control valve which is used in industries

1. CONTROL VALVE
 Control valves are valves used to control conditions
such as flow, pressure, temperature, 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
conditions.[1]
 The opening or closing of control valves is usually
done automatically by electrical, hydraulic or
pneumatic actuators. Positioners are used to control
the opening or closing of the actuator based on
electric, or pneumatic signals. These control
signals, traditionally based on 3-15psi (0.2-
1.0bar), more common now are 4-20mA signals for
industry

2. TYPE OF VALVE
 Ball Valve
 Butterfly Valve
 Gate Valve
 Globe Valve

3. Parts of a Valve
1. Closure member: part of the valve that closes flow
(disk, ball, gate, etc.).
2. Actuator: means of operating the valve –
hand, gear, chain wheel, motor, solenoid, pressure
and flow of the media, air pressure.
3. End fitting: must be specified when buying the
valve - butt weld end, compression flange, pipe
thread, quick disconnect
4. Material: closure member, housing, seat –
stainless steel
5. Packing/seals: seals stem, replaced
6. Seat: where the closure members seals against
the valve housing

4. BALL VALVE
 Sphere with a port in a housing, rotate to
expose channel.
 Applications: Flow control, pressure
control, shutoff, corrosive
fluids, liquids, gases, high temp.
 Advantages – low pressure drop, low
leakage, small, rapid opening
 Disadvantages – seat can wear if used for
throttling, quick open may cause hammer

5. BALL VALVE WORKING
ball valve consisting of a spherical ball located between two
sealing rings in a simple body form. The ball has a hole allowing fluid to pass
through. When aligned with the pipe ends, this gives either full bore or nearly
full bore flow with very little pressure drop. Rotating the ball through 90°
opens and closes the flow passage. Ball valves designed specifically for control
purposes will have characterized balls or seats, to give a predictable flow
pattern.
Ball valves are an economic means of providing control with tight shut-off for
many fluids including steam at temperatures up to 250°C (38 bar g, saturated
steam). Above this temperature, special seat materials or metal-to-metal
seatings are necessary, which can be expensive. Ball valves are easily actuated
and often used for remote isolation and control. For critical control
applications, segmented balls and balls with specially shaped holes are
available to provide different flow characteristics

7. TYPES OF BALL VALVE
HALF BALL VALVE FULL BALL VALVE

8. BUTTERFLY VALVE
 rotating disk on a shaft, in a housing
 Low pressure, large diameter lines where
leakage is unimportant
 Advantages – low pressure drop, small and
light weight
 Disadvantages – high leakage, high actuation
forces so limited to low pressures

10. BUTTERFLY VLAVE WORKING
butterfly valve, which consists of a disc
rotating in trunnion bearings. In the open position the disc is parallel to the pipe wall,
allowing full flow through the valve. In the closed position it is rotated against a seat,
and perpendicular to the pipe wall. Traditionally, butterfly valves were limited to low
pressures and temperatures, due to the inherent limitations of the soft seats used.
Currently, valves with higher temperature seats or high quality and specially
machined metal-to-metal seats are available to overcome these drawbacks. Standard
butterfly valves are now used in simple control applications, particularly in larger
sizes and where limited turndown is required.
A fluid flowing through a butterfly valve creates a low pressure drop, in that the valve
presents little resistance to flow when open. In general however, their differential
pressure limits are lower than those for globe valves. Ball valves are similar except
that, due to their different sealing arrangements, they can operate against higher
differential pressures than equivalent butterfly valves.

11. GATE VALVE
 Sliding disk, perpendicular to flow
 Applications: Stop valves, (not throttling), high
pressure and temp, not for slurries, viscous fluids
 Advantages – low pressure drop when fully
open, tight seal when closed, free of
contamination buildup
 Disadvantages – vibration when partially
open, slow response and large actuating force

12. GATE VALVE
 A Gate Valve, or Sluice Valve, as it is
sometimes known, is a valve that opens
by lifting a round or rectangular
gate/wedge out of the path of the fluid.
The distinct feature of a gate valve is
the sealing surfaces between the gate
and seats are planar. The gate faces
can form a wedge shape or they can be
parallel. Gate valves are sometimes
used for regulating flow, but many are
not suited for that purpose, having been
designed to be fully opened or closed.
When fully open, the typical gate valve
has no obstruction in the flow
path, resulting in very low friction loss.

13. GLOBE VALVE
 three types (globe, angle and Y), disc or plug moved
perpendicular to flow and closes on a ring seat
 Throttling, general purpose flow control valve
 Advantages – faster than gate, seat less wear and
tear, high pressure drop for pressure control
 Disadvantage high pressure drop, require
considerable power to operate (gears and levers),
heavy

14. What are Globe Valves?
 Globe valves are named for their spherical body shape. The two
halves of the valve body are separated by an internal baffle which
has an opening forming a seat onto which a movable disc can be
screwed in to close (or shut) the valve. In globe valves, the disc is
connected to a stem which is operated by screw action. When a
globe valve is manually operated, the stem is turned by a
handwheel. Although globe valves in the past had the spherical
bodies which gave them their name, many modern globe valves
do not have much of a spherical shape, but the term globe valve
is still often used for valves that have such an internal
mechanism. In plumbing, valves with such a mechanism are also
often called stop valves since they don't have the global
appearance, but the term stop valve may refer to valves which are
used to stop flow even when they have other mechanisms or
designs.

15. Globe valves are named for their spherical body shape.
The two halves of the valve body are separated by an
internal baffle which has an opening forming a seat onto
which a movable disc can be screwed in to close (or
shut) the valve. In globe valves, the disc is connected to
a stem which is operated by screw action. When a globe
valve is manually operated, the stem is turned by a
handwheel. Although globe valves in the past had the
spherical bodies which gave them their name, many
modern globe valves do not have much of a spherical
shape, but the term globe valve is still often used for
valves that have such an internal mechanism. In
plumbing, valves with such a mechanism are also often
called stop valves since they don't have the global
appearance, but the term stop valve may refer to valves
which are used to stop flow even when they have other
mechanisms or designs.

17. Valve Symbols
Butterfly Valve
Ball Valve
Gate Valve
Globe
Valve

18. Controlled Variables
Controlled variables are variables
that we want to maintain at constant
or specified values (T, P, flow
rate, level, etc.).

19. Manipulated Variables
Manipulated variables are variables
that we intentionally change to
maintain our controlled variable at a
constant value. We often manipulate
the values by opening or closing a
valve.

20. Measured Variables
Measured variables are variables that
we measure with a meter (often often
the controlled variable or a variable
that we use to calculate the controller
variable).

21. Controller
 A unit that reads an INPUT signal and
a SET POINT, compares the
two, performs a calculation on the
difference, and sends out an
OUTPUT signal.
 Common type of controller: PID =
proportional, integral, derivative

22. Controller
INPUT OUTPUT
meter controller valve
SET POINT
(commonly from
the operator)
(Electrical or pneumatic signal
indicated by dashed line.)

23. Types of Control:
Feed Back
 When the controlled variable changes or
is different than the set point, the
controller adjusts the manipulated
variable to bring the controlled variable
back to the set point value.
 The controlled variable must change (be
different than the set point) for control
action to be taken.