Connection type of the valve

5. Collar connection: This type of connection has only begun to develop in China in recent years. Its principle of connection and sealing is such that when the nut is tightened, pressure is applied to the collar, causing its cutting edges to bite into the outer wall of the pipe; simultaneously, the external conical surface of the collar fits tightly against the internal conical surface of the fitting, thereby ensuring reliable leakage prevention. The advantages of this type of connection are: 1) small size, light weight, simple structure, and easy to assemble and disassemble ； 2) Strong bonding strength, wide range of applications, capable of withstanding high pressure (1000 kg/cm²), high temperatures (650°C), and shock vibrations ； 3) A variety of materials can be used, making it suitable for corrosion resistance ； 4) The requirements for processing precision are not high ； 5) Easy to install at high heights. Currently, the ferrule connection type has been adopted in some small-diameter valve products in China. 6. Clamp connection: This is a quick-connect method that requires only two bolts, and it is suitable for low-pressure valves that are frequently disassembled. 7. Internal self-tightening connection: All of the above connection types rely on external forces to counteract the pressure of the medium in order to achieve sealing. Below is an introduction to the connection type that utilizes medium pressure for self-tightening. Its sealing ring is located at the inner cone, at an angle to the side facing the medium. The pressure of the medium is transmitted to the inner cone, which in turn passes it on to the sealing ring. On the conical surface at this angle, two forces are generated: one that pushes outward parallel to the center line of the valve body, and another that presses against the inner wall of the valve body. The latter component of force is the self-tightening force. The greater the medium pressure, the greater the self-tightening force. Therefore, this type of connection is suitable for high-pressure valves. It saves a lot of material and labor compared to flange connections, but it also requires a certain degree of pre-tensioning in order to function reliably when the pressure inside the valve is not high. Valves made using the self-sealing principle are generally high-pressure valves. There are many other ways in which valves can be connected; for example, some small valves do not need to be removed and are welded directly to the pipes ； Some non-metallic valves use socket-type connections, and so on. Valve users should handle situations according to specific circumstances. 8. There are many other types of valve connections as well; for example, there are small valves that do not need to be removed and are welded directly to the pipes ； Some non-metallic valves use socket-type connections, and so on. Valve users should handle situations according to specific circumstances

Strength performance: The strength performance of a valve refers to its ability to withstand the pressure of the medium. Valves are mechanical components that are subjected to internal pressure; therefore, they must possess sufficient strength and stiffness to ensure they do not crack or deform over long-term use. Sealing performance: The sealing performance of a valve refers to the ability of its various sealing elements to prevent the leakage of the medium, and it is the most important technical parameter for valves. There are three sealing areas in a valve: the contact point between the moving part and the two sealing surfaces of the valve seat ； The fit between the packing and the valve stem as well as the packing box ； The connection between the valve body and the valve cover. The leakage in the former case is called internal leakage, which is what is commonly referred to as poor sealing; it affects the valve’s ability to stop the flow of the medium. For cut-off valves, internal leakage is not allowed. The leaks in the latter two locations are called external leaks, that is, the medium leaks from inside the valve to outside it. Leaks can result in material loss, environmental pollution, and in severe cases, accidents. For flammable, explosive, toxic, or radioactive media, leaks are absolutely unacceptable; therefore, valves must possess reliable sealing properties. Flowing medium: As the medium flows through the valve, pressure loss occurs (that is, a pressure difference before and after the valve), meaning the valve presents a certain resistance to the flow of the medium. The medium must expend energy in order to overcome this resistance. From the perspective of energy conservation, when designing and manufacturing valves, it is necessary to minimize the resistance exerted by the valves on the flowing medium as much as possible. Opening force and opening torque: The opening force and opening torque refer to the force or torque that must be applied in order to open or close a valve. When closing the valve, it is necessary to create a certain sealing pressure between the sealing surfaces of the operating element and the seat. At the same time, it is also required to overcome the friction forces between the valve stem and the packing, between the threads of the valve stem and the nut, at the support points at the end of the valve stem, and in other friction-prone areas. Therefore, a certain closing force and closing torque must be applied. During the process of opening and closing the valve, the required opening and closing forces and torques change, with their maximum values occurring at the final moment of closure or the initial moment of opening. When designing and manufacturing valves, efforts should be made to reduce their closing force and closing torque. Opening and closing speed: The opening and closing speed is expressed as the time required for a valve to complete one cycle of opening or closing. Generally, there are no strict requirements regarding the opening and closing speed of valves, but certain operating conditions impose specific demands on this speed. For example, in some cases rapid opening or closing is required to prevent accidents, while in other cases slow closing is necessary to avoid water hammer effects. These factors should be taken into consideration when selecting the type of valve. Response sensitivity and reliability refer to the degree to which a valve is sensitive to changes in medium parameters and can respond accordingly. For valves such as throttle valves, pressure reducing valves, and control valves that are used to regulate the parameters of a medium, as well as valves with specific functions like safety valves and steam traps, their functional sensitivity and reliability are very important technical performance indicators. Service life: It indicates the durability of a valve, is an important performance indicator for valves, and holds great economic significance. It is usually expressed in terms of the number of opening and closing cycles required to ensure the sealing requirements, or it can also be expressed in terms of the time of use.

The main categories of valve products that valve manufacturers in our country can supply include more than 3,500 different varieties. Over 40,000 specifications. (1) Valves for urban construction: The urban construction sector generally uses low-pressure valves, and there is a current trend toward developing environmentally friendly and energy-efficient types. Environmentally friendly rubber plate valves, balance valves, centerline butterfly valves, and metal-sealed butterfly valves are gradually replacing low-pressure iron gate valves. Valves commonly used in domestic urban buildings include balance valves, soft-sealed gate valves, butterfly valves, etc. (2) Valves for urban heating: In urban heating systems, a large number of metal-sealed butterfly valves, horizontal balance valves, and directly-buried ball valves are required, as these valves help to address hydraulic imbalances in the pipes both longitudinally and laterally, thereby achieving energy savings and thermal balance. (3) Valves for environmental protection: In domestic environmental protection systems, the water supply system primarily requires centerline butterfly valves, soft-sealed gate valves, ball valves, and exhaust valves (used to remove air from the pipelines). Wastewater treatment systems mainly require soft-sealed gate valves and butterfly valves. (4) Valves for city gas: City gas accounts for 22% of the entire natural gas market, resulting in high demand for valves as well as a wide variety of types. Mainly ball valves, plug valves, pressure reducers, and safety valves are required. (5) Valves for long-distance pipelines: Long-distance pipelines mainly carry crude oil, refined products, and natural gas. The valves most commonly used in such pipelines are forged steel three-piece full-bore ball valves, sulfur-resistant flat gate valves, safety valves, and check valves. (6) Valves for petrochemical plants: a. In refining plants, the valves required are mostly pipeline valves, including gate valves, globe valves, check valves, safety valves, ball valves, butterfly valves, and steam traps. Among these, gate valves account for about 80% of the total number of valves; valves constitute 3% to 5% of the total investment in such plants. b. Fiber manufacturing facilities; fiber products mainly fall into three categories: polyester, acrylic, and vinylon. The valves required are ball valves and jacketed valves (jacketed ball valves, jacketed gate valves, jacketed globe valves). c. Acrylonitrile plant. This device generally requires valves manufactured in accordance with API standards, mainly gate valves, globe valves, check valves, ball valves, steam traps, needle valves, and plug valves; among these, gate valves account for about 75% of the total number of valves. d. Ammonia synthesis plant. Due to the differences in ammonia synthesis raw materials and purification methods, the process flows vary, and thus the technical requirements for the valves also differ. Currently, domestic ammonia synthesis plants mainly require gate valves, globe valves, check valves, steam traps, butterfly valves, ball valves, diaphragm valves, control valves, needle valves, safety valves, and high/low temperature valves. Among them, globe valves account for 53.4% of all valves used in such installations, gate valves make up 25.1%, steam traps account for 7.7%, safety valves represent 2.4%, while control valves, cryogenic valves, and others account for 11.4%. e) Ethylene plants: Ethylene plants are key facilities in the petrochemical industry, and they require a wide variety of valves. Gate valves, globe valves, check valves, and lift-type ball valves account for the majority, among which gate valves come first. “Under the 15th Five-Year Plan, the country still needs to build 6 ethylene plants with an annual production capacity of 660,000 tons each, which will result in a significant demand for valves. In addition, large-scale ethylene and high-pressure polyethylene plants also require ultra-high-temperature, as well as low-temperature and ultra-high-pressure valve series products. f. Air separation unit. “\"Air separation\" refers to the process of separating air; such systems primarily require stop valves, safety valves, check valves, control valves, ball valves, butterfly valves, and low-temperature valves. g. Polypropylene plant: Polypropylene is a polymer compound typically produced by polymerizing propylene; this type of plant mainly requires gate valves, globe valves, check valves, needle valves, ball valves, and steam traps. (7) Valves for power plants: The construction of power plants in China is moving toward larger scales; therefore, there is a need for safety valves, pressure relief valves, globe valves, gate valves, butterfly valves, emergency shut-off valves, as well as flow control valves and spherical-sealed instrument globe valves with large diameters and high pressures. (According to the 10th Five-Year Plan, in addition to Inner Mongolia and Guizhou provinces where units of over 200,000 kilowatts can be built, other provinces and cities can only build units of over 300,000 kilowatts.) (8) Valves for metallurgy: In the metallurgical industry, wear-resistant slurry valves (in flow-type globe valves) and regulating steam traps are primarily required for handling alumina. The steelmaking industry primarily requires metal-sealed ball valves, butterfly valves, as well as oxidizing ball valves, stop valves, and four-way directional control valves. (9) Valves for offshore platforms: With the development of oil field exploitation at sea, the demand for valves used in offshore platforms is also increasing gradually. Offshore platforms require shut-off ball valves, check valves, and multi-way valves. (10) Valves for food and pharmaceutical use: This industry primarily requires stainless steel ball valves, non-toxic all-plastic ball valves, and butterfly valves.