Application of High Temperature Hard Sealed Ball Valve in Chemical Fiber Steam
                                        Column:Technical Knowledge Time:2018-07-10

                                        The JIS standard for stainless steel globe valves was introduced before. Now the application of high temperature hard sealing ball valves in chemical fiber steam was introduced. The sealing characteristics of high temperature hard sealing ball valves were introduced. The seat structure and sealing principle of various hard sealing ball valves were analyzed, and the improvement methods of hard sealing structure were put forward. Product Name and Model: High temperature ball valve has been widely used in petrochemical industry, long distance pipeline and urban heating industry due to its small fluid resistance, easy operation, quick opening and closing, good sealing and high reliability. The valve seat material used in PTFE (or filled PTFE) is called soft sealing ball valve, whose service temperature does not exceed 200 C. The seat material is made of metal, called hard sealing ball valve or high temperature ball valve, and the service temperature is higher than 250 C. In recent years, in order to meet the needs of high-temperature working conditions, domestic and foreign ball valve manufacturers have optimized the sealing structure of high-temperature ball valve to reduce its opening and closing torque, prolong its service life and improve its operation performance significantly. The chemical fiber industry plays an important role in the national economic and social development, and is also the main foundation and raw material industry of the country. Over the past two decades, China's chemical fiber industry has made rapid progress. Among synthetic fiber varieties and structures, the output of polyester staple fibers accounts for 1/3 of the total output of chemical fibers in the country. In 1992, Sinopec Energy Conservation Center counted the average comprehensive energy consumption of the five leading staple fiber production enterprises in the system as 0.341 t/t (standard oil), which is obviously different from the domestic level of 0.269 t/t (standard oil).

                                        2. High Temperature Hard Sealed Ball Valve Hard Sealed Structure for Application of Ball Valve in Chemical Fiber Steam

                                        2.1, sealing characteristics

                                        The sealing characteristics of high temperature ball valves are mainly metal sealing pairs, which have the advantages of wide temperature range and little difference in thermal expansion coefficients of various metals. As long as they are properly selected, they can achieve basic consistency, which is conducive to coordinating temperature difference deformation. The disadvantage is that the material has high hardness and the specific pressure required to achieve the seal is high. Even if the pre-tightening force is used to achieve the seal, the wear between the valve seat and the ball body is very large because of the high specific pressure of the seal. Moreover, the friction coefficient of the metal sealing surface is large, which leads to the larger opening and closing moment of the ball valve. Therefore, high temperature ball valves mostly use elastic sealing pairs, which have reliable performance, strong elastic compensation ability, wide temperature range, and are applicable to floating ball valves and fixed ball valves. Under the action of pre-tightening force and fluid pressure, the seat and sphere of high temperature ball valve are pressed tightly, so that the sealing surface of the valve seat is deformed and sealed. The sealing effect depends on the degree to which the non-roundness and micro-roughness of the sphere can be compensated by the seat under the action of fluid pressure and pre-tightening force. Therefore, there must be a sufficient sealing specific pressure QB between the seat and the sphere, which should be satisfied

                                        Qb in type I - The specific pressure must be used to ensure the sealing of valves, MPa

                                        Q - Actual specific pressure of valve working, MPa

                                        [q] - Permissible Specific Pressure of Seat Materials, MPa

                                        2.2. Structural Analysis of High Temperature Hard Sealed Ball Valve Applied in Chemical Fiber Steam

                                        (1) Sealing structure of floating ball valve

                                        The hard sealing high temperature ball valve shown in Figure 1 consists of a valve body, a ball body, a stem, a metal seat and a flexible graphite seal ring between the seat and the valve body. The two seats are symmetrically centered on the stem axis and embedded in the valve body. The seat slides in the body insertion groove. The seal between the seat and the valve body is realized by a flexible graphite seal ring. Because the flexible graphite sealing ring can be compressed and deformed, the ball valve of this structure can not be blocked by the expansion of the sphere in a certain temperature range. The hard sealing ball valve of this structure can be used in the working condition of temperature not exceeding 343 C.

                                        1. Body 2. Sphere 3. Stem 4. Sealing ring 5. Seat

                                        Metal elastic rings are used as seat seals in high temperature ball valves to compensate for the effects of temperature difference, pressure and wear on the sealing performance of ball valves. The valve consists of a valve body, a ball, a stem, a metal seat, a flexible graphite seal ring between the seat and the valve body, a metal elastic ring, a metal elastic ring pressure ring and a gasket. Two seats are a metal seat sliding in the body insertion groove and a deformable metal elastic ring seat. The metal elastic ring seat of the structure ball valve can be deformed when the ball is heated and expanded, so that the ball can not be stuck and can not move.

                                        Application of High Temperature Hard Sealed Ball Valve in Chemical Fiber Steam 1. Seal Ring 2. Seat 3. Body 4. Sphere 5. Stem 6. Pressure Ring 7. Metal Elastic Ring 8. Sealing Gasket

                                        The main valves of Shanghai Qizhong Valve Co., Ltd. are: globe valves, electric globe valves high temperature ball valves using disc spring loading sealing pair structure. The valve is composed of body, ball, stem, back seat, back seat seal ring, front seat, front seat seal ring, pressure ring and disc spring. The front seat, the front seat seal ring and the pressure ring are one assembly, and the disc spring is pressed on the assembly. The disc spring is pressurized after assembly of the ball valve. On the one hand, it provides the initial force for the valve seal, on the other hand, it compresses the sealing ring between the seat and the valve body to seal between the seat and the valve body. The two seats of the structure ball valve are symmetrically embedded in the valve body with the stem axis as the center. The seat can slide in the valve body insertion groove, the seat assembly slides when the ball is heated and expanded, and the disc spring is compressed and deformed to avoid the ball being stuck and unable to move.

                                        Characteristic and application of high temperature hard sealing ball valve in chemical fibre steam application product:

                                        The design of full-diameter floating ball valve seal structure has the advantages of large flow capacity, small flow resistance, small switching moment, high temperature and non-blocking.

                                        The sealing structure of the heightened packing box is adopted, and the filling material is flexible graphite. The outer seal is reliable.

                                        The valve seat is equipped with a disc spring set, which can effectively absorb the thermal expansion of the sphere and the valve seat at high temperature.

                                        Flange structure is used to connect the two ends of the valve, and stainless steel toothed cushion is used for the middle flange+


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