier caused the boat to sink above the engine - its seems from this reply, it wouldn't

 

Alex

 

Saga seem to have a comprehensive list of exclusions. When I asked them for a quote including contents, they stated that the policy excluded damage to all breakables. I asked them to define breakables, and they said it meant "anything that could break or be broken". If you exclude wear and tear as well as breakages, they've wriggled out of almost everything!