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Author Topic: Cooling Water  (Read 2588 times)

toesupwa

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Cooling Water
« on: September 22, 2007, 11:43:44 PM »

I'm building a wartime tug and am using watercooling to cool the ESC.

The 'outflow' from the system is in a scale position as per the full size and i have a pump to move water through the system. I'm considering connecting the pump to the motor (electrically) to get the water flow to increase with motor speed

Would the outflow from the cooling on a full size tug increase with engine speed (geared to the motor) or would it stay a constant speed?
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Ghost in the shell

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Re: Cooling Water
« Reply #1 on: September 22, 2007, 11:51:19 PM »

To be honest I dont know, however I'd guess it would be driven mechanically off the crank, much in the same way that an automobile water pump works, so it would probably change depending on the RPM of the motor. 
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boatmadman

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Re: Cooling Water
« Reply #2 on: September 22, 2007, 11:56:07 PM »

Not sure about that, I tend to think water pumps would be separately driven, - however, in an early boat with no automatic temperature control, valves were adjusted manually to maintain the correct temperatures, so the flow would increase somewhat as the engine temps rise.

I know I had to do it manually as a junior engineer many years ago!
Ian
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Bunkerbarge

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Re: Cooling Water
« Reply #3 on: September 23, 2007, 06:42:02 PM »

Only if the water pump is driven by the engine which is not usually the case at this size.

Usually the main sea water cooling pump will be electrically driven, with a stand by arrangement, and the cooling load is controlled by a by-pass valve either automatically or manually controlled.

The only ones I have actually come across on larger ships being driven by the engine are the fresh water cooling circuit pumps so I think in the vast majority of cases for this size vessel and above the outlet from your sea water cooling system will remain constant. 

You will notice small engines such as lifeboat engines, small fishing vessels etc have engine driven sea water pumps but these tend to be only on small engines.
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Ghost in the shell

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Re: Cooling Water
« Reply #4 on: September 23, 2007, 08:48:34 PM »

is it actually sea water then that is flowing through the engine on big marine diesels, or is the sea water cooling the coolant though a heat exchanger?
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Shipmate60

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Re: Cooling Water
« Reply #5 on: September 23, 2007, 08:57:56 PM »

The seawater is pumped through a Heat Exchanger and over the side, that is what you see, the overboard discharge.
Most machinery has its own outlet, but can be in groups.
ie
Port Main Engine, Port Side
Stbd Main Engine, Stbd side
The generators can be on a cross-connection pipe so can outlet either side, even with 4 running.
Other machinery has their own outlets, eg Fire Pump, Emergency Fire Pump, Emergency Compressor etc.
So in theory you can have quite a few or 1 for single Main Engine, and one for Generator.

Bob
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Colin Bishop

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Re: Cooling Water
« Reply #6 on: September 23, 2007, 09:03:12 PM »

Most discharges are in the area of the engine rooms as would be expected but I have noticed that on a lot of ships, particularly older ones, there are frequently quite substantial discharges just above the waterline in the forward part of the ship. What are these likely to be?
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boatmadman

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Re: Cooling Water
« Reply #7 on: September 23, 2007, 09:04:40 PM »

Just to clarify a little more, engine cooling systems are closed systems of treated water to reduce/eliminate scale formation and corrosion. These closed systems are then cooled by the sea water via the heat exchanger.

Ian
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Bunkerbarge

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Re: Cooling Water
« Reply #8 on: September 23, 2007, 09:18:07 PM »

Just to clarify a little more, engine cooling systems are closed systems of treated water to reduce/eliminate scale formation and corrosion. These closed systems are then cooled by the sea water via the heat exchanger.

Ian

On larger boats and ships yes, but on smaller engines such as small fishing boats, outboards and lifeboat engines etc. you may well find an engine driven pump pumping seawater.

Colin, discharges further forward could be ballast discharges, anchor washing systems or even auxilliary cooling systems for such equipment as refridgeration etc.  You may well find also scupper discharges from deck drains above the water line.

Really old steamers didn't reclaim thier condensate, they actually used sea water for feed, so you might have condensate discharges from deck machinery, winches etc.  Then, of course, the early steamers with crew living in the foc's'le would also have the thunderbox discharge directly overboard at round about water line level.  I bet they kept one eye on that when they were touching up the hull paintwork!!!
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boatmadman

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Re: Cooling Water
« Reply #9 on: September 23, 2007, 10:18:49 PM »

smallest boat I was ever on was 17000t!

thunderbox  O0 long time since heard that one!
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HS93 (RIP)

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Re: Cooling Water
« Reply #10 on: September 23, 2007, 10:26:50 PM »

Just out of interest what tug is it ?

Peter
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toesupwa

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Re: Cooling Water
« Reply #11 on: September 24, 2007, 09:05:14 AM »

Its a wartime tug (that still exists) out of San Pedro, LA called 'Angels Gate'...

Originally she was ST695 built in 1944 and a design type 327
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catengineman

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Re: Cooling Water
« Reply #12 on: October 04, 2007, 06:55:46 PM »

Hi, I offer this as some information only.
If you intend to cool your ESC's (I cool mine) I would recommend that you use a small pump rated for constant use as to my sadness I found that installing car washer pump type units failed as they are not built to run for very long periods, the heat from the electric motor melted the pump back plate and hence a water ingress occurred (costly)
A scoop from behind the screws will send water through the system (cooling) and you will see it as the vessel passes.

R,
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toesupwa

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Re: Cooling Water
« Reply #13 on: October 09, 2007, 02:15:57 PM »

If you intend to cool your ESC's (I cool mine) I would recommend that you use a small pump rated for constant use...

Yes catengineman
I'm using a small 'micro' pump by Sensidyne that is able to pump small quantities of water / Air to produce scale amounts of water at the outflow and just enough for ESC cooling.
I have been using one of these pumps in one of my other boats with the same set up as i intend to use on Angels Gate and as yet, the pump seems to be working without any problems..

http://www.sensidyne.com/products.php?ID=1286
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Ghost in the shell

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Re: Cooling Water
« Reply #14 on: October 10, 2007, 09:44:40 AM »

the idea of the pick up, that is far simpler, and more reliable. 
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