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Cooling Water Exchanger


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#1 vvsastry66

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Posted 16 October 2008 - 12:40 AM

Dear Friends,

Could any one tell me, if a cooler, with cooling water on tube side, with cooling water supplied from a cooling tower, is placed above 10 metres elevation, should the cooler tube side to be designed for full vacuum?

Regards
Sastry

#2 fallah

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Posted 18 October 2008 - 06:54 AM

QUOTE (vvsastry66 @ Oct 16 2008, 01:40 AM) <{POST_SNAPBACK}>
Dear Friends,

Could any one tell me, if a cooler, with cooling water on tube side, with cooling water supplied from a cooling tower, is placed above 10 metres elevation, should the cooler tube side to be designed for full vacuum?

Regards
Sastry

Yes,because of:
a)possibility of circulating pump trip
b)elevation above 10 meters from grade


#3 Art Montemayor

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Posted 18 October 2008 - 10:23 AM

Sastry:

A cooling water piping system is routinely found at elevations 10 meters high (above the cooling water pumps' centerline) - and sometimes even higher. I've used cooling water lines as high as 70 feet (21 meters) above the cooling water pumps.

You probably know what you are referring to, but you don't even mention it - the possibility of pulling a backward syphon of water in the elevated pipe upon cooling water flow failure (pump shutdown, for example) with a downstream valve shutoff. Gravity would pull the elevated water back into the cooling water pumps (which are located next to atmospheric cooling water towers) and pull a vacuum. This is what you are concerned with, isn't it? You really should explain in detail what you are referring to. It helps the responder to stay on the same logical path and avoids a lot of needless and unrelated chatter.

When you have a cooling water cycle like the one you describe, it is routine to study the vacuum possibility and, as such, one looks at the vacuum resistance of all components. I think you will find that a typical 14 bwg, 3/4" condenser tube can normally withstand the pull of vacuum. Smaller tubes will withstand it easier. But regardless of the tubes, the entire tubeside should be protected - and this is normally done with a simple vacuum breaker installed in the line, at the highest point of the cooling water circuit.

The principle of a vacuum breaker can be applied with a spring-loaded device or, as I have done in the past, with a simple vertical standpipe that is designed in accordance with the maximum TDH that can be developed by the cooling water pumps. The standpipe has no moving parts and is virtually maintenance-free.

Therefore, the answer to your question, "should the cooler tube side to be designed for full vacuum?" is NO.


#4 djack77494

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Posted 20 October 2008 - 09:14 AM

A simple but elegant solution to a perennial problem. Vacuum is typically not a problem with tubing & smaller bore piping, but could be a problem with the heat exchanger channels.

#5 Qalander (Chem)

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Posted 20 October 2008 - 11:15 PM

QUOTE (djack77494 @ Oct 20 2008, 07:14 PM) <{POST_SNAPBACK}>
A simple but elegant solution to a perennial problem. Vacuum is typically not a problem with tubing & smaller bore piping, but could be a problem with the heat exchanger channels.


Dear vvsastry66 hello/Good Morning,
May I just add my little bit in my way.
The situation has been truly explained by Our 'Art' and 'Doug'.
However it is neither customary nor practicable to limit process piping and equipment placement be governed by Cooling water/Tower Grade level.
But an active effort/consideration for all-time CW flow availability is positively ensured to avert any consequential problems ;
One of those identified and mentioned by you in the opening post.
Additionally it is among good engineering practices to have proper fabrications/thicknesses ensured for equipment in critical services through double or even triple checks/reviews.
Hope this helps
Regards
Qalander




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