Process_Presentation_on_Control_Valve_De.ppt
- 1. PROCESS PRESENTATION ON CONTROL VALVE DESIGN BY ELOHO ASOMBA 26-Aug -2011
- 2. CONTROL VALVE DESIGN TYPES OF VALVES TYPES OF VALVE CHARACTERISTICS WHY IS PROPER VALVE SIZING IMPORTANT SIZING CONTROL VALVE PROCEDURE
- 6. GATE VALVE
- 8. CHECK VALVE
- 9. NEEDLE VALVE
- 10. ANGLE VALVE
- 11. BUTTERFLY VALVE
- 14. TYPES OF VALVE OPERATION CHARACTERISTICS EQUAL PERCENTAGE QUICK OPENING LINEAR
- 17. CONTROL VALVE DESIGN STEPS 1. DETERMINE Cv 2. DETERMINE IF THERE ARE UNUSUAL CONDITIONS
- 18. STEP 1
- 19. DETERMINATION OF Cv Select appropriate equation Calculate initial Cv based on assumed Xt Select from manufacturer’s catalogue Cv greater than calculated Cv Re- calculate Cv based on manufacturer’s catalogue value for Xt Iterate till calculated Cv equals manufacturer’s Cv
- 24. FACTORS AFFECTING DETERMINATION OF CV Cv-Operating conditions maximum flow and minimum flow Fluid properties e.g vapor pressure Rangeability (valve travel with relation to Cv) of valve
- 25. STEP 2
- 26. UNUSUAL CONDITIONS SOURCE OF PIPE VIBRATION CAVITATION LEADING TO VALVE BODY DAMAGE WHICH IN TURN PASSES ON TO THE PIPING SYSTEM FLASHING IN VALVE RESULTING TO BUBBLE COALESCE CAUSING SLUG OR PLUG IN PIPES AT LOW DOWNSTREAM PRESSURE
- 27. TERMINOLOGIES Vapor pressure Vena contracta Cage / Trim Cavitation Flashing
- 29. VALVE TRIM (VALVE INTERNALS)
- 30. VALVE TRIM
- 32. REMEDIES
- 33. Replace valve with TRIM of larger FL value Increase back pressure downstream of valve Install valve at a lower elevation than the inlet and outlet lines Install two valves in series Use oversize valve body
- 34. THANKS
- 35. QUESTIONS (Q) What is CV factor? (A) CV is a dimensionless value that relates the volume of flow through a valve in (gpm) that gives 1 psi pressure drop across a valve at 60oF . (Q)What is Dp (pressure drop)? (A) Dp is the difference between initial pressure and final pressure in a defined system. Why is Dp important? (A) Dp is what makes flow possible Dp will enable the designer to know the energy that would be necessary to flow a fluid to the required point at the expected arrival pressure (Q)What factors determine Dp across a valve (A)i Flow path within the valve, ii Fluid flow rate (Q)A full bore 1” ball valve has a CV of 40 and a diaphragm valve of equal nominal size (1’’) has a CV of 15. Why is the difference in CV of these valves? (A)A diaphragm valve has a more tortuous internal than a ball valve