Control Valve , Control Valve Body Parts and it's type.

 CONTROL VALVE

INDEX- 

1 . Basic Definition of control valves.
2. Components of Control Valves.
3. Basic Parts of Control Valves.
4. Details of Control Valve Actuator.
5. Types of Control Valves.
6. Control Valves P&ID Symbol.
7. How to Install Control Valves.
8. Application of Control Valves.

1 . Basic Definition of control valves.

• A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. 
• A control valve regulates the rate of fluid flow as the position of the valve plug or disk is changed by an actuator.
•  Control valves are used to maintain a process variable as close as possible to the desired set point.

• Control valves are control devices that are used to manage and control fluid flow, pressure, temperature, or liquid level by varying the flow passage size.
•  In process systems of production wells, oil and gas plants, Chemical and Petrochemical industries, refineries, and power plants, Control valves are frequently used to control or manage any of the process parameters.
• Valves are an essential part of any piping system that conveys liquids, gases, vapors, slurries and mixtures of liquid and gaseous phases of various flow media.

In simple language

The control valve is an automated valve that can make precise adjustments to regulate and monitor any commodity flowing through a piping system. 

The main goals of different control valve parts:

• Controlling the flow direction
• Relieving the system from specific pressures
• Increasing or decrease the flow
• Turning the flow on or off
• Regulating the flow or process pressure

2. Components of Control Valves.

Main parts of Control Valves

• Actuator  parts 

• Body Parts

Actuator parts 

• Control Valves are classified as either a Pneumatic, Motorized or Electric and Hydraulics.

• In Refinary commonly used in our industry, it is Pneumatic Actuator  or controlled by the wind itself. 

• For easy maintenance Actuator simple structure.

components of the Actuator in Control Valves.

1. Rain Cap

Rain Cap I pray for them not to let water flow into the Actuator for Action of the Air to Open Actuator is that the wind will be from the bottom of the Actuator so the holes are left blank. Find something else to disabled To keep water when it rains. And must be taken off the air valve at the back.

2. Eye Bolt

Eye Bolt for use on the hook. Moving the valve during maintenance time.

3. Diaphragm.

Diaphragm is flexible. To change the incoming wind power and power passed to Diaphragm plate to make Actuator Stem Cell.

4. Spring
Spring is in the Yoke Actuator Case or, depending on the design of the manufacturer. It will act as a force for Actuator Stem Cell and a strong wind from the opposite direction to the plate Diaphragm.

5. Actuator Stem
Actuator Stem is interconnected with Actuator Valve Stem.

6. Diaphragm case.
Diaphragm Case are the parts that are used for packing Diaphragm plate consists of two parts: the upper and lower sections.

7. Scale plate.
Scale Plate is based on the position of the valve between 0-100%.
Stem Connector is the link between them for Actuator Stem and Plug Stem..

8. Yoke.
Yoke is a component that is used for connecting sections of the Actuator and Valve Body.

2. Components of Body Parts in Control Valves.

• Packing Flange is used for compression of the stud bolt to make the most of all the Gland Packing tight and fluid can not leak out of the neck Bonnet.

• Packing Follwer is the strength of Packing Flange Gland Packing tightly compressed to tighten over time.

• Gland Packing is important that we prevent the leakage of fluid up to the neck and is in direct contact with Bonnet Plug Stem The choice of material and type to fit so there is a huge need.Most of the material used is PTFE or Graphite and maintenance each time. The need to change the Gland Packing all times.

• Valve Stem is the strength of the Actuator and connected to Plug.

• Bonnet was primarily used for supporting the position of the Plug-time scroll up, scroll down to find it. No left and right But some manufacturers cut output to reduce the Bonnet Cost for the production and sale of the valve. The maintenance is also difficult. It is not to come and support the position of the Plug and Seat to meet constantly Lapping.
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• Gasket is a device used to prevent leaks during the assembly of iron and steel as well as between the Body and Bonnet.

• Guide Ring is located in Bonnet order to align Plug straight up. Another reason for having Guide Ring Bonnet, instead of doing all the reason to reduce maintenance time Cost. Because this section is always exposed to Stem Plug sometimes wear if not Guide Ring may be a whole instead of only replacing Bonnet Guide Ring.

• Guide Bushing is used for supporting   Guide Ring again.

• Valve Plug is essential to use the force of fluid flow. And determine the flow properties as Linear, Equal Percentage or Quick Opening.

• Seat Ring is a component that is part of Valve Body and given the size of the Rated Cv of the valve and which supports Plug and Plug and Seat Ring must be close together. To be able to follow the Class Leakage as needed.

• Valve Body  a major component of the round and get direct contact with the fluid. The connection to the pipeline Therefore, the size and material must be chosen accordingly. Read more at PT Rating by Valve Body structure is a frequently encountered .
  
  
  

4. Details of Control Valve Actuator.

• The actuator of a control valve is the assembly that provides power for moving the control valve mechanisms.
•  In a control valve loop, actuators move the plug, ball, or vane upon receipt of a signal from the control system to allow or disallow full or partial flow. 
• There are three types of actuators in a Control Valve. They are

• Pneumatic Actuators

• Electric Actuators and

• Hydraulic Actuators.

1.Pneumatic Actuators

• Pneumatic Actuators are the most basic and widely used control valve actuators that use an air or gas signal from an external source to produce a modulating control action.
•  The top port sends the pneumatic signal to the actuator that exerts pressure on the diaphragm plate to move the valve stem. On loss of driver power, pneumatic actuators provide a fail-safe response.

• Pneumatic actuators are designed to operate a piston within a closed cylinder. Pressure from an external air or gas source powers the actuator, moving the cylinder to fully open or close the valve, or partially modulate its open/close movement.

• Depending on the valve type, the pneumatic actuator valve can either operate in a 90-degree horizontal direction or in a linear up and down motion.

Advantages of a Pneumatic Actuator.

• High Force & Speed Of Movement
• High Durability
• High Reliability
• Clean Technology
• Cost Effective

2.Electric Actuators:- 

• Electric Actuators of a control valve are motor-driven devices. 
• A motor rotates when an electrical signal is received. 
• A gear reduction drive converts this rotating motion into a linear motion to drive the control valve stem for flow modulation. 
• They are used for On-OFF applications in isolation services and for continuous positioning control.

 Advantages

1. Very accurate control and positioning
2. Able to stop at any point of the stroke
3. Easy to set acceleration and deceleration
4. No external sensors
5. Low operating costs
6. Help adapt machines to flexible processes
7. Superior performance at high speeds
8. Minimal maintenance
9. Low risk of contaminations.

Disadvantages

1. Non-explosion proof
2. Sensitive to vibration
3. More complex technology
4. High speeds, less thrust
5. High thrust, less speed

3. Hydraulic Actuators.

• Control Valve Hydraulic actuators use a hydraulic oil as the signal fluid.

•  When the force required to move the valve stem is high, hydraulic actuators are used. 

• Due to non-compressibility of the liquid they exhibit stable positioning.

• Control Valve Hydraulic actuators use a hydraulic oil as the signal fluid.

• The purpose of a flow control valve is to regulate the flow rate in a specific portion of a hydraulic circuit. 

• A hydraulic valve is a mechanical device designed to control the direction of liquid, usually oil, through a hydraulic circuit. Crucial to any hydraulic system, they can regulate the speed of motors and movement of cylinders.

5. Types of Control Valves:-

   Control Valve  

              1. Flow Control Valve 

2.. Temperature control valve.

3. Pressure Control Valve.

4. Temperature Control Valve.

Types of Control Valve on the basic of function.

6. Control Valves P&ID Symbol.

7. How to Install Control Valves.

• Control valves are normally installed in a horizontal orientation in a straight pipe run preferably away from elbows.

•  The actuator is kept in a vertical position.

•  A bypass valve is installed for continuous operation during control valve inspection and maintenance. 

• Upstream and downstream isolation valves and drains are added in the piping system to isolate the control valve for maintenance. 

• The following figure shows a typical control valve installed is a piping system.  

8. Application of Control Valves.

• By its name, a control valve is a valve with the purpose of control. 
• A typical control valve application could be for flow, temperature, pressure or liquid level control. 
• The control valve is opened and closed by a control signal which can be pneumatic, electric or hydraulic.
• The primary purpose of a control valve is to regulate the rate of the fluid flow by varying the size of the flow passage. 
• Control valves are most commonly used for consequential control of process quantities including pressure, temperature, and the liquid level.

 

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Afzal.