In the plumbing and tube sector, valves are used to regulate fluid by opening, closing, or partially blocking fluid substances. Valves are devices or natural objects used to direct or control the flow of fluids. Valves are technically fittings, but because of their complex and diverse applications and structures, they are usually discussed as a separate chapter. The core physical principle used by valves is that fluid always flows from high pressure to low pressure.

In history, the simplest and oldest valve was just a freely hinged flap, which fell to prevent fluid from flowing in a specific direction, but was pushed away by the flow in the opposite direction. This kind of valve is called a check valve because it can prevent or check the flow in one direction.

Modern control valves can regulate downstream pressure or flow, and can run on sophisticated automated systems to achieve complex objectives.

Valves and pumps

In practical applications, valves and pumps are two interacting fluid control facilities that work together to achieve their goals. A pump is equipment that moves liquid through its mechanical action. According to the method used by the pump to move fluid, it can be divided into three main types including direct lift, displacement and gravity methods. In other words, there are direct lift pump, displacement pump, and gravity pump. The pump is usually operated by a reciprocating or rotating mechanism, and consumes energy to generate mechanical force to move the fluid.

The mechanical pump can be submerged in the fluid pumped by the pump or can be placed outside the fluid. Pump displacement methods can be divided into positive displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valve-less pumps. In addition, there are two basic types of pumps, namely positive displacement pumps and centrifugal pumps.

The pump can be operated by a variety of power sources, such as manpower, electricity, engines and even wind power. These energy devices can have various shapes and sizes.

Composition of valves

The main components of the most commonly used types of valves are divided into two parts: valve body and bonnet. Together, these two parts build a housing that contains the fluid flowing through the valve. The body of the valve is also the housing of the valve, which contains internal parts. The bonnet is the part of the housing through which the valve stem passes, forming the guide and seal of the valve stem, and the bonnet will be screwed into the valve body. The valve body is usually made of metal or plastic, and has to be rigid. The metal material of the valve body may be brass, bronze, gunmetal, cast iron, steel, alloy steel and stainless steel. In some special cases, such as in seawater desalination plants for regulating seawater, duplex valves and super duplex valves is usually used, because in that case, the valve must have corrosion resistance to resist the warm seawater.

The bonnet serves as a cover for the valve body. The bonnet is usually screwed into the valve body semi-permanently, or it can also be bolted to the valve body. During the production of the valve, the inner parts are put into the valve body, and then the bonnet is installed to fix all the inner parts together. Many valves do not contain bonnets. For example, plug valves and ball valves, these valves are assembled in different ways. In the same way, valves of different styles can be connected to the pump and operate together.

Industrial pumps have a wide range of applications, such as pumping water from wells, aquarium filtration work, pond filtration tasks, water cooling and fuel injection in the automotive industry, oil and natural gas pumping or operating cooling towers. In the field of machine tools, pumps are used to transport cutting fluids and coolants. In the medical industry, pumps are often used as artificial substitutes for human body parts, especially artificial heart and penile prostheses.

The number of impellers determines the working method and the strength of liquid delivery of pump. A pump containing only one rotating impeller is called a single-stage pump, and a pump containing two or more rotating impellers is called double or multi-stage pump.


The development and research of valve is very popular in the pneumatic and hydraulic fields because they can be widely used for household and industrial purposes. Through various designs and modifications on the valve unit, one can use the valve to control a variety of liquid substances, thereby realizing the idea of intelligent management.

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