Questions on Control Valves and Accessories

List of Questions and answers on Control Valves and Accessories used in industrial measurement and control.

  1. State the combinations of pneumatic actuator and globe valve body required
    to provide:
    a) air to open action;
    b) air to close action.

  2. State and sketch the three flow characteristics for the most common globe

  3. State a typical application for each of the three flow characteristics and
    explain why it is the most appropriate selection for that application.

  4. State the effect of unbalanced force on valve position and explain with an
    example, how bench setting would correct this problem.

  5. Briefly explain at least three advantages a positioner gives when it is used
    in conjunction with a control valve.

  6. Describe the fail state for a given valve.

  7. Sketch and describe a system pump head vs flow curve set to define
    installed valve differential conditions.

  8. Explain, with a diagram, how a three-way solenoid valve can be used for
    ON/OFF control of a pneumatic valve.

  9. State the formula which describes a control valve Cv factor. What is the Cv
    for a valve which will pass a water flow of 100 USGPM with a pressure drop
    of 25 psi? What flow would this valve pass when the pressure drop is 49

  10. State why it is often advisable to use different sized valves in parallel when
    the process variable has a very large flow range.

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