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leaking calorifier, advice please.


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Just got back to the boat after a shopping trip to find the water pump cycling on and off for no apparent reason, eventually traced it to a leaky calorifier which has split near the top of the tank.

I've turned the water off for now and called the local boatyard who unfortunately can't look at it till Wednesday, so is there anything special I need to be doing in the meantime to minimise any issues. I'm  thinking I can turn the water off and on when needed and assuming the engine water circuit will be ok even though there is no water in the calorifier to heat.

Sadly there isn't. an isolation valve for the calorifier.

Any advice would be most welcome.

 

 

 

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3 minutes ago, waterdog said:

Any advice would be most welcome.

 

First of all, fit an accumulator if you don't already have one.

 

The split can be soldered or brazed over but you'll need to drain the calorifier first.

 

A better fix is to replace it. 

 

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9 minutes ago, Mike the Boilerman said:

First of all, fit an accumulator if you don't already have one.

 

The split can be soldered or brazed over but you'll need to drain the calorifier first.

 

A better fix is to replace it. 

 

Thanks Mike, there is an accumulator on the cold feed, do you suggest a 2nd one (expansion tank ?) on the hot circuit ? and yes replacing the calorifier is the preferred option. 

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1 minute ago, waterdog said:

Thanks Mike, there is an accumulator on the cold feed, do you suggest a 2nd one (expansion tank ?) on the hot circuit ? and yes replacing the calorifier is the preferred option. 

Yes he did, and yes it would :)

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A second one on the hot water calorifier is essential if there is a non-return valve anywhere in the cold feed supply to it from the pump. Manufacturers often conceal one inside the cold water tapping.

 

If there is definitely no cold feed NRV then a decent sized pump accumulator will suffice.

 

 

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Thanks guy's, hopefully there is a schematic attached to this post and it looks like there is an nrv fitted. 

 

We've had this boat four months but our previous boat was a share and it had two calorifiers burst in 3 years, no hot accumulator on that boat either. 

 

Is there anything I should / should not be doing till I get to the boatyard next Wednesday?

IMG_20190810_162131315.jpg

PS, where in the above drawing should the accumulator be fitted?

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I once repaired a radiator in a Hillman Imp with Super Epoxy. The split had appeared where the radiator flexed when the engine was revved, so I was not overly confident. I sanded and coated it, when dry sanded and recoated. I hoped it would last a month 'til  I could afford to replace it, but it was still going strong 12 months later. Yes, fit an expansion vessel. You could use the PRV pipe if there is enough room by it. It could be more convenient. Also, there is no reason why you should not use a flexible hose for connection. A heating spares stockist should be able to find one that is used in a boiler. This gives you more options.

 

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An isolation valve in series with the non return valve can be very useful. It doesn't look like you have one in your diagram, When my first cauliflower failed, again with no expansion vessel, the valve meant that I could drain down the calorifier and still use the cold water system until the new cylinder and expansion vessel arrived. Something I'd recommend getting fitted while it is in bits. Put it on the inlet side, not the outlet!

 

Jen

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7 minutes ago, Jen-in-Wellies said:

When my first cauliflower failed, again with no expansion vessel,

 

And as an aside, I'd point out again that threads about split calorifiers seem always to be about those with no expansion vessel on enquiry. 

 

I'm not sure I've ever seen a thread on here about a split calorifier that had an expansion vessel fitted. Adding one seems a sensible precaution but whenever I suggest it, I seem to get a stream of responses saying theirs has no expansion vessel and it has been fine for 20 years.  Well it would be, until it splits!

 

Just sayin', in case anyone wants to listen :)

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28 minutes ago, Mike the Boilerman said:

I'm not sure I've ever seen a thread on here about a split calorifier that had an expansion vessel fitted

Would a pressure relief valve be an equally a acceptable solution?

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8 minutes ago, MartynG said:

 

Would a pressure relief valve be an equally a acceptable solution?

No.  The prv is more like 3.5bar, whereas pump pressure is typically 1.8 bar, so much greater wall stress of the calorifier if no expansion vessel, therefore a shorter life before fatigue cracks develop.

 

added - the prv is for ‘emergency’ over pressure relief to prevent bursting, it is not for reducing cyclic stresses.  So don’t think you don’t need a prv if you have an expansion tank, you do.

 

Added again - As an aside, stresses within the design capability repeatedly applied can cause fatigue failure which until the Comet aircraft failed (google if you don’t remember) were not understood.

Edited by Chewbacka
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Thanks everyone, all advice gratefully noted, we will be getting a new tank, accumulator and isolation valve fitted so hopefully this will now be a one time fix.

 

Our experience with the share boat and now on our own boat is that in all the failures,  the tanks were vertical, there was no hot accumulator and they all had prv's so it looks like the presence of a prv will not save the tank.

 

Interestingly, all three tanks failed near the top shoulder of the tank, near the join between the vertical sides and the domed top.

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17 hours ago, Tony Brooks said:

anywhere in the dotted line (hot pipes)

I would suggest that it preferable should be on the cold inlet to the calorifier, after the NRV, on the PRV pipe would be fine.

The expansion vessel will last longer than if it is on the hot water side.

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1 minute ago, Tonka said:

well having had a narrowboat since 1980 (3 of) none of them had an accumulator in the hot water side and none of them burst or split. Have I been lucky. They do have a prv fitted in the hot water tank though.

Maybe excess pressure was never a problem if it was released most times a tap (hot or cold) was turned on and taps were frequently used during water heating, or maybe your water was not that hot, so not much expansion etc.  Lots of reasons why, but is it worth the risk to not have one??

 

Thinking about it, heating the tank at night using an immersion heater to a high temp when everybody is asleep and not drawing water, is probably the worst case.

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2 minutes ago, waterdog said:

Thanks everyone, all advice gratefully noted, we will be getting a new tank, accumulator and isolation valve fitted so hopefully this will now be a one time fix.

 

Our experience with the share boat and now on our own boat is that in all the failures,  the tanks were vertical, there was no hot accumulator and they all had prv's so it looks like the presence of a prv will not save the tank.

 

Interestingly, all three tanks failed near the top shoulder of the tank, near the join between the vertical sides and the domed top.

Classic failure point, the stresses cause cracks where the copper can't freely expand due to the rigid angle of the top bend. You may well find that the bottom concave plate is distorted too.

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4 minutes ago, waterdog said:

Thanks everyone, all advice gratefully noted, we will be getting a new tank, accumulator and isolation valve fitted so hopefully this will now be a one time fix.

 

Our experience with the share boat and now on our own boat is that in all the failures,  the tanks were vertical, there was no hot accumulator and they all had prv's so it looks like the presence of a prv will not save the tank.

 

Interestingly, all three tanks failed near the top shoulder of the tank, near the join between the vertical sides and the domed top.

That is where the stress will be high as the top constrains the sides, and the bending is confined to a small zone.

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11 minutes ago, Tonka said:

well having had a narrowboat since 1980 (3 of) none of them had an accumulator in the hot water side and none of them burst or split. Have I been lucky. They do have a prv fitted in the hot water tank though.

I'm sure I've read somewhere where it was suggested that modern tanks are not as robust as they once were so calorifier failures are becoming more common due to stress fractures. It kind of makes sense if this is the case that people don't experience any problems with no accumulator if the tank is stronger in the first place.

Edited by waterdog
remove unnecessary apostrophe
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22 minutes ago, Chewbacka said:

Added again - As an aside, stresses within the design capability repeatedly applied can cause fatigue failure which until the Comet aircraft failed (google if you don’t remember) were not understood.

 

Exactly this. 

 

A PRV will reduce neither the amplitude nor the frequency of the pressure cycles in the calorifier. Fitting a decent sized accumulator smooths out the pressure swings and reduces the number of them too, so the inevitable metal fatigue split in the copper arrives so very much later than it otherwise would - years and years later. 

 

 

Edited by Mike the Boilerman
Improve clarity.
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1 hour ago, waterdog said:

I'm sure I've read somewhere where it was suggested that modern tanks are not as robust as they once were so calorifier failures are becoming more common due to stress fractures. It kind of makes sense if this is the case that people don't experience any problems with no accumulator if the tank is stronger in the first place.

It would not surprised me if the copper sheet is thinner now than 20 years ago.

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3 hours ago, Boater Sam said:

I would suggest that it preferable should be on the cold inlet to the calorifier, after the NRV, on the PRV pipe would be fine.

The expansion vessel will last longer than if it is on the hot water side.

 

How so? Anywhere downstream of the NRV is all part of the same hot water vessel. So the water on the cold feed after the NRV will be heated and is effectively part of the hot water side.

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