Control valves are
valves used to control
conditions such as flow,
and liquid level by fully
or partially opening or
closing in response to
signals received from
controllers that compare
a "setpoint" to a "process
variable" whose value is
provided by sensors that
monitor changes in such
CONTROL VALVE SIZING
The control valve shall be of globe body
design with single port. The valve trim,
shall be suitable for quick removal without
any cutting or welding.
Sizing shall be accordance with ANSI/ISA
Valve outlet velocity does not excesed 8
m/sec for liquid service and 150 m/sec for
CONTROL VALVE SIZING
The valve sizing shall be suitable for
obtaining maximum flow conditions with
valve opening at approx 80% of total valve
stem travel and minimum flow conditions
with valve stem travel not less than 10% of
total valve stem travel.
All valves shall capable of handling at least
120% of required maximum flow.
Valve body rating shall meet the pressure
and temperature requirement as per ANSI B
Conform to requirement of ANSI for dimensions,
material thickness and material specification for their
respective pressure class.
All valves shall be globe body design.
All valves connected to vacuum on down stream side
shall be provided with packing suitable for vacuum
application (e.g double vee type chevon packing).
Extension bonnets shall be provided when the
maximum temperature of flowing fluid is greater than
275 deg c.
If the downstream is subjected to vacuum, flow
direction of the fluid shall be to close.
TOP GUIDED CONTROL VALVE
valves may be
used for tight shutoff
because these valves
are unbalanced, they can
require more force from
the actuator to achieve
shutoff if the flow is
under the plug.
CAGE GUIDED VALVES
have a cylindrical plug
guided through a guide.
The increased guiding
area is desirable for high
pressure drop, high
noise, and anticavitation
Unbalanced types can
provide a tight shutoff if
For balanced styles, the
plug is vented and the
interacts with the top
and bottom side of the
DOUBLE SEATED CONTROL VALVE
valves are used to a
lot of industrial
applications due to
reduction in actuator
force, a great flow
capacity and a deal of
cannot provide the
same shutoff capability
as the single-ported
Characterized Cages/Trim for Globe valve
PTFE if fluid
temperature is less
than 180 deg C.
Graphite if fluid
temperature is more
than 180 deg C.
All valves connected to
vacuum on down
stream side shall be
provided with packing
suitable for vacuum
application (e.g double
vee type chevon
Cavitation is a two stage phenomena
with liquid flow.
The first stage is the formation of vapor bubbles in the
liquid as the fluid passes through the trim and the
pressure is reduced below the fluid's vapor pressure.
The second stage is the collapse of the vapor bubbles as
the fluid passes the vena contracta and the pressure
recovers and increases above the vapor pressure.
The collapsing bubbles are very destructive when they
contact metal parts and the bubble collapse may produce
high noise levels.
control valves can
have four negative
• Restricts fluid flow
• Causes severe vibrations
• Erodes metal surfaces
• Generates high noise
ANTI CAVITY TRIM
The anti cavity trim of
control valve shall be
multi stage ,multi path
ISA- RP75.23 – 1995,
Evaluating Control Valve
The High FL Factor (
pressure recovery factor)
shall be 0.98 or better.
Cavitation is alleviated by anti-cavitation
Steam conditioning valve
conditioning valve is
primarily used in
industrial and utility
power plants for the
auxiliary and process
BODY MATERIALS- Alloy steel as per ASTM – A217 GR WC 9
TRIM MATERIAL-- 440 C series SS
LOW FLASHING/CAVITATION SERVICES
BODY MATERIALS--Alloy steel as per ASTM A – 217 GR WC 6
TRIM MATERIAL- 17-4 PH SS
Non flashing/non cavitation services
BODY MATERIALS- carbon steel ASTM A216 Gr WCB Fluid temp
below 275 deg C and above 275 deg C – ALLOY STEEL A217 GR WC 9
and 316 SS for DM water service etc
TRIM MATERIAL -316SS stellited with stellited faced guide
posts and bushings.
Design Practices to Minimize
Corrosion in valves can be minimized or eliminated by
selecting materials that do not react with the fluid or
with the material around them.
Corrosion is the deterioration of a metal by reaction
with the environment.
Corrosion is generally controlled by selecting corrosion
Corrosion resistance of a component can be improved
by plating, cladding, overlaying, or heat-treating of
the wetted surfaces.
The rate of corrosion is influenced by the fluid velocity
media and temperature.
CONTROL VALVE SEAT LEAKAGE
CLASSIFICATION (ANSI/FCI 70-2-1991)
S.N LEAKAGE CLASS MAX LEAKAGE
1 I ---
2 II 0.5 % of rated capacity
3 III 0.1 % of rated capacity
4 IV 0.01 % OF RATED
5 V 0.0005 ml per minute
of water per inch of
orifice per psi
Control valve induced
noise shall be limited to
85 db at 1 mtr from
valve surface under
The noise abetment shall
be achieved by valve
body and trim design or
by use of silencers.
Noise calculation shall be
as per ISA-75-17-1989.
VALVE with Cage-Style
Valve body ends shall be either butt
welded/socket welded, flanged .
The welded ends wherever required shall be
butt welded type as per ANSI B 16.25 for
control valves of sizes 65 mm and above.
For valves size 50 mm and below welded ends
shall be socket welded as per ANSI B 16.11
Flanged ends wherever required shall be of
ANSI pressure-temperature class equal to or
greater than that of control valve body.
The basic types of
· Electric motor
· A combination of
valve positioners and
remote calibration &
signal on input signal
4-20 m Amp &
connected with hart
i) Non destructive test - ANSI B-16.34
ii) Hydrostatic shell test - ANSI B 16.34
iii) Valve seat leakage- ANSI- B 16.34.
iv) Functional test: The fully assembled
valves including actuators control
devices and accessories shall be
functionally tested .
v) CV test: CV test - ISA 75.02
ANSI/ISA-75.01.01 (IEC 60534-2-1 Mod) - 2007 - Flow
Equations for Sizing Control Valves
ANSI/ISA – SP75.02, 1996, “Control Valve Capacity Test
Procedure”, October 1996
ISA- RP75.23 – 1995, “Considerations for Evaluating
Control Valve Cavitation”, Recommended Practice, June
ANSI/ISA-75.19.01-2001 (R2007) - Hydrostatic Testing
of Control Valves
ISA-75.17-1989 - Control Valve Aerodynamic Noise