Engineering: FRESH WATER GENERATOR

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FRESH WATER GENERATOR

Printed From: Jobships.com
Category: Maritime Knowledgebase
Forum Name: Engineering
Forum Discription: Topics related to Shipboard Machinery, equpment and process are discussed here.
URL: http://www.jobships.com/forum//forum_posts.asp?TID=252
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Topic: FRESH WATER GENERATOR

Posted By: deba prasad saha
Subject: FRESH WATER GENERATOR
Date Posted: 28 Sep 2006 at 8:16am

AS DISTILATE WATER PUMP IN FRESH WATER GENERATOR IS CENTRIFUGAL PUMP ,REQUIRES POSITIVE SUCKTION.HOW IS IT DONE IN FRESH WATER GANERATOR,WHERE WE MAINTAIN VACUUM.

Replies:

Posted By: Alok Govil
Date Posted: 23 Oct 2006 at 6:03am

Distillate pump is usually placed in a position where the suction has a 'head' - difference in height between condenser lowest point and the pump - this neutralizes the vacuum effect. This is the reason for drop in distillate pump efficiency if the seal is no good.

Posted By: PERI AVADHANI
Date Posted: 12 Nov 2006 at 10:49pm

Hi,

Centrifugal pumps are inhrently not self priming, but are able to take suction. Consider the pumps like ballast, bilge etc which are placed much above the ballast tanks but are able to take suction.

Here the only problem with the centrifugal pumps is that they are not self priming. SO in FWG the distillate pump is placed below the datum of the condensate collection level. Hence no problem with priming.

Posted By: chandrashekar krishna reddy
Date Posted: 10 Dec 2006 at 10:53pm

Hello Mr. Saha,

FWG distillate pump always has some NPSH, since it is placed below the condensate water level. Problem would occur only if there is atmospheric pressure at the eye of the pump and the condensate is under vacuum. But here pressure (ie vacuum inside the shell) is same on condenste and up to pump suction (considering that the seal is in good condition). So, the pressure at the suction side of the pump is more than that of the condensate by an amount equal to its head. hense there is no problem.

Posted By: SRINIVAS ANGA
Date Posted: 22 Feb 2007 at 4:44am

IN FWG DISTILLATE PUMP IF THERE A SMALL LEAK IN MECHANICAL SEAL OR GLAND PACKING IT CAN BE DEALT WITH BY DIRECTING WATER DIRECTLY WHILE STARTING, ONCE PUMP TAKES SUCTION IT CAN RUN QUITE WELL.

Posted By: bhavik padaria
Date Posted: 13 Apr 2007 at 10:39pm

the centrifugal paump does not require positive suction ..

but if positive suction is provided is it is easy to overcome the force or pressure required to deliver the liquid.also the positive suction head ensures that p/p is always primed ..

the vacuum in FWG is in the shell ...

the p/p is of the capacity to produce sufficient vacuum in the suction side