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Control Valve Actuation

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Setpoint Integrated Solutions is a leader in Control Valve actuation technology across industry segments.

Brannon Gant - Regional Sales Manager

Published in: Engineering
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Control Valve Actuation

  1. 1. WHEN ACCURACY MATTERS Introduction Actuation Technology
  2. 2. WHEN ACCURACY MATTERS What is Pneumatics?What is Pneumatics? • Pneumatics is an application of fluid power. Pneumatics uses air, which is compressible. Most industrial pneumatic applications use pressures of about 40 to 100 pounds per square inch (psi) • Advantages of pneumatics – The working fluid is very light in weight so supply hoses are not heavy. – Because the working fluid is (mostly) just air, there is usually no need for a return line for the working fluid and leaks of the working fluid tend not to be messy. – Because air is compressible, the equipment is less likely to be damaged by shock. The air in pneumatics absorbs excessive forces due to sudden valve closures or shift, etc.
  3. 3. WHEN ACCURACY MATTERS • What is torque? – By definition “Torque” is a turning or twisting force. Usually a force on a moment arm (lever). Torque is expressed in terms ofTorque is expressed in terms of inch pounds or foot pounds for theinch pounds or foot pounds for the U.S. and Newton-meters for S.I.U.S. and Newton-meters for S.I. (international).(international). It’s magnitude can be increasedIt’s magnitude can be increased by increasing the force or theby increasing the force or the length of the moment arm, or both.length of the moment arm, or both. The Turning Force - TorqueThe Turning Force - Torque Torque can be calculated by: T = F x M.A. Where: T = Torque in in. lbs. F = force in Pounds M.A. = Moment Arm in inches (“r” on above graphic)
  4. 4. WHEN ACCURACY MATTERS ForceForce • The most common device used to generate the force for making torque by actuators is compressed air working in a linear cylinder as shown below. • This generates the linear force which, thru the lever arm, is converted to torque
  5. 5. WHEN ACCURACY MATTERS Crank ArmCrank Arm • The “Crank Arm” uses a lever attached to the valve stem which is “pushed” by the linear cylinder The torque output from a crank arm: Torque at center of Stroke T = P x A x MA Torque at beginning and end of stroke: T = P x A x Cos. 45°x MA Where: T = Torque in in. lbs. P = Operating Pressure in psig MA = Moment Arm in Inches A = Area of the piston in square inches.
  6. 6. WHEN ACCURACY MATTERS Power to the LeverPower to the Lever • Scotch Yoke actuators generate torque on the lever arm principle.  The lever arm length is the distance between the center of the pinion and the thrust pin bearing interface to the yoke..  Force is applied to the pinion thru air pressure on the piston and is converted to torque thru the lever arm length.
  7. 7. WHEN ACCURACY MATTERS Scotch Yoke MechanismScotch Yoke Mechanism Typical Torque CurveTypical Torque Curve TORQUE 0 45 90 100% Break 50% Run 80% End Typical Ball Valve Scotch Yoke Mechanism Rotation of Actuator
  8. 8. WHEN ACCURACY MATTERS Pneumatic Linear to Rotary Scotch Yoke Piston Actuator Double Acting/Spring Return • Advantages – Spring Return Failure – High Torque Output – Adjustable Limit Stops
  9. 9. WHEN ACCURACY MATTERS Pneumatic Linear to Rotary Scotch Yoke Piston Actuator Single Acting • Advantages – Spring Return Failure – High Torque Output – Adjustable Limit Stops
  10. 10. WHEN ACCURACY MATTERS Lever Arm for Rack & PinionLever Arm for Rack & Pinion • Rack & Pinion actuators generate torque on the lever arm principle. – The lever arm length is the distance between the center of the pinion and the gear tooth, as shown to the left. – Force is applied to the rack thru air pressure on the integral piston/rack and is converted to torque thru the lever (moment) arm length; rotating the pinion. LeverarmLeverarm lengthlength Looking down from top of actuator
  11. 11. WHEN ACCURACY MATTERS Pneumatic Linear to Rotary Rack &Pinion Piston Actuator Single Acting • Advantages – Compact Size – Spring Return Failure – High Torque – Adjustable Limit Stops
  12. 12. WHEN ACCURACY MATTERS Pneumatic Linear to Rotary Rack & Pinion Piston Actuator Double Acting • Advantages – Compact Size – High Torque – Adjustable Limit Stops
  13. 13. WHEN ACCURACY MATTERS Pneumatic Rotary Vane Actuator Double Acting • Advantages – Compact Size – High Torque – Adjustable Limit Stops – Light Weight
  14. 14. WHEN ACCURACY MATTERS Torque Output ComparisonTorque Output Comparison
  15. 15. WHEN ACCURACY MATTERS • Advantages – Rolling Diaphragm – Constant Area – Ease of Maintenance – 1 Serviceable Softgood – Cost effective – Compact & Light Weight Pneumatic Linear to Rotary Lever Arm Diaphragm Actuator
  16. 16. WHEN ACCURACY MATTERS Manual Override • Single Acting • ATO/FC – Side Mounted H/W CAMFLEX II
  17. 17. WHEN ACCURACY MATTERS Pneumatic multi-spring diaphragm actuator •Fail Closed
  18. 18. WHEN ACCURACY MATTERS • Advantages – Multiple spring ranges – Field reversible – Constant diaphragm area – Reduced inventory – Cost effective – Compact Pneumatic multi-spring diaphragm actuator •Fail Open
  19. 19. WHEN ACCURACY MATTERS Manual Override • Single Acting • ATC/FO – Side Mounted H/W
  20. 20. WHEN ACCURACY MATTERS Pneumatic single spring diaphragm actuator •Fail Open
  21. 21. WHEN ACCURACY MATTERS • Advantages – Simple – Low friction – Cost Effective – Simple to maintain • Disadvantages – Diaphragm area not constant – Not field reversible Pneumatic single spring diaphragm actuator •Fail Closed
  22. 22. WHEN ACCURACY MATTERS Manual Override • Single Acting • ATC/FO – Allows local Override
  23. 23. WHEN ACCURACY MATTERS • Piston or Cylinder Actuators are typically used: – where high delta-p shut offs are required – Long strokes are required – Heavy Cycling – Spring Return Plus Air Assist Spring Return Piston Actuators
  24. 24. WHEN ACCURACY MATTERS Piston Actuators • Single acting with spring return • Double acting with or without spring return • Leakage across piston is prevented by a seal on the piston. • Advantages – Capable of High Thrust – Stable at high DP – Long travels are available • Disadvantages – Higher frictional loads than spring diaphragm actuators.
  25. 25. WHEN ACCURACY MATTERS Manual Override • Single Acting/Double Acting – Hydraulic Hand Pump – Directional & Bi-Directional Operate to Retract
  26. 26. WHEN ACCURACY MATTERS •Required Force = (Class IV seat load) + (Packing friction) + (Process force) Actuator Sizing - Seat Load Force - Packing Friction - Shutoff Force
  27. 27. WHEN ACCURACY MATTERS ANSI/FCI 70-2 Leakage ClassANSI/FCI 70-2 Leakage Class • Class I no test procedure • Class II 0.50 % of rated Cv (air) • Class III 0.10 % of rated Cv (air) • Class IV 0.01 % of rated Cv (air) • Class V 0.0005 ml/min of water per inch of orifice dia. per psi • Class VI ml/min per orifice dia. (air)
  28. 28. WHEN ACCURACY MATTERS •Required Force = (Class IV seat load) + (Packing friction) + (Process force) •Class IV Seat load Pressure (C1) •C1 = (π) x (Seat Diameter) x (Seating Force) •Seating Force is determined by shutoff class •Seating Force= 30 lbs/inch Class II, III, IV 150 lbs/inch Class V 50 lbs/inch Class VI •C1 = (3.14) x (1.625 inch) x (30 lbs/inch) •C1 = 153.08 pounds •Seat Diameter Actuator Sizing
  29. 29. WHEN ACCURACY MATTERS Soft Seal Metal Seal
  30. 30. WHEN ACCURACY MATTERS •Required Force = (Class IV seat load) + (Packing friction) + (Process force) • Valve packing friction load (C2) • C2 =(Friction Coefficient) (3.14) (Stem dia.) (Packing Height) (Packing load) • Friction Coefficient is a function of the packing material • Friction Coefficient = .03 Teflon .15 Graphite • Packing Load is a function of inlet pressure • If inlet pressure is>1000psi Load=1000psi • If inlet pressure is <1000 psi Load=Inlet Pressure • C2 = (0.03) x (3.14) x (0.50”) x (1.1”) x (1000Psi) • C2 = 51.81 pounds PackingHeight Actuator Sizing
  31. 31. WHEN ACCURACY MATTERS •Required Force = (Class IV seat load) + (Packing friction) + (Process force) • Process Force (C3) • C3 =Area of Orifice = (Seat Diameter) (π/4) • = (1.625”)2 (0.7854) • C3 =Area of orifice = 2.07 sq. inch (2.0739) • C3 =Process Force = (90 PSIG inlet) (2.07 sq. in) • C3 =Process Force = 186.3 pounds 90 PSI Inlet Actuator Sizing
  32. 32. WHEN ACCURACY MATTERS •Required Force = (Class IV seat load) + (Packing friction) + (Process force) •Required force = (153.08 pounds seating force) + (51.81 pounds packing friction) + (186.3 pounds process force) • Required force to Close= 391.19 pounds Actuator Sizing
  33. 33. WHEN ACCURACY MATTERS Valve Required Force to Open Flow to Open • Required Force = (Packing Friction) – (Process Force) • Required force =(51.81 pounds packing friction) - (186.3 pounds process force) • Required force to Open= -134.49 pounds Based on Physics (Select Actuator to be (Packing Friction) • Required force= 51.81 pounds
  34. 34. WHEN ACCURACY MATTERS Flow to Open Direction
  35. 35. WHEN ACCURACY MATTERS Flow to Close Direction
  36. 36. WHEN ACCURACY MATTERS Unbalanced Trim • Valve closure member which is under unbalanced dynamic forces induced by process media. • Process force tends to influence trim generating additional forces in the flow direction. • Unbalanced Trim in moderate to hi-pressure applications required larger thrust actuators.
  37. 37. WHEN ACCURACY MATTERS Unbalanced Trim • Globe Valve • Unbalanced Design • Post Guided • Lo-dB Trim • Class-IV & Class-V Shut-Off • Flow To Open
  38. 38. WHEN ACCURACY MATTERS Balanced Trim • Valve closure member which is equalized/ balance with dynamic forces induced by process media. • Balance trim designs include Semi-Balanced and Fully-Balanced. • Balanced Trim in moderate to hi-pressure applications required much smaller thrust actuators compared to unbalanced trim.
  39. 39. WHEN ACCURACY MATTERS Balanced Trim • Globe Valve • Fully-Balanced Design • Cage Guided • Composite Polymer Balancing Seal • Class-V Shut-Off • Flow To Open
  40. 40. WHEN ACCURACY MATTERS Semi - Balanced Trim • Globe Valve • Semi-Balanced Design • Dual Post Guided • Double-Port (Seat) Design • Class-III Shut-Off
  41. 41. WHEN ACCURACY MATTERS Questions?Questions?

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