Introduction

Valves are considered one of the most important components in any hashtag#industrial and instrumentation system. The main function of valves is to regulate the fluid flow in the system. Valves have different types and are installed in different places of the system according to the need and type of process.

In terms of operation, valves can be divided into two main categories: manual and automatic. In some chemical and pharmaceutical industries, the accuracy of the valve is an important factor, that's why mechanical valves play a significant role in the processes.

Among different applications of valves, the following can be mentioned:

• Controlling the fluid flow
• Backflow prevention
• Control the flow path
• Controlling the process pressure

According to the needs of the processes, the valves are designed and built in various types, among the most used valves, the following can be mentioned:

Globe valves

Globe valves have a disk-shaped plug that is located inside the valve. The valve can be closed up and down by moving the disk up or down. The flow in ball valves follows an S-shaped path. According to this design, the fluid flow changes direction twice. This phenomenon results in a high-pressure drop in this type of valve. The most important feature of these valves is zero leakage when they are shut off.

Needle valves

Needle valves are a type of valve in which a needle-shaped piece is responsible for controlling the flow. This needle piece is surrounded by threads and moves in and out of an orifice. This group of valves is mainly installed in the routes where flow control is supposed to be done with high precision.

Needle valves have the same function as ball valves, Except for two differences.

One; Needle valves are smaller than ball valves and are mostly used in precision instrument processes. These valves have the ability to change the flow in low values with high accuracy.

Two; a needle is used as a plug instead of a disk in this type of valve.

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Ball valves

These valves have a ball-shaped obstructor that is fastened between two cups. These valves are used to quickly shut off the flow or isolate a part of the system.

Ball valves are designed to be operated fully open or fully closed. These valves are opened and closed by turning the globe 90 degrees using a lever. The spherical plug enables us to control the flow through the valve precisely. There was no need to generate high torque to open these valves, and there is little possibility of leakage when they are closed.

Diaphragm valves

This type of valve uses a diaphragm to open the fluid flow only in a forward direction, so the fluid can only move in one direction and it cannot move in the opposite direction. The reason for naming these valves is the presence of a flexible disc inside the body, which is placed on the upper part of the valve to create a proper seal with the valve seat. This disc is the most important part of diaphragm valves. Diaphragm valves are among the most widely used valves in food, oil and gas, pharmaceutical, steel, and petrochemical industries. Due to their strong sealing and the absence of any leakage, these valves are suitable for installation in processes with toxic and dangerous fluids.