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Calorifier safety valve drain

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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 Topic: Calorifier safety valve drain
    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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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 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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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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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: 30 July 2022 at 21:05
2 lires seems fine. On Bloto today, and my wife says the pump runs less and doesnt sound as harsh. Result!   The treasurer is Happy!
Perry
PS I see your in Belgium, My mother in law was borm Antwerp [Folkstraat], still got familt there.


Edited by perry - 30 July 2022 at 21:06
Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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martijnvdh View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote martijnvdh Quote  Post ReplyReply Direct Link To This Post Posted: 30 July 2022 at 20:53
Hi Perry,
What size accumulator did you fit?
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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: 29 July 2022 at 10:37
The thermal expansion coefficient for water is approx 210 ppm/deg C
To heat your calorifier by electric or engine to same temperature will have same expansion.
water heated from 20-60 deg C will expand 40* 210 e-6 *20000 ccm = approx 170ccm
Ignoring the expansion of the tank volume  approx <1ccm

In some yachts the numerous rubber hoses in the hot water system will accomodate this amount of expansion. Some calorifiers are plain steel [NOT:- Copper, stainless, acier inox, rostfreier Stahl] pressure vessels with vitreous enamel liner. heat and pressure cycling may limit their life as the vitreous enamel coat detaches.

Yes,  one solution is to turn pump off, open tap to de-pressurise system every time you heat the calorifier.
We forget this  and so have fitted the pressure accumulator vessel which also benefits by reducing the pump cycles.
Bottom line is a good system should be built to work with thermal expansion of water, not just vent off to protect the pressure vessel.
Regards
Perry


Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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MasterKeil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MasterKeil Quote  Post ReplyReply Direct Link To This Post Posted: 29 July 2022 at 09:01
1. When the water is heated electrically then the overpressure valve should not open. If it opens, then the thermostat is not adjusted correctly.
2. When the water is heated by the engine, then the thermostat is bypassed. To prevent overheating and the overpressure to open we alway switch off the pressure pump and open the hot water tap. Then there is some water coming out of the tap, after a few minutes it stops. Then the water has expanded enough.
Hanse 370#640 "Nemesis"
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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: 28 July 2022 at 18:32
If you fit a pressure accumulator the expansion of the heated water will not excede the blow off pressure of the pressure relief valve.
Having said that the PRV fitted to my old Isotherm Calorifier was very low quality similar can be bought from China. I have sourced a better quality domestic PRV from local plumber shop, but you have to fit an additional one way valve [our plumbers call them "check Valves]. As the Iso therm PRV has an inbuilt one way valve.
I recently bought a replacement for the failed [corrosion]  Isotherm calorifier and an accumulator from UK company [Surejust]. same price as Isotherm, but made of quality materials with good valves.

Regards
Perry

Current Yacht Hanse 315 2007
Last Yacht Hanse 301 Round GB in 2017
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S&J View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote S&J Quote  Post ReplyReply Direct Link To This Post Posted: 28 July 2022 at 18:31
I think this is poor design by Hanse.  
Mine seems to produce more overflow from the electric heater than the engine.
On the 458 there is a dedicated sea-cock that drained the recess for the cockpit hatch slides.  Thinking of diverting my small bore pipe to this to avoid having to empty the bottle.  Haven't found a suitable way to add the plastic tube to the wider drainage tube yet...
H458 #159 Primal Mediterranean cruising
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