CONTROL VALVE & SIZING: Selection & maintenance

OBJECTIVE

  • Understand what happens inside a control valve from basic fluid mechanics point of view
  • Appreciate the difference between cavitation and flashing, and know what choked flow is
  • Do simple calculations to determine CV values
  • Recognise severe service applications and have an appreciation for the methods of tackling the problems associated with such applications
  • Know about all the different types of control valves commonly in use and understand the relative advantages of each
  • Choose between different characteristics on offer and specify seat leakage rates
  • Size actuators for linear and rotary applications and know the relative advantages of pneumatic, hydraulic and electric types
  • Have a basic understanding on how to select materials for bodies, trims, packing boxes, and gaskets
  • Make use of a computer sizing program to assist with the selection of control valves
  • Understand the failure modes for control valves and demonstrate new approaches to troubleshooting

OUTLINE

  1. INTRODUCTION TO CONTROL VALVE THEORY
    • Introduction
    • Definition of a control valve
    • Energy types
    • What is happening inside a control valve
    • Cavitation
    • Flashing
    • Choked Flow
    • Valve Coefficient Cv
  2. DIFFERENT TYPES OF CONTROL VALVES
    • Globe Valves
    • Butterfly
    • Eccentric disk
    • Ball
    • Rotary Plug
    • Diaphragm and Pinch
  3. CHARACTERISTICS
    • Equal percent
    • Linear
    • Quick opening
    • Selection method
  4. HIGH PRESSURE DROP APPLICATIONS
    • Cavitation Control
    • Cavitation Elimination
    • Low Noise
    • Diffuser Plates
    • Chokes
    • Disk Stack Technology
    • Pressure Balanced Trim
  5. USE OF COMPUTER PROGRAM FOR VALVE SIZING
  6. EXAMPLES OF HIGH PRESSURE DROP APPLICATIONS
    • Water – pump bypass
    • Steam – turbine bypass
    • Gas – pressure reducing
    • Oil – choke valve
  7. ACTUATORS
    • Pneumatic
    • Hydraulic
    • Electric
    • Sizing on rotary valves
    • Sizing on linear valves
    • Mounting considerations
    • Manual overrides
    • Accessories
  8. POSITIONERS
    • Basic principles
    • Conventional pneumatic
    • Conventional electro-pneumatic
    • Smart Positioners
    • Feedback options