VALVES
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VALVES
ControlValves
PressureRelief Valves
On-offValves
Check Valves
Valves
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ON-OFF VALVESGate Valves
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ON-OFF VALVESBall Valves
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ON-OFF VALVESPlug Valves
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ON-OFF VALVESStopping the flowProviding tight shutoff when being closedProviding low pressure drops when being fully openedMost of control valves can be used for on-off duty, especially ball valvesGate valves are often used in on-off service
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CHECK VALVES
Prevent reversal of flow
Open with forward flow and close against
reverse flow
Types of check valves– Lift check valves– Swing check valves– Tilting-disk check valvesChE 4253 - Design IChE 4253 - Design I
CHECK VALVESLift Check Valves
• depend on gravity for operation
• high pressure
services
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CHECK VALVESSwing Check Valves
• closure member swingsabout a hinge
• employed along with gate valve
• low fluid velocities• flow reversals are
infrequent
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CHECK VALVESTilting-Disk Check Valves
• closure member rotatesabout a point betweenthe center and edge of disc
• spring loaded• more expensive• more difficult to repair
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CONTROL VALVES
General characteristics and functions
Types of control valves
Flow characteristics
Valve selection
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CONTROL VALVESGeneral characteristics and functions
Used to regulate the flow automatically to
any desired amount
High pressure drop
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CONTROL VALVES
Types of control valves
Globe valves
Ball valves
Butterfly valves
Plug valves
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CONTROL VALVESGlobe Valves
Linear stem motionSignificant pressure dropControl the flow Good in service with fluid containing no solid
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CONTROL VALVESBall Valves
Rotary stem motionSmall frictionSmall pressure dropHigh flow capacityProvide tight shutoffWell suited for on-off serviceNot good in throttling service
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CONTROL VALVESButterfly Valves
Rotary stem motionSmall pressure dropLarge flow capacityGood service with fluid with or without solidHandle on-off dutyHandle throttling duty
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CONTROL VALVESPlug Valves
Rotary stem motionProvide tight shutoffMultiport plug valves can be used to simplify the piping systemWell suited for on-off service
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CONTROL VALVESInherent Flow Characteristics
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CONTROL VALVESValve Selection
Characteristics of each type of control
valves
Pressure of the system
Temperature of the system
Type of flowing fluid
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VALVESEnergy Balance
Total energy balance
The energy balance is reduced to
( ) ( ) ( ) ∑ ∑−+∑ ++−∑ ++=++Δ WQO KEPEHI KEPEHKEPEU
02
22
=⎟⎟⎠
⎞⎜⎜⎝
⎛ −+− OI
OIvvHH ρ
OI HH =
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VALVESPressure Drop
FWvdPzg o δρ
−=⎟⎟⎠
⎞⎜⎜⎝
⎛Δ++Δ ∫ 2
2
2
22
2
vKhF
vFdP
L ==
⎟⎟⎠
⎞⎜⎜⎝
⎛Δ−−=
δ
ρρδ
⎟⎟⎠
⎞⎜⎜⎝
⎛Δ−−=Δ
22
22 vvKP ρρ
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VALVESPressure Drop Across Control Valves
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VALVESConfiguration of Piping Associated
with a Control Valve
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VALVESJoule-Thomson Effect
Isenthalpic expansion
μJT > 0 , T decreases
μJT < 0 , T increases
HJT P
T⎟⎠⎞
⎜⎝⎛∂∂
=μ
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PRESSURE RELIEF VALVESPurposes and Operating Conditions
Pressure relief valves are designed to
protect a system from being over-
pressurized
P < 10,000 psia
T < 1,0000F
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PRESSURE RELIEF VALVESTypes of Pressure Relief Valves
Direct-loaded relief valves
Pilot-operated relief valves
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PRESSURE RELIEF VALVES
Direct-loaded Relief Valves
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PRESSURE RELIEF VALVESSafety Valves
PRESSURE RELIEF VALVESRelief Valves
PRESSURE RELIEF VALVESSafety-Relief Valves
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PRESSURE RELIEF VALVESSizing Valves for Liquid Services
Piping:
Viscous liquid:
Pressure vessels:
dPSQA
2.27=
ud KPSQA
2.27=
pd KPSQA
2.27=
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