Classification of valves
Thread Content
There are many types of valves. With the continuous improvement of the process flow and performance of various complete sets of equipment, the types of valves are still increasing, but in general they can be divided into the following categories:: Classified by use and function Product Category Name Purpose Product Segmentation Name Cut-off valves are mainly used to cut off or connect medium flow gate valves, stop valves, diaphragm valves, ball valves, plug valves, butterfly valves, plunger valves, ball plug valves, needle instrument valves and other regulating valves. Regulating valves, throttle valves, pressure reducing valves, check valves, etc., used to regulate the flow and pressure of the medium, check valves of various structures, used to prevent the backflow of the medium, diversion valves, safety valves of various structures, such as distribution valves and traps, used to separate, distribute or mix media. Used for safety protection when the medium is overpressured. Various types of safety valves are classified by pressure. Product type name. Pressure index. Vacuum valve. Valves with working pressure lower than standard atmospheric pressure. Low-pressure valves. Nominal pressure PN＜1.6MPa valves. Medium-pressure valves. Nominal pressure PN2.5~6.4MPa valves. High-pressure valves. Nominal pressure PN10.0~80.0MPa valves. Ultra-high pressure valves. Valves with nominal pressure PN＞100MPa. Classification by medium temperature. Product type name. Temperature index. High temperature valves. >450℃ valves, medium temperature valves, 120℃～450℃ valves, normal temperature valves -40℃～120℃ valves, low temperature valves -100℃～-40℃ valves, ultra-low temperature valves <-100℃ valves, product types are classified according to valve body material Name Material Type Non-metal material valves such as ceramic valves, fiberglass valves, plastic valves Metal material valves such as copper alloy valves, aluminum alloy valves, lead alloy valves, titanium alloy valves, Monel alloy valves Cast iron valves, carbon steel valves, cast Steel valves, low alloy steel valves, high alloy steel valves, stainless steel valves, metal valve body lining valves such as lead lined valves, plastic lined valves, enamel lined valves, classified by nominal diameter, product type, name, temperature index, small diameter valve, DN≤40mm valve Valve with medium door diameter DN50～300mm Large diameter valve DN350～1200mm Valve Extra large diameter valve DN≥1400mm Valves are classified according to the way of connecting to the pipeline. Flange connection valves (Flange) There is a flange on the valve body, which is flanged to the pipeline and threaded to the valve (Threading). The valve body is equipped with internal threads or external threads, and is threaded to the pipeline to connect the valve to the valve (Welding). There is a clamp on the valve body, which is connected to the pipe by a clamp sleeve. The valve is connected by a clamp sleeve to the pipe. It is classified according to the general classification method. This classification method is divided by principle, function and structure. It is currently the most commonly used classification method internationally and domestically. General gate valves, globe valves, throttle valves, instrument valves, plunger valves, diaphragm valves, plug valves, ball valves, butterfly valves, check valves, pressure reducing valves, safety valves, traps, regulating valves, bottom valves, filters, blowdown valves, etc.
A valve is a pipe fitting. It is a device used to change the channel cross section and the direction of medium flow, and control the flow of the conveyed medium. Specifically, valves have the following uses:: (1) Connect or cut off the medium in the pipeline. Such as gate valves, globe valves, ball valves, plug valves, diaphragm valves, butterfly valves, etc. (2) Regulate and control the flow and pressure of the medium in the pipeline. Such as throttle valve, regulating valve, pressure reducing valve, safety valve, etc. (3) Change the direction of medium flow in the pipeline. Such as distribution valve, three-way cock, three-way or four-way ball valve, etc. (4) Prevent the backflow of media in the pipeline. Such as various check valves, bottom valves, etc. of different structures. (5) Separation medium. Such as steam traps and air traps of various structures. (6) Indicate and adjust the liquid level. Such as liquid level indicator, liquid level regulator, etc. (7) Other special purposes. Such as temperature regulating valve, overcurrent protection emergency shut-off valve, etc. Among the above-mentioned various general valves, the number of valves used to connect and cut off the flow of media in pipelines accounts for about 80% of the total number of valves. At present, my country's valve manufacturers can provide nearly 3,500 varieties of valve products. More than 40,000 specifications, roughly distributed in the following fields: (1) Used in urban buildings (2) Used in urban heating (3) Used in environmental protection (4) Used in city gas (5) Used in long-distance pipelines (6) Used in petrochemical plants: a. Refining unit ； b. Chemical fiber equipment ； c. Acrylonitrile device ； d. Ammonia synthesis device ； e. Ethylene device ； f. Air separation unit ； g. Polypropylene device (7) Pulp and paper industry (8) Used in power stations (9) Used in metallurgy (10) Used in offshore platforms (11) Used in food and medical valves
The following table is a description of the valves commonly used in our chemical companies. No. Name Structural Features Performance 1. There is a valve core and valve seat in the valve body of the straight-through single-seat valve. The leakage is small and the pressure difference between the front and rear of the valve is small. 2. There are two valve cores and valve seats in the valve body of the straight-through double-seat valve. The flow coefficient and allowable pressure difference are larger than those of single-seat valves of the same caliber, but the pressure resistance is lower. 3. Except that the valve body is right-angled, the other structures of the angle valve are similar to those of the straight-way valve. It is suitable for fluids with high viscosity or containing suspended particles, but the input and output pipes need to be installed in an angular shape. 4 Diaphragm valves replace the valve seat and valve core assembly with a corrosion-resistant lining and corrosion-resistant diaphragm. It is suitable for fluids with strong corrosion, high viscosity or containing suspended particles and fibers, but has low pressure and temperature resistance. 5 The eccentric rotary valve is composed of a spherical valve core, a valve seat, a rotating shaft, a push rod and other components. The center line of the spherical valve core deviates from the center line of the rotating shaft. During operation, the rotating shaft drives the valve core to rotate eccentrically. The flow path resistance is small, the flow coefficient is good, and the sealing is good. It is suitable for media with large pressure difference, high viscosity and particles. The general pressure resistance is less than 6.4MPa. 6 Butterfly valve, also known as flap valve, consists of valve body, valve plate, valve plate shaft and other components. It is suitable for situations with large diameter, large flow rate and thick slurry and suspended particles. However, the fluid produces a large unbalanced torque on the valve body, and generally the allowable pressure difference of butterfly valves is small. 7 Sleeve valve is also called cage valve. Its valve body is similar to that of a general straight-through single-seat valve. There is a cylindrical sleeve inside the valve, and the valve core moves within the sleeve. It is suitable for situations where the liquid produces flash evaporation, cavitation and the gas flow rate at the vena contracta exceeds the speed of sound. ； Not suitable for media containing particles. 8 The ball valve core is spherical and has a cylindrical through hole. The flow path resistance is small, the flow coefficient is good, the sealing is good, and the adjustable range is large. It is suitable for media with high viscosity, fiber and particles, and is expensive. O-shaped ball valves are generally controlled by two positions, and V-shaped ball valves are continuously adjusted.