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Minimum Safe Recyle Process Flow Schemes For Centrifugal Pumps




Minimum Safe Recyle Process Flow Schemes For Centrifugal Pumps On the eve of the new year designated as 2013 as per the Gregorian calendar, I wish the members and readers of "Cheresources" a very happy and prosperous new year. Before moving on to the topic at hand, I wish to express my sincere thanks to Chris Haslego and Art Montemayor for providing this wonderful gift of "Cheresources" to the chemical engineering community and sustaining and nurturing it unselfishly for more than a decade without any monetary motives.

I sincerely wish that venerable institutions like the American Institute of Chemical Engineers (AIChE) and the European Federation of Chemical Engineers (EFCE) acknowledge the contribution of "Cheresources" as a web center of learning for aspiring and established chemical engineers in their bulletins.

Moving on to the topic at hand "minimum safe recycle flow" for centrifugal pumps has been discussed in numerous posts on "Cheresources". This has included the need for minimum safe recycle flow as well as the various possible process flow schemes that can be implemented for minimum safe recycle flow. In fact one of the blog entries in my blog relates to minimum safe recycle flow which discusses the basics of minimum safe recycle flow and also provides a calculation spreadsheet for calculating the minimum safe recycle flow given the allowable temperature rise, the shut-off head and the efficiency at shut-off. I wish to express my thanks to the readers of my blog for the positive response in terms of the views for the blog article and the number of downloads for the spreadsheet. For those who have not read this blog entry, they can find it at the link below:

http://www.cheresour...ntrifugal-pump/

The process flow schemes for minimum safe recycle flow has also been debated many times on the forum and I had participated in one of the forum discussions for minimum recycle flow wherein I had also posted a schematic for minimum recycle flow as an excel sheet. There were many enlightening comments made by knowledgeable members of the forum such as Katmar, djack77494, Joe Wong and Zauberberg during the discussion. The link is provided below:

http://www.cheresour...aded#entry21110

This enlightening discussion had remained in the back of my mind and I had thought of developing several process flow schemes including process control for minimum safe recycle flow using a proper drawing tool (AutoCAD) with my comments and observations.

Today's blog entry shares those schemes as .jpg files as part of this blog entry. The process flow schemes show the process scheme along with controls and at the bottom are provided comments related to merits and demerits of each scheme.

A note of caution to all the readers, please note that these scheme do not encompass everything related to minimum safe recycle flow and more permutations and combinations can be employed depending on the particular process and it's requirement. These schemes are based on my personal knowledge and understanding of minimum safe recycle flow and thereby no warranty, explicit or implicit is provided for the successful implementation of these schemes.

The schemes are referred as Schemes 1 to 7 in the attached .jpg files.

I certainly do hope to have a lot of comments on these schemes form the readers of my blog. Probably better schemes and controls will emerge once a discussion gets rolling and experienced chemical engineers share their experiences related to minimum safe recycle flow. Enjoy reading and studying the schemes.

Regards,
Ankur.

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Dear Ankur,

 

Thank you for sharing this knowledge.

 

I think one more option would be to put the recycle in the pump suction. 

 

 

Regards,

nmh

Dear Ankur,

 

Is it possible to use a back pressure regulator instead of using a pressure control valve?

 

 

Regards,

Sharon.

Dear Ankur,

 

Is it possible to use a back pressure regulator instead of using a pressure control valve?

 

 

Regards,

Sharon.

Sharon,

 

I have never liked back-pressure regulators since they do not give good pressure control and for services like minimum continuous recycle flow I would not be comfortable using them. This is specifically true when the liquid contains rust / corrosion or other solid particles which can plug the sensing line. 

 

Regards,

Ankur.

Thank you very much Ankur for sharing this and a lot of other sources of knowledge and comprehension.

 

Regards

 

Stefano

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