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Typical Turndown Ratios Of Processing Equipment


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#1 daraj


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Posted 05 June 2017 - 01:27 AM

Hi all,


      when I am performing a design(simulator based) for scaling up an existing plant(which consists of columns, vessels, exchangers etc.) to enhance capacity, the sizes of various processing equipment are bound to get bigger. So a turndown check need to be performed  to know how low of a feed the plant can take. For columns, this mean sometimes we might have to work with vendors like say Sulzer, to know the turndown ratios of columns based on distributor specifications etc.  But even before I get there, I want to know what sort of equipment do you need to perform turndown checks besides columns(they are expensive and constitute major equipment) and are there any typical turndown ratios for processing equipment such as below?


1. shell and tube thermosyphon reboilers

2. kettle reboilers

3. decanters

4. flash vessels

5. pumps


for instance are there any type of equipment for which I need not unduly worry about a 50% turndown? i.e equipment that are known to turndown well? for instance, maybe storage vessels or reflux drums.


if there are any resources/links that point to turndown ratios(typical) of processing equipment, that would be helpful also.


please let know your thoughts

#2 spchauhan12


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Posted 23 June 2017 - 03:59 AM

Dear daraj,


      Turn down is ratio of minimum controllable flow rates to maximum controllable flow rates for a given system.


For example: 50:1 turndown means that you can control from 2% to 100% of flowrate.  2:1 turndown means that you can only control from 50% to 100% of flowrate


It refers to overall plant , Process equipments & Instruments  & can be asked by Project / Client owner who oprates the plant.



Hope this resolves your query pertaining to Turn -down. 






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