ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

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Pengze
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ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by Pengze »

Hello,
Could anyone tell me, is there a formula or minimum & maximum height for installing diesel engine's jacketwater (freshwater)expansion (header) tank in the engine room?
Also, what is the reserve capacity for the header tank which caters for an engine whose total capacity is 800 litres & using independent centrifugal pump?
The pump's capacity is 100m3/hr@ 23M @ 15KW.
Thanks.
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JK
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by JK »

Height of the expansion tank above the engine JW pump should be in the manufacturers information.
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by Madzng »

Each engine maker will have different requirements, but the basic reasons for having an expansion tank include the following;

1. To allow for the expansion/contraction of the water as its temperature changes.
2. To prevent the cooling water gassing up at the pump suction, by ensuring a positive suction head, and prenventing air being drawn in throught the pump shaft gland.
3. To collect the returns from the vents and keep the system closed.

The maximum height of the tank will depend upon the maximum cooling water pressure allowed by the engine maker, and it should be ensured that this pressure is not exceeded with the cooling water pump running.

The requirements for the expansion tank fitted for a Wartsila 32 engine;
a tank volume of minimum 10% total system volume,
a pressure of 70 - 150 kPa at the pump inlet,
An inspection hatch, a level gauge, a low level alarm and necessary means for dosing of cooling water additives should be fitted.
The vent pipes should enter the tank below the water level. The vent pipes must be drawn separately to the tank.
The balance pipe down from the expansion tank must be dimensioned for a flow velocity not exceeding 1.0...1.5 m/s in order to ensure the required pressure at the pump inlet with engines running. The flow through the pipe will depend upon the number of vent pipes to the tank and the size of the orifices fitted in the vent pipes.

The requirements for your engine may differ slightly from the above, the engine maker will normally be happy to help.
Pengze
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by Pengze »

Hello Gentlemen,
Thank you very much for your kind info.
I would like to clarify once again, whether the tank height is calculated from the suction of the pump inlet OR from the jacketwater outlet / discharge manifold of the engine ? Because there is some dispute among my colleagues.

As to the phrase, 'the vent pipes should enter the tank below the water level', do you mean that the vent pipe or jacketwater outlet vent from the engine should always be submerged in water inside the tank, why is that so? Appreciate if you can explain further on this theory.

How about the Formula for the calculation of the height?

Keep up the good work and make this a better world to live in.
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The Dieselduck
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by The Dieselduck »

I would venture to say that there is no real formula for figuring it out because, it is up to the manufacturer's recommendations, and I would say its probably the height from the pump suction. The pressure is usually not that great, probably around one bar for smaller engines, 2-3 for larger ones. Unless you are asking the basic engineering formula of finding out pressure of a liquid at height "(constant of liquid or density) x (gravity) x (height) = (pressure)"

The pipes should be under water, I assume to prevent any air getting back into the system in times of surging.

Cheers,
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Pengze
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by Pengze »

Dear Mr.Martin,
Appreciate your effort. What is the value of the 'gravity' as in the engineering formula?Thanks & looking forward to your kind reply.
With Best Wishes from me.
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by The Dieselduck »

Gravity is ~9.81 m/s2.
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by Pengze »

Dear Mr.Martin,
Thank you very much for your help.
It certainly helps.
Have a nice day.
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by daave »

Hi, it might be late to post a reply but it's'the fist time i check out this forum. As to answer the expansion tank height question, i just want to say that you must not forget that it is to be high enough above sea water level to prevent sea water from getting into jacket water in case of jacket water cooler failure. If some tubes in your jacket water cooler leek and your jacket systeme is not under pressure, you have to have a greater jacket water head than the sea water head other ways, sea water will get in your jacket water system.
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Re: ENGINE JACKETWATER'S EXPANSION(HEADER)TANK

Post by WartsilaRoadWarrior »

I agree Martin. I know generally speaking we look for a static pressure of "around" 1 Bar. In some installations it may be necessary to fit a pressure cap if the exp Tk cannot be located high enough...

J

The Dieselduck wrote:I would venture to say that there is no real formula for figuring it out because, it is up to the manufacturer's recommendations, and I would say its probably the height from the pump suction. The pressure is usually not that great, probably around one bar for smaller engines, 2-3 for larger ones. Unless you are asking the basic engineering formula of finding out pressure of a liquid at height "(constant of liquid or density) x (gravity) x (height) = (pressure)"

The pipes should be under water, I assume to prevent any air getting back into the system in times of surging.

Cheers,
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