control valve types
Post on 09-Aug-2015
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WHEN ACCURACY MATTERS
• IEC Definition: A power operated device which changes the fluid flow rate in a process control system. It consists of a valve connected to an actuator that is capable of changing the position of the closure member in the valve in response to a signal from the system
• ISA Definition: A power operated device which modifies the fluid rate in a process control system. It consists of a valve connected to an actuator mechanism that is capable of changing the position of a flow controlling element in the valve in response to a signal from the controlling system.
Control Valve DefinitionControl Valve Definition
WHEN ACCURACY MATTERS
5050PSIGPSIGTANKTANK
PCSupply
Steam
P1 = 75-100 psig
Positioner
Analog Electro-Pneumatic Control Signal4-20mA
Process Variable4-20mA
Where does a CV fit in the Control SystemWhere does a CV fit in the Control System
WHEN ACCURACY MATTERS
• Feature– Ruggedly built for high cycle
service
– Always provides tight shutoff
– Valve bore approximates line size
– Always provide system effect with travel change
– Used to alter flow in response to control signal
– “Absorbs "large amount of energy
• On-Off Valve– No
– Yes
– Yes
– No
– No
– No
• Control Valve– Yes
– No
– No
– Yes
– Yes
– Yes
Control Valve vs On/Off ValveControl Valve vs On/Off Valve
WHEN ACCURACY MATTERS
Typical Isolation Valves Typical Isolation Valves
HP Butterfly Full Port Ball Sleeve Lined Plug Manual Globe Manual Gate
WHEN ACCURACY MATTERS
Control Valve Hierarchy Control Valve Hierarchy
Pressure Drop
HPBV Ball Rotary Globe
Globe Severe Duty
WHEN ACCURACY MATTERS
Control Valve TypesControl Valve Types
• Reciprocating– Globe
– Angle
– Severe Service
• Rotary– Butterfly
– Ball
– Rotary Globe
WHEN ACCURACY MATTERS
High Performance Butterfly ValvesHigh Performance Butterfly Valves
Better Control
WHEN ACCURACY MATTERS
Types of Butterfly ValvesTypes of Butterfly Valves
Concentric Centerline
Single Offset (Eccentric)
Double Offset (HPBV)
2
1
2
1
3
Tripple Offset
WHEN ACCURACY MATTERS
Segmented Ball Segmented Ball Control ValveControl Valve
Un-Restricted Flow Path
Un-Restricted Flow Path
Partially Open
WHEN ACCURACY MATTERS
Segmented Ball ValvesSegmented Ball Valves
• Partial Ball – 90 Deg. Rotation• High Capacity & High Turndown• Characterized Segmented Ball• Single Metal or Soft Seat
Notice the Single Clamped Seat
Notice the Characterization
WHEN ACCURACY MATTERS
Single Port Unbalanced Single Port Unbalanced
• Globe Valve• Unbalanced Design• Post Guided• Lo-dB Trim • Class-IV & Class-V Shut-
Off• Flow To Open• Flow To Close
WHEN ACCURACY MATTERS
LEAKAGE CLASSESLEAKAGE CLASSES
• CL IV, Standard– .01% of Rated Cv
• CL V, Optional– Reduced Pressure Drop Capability Due
to Higher Seat Loads Required
• CL VI, Optional– Plug with PTFE Seal Ring
WHEN ACCURACY MATTERS
QUICK CHANGE TRIMQUICK CHANGE TRIM
• Maintenance Advantage
• Seat Ring Held in Place by the Seat Ring Retainer (A Type of Cage)
• Seat Ring Gasket Required
WHEN ACCURACY MATTERS
TRIM TYPESTRIM TYPES
• Contoured Trim– Full Area– Reduced Area
• Single Stage Lo-dB and Anti-Cavitation
• Two-Stage Lo-dB and Anti-Cavitation
WHEN ACCURACY MATTERS
LOW NOISE PRODUCTSLOW NOISE PRODUCTS
• LO-DB Trim Reduces the Sound Level up to 15 dBA Over Conventional Trim, Depending on the P1/P2 Ratio.
SINGLE-STAGE Lo-dB TRIM
WHEN ACCURACY MATTERS
Venturi Seat RingVenturi Seat Ring
Extreme Conditions
High Pressure Drops
Sever Coking Conditions
Flashing Liquids
Emergence Blow Down
WHEN ACCURACY MATTERS
Single Port Balanced Single Port Balanced
• Globe Valve
• Fully-Balanced Design
• Cage Guided
• Composite Polymer Balancing Seal
• Class-V Shut-Off
• Flow To Open
WHEN ACCURACY MATTERS
CAGE GUIDED VALVESCAGE GUIDED VALVES
• The cage provides positive alignment and control of the plug
• The cage can modify or “characterize” the flow
The Cage Serves Two Major Functions
WHEN ACCURACY MATTERS
CAGE GUIDED - PRESSURE BALANCEDCAGE GUIDED - PRESSURE BALANCED
TYPICAL APPLICATIONS• Clean Process Fluids• High Pressure, High Temperature, Noise, and
Cavitation
LIMITATIONS• Slurries or Gritty or Dirty Processes• Less Capacity Compared to Rotary Valves• Larger and Heavier than Most Rotary Valves
WHEN ACCURACY MATTERS
CAGECAGE
• Acts as Sealing Surface for Plug Seal Ring
• Retains Seat Ring
• Provides Throttling Orifice
• Guiding Surface
WHEN ACCURACY MATTERS
SEAL RINGSSEAL RINGS
• Metal Seal Ring– Class II – Temp: -320oF to 650oF
• PTFE Seal with Backup– Meets Class IV Seat Leakage– Temp: -20oF to 300oF
• Graphite Seal Ring– Meets Class IV Seat Leakage– Temp: -320oF to 1050oF
WHEN ACCURACY MATTERS
Pressure Energized Seal RingPressure Energized Seal Ring
• Pressure Energized PTFE Plug Seal
• Class V Leakage• Max Temp: 450oF
(600oF)• Uni-Directional• Higher Shutoff
Capability
WHEN ACCURACY MATTERS
AUXILIARY PLUGAUXILIARY PLUG
• Flow-To-Close Direction Only
– Approx. 10 dB Less Attenuation Than F-T-O
• Tight Shutoff at High Temperature
• Class IV, Class V Leakage
• “Dead” Travel in Closed Position = 0.050”
WHEN ACCURACY MATTERS
AUXILIARY PLUGAUXILIARY PLUG
• Cage Guided• Balanced• Single Seated• Captured Seat Ring (QC)• Pilot Trim
Stem
Packing Ring (S)
Cage
Balancing Seal
Packing Follower
Auxiliary Pilot Plug
Body
Seat Ring
Guide Bushing
Plug (Main)
Bonnet
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