1.
Globe Control Valve
A Globe valves is a linear motion valve and are primarily designed to stop, start and regulate flow. The
disk of a Globe valve can be totally removed from the flow path or it can completely close the flow path.
Conventional Globe valves may be used for isolation and throttling services. Although these valves
exhibit slightly higher pressure drops than straight through valves (e.g., gate, plug, ball, etc.), they may
be used where the pressure drop through the valve is not a controlling factor.
The globe valve is used for throttling flow control. Shut off is accomplished by moving the disc against
the flow stream rather than across it as in the case with a gate valve. The flow pattern through a globe
valve involves changes in direction, resulting in greater resistance to flow, causing high pressure drop.
The globe valve is an excellent valve to use in high pressure operation of steam. Our globe valves are
factory-made with quality material for long term use.
Control valves are used to control such as pressure, flow, level, and temperature by fully or partially
opening or closing in response to signal received from controllers that compare a “Setpoint” to a
“Process Variable” whose value is provided by the sensors that monitor changes in such conditions.
A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type
element and a stationary ring seat in a generally spherical body.
Globe valve is the most commonly used control valve in industries. Globe valves are available in
different sizes. Globe valve is used on water and steam line both. Globe Valve is used where the
pressure is high.
Control Valve has 2 parts.
1 . Actuator.
2 . Body.
Parts of actuator :
Diaphragm
O- Ring
Spring
Wheel.
Parts of Body:
Plug
Plug stem (Spindle).
Balancing Ring
Seat
Cage
Valve position indicator.
Gland
Chuck- Nut
Bonnet
control-valve-internal
Work of different Parts of a Control Valve
Diaphragm:
The diaphragm is the most important part of a control valve. Spring remains on the diaphragm. Air
firstly come on diaphragm then applied to spring. If the Diaphragm is damaged control valve does not
work. The diaphragm is damaged due to access air applied to the control valve.
O- Ring:
O- Ring is used to prevent air leakage.
Spring:
Spring is used to provide movement to a control valve. On apply air, spring is compressed and the
control valve is operated.
Wheel:
The wheel is used for manual or auto operation of a control valve.
Coupling:
Coupling is used to connect the actuator to the body of a control valve.
Plug:
The plug is the most important part of a control valve body. Seat remains in the plug. The lower smooth
part of the plug is known as the seat.
Plug Stem:
Plug stem is also known as a spindle. Plug stem is connected by the coupler to the actuator through this
plug stem.
Seat:
The seat is the important part of a control valve body. KiWhen the control valve is fully closed it is Used
to prevent the leakage. It means when the seat is damaged control valve will leakage on full closed.
Balancing Ring:
Balancing Ring is made up of Teflon or metal (Graphite), depending on the class of Control Valve.
Balancing Ring is also used to Prevent leakage from control valve body.
Bonnet :
Bonnet is the Outer cover Of a Control Valve Body.
Globe valves are of 2 types :
1. Air to open or normally closed.
2. Air to close or normally open.
air-to-open-and-air-to-close:
Air to open control valve is a valve which remains in closed position in absence of air. On applying air it is
operated and starts opening. It is also called Normally Closed Valve.
Air to close control valve is a valve which remains in open position in absence of air. On applying air it is
operated and starts closing. It is also called Normally open Valve.
How a Control Valve Works?
Firstly air is applied on Diaphragm then
Air Goes to Spring, Spring is compressed on applying air and control valve is operated.
Role of Wheel in a Control Valve
The wheel is used to operate a control valve manually. In some valves, the neutral position is given. In
the neutral position control valve is operated through the air.
In other position, different from neutral position control valve is operated through the wheel manually.
In some control valves, this wheel is not given. Ki
Control Valve with the wheel is called the control valve with manual function.
In the control valves in which neutral position is not given if the wheel is moving freely control valve is in
auto mode it will be operated through air signal.
if the wheel is not moving freely control valve is in manual mode, It will be operated through wheel
operation and in this case air supply is off.
Advantages and disadvantages of Globe valves:
ADVANTAGES:
1. Good shutoff capability
2. Moderate to good throttling capability
3. Shorter stroke (compared to a gate valve)
4. Available in tee, wye, and angle patterns, each offering unique capabilities
5. Easy to machine or resurface the seats
6. With disc not attached to the stem, valve can be used as a stop-check valve
DISADVANTAGES:
1. Higher pressure drop (compared to a gate valve)
2. Requires greater force or a larger actuator to seat the valve (with pressure under the seat)
3. Throttling flow under the seat and shutoff flow over the seat
4. Typical Applications of Globe valves
Applications of Globe valves:
Cooling water systems where flow needs to be regulated
Fuel oil system where flow is regulated and leak tightness is of importance
High-point vents and low-point drains when leak tightness and safety are major considerations
Feed water, chemical feed, condenser air extraction, and extraction drain systems
Boiler vents and drains, main steam vents and drains, and heater drains
Turbine seals and drains
Turbine lube oil system and others
The actuator is connected from the body through a coupler.
Globe Control Valve
