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I would like to know in a plant that has different coolers that run off one cooling tower is it OK to pinch on cooling water when the cooling needs vary in different parts of the plant? I have worked in several different plants and this is usually an accepted practice but now I'm in a new plant and operators oppose pinching on the cooling water valves. Currently we are running cooling water at 90 degrees which in are second stage chiller I think is too hot and overloads the refrigeration unit but if we pinched cooling water at inlet discharge coolers and used compressors discharge temp to maintain our front in temp it would be a much better way to run the plant.
 
Answers
07/10/2011 A: Abraham Emamnuelxp, JC Equipments Pvt Ltd, emmanuelxp@gmail.com
You try this link : Cooling Towers
30/08/2010 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Some will quote two reasons why it is a bad idea to “pinch” some CW valves to help other coolers, namely, (1) high CW outlet temperature will result in fouling, and (2) the gates in the pinched valves will erode, as they are not made for throttling. However, my experience is as follows: Every summer, I balanced cooling requirements by pinching certain outlet valves at users. Doing so helped the overall cooling operation. Every 12 years we replaced gates in a few valves. None of the coolers fouled prematurely as we were careful to maintain reasonable CW outlet temperatures at all coolers.
30/08/2010 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Unless you know that specific exchangers are water hogs that are already operating at high tube velocities, it is generally not recommended to pinch in cooling water flow to exchangers. By pinching in on exchangers you are restricting flow, which will lower tube velocity. Reduced velocity will promote fouling, which can cause you to lose performance.on the pinched in exchangers. Then when you start losing performance you can't regain it because they are fouled. Now instead of having one problem exchanger, you have a bunch of them.
A better approach is find ways to increase flow to the problem exchanger. Changing the tube pass configuration can be a cheap way to increase flow to a given exchanger without significantly robbing flow from the rest of the system. Booster pumps are sometimes used, especially when the problem exchangers are elevated as the head loss in getting up to the coolers can actually draw a vacuum at the exchanger.