ISA’s SP75.25 Control Valve Dynamic Testing Subcommittee Update

A ccording to Cullen Langford, chairman of the SP75.25 sub-committee, progress has been outstanding with a high level of professional interaction among committee members. In some cases data and charts brought to sub-committee meetings have been so similar they are nearly interchangable. Mr. Langford hails the support of ISA and the sub-committee’s aggressive use of the Internet for expediting the standards progress.

Mr. Langford says, ‘Measurement technology has greatly improved over the past 20 years, digital control systems offer very advanced capabilities, and process knowledge is better than ever; it was time to address the one remaining weak link in process control.’

Sub-committee membership consist of users, valve and actuator manufacturers, and control valve experts such as Jim Arant, Cullen Langford, and Bill Bialkowski.

SP75.25 has a charter to develop a standard to define the terms and the methods to test and specify valves with respect to static and dynamic response.

Subcommittee activities have included:

Studying control valve user requirements for dynamic performance of control valves;

Defining terms, performance categories, test methods and instrumentation, performance paratmeters, and specification and ordering requirements;

Evaluation of existing and proposed methods of separately bench-testing valve actuators and body subassembly modules for dynamic performance capabilities;

Writing standards and/or recommended practices for testing control valves for dynamic performance parameters on the workbench, in a laboratory, and in the process; and

Writing standards and/or recommended practices for bench-testing valve actuators and body subassembly modules for dynamic performance capabilities.

The result of the committee’s work is two documents with the same title, ‘Test Procedures for Control Valve Response Measurement from Step Inputs.’ The first document is the standard and the second is a technical report that explains the standard. The two documents should be used together. Balloting is expected sometime in 1999.

Other ISA contol valve subcommittees Under the guidance of the SP75 Control Valve Standards committee, numerous other subcommittees regularly address control valve related topics.

SP75.01 – Control valve sizing equations;

SP75.02 – Control valve capacity test procedures;

SP75.03 – Hydrostatic testing of control valves;

SP75.04 – Control valve stability;

SP75.05 – Control valve terminology;

SP75.07 – Control valve noise measurement and prediction;

SP75.08 – Control valve face-to-face dimensions;

SP75.09 – Digital final control elements/digital actuators;

SP75.10 – Flexible clamp or pinch valves;

SP75.11 – Control valve flow characteristics and rangeabiltiy;

SP75.13 – Valve positioner performance;

SP75.14 – Control valve data sheets;

SP75.15 – Process data presentation;

SP75.23 – Control valve cavitation;

SP75.24 – Control valve actuator sizing and selection; and

SP75.25 – Control valve dynamic testing.

For more information on ISA subcommittee activities, visit www.isa.org/sc/home .

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