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Pressure Recovery & Cavitation: ABB Control Valves Technical Support

The document discusses pressure recovery and cavitation in control valves. It explains how flow contracts through a valve's trim, creating a pressure drop and vena contracta. Pressure recovery depends on trim design, with some designs allowing higher recovery than others. Cavitation can occur if the pressure drop causes the fluid's pressure to drop below its vapor pressure, forming vapor bubbles that can damage valves. The cavitation index equation is provided to calculate cavitation risk based on the pressure drop, recovery factor, and inlet/vapor pressures. Examples of cavitating ball valves are shown.

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122 views16 pages

Pressure Recovery & Cavitation: ABB Control Valves Technical Support

The document discusses pressure recovery and cavitation in control valves. It explains how flow contracts through a valve's trim, creating a pressure drop and vena contracta. Pressure recovery depends on trim design, with some designs allowing higher recovery than others. Cavitation can occur if the pressure drop causes the fluid's pressure to drop below its vapor pressure, forming vapor bubbles that can damage valves. The cavitation index equation is provided to calculate cavitation risk based on the pressure drop, recovery factor, and inlet/vapor pressures. Examples of cavitating ball valves are shown.

Uploaded by

Deepika
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPT, PDF, TXT or read online on Scribd
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ABB Control Valves Technical Support

Pressure Recovery
&
Cavitation

ABB Control Valves ABB


Flow Path through a Control Valve -
Analogy
Minimum
Geometrical
Flow Area

Streamlines Contract as Vena Contracta


Flow Approaches Restriction (Minimum Flow Area)

ABB Control Valves ABB


Variation in Pressure and Velocity

P1

Pressure
Velocity P
Variation
Variation

P2

Valve Trim Valve


Inlet Trim Exit Vena Outlet
Inlet Contracta

ABB Control Valves ABB


Pressure Recovery

P

Low
Recovery

High
Recovery

Valve Trim Valve


Inlet Trim Exit Vena Outlet
Inlet Contracta

ABB Control Valves ABB


Cavitation

P1

P

P2

PV
PVC’

Valve Trim Valve


Inlet Trim Exit Vena Outlet
Inlet Contracta

ABB Control Valves ABB


Cavitation Calculation

CI = P - Cf Ki(P1 - Pv)
2

CI = Cavitation Index
P = Pressure Drop
Cf = Pressure Recovery Factor
Ki = Coeff. of Incipient Cavitation
P1 = Inlet Pressure
Pv = Vapour Pressure
ABB Control Valves ABB
Cavitating Ball Valve

ABB Control Valves ABB


Cavitating Ball Valve

ABB Control Valves ABB


Cavitating Ball Valve

ABB Control Valves ABB


Cavitation

ABB Control Valves ABB


Cavitation

ABB Control Valves ABB


Cavitation

ABB Control Valves ABB


Cavitation

ABB Control Valves ABB


Cavitation

ABB Control Valves ABB


Cavitation

ABB Control Valves ABB


ABB Control Valves ABB

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