Valve parts structure

Valve parts structure

What are the parts structure of the valve? The valve consists of valve body, valve cover, valve trim, valve disc, valve seat and other valve parts structure. We are an industrial valve supplier from China. We provide a complete sales system. Our valve customization service includes valve production. with design. If you need to buy a valve, please contact us!

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Valve parts structure

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Parts structure of the valve 

The valve is a mechanical device that controls the flow and pressure in a system or process, which is why it is a fundamental element for piping systems that transport liquids, gases, steam, sludge, etc. Various types of valves are available, including: gate valve, ball valve, ball valve, butterfly valve, check valve, diaphragm valve, pinch valve, pressure reducer valve, control valve, and many more. In addition, for each of these types, different models with different characteristics and capabilities are available.

The valves can be operated automatically, manually, by pneumatic or hydraulic actuators. The main functions performed by a valve are: stop, start, reduce, increase, regulate the flow, control the flow direction or process pressure, release a certain pressure in a piping system. Regardless of type, all valves have the following basic components: body, bonnet, trim (internal

components), actuator and gasket.


The valve body is also called a casing and holds all parts together, receiving inlet and outlet pipes via threaded, bolted or welded joints. 

The valve body is the first pressure limit of the valve and duqnue withstands the fluid pressure load of the connecting pipe. 

The valve bodies are cast or forged into various shapes and each component has a specific function and is built with materials suitable for that function.


It is also called a cap and is the second most important boundary of the pressure valve, also available in many designs and styles.

The bonnet is manufactured from the same material as the valve body and is usually fixed to the body by threaded, bolted or welded joints.

During the manufacturing of the valve, the internal parts (such as stem, disc, etc.) are inserted into the valve body and, immediately after, the cap is fixed to hold the various elements together.

The connection of the hood to the body is considered pressure limit and, therefore, the welded joints or bolts that connect the bonnet to the valve body are the pressure sealing parts.


The internal parts of the valve that are removable and replaceable in contact with the moving fluid are called trims, a series of components including: valve seats, discs, cable glands, gaskets, guides, bushings and internal springs. However, the valve body, bonnet, and packing, which are in contact with the fluid, are not included in the trim.

The basic movement of the valve and the control of the flow are possible thanks to the trim. The components of the valve trim are designed and built with a very wide variety of materials, since according to the material it is possible to offer different strength and strength properties, which therefore depend on the characteristics of the fluid, the chemical composition, pressure, temperature, flow rate, speed and viscosity.

The liner material can be created with the same material as the valve body or valve cover, or with a different material depending on the needs of use.


This element accelerates or stops the flow, through its position, and is the third most important main pressure limit. With the valve closed all system pressure is exerted on the disc, therefore, the disc is a pressure dependent component which is generally made with a hard surface to provide good wear resistanceMost tubes get their name from the design of their discs.


The valve seat, also known as the seal ring, provides a bearing surface for the disc and the same valve can have one or more seats.

In the case of a ball or swing check valve, there is usually a seat that forms a seal with the disc to prevent flow. In the case of a penstock there are two seats: one upstream and one downstream.

To improve the wear resistance of the seal ring, the surface is usually hardened by welding and then machining the contact surface of the seal ring.

The seal ring is not considered a pressure limiting component because the body has a wall thickness sufficient to withstand the pressure.


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OEM & ODM XinHui valve Applications

D341H国标法兰式蝶阀Butterfly valve


单击 “编辑” 按钮更改此文本。这是测试文本。



D341H国标法兰式蝶阀Butterfly valve


单击 “编辑” 按钮更改此文本。这是测试文本。



D341H国标法兰式蝶阀Butterfly valve


单击 “编辑” 按钮更改此文本。这是测试文本。



D341H国标法兰式蝶阀Butterfly valve


单击 “编辑” 按钮更改此文本。这是测试文本。



D341H国标法兰式蝶阀Butterfly valve


单击 “编辑” 按钮更改此文本。这是测试文本。




The main parts of the control valve are:
 Air locator
The principle of the pneumatic positioner is that the positioner receives the signal from the output device and changes the pressure of the actuator bladder according to the size of the signal. When the valve stem of the pneumatic control valve is subjected to an unbalanced force and the valve position changes, the positioner feedback device will transmit the valve position to the positioner to form a closed control loop and the positioner will compensate for the changes in valve position control. Most pneumatic control valve service establishments use this type of positioner.
  Speed up
The speed boost of the pneumatic control valve (pneumatic amplifier) is used when the actuator capacity is large or the pipe distance between the tool and the actuator is long, in order to improve the response speed of the positioner to check the actuator. When the input signal suddenly increases (the positioner output pressure), a pressure difference is created between the input signal and the amplifier. Under the action of this pressure difference, the pneumatic control valve speed increase diaphragm moves down to open the air supply port to reduce the pressure difference, so as to realize the function of large flow control in proportion to small flow.
   Relief Valve
It is the key component to realize the valve fault hold position. When the air supply is interrupted (air leak or pressure drop to the set value), this assembly will automatically cut off the connection channel between the instrument air and the actuator. Maintain the diaphragm chamber pressure signal at the state prior to the occurrence of the fault until the air source fault is cleared and the air supply line returns to normal. 
1. Valve body: it is the channel through which the fluid flows and withstands the force when the
pressure of the fluid is forced to close. The connection between the valve body and the piping
includes the screw connection, the flange connection and the weld connection.
2. Bonnet: The connection between the bonnet and the valve body includes the screw connection, the
flange connection and the medium pressure self-seal.
3. Packing gland: prevent fluid from escaping and ensure a seal between the valve cover and the valve stem. After the soft seal added in the stuffing box has been squeezed by the stuffing box, it is pressed firmly onto the valve stem and packing box wall to achieve a reliable seal.
4. Valve stem: is used to transmit the driving force and make the valve core move. The valve stem
should have sufficient strength, stiffness and wear resistance.
5. Disc and sealing surface: The disc is the main working part of the valve, and the part in contact with the valve seat is called the sealing surface. When the valve is closed, the sealing surface can ensure the sealing of the valve. For the regulating valve, it must have good regulating performance. 


჻ Seat
჻ Disc
჻ Gland
჻ Gasket
჻ Guide
჻ Bushing and Internal Spring
 Together known as valve trim 

valve trim

The detachable and replaceable valve internal parts in contact with the flowing medium are collectively referred to as valve trims. These components include valve seats, discs, glands, gaskets, guides, bushings and internal springs. The valve body, bonnet, packing, etc. are also in contact with the flowing medium and are not considered trim.

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