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Calorifier safety valve drain

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Martin&Rene View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Martin&Rene Quote  Post ReplyReply Direct Link To This Post Posted: 01 August 2022 at 17:52
A well documented theme.  Look here for my comments and also follow the link;



The bottom line for solutions is
*   Install an accumulator.  But I cannot find space on a 341.
*   Follow a procedure of switching off the pump and relaxing the system when starting the engine or turning on the heater.  We do this nearly all the time.
*   Run a small pipe from the PRV up to and out through a hole drilled in the stern shower outlet. somebody has said this is not advisable in a hard water area as you could get scale build up in the pipe, but that is not a problem in Scotland.   Interestingly, when I take it off at the end of the season to drain the system, there is often not much water in it.

Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout, normally based in Scotland
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 03 August 2022 at 08:04
I blanked the valve off in 2005 & just remember not to overtighten the hot taps in the heads & the sink ( there is no need to force them anyway)when starting the engine or shore power if the water is cold. The tap sometimes drips a small amount into the sink, but that is no big deal. If I am using a lot of water & it is being heated by shore power, the tap is being turned on & off , thus releasing pressure anyway.
At the end of the year I drain off the water by disconnecting a hose so do not have to use the safety valve to release water


Edited by samuel - 03 August 2022 at 08:07
Daydream Believer- Hanse 311- No GBR9917T- Bradwell Essex
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perry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote perry Quote  Post ReplyReply Direct Link To This Post Posted: 03 August 2022 at 08:32
Pressure vessel with no pressure release valve?
If your immersion heater over temperature cut-out fails you will boil the water to steam and the calorifier looks like a bomb. Steam explosions were the problem in early steam engine boilers, and so the PRV was invented.
Sounds pretty dangerous to ignor safety history? typically pressure vessel safety regulations also prevent pipe connections to PRV outlet, this is in order that the blow off [preventing explosion]  cannot be restricted.

You are relying on the rubber hoses to be your accumulator, and you havent had a problem, 'so far so good'.
I think over pressurising the calorifier is just not a good idea, please see my previous comment on Isotemp mild steel pressure vessels with vitreous enamel interior coating for corrosion resistance.
Regards
Perry


Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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samuel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote samuel Quote  Post ReplyReply Direct Link To This Post Posted: 03 August 2022 at 13:25
Originally posted by perry perry wrote:

Pressure vessel with no pressure release valve?
If your immersion heater over temperature cut-out fails you will boil the water to steam and the calorifier looks like a bomb. Steam explosions were the problem in early steam engine boilers, and so the PRV was invented.
Sounds pretty dangerous to ignor safety history? typically pressure vessel safety regulations also prevent pipe connections to PRV outlet, this is in order that the blow off [preventing explosion]  cannot be restricted.

You are relying on the rubber hoses to be your accumulator, and you havent had a problem, 'so far so good'.
I think over pressurising the calorifier is just not a good idea, please see my previous comment on Isotemp mild steel pressure vessels with vitreous enamel interior coating for corrosion resistance.
Regards
Perry

I do not think there would be a problem. It is nothing like a pressure vessel in a steam engine. That would have a void for large quantities of steam in the vessel. This has steam that is compressed & can release pressure extremely quickly. Water does not do that. These calorifiers are virtually all filled with water. When testing steam boilers the method includes filling the vessel with water & pressurising the tank. If it fails, a bit of water seeps out of a seam. There is no violent bang. In my installation it would be more liable to blow a plastic pipe fitting long before it got to danger state.

 I do not let the water run dry. If it does the tap would be open or the shore power would be turned off. The thermostat would trip. It is not set to scald. Engine temp will not boil the water, unless there was a major engine fault & the engine alarm would go off long before that.


Edited by samuel - 03 August 2022 at 13:32
Daydream Believer- Hanse 311- No GBR9917T- Bradwell Essex
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