In this day and age of automated computer control valve sizing, the logic and theories behind it are invisible. In his presentation, Al Holton of Allagash Valve & Controls will look at the basic principles that apply and how they affect the application and installation of a wide range of control valve types. He will also review the reasoning behind valve type selection.

1. Basic Control Valve Sizing and Selection

2. DeZurik Operation October 2005 Valve Sizing What is Valve Sizing? It is a procedure by which the dynamics of a process system are matched to the performance characteristics of a valve. This is to provide a control valve that will best meet the needs of managing flow within that process system.

4. DeZurik Operation October 2005 Valve Sizing Basic information requirements for effective valve sizing For the system: Pressure before and after the control valve, Δ P Flow rate, quantity and units, Q Process temperature with units, T Properties of the media, (viscous, fiber suspension, gaseous its vapor pressure, sometimes molecular weight) For the control valve: Flow capacity (Cv), inherent throttling curve, Kc (Cavitation Index), FL² (Critical Flow factor)

8. DeZurik Operation October 2005 Valve Sizing - Cavitation What is cavitation and what does it do to valves ? Cavitation is a 2-stage activity where a portion of the liquid media drops below vapor pressure. This part will boil (vaporize). In stage two, slightly downstream, pressure recovery takes place and the vapor bubbles collapse. The condition known as “critical flow” is an extension of cavitation in that it simply gets worse as the pressure drop increases. This is to the point that changes (reductions) in downstream pressure no longer influence flow rate.

12. DeZurik Operation October 2005 Valve Sizing What is “Flashing”? It is a condition where the downstream pressure is below the vapor pressure of the incoming fluid and allows some of the liquid to become vapor. Flashing does not create noise or damage in the valve as with cavitation. It can, however, create damage to the downstream piping due to high velocity. A control valve will function quit well under these circumstances. Yes!

13. DeZurik Operation October 2005 Valve Sizing Characteristics Systems driven by centrifugal pumps lose pressure two ways As the flow increases the pump pressure declines As the flow increases pipeline friction losses increase Using a valve with equal percentage or parabolic characteristics will produce an installed characteristic that is more linear.

15. DeZurik Operation October 2005 Valve Sizing What is desired ? - After installation, generally it should be near linear. Why? - To provide a more predictable flow change in response to each incremental valve position change

22. DeZurik Operation October 2005 Globe Valves

23. DeZurik Operation October 2005 Globe Valves How do they work? - By linear (stroke) action - A contoured plug is lifted out of a seat ring to allow flow to pass - In most (not all) cases flow comes in “under the seat” - Conversely, pushing the plug down into the seat causes closure Flow in

24. DeZurik Operation October 2005 Globe Valves Unbalanced / Balanced Trim - Unbalanced has system pressure acting against the full area of the seat Single seated plug styles are unbalanced - Balanced has provisions for offsetting system pressure Available in double seated plug or balanced cage styles

25. DeZurik Operation October 2005 Globe Valves Bodies & Bonnets - Configured as required to meet valve style and ANSI Class considerations - Removable bolted bonnets retain and/or support the trim components

26. DeZurik Operation October 2005 Globe Valves 3 Way configurations for Mixing and diverting. -Temperature control - Blending

27. DeZurik Operation October 2005 Globe Valves Trim Components - Stem, plug, seat, cage (if that style) & guiding components - Made of alloy materials - Optional hardened seating surfaces when required Top guided style Cage guided style

28. Noise and cavitation control trims By directing flow through a series of staged drops, these trims eliminate cavitation in liquid flow and provides multiple pressure breakdown for noise attenuation

30. DeZurik Operation October 2005 Rotary Control Valves

31. DeZurik Operation October 2005 Rotary Control Valves Design & Construction ANSI & ISA Face to Face

32. DeZurik Operation October 2005 Rotary Control Valves V ported valves : Uses a ball segment that is Always in contact with the seat. Up to 100:1 rangability. Eccentric type: Uses a plug that cams away from the seat during opening Ideal solution for erosive services Such as slurries and steam. Available with a range of flow capacities.

33. DeZurik Operation October 2005 High performance Butterfly Valve Ideal economic choice for larger line sizes 50:1 Rangeability Modified equal percent flow Characteristic Fast accurate response to Control signal

35. Actuators

49. Generic Control Valve Types Features Comparison

53. DeZurik Operation October 2005 Rotary Control Valves