CHEMICAL ENGINEERING DESIGN & SAFETY

CHE 4253

Prof. Miguel Bagajewicz

Valves

VALVES

ControlValves

PressureRelief Valves

On-offValves

Check Valves

Valves

ChE 4253 - Design I

ON-OFF VALVES Stopping the flow Providing tight shutoff when being closed Providing low pressure drops when being fully

opened Most of control valves can be used for on-off duty,

especially ball valves Gate valves are often used in on-off service

ChE 4253 - Design I

ON-OFF VALVESGate Valves

ChE 4253 - Design I

ON-OFF VALVESBall Valves

ChE 4253 - Design I

ON-OFF VALVESPlug Valves

ChE 4253 - Design I

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 valves

ChE 4253 - Design I

CHECK VALVESLift Check Valves

• depend on gravity for operation

• high pressure

services

ChE 4253 - Design I

CHECK VALVESSwing Check Valves

• closure member swingsabout a hinge

• employed along with gate valve

• low fluid velocities• flow reversals are

infrequent

ChE 4253 - Design I

CHECK VALVESTilting-Disk Check Valves

• closure member rotatesabout a point betweenthe center and edge of disc

• spring loaded• more expensive• more difficult to repair

ChE 4253 - Design I

CONTROL VALVESGeneral characteristics and functions

Used to regulate the flow automatically to

any desired amount

High pressure drop

ChE 4253 - Design I

CONTROL VALVES

Types of control valves

Globe valves

Ball valves

Butterfly valves

Plug valves

ChE 4253 - Design I

CONTROL VALVESGlobe Valves

H Linear stem motionH Significant pressure

dropH Control the flow H Good in service with

fluid containing no solid

ChE 4253 - Design I

CONTROL VALVESBall Valves

H Rotary stem motionH Small frictionH Small pressure dropH High flow capacityH Provide tight shutoffH Well suited for on-off

serviceH Not good in throttling

serviceChE 4253 - Design I

CONTROL VALVESButterfly Valves

H Rotary stem motionH Small pressure dropH Large flow capacityH Good service with fluid

with or without solidH Handle on-off dutyH Handle throttling duty

ChE 4253 - Design I

CONTROL VALVESPlug Valves

H Rotary stem motionH Provide tight shutoffH Multiport plug valves can

be used to simplify the piping system

H Well suited for on-off service

ChE 4253 - Design I

CONTROL VALVESInherent Flow Characteristics

ChE 4253 - Design I

VALVESPressure Drop Across Control Valves

ChE 4253 - Design I

VALVESConfiguration of Piping Associated

with a Control Valve

ChE 4253 - Design I

VALVESJoule-Thomson Effect

Isenthalpic expansion

µJT > 0 , T decreases

µJT < 0 , T increases

HJT P

T

∂∂

=µ

ChE 4253 - Design I

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

ChE 4253 - Design I

PRESSURE RELIEF VALVESTypes of Pressure Relief Valves

Direct-loaded relief valves

Pilot-operated relief valves

ChE 4253 - Design I

PRESSURE RELIEF VALVES

Direct-loaded Relief Valves

ChE 4253 - Design I

PRESSURE RELIEF VALVESSafety Valves