ISA TR96.05.01 PDF

ISA-TR96.05.01-2017:

• is informative and does not contain any mandatory requirements.

• is limited to automated valves normally operating in either a full open or full closed position.

• introduces the concept of margin analysis as a method of assessing PST results.

• relates loss of functional margin with possible failure modes and discusses the effectiveness of different PST approaches in identifying a loss of functional margin.

• discusses the possibility and effects of over-stroking the automated valve.

• discusses the possibility and effects of over-torqueing the stem of the automated valve.

• discusses the rationalization/justification in performing PST (benefits vs risk).

The boundary of the automated valve includes the following:

a) Valve, Actuator, Control Systems, Ancillary Components, and Monitoring Devices

b) Actuation media regulation and filtration system

c) Actuated valves whose safe position is specified

d) Automated valves that employ only pneumatic or hydraulic actuators

e) Guidance related to testing of electric valve actuators is provided in ANSI/ISA-96.02.01 and are excluded from the scope of this technical report

Guidance is provided for the following:

a) Identifying when partial stroke testing may be useful

b) Various criteria to consider when selecting the partial stroke method, e.g., automated versus manual test execution, spurious trip potential, actuator force or torque output, and on-line maintainability

c) The advantages and disadvantages of four basic methods of partial stroke testing: mechanical limiting, travel limiting, position based, and solenoid operated valves

d) The capability and limitations of the four measurement, analysis, and acceptance criteria approaches used to assess PST results.