IEC 60534-2-1/ ISA 75.01.01 - Clarification on value limitation of k 1

[TNSB]

All,

I have been facing a question from a customer for the limitation of value of Specific heat ratio.
The IEC standard 60534-2-1 states that the limit for Specific heat ratio (gamma) value is 1.08<gamma<1.65.

Though the IEC version 2007 states that

If the specific heat ratio for the flowing fluid is not 1.40, the factor F? is used to adjust xT. Use the
following equation to calculate the specific heat ratio factor: Fk=gamma/1.4,

the version 2011 adds another point that, Reasonable accuracy can only be maintained when the specific heat ratio, is restricted to the range 1,08 -1,65.

Could you explain what holds this value from going beyond or below the mentioned limit? Or anyone who has handled this issue can you advise how to handle this problem wit the customer?

Any ray of hope would be highly helpful..

Regards,
TNSB

 

[hsbcn]

I think this Masoneilan control valve sizing handbook may be of use to you:

http://www.dressermasoneilan.com/documents/.../OZ1000-0304-0509-web.pdf

Good luck!

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[TNSB]

Thanks a lot for the link hsbcn!
From the book, I understand, the assumption that, Fk is linearly related to k on which the Cv equation is built may go false if it exceeds the limits.

Have I understood the point correct?

Regards,
TNSB