Valve parts structure

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.

BODY

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.

COVER

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.

TRIM

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.

DISC

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 resistance. Most tubes get their name from the design of their discs.

VALVE SEAT

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.