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Describe the forces at work tending to create instability in control valves, including inherent and installed stability. Define design improvements to improve inherent stability. Include general guidelines for improved system design for better stability. Establish degree of stability expected of a specific control valve in a particular application of a given flow control system. Provide terminology and definitions required with the above-stated scope.


To describe the nature of instability in control valves. To provide general guidelines through design improvements that improve inherent valve stability. Described differences between inherent and installed valve stability. To combine all these factors into a standard or recommended practice for the user to select the stability level for the application and be able to communicate this to the control valve manufacturer.

A Word from the Chairman

The Recommended Practice ISA-75.18 was withdrawn and replaced by Technical Report ISA-TR75.04.01-1998 (R2006), Control Valve Position Stability. 

For information about upcoming ISA75.04 meetings and other ISA75 and ISA96 meetings, please visit the ISA75 page.

For more information, please contact

Eliana Brazda
ISA Standards Administrator
(919) 990-9228