Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

3-Stage Propane Ref Performance

0

Control Valve Flow Direction


6 replies to this topic
Share this topic:
| More

#1 shahidulislam48

shahidulislam48

    Gold Member

  • Members
  • 95 posts

Posted 16 April 2017 - 06:13 AM

Hello,

 

What are the criteria that have to be considered during "under flow" or "over flow" selection for glove type control valve?

 

Many thanks

Shahidul



#2 Chemitofreak

Chemitofreak

    Gold Member

  • Members
  • 61 posts

Posted 17 April 2017 - 04:23 AM

Hi,

 

I guess by overflow and underflow you mean maximum flow and minimum flow:

 

a) Max Flow = Design Margin x Normal Flow (Design Margin is generally 10% for process and 15-20% for utilities)

 

B) Min Flow = Based on Turndown requirement



#3 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,682 posts

Posted 17 April 2017 - 05:32 AM

Or you refer to "flow-to-open" and "flow-to-close" terminology? If yes, read more at https://blog.craneen...ow-to-close-ftc



#4 shahidulislam48

shahidulislam48

    Gold Member

  • Members
  • 95 posts

Posted 17 April 2017 - 06:54 AM

Hi,

 

Thanks for your answers.

 

Although I don't clear about the answer from chemitofreak.

 

According to the reply of Zauberberg, yes you are right.  I was asking about that.

Although I had visited that site before it doesn't clearly convey the message of selecting right flow direction for different process criteria.

 

I would like to have some information that would lead me to choose right flow directions from different considerations.

 

Many thanks.



#5 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,682 posts

Posted 17 April 2017 - 08:52 AM

See attached file. This should answer your query.

Attached File  fail-safe.pdf   177.43KB   34 downloads



#6 shahidulislam48

shahidulislam48

    Gold Member

  • Members
  • 95 posts

Posted 18 April 2017 - 10:22 PM

Thanks Zauberberg for your co-operation by sharing that file.

It really helps.



#7 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,682 posts

Posted 19 April 2017 - 04:38 AM

The last few paragraphs of the attached text provide direct answers on your question (see also below).

 

Following the incremental safety logic, you would choose a flow-to-open arrangement for e.g. pressure control valve, and a flow-to-close arrangement for e.g. hot oil flow to reboiler.

 

If there are dedicated safety instrumented system (SIS) valves for isolation/venting, following this philosophy may be an unnecessary overkill - it all depends on the actual facility and the associated risks. I personally see these arrangements as important safety features only in cases when there are no dedicated isolation/blowdown valves, operated by the SIS.

 

Attached File  open-and-close.png   29.46KB   2 downloads

 






Similar Topics