The importance of valves in pipeline design Pipeline water transfer technology

The importance of valves in pipeline design Pipeline water transfer technology

In fluid piping systems, valves are control elements whose main role is to isolate equipment and piping systems, regulate flow, prevent backflow, regulate and discharge pressure. Because the pipeline system to choose the right valve is very important, so, to understand the characteristics of the valve and the selection of valve steps and basis also become crucial. The importance of valves in pipeline design..
In fluid piping systems, valves are control elements whose main role is to isolate equipment and piping systems, regulate flow, prevent backflow, regulate and discharge pressure. Because the piping system to choose the most suitable valve is very important, so, to understand the characteristics of the valve and the selection of the valve steps and basis also become crucial.
The importance of valves in piping design
1. Valve characteristics are generally of two kinds, service characteristics and structural characteristics.
Use characteristics: it determines the main use of the valve performance and range of use, belong to the valve use characteristics are: valve category (closed circuit valve, regulating valve, safety valve, etc.); Product type (gate valve, globe valve, butterfly valve, ball valve, etc.); The main parts of the valve (valve body, cover, stem, disc, sealing surface) material; Valve transmission mode, etc. Structural characteristics: it determines the installation of the valve, repair, maintenance and other methods of some structural characteristics, belonging to the structural characteristics are: the structural length of the valve and the overall height, and the pipe connection form (flange connection, thread connection, hoop connection, external thread connection, welding end connection, etc.); The form of sealing surface (insert ring, thread ring, surfacing, spray welding, body body); Valve stem structure form (rotating rod, lifting rod), etc.
2. The steps and basis of valve selection are as follows:
⑴ Selection steps
Clear valve in equipment or device use, determine the working conditions of the valve: applicable medium, working pressure, working temperature and so on.
(2) Determine the nominal size and connection method of the pipe connecting with the valve: flange, thread, welding, etc.
(3) Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage.
④ According to the pipeline transmission medium, working pressure, working temperature to determine the selected valve shell and inner parts of the material: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloy, etc.
⑤ Choose the type of valve: closed-circuit valve, regulating valve, safety valve, etc.
⑥ Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.
Determine the parameters of the valve: for automatic valve, according to different needs to determine the flow resistance, discharge capacity, back pressure, and then determine the nominal diameter of the pipeline and the diameter of the seat hole.
⑧ to determine the selected geometric parameters of the valve: structure length, flange connection form and size, open and close after the valve height direction of size, connection of the bolt hole size and number, the size of the entire valve shape.
⑨ Use the available information: valve product catalog, valve product samples, etc., to select the appropriate valve products.
The basis for choosing the valve
(1) the use of the selected valve, operating conditions and control mode.
(2) The nature of the working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is flammable, explosive medium, medium viscosity and so on.
③ Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade and so on.
(4) Installation size and appearance size requirements: nominal diameter, connection with the pipe and connection size, appearance size or weight limit.
⑤ Additional requirements for the reliability of valve products, service life and explosion-proof performance of electric devices. According to the above selection of valve basis and steps, reasonable and correct selection of the valve must also be a detailed understanding of the internal structure of various types of valves, in order to be able to preferentially choose the valve to make a correct choice. The ultimate control of the pipeline is the valve. Valve opening and closing parts control the flow of media in the pipeline, the shape of the valve flow channel enables the valve to have a certain flow characteristics, which must be taken into account when selecting the valve suitable for installation in the pipeline system.
The following are the principles to be followed when selecting valves
(1) The valve with the cut-off and open medium flow passage is a straight-through valve, the flow resistance is small, usually selected as the valve with the cut-off and open medium. Downward closed valve (globe valve, plunger valve) because of its tortuous flow path, flow resistance is higher than other valves, so less selected. Closed valves may be used where high flow resistance is permitted.
The control flow valve is usually easy to adjust the flow of the valve as the control flow. Downward CLOSING valves (such AS GLOBE valves) ARE SUITABLE FOR THIS PURPOSE BECAUSE THE SEAT size IS PROPORTIONAL TO THE STROKE OF THE SHUTOFF. Rotary VALVES (PLUG, butterfly, BALL valves) and FLEXURE BODY VALVES (PINCH, DIAPHRAGM) ARE ALSO AVAILABLE FOR THROTTLING CONTROL, but USUALLY ONLY IN a limited range of valve DIAMETERS. Gate VALVE IS A disc shaped gate to the circular seat port to do transverse motion, it only in close to the closed position, can better control the flow, so usually not used for flow control.
⑶ The valve with reversing shunt according to the need of reversing shunt, this valve can have three or more channels. Plug and ball valves are more suitable for this purpose, and therefore, most valves used for reversing and diverting are selected as one of these valves. However, IN SOME CASES, other TYPES OF VALVES MAY ALSO BE USED AS commutATION diverTERS, PROVIDED THAT TWO or MORE VALVES ARE properly connected to EACH other.
⑷ Valve with suspended particles medium with suspended particles in the medium, ** is suitable to use the closing parts along the sealing surface of the sliding valve with wiping effect. If THE SHUTOFF IS VERTICAL TO THE BACK AND FORTH MOVEMENT OF THE SEAT, PARTICLES MAY BE TRAPPED, SO THIS VALVE IS ONLY SUITABLE FOR BASICALLY CLEAN MEDIA UNLESS THE SEALING MATERIAL ALLOWS FOR PARTICLES TO BE EMBEDDED. Ball valves and plug valves wipe the sealing surface during opening and closing, so they are suitable for use in media with suspended particles. At present, whether in petroleum, chemical industry, or in other industries of the pipeline system, valve application, operation frequency and service are changing, to control or eliminate even the low leakage, the important and key equipment is the number of valves. The ultimate control of the pipeline is the valve, the valve in all fields of service and reliable performance is.
Pipeline water transfer technology Pipeline water transfer has the advantages of water saving, energy saving, land saving, fast water transfer speed, timely water supply, and convenient for farm machinery operation in the field. Pipeline water transmission technology can be divided into low-pressure pipeline water transmission technology in well irrigation area and pipeline water transmission technology in canal irrigation area according to water source conditions.
Low pressure pipeline water transfer technology in well irrigation area
Area of low pressure pipe delivery system by water (shaft), water delivery pipe network and the outlet of three parts  at present has formed a relatively mature technology system suitable for China’s national conditions. In the future, the key to improve is the standardization, standardization, serialization of pipe fitting products and the supporting application of field thyristor system.
Pipeline water transfer technology in canal irrigation area
The water supply system of canal irrigation area has the characteristics of large flow, many levels of system and complex hydraulic condition. Its popularization and application is still in the pilot stage in China, and it has a great potential for development. In the future, we should take the development and production of large-caliber pipes with low quality as a breakthrough, vigorously carry out the promotion and application research, and form a mature supporting technical system integrating planning and design, selection of pipes and fittings, construction technology and operation management.
Soft thyristor system
The soft thyristor is made of plastic, rubber or canvas and other materials. It has the advantages of low cost and easy application, but its service life is relatively short.
Hard thyristor system
Hard thyristors are made of PVC or aluminum pipes, equipped with quick joints, and can be assembled in the field according to furrow conditions. Compared with the soft thyristor system, the service life is long, but the cost is relatively high.