Basic Parts of Control Valves

Basic Parts of Control Valves

A valve is a mechanical device that regulates fluid flow and pressure in a system or process. Any of the following functions are performed by a valve to control system or process fluid flow and pressure.

a) Controlling fluid flow by stopping and starting it

b) Varying the volume of fluid flow (throttling)

c) Changing the flow direction of fluid

d) Controlling the pressure in a downstream system or process

f) Relieving overpressure in a component or piping system

There are numerous valve designs and types that fulfil one or more of the above-mentioned purposes. A wide range of valve types and designs can be securely accommodated.

Basic Parts of Control Valves

Regardless of type, all valves have the following basic parts: the body, bonnet, trim (internal elements), actuator, and packing. The basic parts of a valve are illustrated in Figure 1.

Control Valves mainly have Two parts:

1) Actuator Part

2) Body Part for easy understanding.

1. Actuator Part

For valve control, it can be Phenumatic, Motorized, or Hydrolics, but the most frequent type in our industry is Phenumatic Actuator Actuator, which is controlled by the wind. Actuator has a simple structure that includes the Yoke for easy maintenance.

The Actuator’s several components

Cap for rainy days I pray that they do not allow water to flow into the Actuator for Action of the Air to Open Actuator since the wind will be blowing from the bottom of the Actuator, leaving the holes blank. Find another thing to disable. When it rains, to store water. And the air valve in the back must be removed.
For use on the hook, an eye bolt. The diaphragm of the valve can be moved. To modify the direction of the oncoming wind.

The spring is in the Yoke Actuator Case or, depending on the manufacturer’s design. It will act as a force for Actuator Stem Cell and a powerful wind from the plate Diaphragm’s opposite direction.
Actuator Stem and Actuator Valve Stem are linked.
The packing elements are known as diaphragm cases. The upper and lower regions of the diaphragm plate are separate.

The Scale Plate is dependent on the valve’s location between 0 and 100 percent.
Actuator Stem and Plug Stem are connected via a Stem Connector.
The yoke is a component that connects the Actuator and Valve Body portions.

2. Body Part

The Bonnet valve is a part of the Body Valve, and this section is directly exposed to the fluid (fluid), so choosing the appropriate qualifications material (material) as well as Fluid kind, Temp, Pressure, and so on is important.

  • To get the most of all the Gland, a packing flange is employed to compress the stud bolt. The neck Bonnet must be packed tightly so that fluid does not leak out.
    The strength of the Packing Flange Gland is the Packing Follower. Packing is tightly compacted and will continue to tighten with time.
    Yoke Makes Nut Claim
  • Gland packing is critical for preventing fluid leaking up the neck and is in direct contact with the Bonnet Plug Stem.
  • The Actuator’s strength is represented by the Valve Stem, which is connected to the Plug.
    The Bonnet was largely utilized to sustain the position of the Plug-time scroll up and down to locate it. There is no such thing as left and right. However, several manufacturers reduced output to lower the Bonnet Cost of the valve’s production and sale. The upkeep is also a challenge. It is not to arrive and assist the Plug and Seat position to meet.
  • During the assembly of iron and steel, as well as between the Body and Bonnet, a gasket is employed to prevent leakage.
    In order to align Plug straight up, a Guide Ring is located in the Bonnet. Another incentive to use a Guide Ring Bonnet instead of doing everything else is to save money on maintenance time. Because this piece is constantly exposed to Stem Plug wear, if the Guide Ring is not replaced.
  • The Guide Bushing is utilized to support the Guid Ring once more.
    The employment of the force of fluid flow necessitates the use of a valve plug. And choose between Linear, Equal Percentage, or Quick Opening flow qualities.
    Seat Ring is a component of the Valve Body that supports Plug and Plug and Seat Ring must be near together given the size of the Rated Cv of the valve. To be able to keep up with the Class Leakage.

The Valve Body is a key component of the round valve and comes into direct contact with the fluid. The pipeline is connected. As a result, the size and material must be selected appropriately. More information can be found at The PT Rating by Valve Body Structure is a very common 1. Single-Ported has one plug and one seat. Double-Ported has two plugs and two ports. Two-Way Valve is what it’s called. There will be two connections (one inbound and the other outbound).

Trim Set the control valve (Trim Control Valve) is a term used by Plug Stem Seat Ring to refer to the process of setting trim (trim set).

The key to controlling the control valve will be the positioner or position. The industry standard device for converting signals (signal standard), such as 4-20 mA, 3-15 psi as wind power to propel Actuator head movements.

Explain in detail about main valve parts ?

Valve Body

The major pressure boundary of a valve is the body, often known as the shell. Because it is the framework that keeps everything together, it is the most important component of a valve assembly.

The body of a valve, which acts as the first pressure boundary, resists fluid pressure loads from connecting pipework. Through threaded, bolted, or welded couplings, it receives inlet and output pipes.

Valve bodies come in a variety of shapes, which are cast or forged. While a sphere or cylinder would theoretically be the most cost-effective shape for resisting fluid pressure while a valve is open, there are other additional factors to consider.

Many valves, for example, require a partition across the valve body to support the throttling orifice, which is the seat opening. It’s impossible to tell how much weight is on the body when the valve is closed. Loads on a simple sphere and more sophisticated shapes are likewise distorted by the valve end connections.

Additional key variables are ease of manufacture, assembly, and pricing. As a result, the basic shape of a valve body is often not spherical, but rather varies from simple block shapes to extremely complex configurations in which the bonnet, a removable element that allows for assembly, is incorporated into the pressure-resisting body.

A popular way for lowering the overall size and expense of a valve is to narrow the fluid channel (venturi effect). In some cases, bigger ends are added to the valve to allow it to connect to a larger line.

Valve Bonnet

The bonnet is the cover for the valve body’s opening. The body is separated into two parts that bolt together in some configurations. Bonnets, like valve bodies, come in a variety of styles. Some bonnets serve only as covers for valves, while others house valve internals and accessories such the stem, disc, and actuator.

Valve bonnets, while required for most valves, are a source of concern. Bonnets complicate valve manufacturing, increase valve size, and account for a considerable amount of valve costs, as well as being a source of potential leakage.

Valve Trim

The trim of a valve refers to the interior components of the valve as a whole. A disc, seat, stem, and sleeves to guide the stem are usually included in the trim. The disc and seat interaction, as well as the relation of the disc position to the seat, determine the performance of a valve.

Basic motions and flow control are achievable thanks to the trim. The disc glides near to the seat in rotational motion trim designs, causing a change in flow opening. The disc raises perpendicularly away from the seat in linear motion trim designs, forming an annular aperture.

Disk and Seat

The disc is the third primary principal pressure barrier for a valve with a bonnet. The disc has the power of allowing and disallowing fluid passage. If the outlet side is depressurized, full system pressure is applied across the disc when the disc is closed.

As a result, the disc is a pressure-retaining component. To provide durability, discs are often forged and, in certain cases, hard-surfaced.

The surface of the seal rings is frequently hard-faced by welding and then machining the contact surface of the seal ring to improve wear resistance. When the valve is closed, a fine surface quality of the Seating area is required for excellent sealing. Because the body has sufficient wall thickness to resist design pressure without relying on seal rings, they are not normally considered pressure boundary parts.


The stem, which connects the actuator with the disc, is in charge of disc positioning. Stems are usually forged, with threaded or welded connections connecting them to the disc. A fine surface quality of the stem in the area of the seal is required for valve designs that require stem packing or sealing to prevent leakage. A stem isn’t usually thought of as a pressure boundary element.

Rising stems and non-rising stems are the two types of valve stems. Observation can easily distinguish between these two sorts of stems. As the valve is opened, the stem of a rising stem valve rises over the actuator. Because the stem is threaded and matched with the bushing threads of a yoke that is either an intrinsic part of or affixed to the bonnet, this happens.

Valve Actuator

The stem and disc assembly are controlled by the actuator. A manually operated hand wheel, manual lever, motor operator, solenoid operator, pneumatic operator, or hydraulic ram are all examples of actuators. The actuator is supported by the bonnet in some designs. A yoke affixed to the bonnet supports the actuator in other versions.

Actuators, with the exception of a few hydraulically driven valves, are located outside of the p

Valve Packing

To avoid leakage from the gap between the stem and the bonnet, most valves employ some type of packing. A fibrous material (such as flax) or another compound (such as Teflon) that forms a seal between the internal portions of a valve and the outside where the stem extends through the body is known as packing.

To prevent fluid loss and damage to the valve, the packing must be adequately compressed.

Introduction to the Types of Valves

A wide range of valve types has been developed due to the variety of systems, fluids, and environments in which valves must work. Globe valves, gate valves, ball valves, plug valves, butterfly valves, diaphragm valves, check valves, pinch valves, and safety valves are examples of common types. Each type of valve was created to satisfy a unique requirement.

Some valves can throttle flow, while others can merely stop it, while others perform well in corrosive environments and handle high-pressure fluids. Each valve type has its own set of benefits and drawbacks. Understanding these variances and how they affect Valve’s application or functioning is critical to a facility’s success.

Although all valves have the same basic components and function to control flow in some fashion, the method of controlling the flow can vary dramatically. In general, there are four methods of controlling flow through a valve.

  1. Move a disc, or plug into or against an orifice (for example, globe or needle type valve).
  2. Slide a flat, cylindrical, or spherical surface across an orifice (for example, gate and plug valves).
  3. Rotate a disc or ellipse about a shaft extending across the diameter of an orifice (for example, a butterfly or ball valve).
  4. Move a flexible material into the flow passage (for example, diaphragm and pinch valves).

Types of valves

Gate valves are commonly employed in systems where a completely open valve with low flow resistance is sought with no need to restrict the flow.

Globe valves are utilized in systems that require good throttling characteristics and low seat leakage while yet allowing for a somewhat significant head loss in an open valve.

Ball valves have poor throttling and enable for rapid quarter-turn on-off actuation.

Check valves open automatically to allow flow in one direction and close to restrict passage in the other.

A stop check valve is a hybrid of a lift check valve and a globe valve, combining the best features of each.

Safety/relief valves are used to safeguard a system against over-pressurization automatically.


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