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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