The so-called dual-phase stainless steel, in its solution quenching structure, ferrite phase and austenite phase each account for half, and generally the minimum phase content may reach 30%. Due to the characteristics of dual-phase structure, DSS has the advantages of both ferritic stainless steel and austenitic stainless steel by correctly controlling chemical composition and heat treatment process. 1. Compared with austenitic stainless steel, duplex stainless steel has the following advantages: (1) The yield strength is more than twice that of ordinary austenitic stainless steel, and it has enough plastic toughness required for molding. The wall thickness of the storage tank or pressure vessel made of duplex stainless steel is 30-50% less than that of ordinary austenite, which is beneficial to reduce the cost. (2) Excellent stress corrosion cracking resistance. Even duplex stainless steel with the lowest alloy content has higher stress corrosion cracking resistance than austenitic stainless steel, especially in the environment containing chloride ions. Stress corrosion is a prominent problem that ordinary austenitic stainless steel is difficult to solve. (3) The corrosion resistance of 2205 duplex stainless steel is better than that of ordinary 3 16L austenitic stainless steel, while super duplex stainless steel has extremely high corrosion resistance. In some media, such as acetic acid and formic acid, it can even replace high-alloy austenitic stainless steel and even corrosion-resistant alloys. (4) It has good local corrosion resistance. Compared with austenitic stainless steel with the same alloy content, its wear resistance and fatigue corrosion resistance are better than those of austenitic stainless steel. (5) The linear expansion coefficient is lower than that of austenitic stainless steel, and it is close to that of carbon steel, so it is suitable for connecting with carbon steel, which has important engineering significance, such as producing composite plates or linings. (6) Whether under dynamic load or static load, it has higher energy absorption capacity than austenitic stainless steel, which has obvious advantages for structural parts to deal with sudden accidents such as collision and explosion, and has practical application value. Compared with austenitic stainless steel, duplex stainless steel has the following disadvantages: (1) is not as universal as austenitic stainless steel, for example, its service temperature must be controlled below 250 degrees Celsius. (2) Its plastic toughness is lower than that of austenitic stainless steel, and its cold and hot processing technology and formability are not as good as that of austenitic stainless steel. (3) There is a brittle zone at medium temperature, so it is necessary to strictly control the technological system of heat treatment and welding to avoid the appearance of harmful phases and damage the performance. 2. Compared with ferritic stainless steel, duplex stainless steel has the following advantages: (1) comprehensive mechanical properties are better than ferritic stainless steel, especially plastic toughness, and it is not as sensitive to brittleness as ferritic stainless steel. (2) Except for stress corrosion resistance, other local corrosion resistance properties are better than ferritic stainless steel. (3) Cold working process performance and cold forming performance are far superior to ferritic stainless steel. (4) The welding performance is far superior to ferritic stainless steel, and preheating before welding and post-welding heat treatment are generally unnecessary. (5) The application range is wider than that of ferritic stainless steel. Compared with ferritic stainless steel, duplex stainless steel has the following disadvantages: high content of alloying elements, relatively high price, and generally ferrite does not contain nickel. To sum up, we can generally see the service performance and technical performance of DSS. With its superior mechanical and corrosion-resistant comprehensive properties, it has won the favor of users and become an excellent corrosion-resistant engineering material that saves both weight and investment. What is a ball valve? Working principle The ball valve can rotate 90 degrees. The cock body is a sphere with a circular through hole or channel passing through its axis. Ball valve is mainly used to cut off, distribute and change the flow direction of medium in pipeline. It only needs to rotate 90 degrees and a small rotating torque to close tightly. Ball valves are best used as switches and globe valves, but recent developments have designed ball valves for throttling and controlling flow, such as V-shaped ball valves. The main features of the ball valve are compact structure, reliable sealing, simple structure and convenient maintenance. Sealing surface and spherical surface are often closed, which is not easy to be eroded by medium and easy to operate and maintain. It is suitable for general working media such as water, solvent, acid and natural gas, as well as oxygen, hydrogen peroxide, methane and ethylene, and has been widely used in various industries. Ball valve body can be integrated or combined. Advantages: 1 The fluid resistance is small, and the full-diameter ball valve has basically no flow resistance. 2. Simple structure, small volume and light weight. 3. Close and reliable. It has two sealing surfaces. At present, all kinds of plastics are widely used in the sealing surfaces of ball valves, which has good sealing performance and can achieve complete sealing. It is also widely used in vacuum systems. 4. Convenient operation, rapid opening and closing, only 90-degree rotation from full opening to full closing, which is convenient for remote control. 5. Convenient maintenance, simple ball valve structure, movable sealing ring and convenient disassembly and replacement. 6. When fully opened or closed, the sealing surfaces of the ball and the valve seat are isolated from the medium, and when the medium passes through, it will not cause corrosion of the valve sealing surface. 7. Wide application range, from small diameter to several millimeters to several meters, from high vacuum to high pressure. 8. Because the ball valve has wiping characteristics during opening and closing, it can be used in media with suspended solid particles. Classification and characteristics 1. The ball of a floating ball valve floats. Under the action of medium pressure, the sphere can produce a certain displacement and press it on the sealing surface of the outlet end to ensure the sealing of the outlet end. The floating ball valve has simple structure and good sealing performance, but the load of the ball bearing the working medium is all transferred to the outlet sealing ring, so it is necessary to consider whether the sealing ring material can bear the working load of the ball medium, and the ball may deviate when it is impacted by high pressure. This structure is generally used for medium and low pressure ball valves. 2. Fixed ball valve The ball of the ball valve is fixed and does not move after being pressed. Ball valves with fixed balls all have floating seats. After being pressed by the medium, the valve seat moves, so that the sealing ring is pressed tightly on the sphere to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, which has small operating torque and is suitable for high-pressure and large-caliber valves. In order to reduce the operating torque of ball valves and increase the reliability of sealing, oil-sealed ball valves have appeared in recent years. Special lubricating oil is injected between the sealing surfaces to form an oil film, which not only enhances the sealing performance, but also reduces the operating torque, and is more suitable for high-pressure large-caliber ball valves. 3. Elastic ball valve (i.e. orbital ball valve) The ball of the ball valve is elastic. Both the ball and the seat sealing ring are made of metal, and the sealing pressure is very high. The pressure of the medium itself can not meet the sealing requirements, and external force must be applied. This valve is suitable for high temperature and high pressure medium. The elastic sphere obtains elasticity by opening an elastic groove at the lower end of the inner wall of the sphere. When the channel is closed, the wedge-shaped head of the valve stem is used to make the ball expand and press the valve seat to realize sealing. Before rotating the ball, loosen the wedge head, and the ball will return to its original state, so that there is a small gap between the ball and the valve seat, which can reduce the friction and operating torque of the sealing surface. 4.v-ball valve This ball valve is a fixed ball valve and a single-seat sealed ball valve. Its regulating performance is the best among ball valves, and its flow characteristic is equal percentage, with adjustable ratio of 100: 1. Its V-shaped notch has shearing effect with metal valve seat, which is especially suitable for media containing fibers, tiny solid particles and slurry. 5. Three-way ball valve Three-way ball valve has T type and L type. T-shape can make three orthogonal pipes communicate with each other, cut off the third channel, and play the role of shunt and confluence. L-shaped pipes can only connect two orthogonal pipes, and can not keep the interconnection of the third pipe at the same time, but only play a distribution role. Product function: 1. The three-way ball valve is structurally integrated, with four-sided valve seats sealed, few flange connections and high reliability. 2. The tee ball core is divided into T-type and L-type, with long service life, large circulation capacity and small resistance. 3. Ball valves are divided into single-acting type and double-acting type according to action types. The characteristic of single-acting type is that once the power source fails, the ball valve will be in the state required by the control system. The temperature and pressure limit nameplate shows the maximum working pressure allowed by the ball valve at the highest and lowest working temperatures. Using PTFE or RTFE seats and seals, the working temperature should be between -290℃ and 2000℃ ... The working temperature of other types of seats and seals should be checked by KI factory. The nominal pressure rating (PN) of the valve can indicate the maximum working pressure of the valve at room temperature. (For example, PN4.0 means that when the working temperature is-290 C ~ 380 C, the maximum working pressure is 40 Bar(4.0MPa). For matters needing attention of electric or pneumatic actuators, please refer to their corresponding instructions. Install 1) Remove the protective covers on both sides of the flange end, and rinse and clean with the valve fully open. 2) Before installation, the whole machine shall be tested according to the specified signal (electricity or gas) (to prevent the vibration caused by transportation from affecting the performance), and it can be installed on line only after it is qualified (the wiring shall be in accordance with the circuit diagram of electric actuator). 3) Before preparing to connect with the pipeline, the residual impurities in the pipeline must be cleaned and removed (these substances may damage the valve seat and ball). 4) When installing, do not use the actuator part of the valve as a lifting point to avoid damaging the actuator and accessories. 5) The valve shall be installed in the horizontal or vertical direction of the pipeline. 6) The pipeline near the installation point shall not sag or bear external force, and the deviation of the pipeline can be eliminated by pipeline bracket or support. 7) After connecting with the pipeline, please cross-lock the flange connecting bolts with the specified torque. Before operating and using 1), make sure that the pipes and valves have been flushed. 2) The operation of the valve drives the valve stem to rotate according to the input signal of the actuator: when the valve rotates forward 1/4 turns (90), the valve is closed. When the valve rotates in the opposite direction 1/4 turns (90), the valve opens. 3) When the directional arrow of the actuator is parallel to the pipeline, the valve is in an open state; When the indicating arrow is perpendicular to the pipeline, the valve is closed. Maintenance has a long service life and maintenance-free period, which will depend on the following factors: normal working conditions, harmonious temperature/pressure ratio and reasonable corrosion data. Note: When the ball valve is closed, there is still pressurized fluid in the valve body. Before maintenance, release the pipeline pressure and keep the valve in the open position. Before maintenance, disconnect the power supply or air supply. Before maintenance, disconnect the actuator from the bracket. Disassembly and disassembly can only be carried out after the upstream and downstream pipelines of the ball valve are depressurized. During disassembly and reassembly, care must be taken to prevent the sealing surface of parts, especially non-metallic parts, from being damaged. Use special tools when taking out the O-ring ● Tighten the bolts on the flange symmetrically, gradually and evenly during assembly ● The cleaning agent should be compatible with rubber parts, plastic parts, metal parts and working medium (such as gas) in the ball valve. When the working medium is gas, the metal parts can be cleaned with gasoline (GB484-89). Non-metallic parts are cleaned with pure water or alcohol ● The decomposed individual parts can be cleaned by soaking. Metal parts that are not decomposed by non-metal parts can be scrubbed with clean silk cloth soaked with cleaning agent (to prevent fibers from falling off and sticking to the parts). When cleaning, remove all grease, dirt, glue, dust, etc. Adhesion to the wall ● Non-metallic parts should be taken out of the cleaning agent immediately after cleaning, and should not be soaked for a long time ● After cleaning, they should be assembled after the cleaning agent on the wall volatilizes (it can be wiped with silk cloth that has not been soaked with cleaning agent), but they should not be put on hold for a long time, otherwise they will rust and be polluted by dust ● New parts should also be cleaned before assembly ● Lubricate with grease. Grease should be compatible with metal materials, rubber parts, plastic parts and working medium of ball valve. For example, when the working medium is gas, special 22 1 grease can be used. Apply a thin layer of grease on the surface of the installation groove of the seal, a thin layer of grease on the rubber seal, and a thin layer of grease on the sealing surface and friction surface of the valve stem ● During the assembly process, metal chips, fibers, grease (except those specified for use), dust, other impurities, foreign bodies, etc. Do not contaminate, adhere to or stay on the surface of the parts or enter the cavity (1), and the packaging should be re-locked. If there is slight leakage at the packing, the stem nut should be re-locked. Note: Don't lock it too tightly. At ordinary times, when the lock 1/4 is turned to 1, the leakage stops. 2), replace the valve seat and seal a), remove the valve in the half-open position, flush and remove the possible dangerous substances inside and outside the valve body. Close the ball valve, remove the connecting bolts and nuts on the two flanges, and then completely remove the valve from the pipeline. Disassemble the drive device-actuator, connecting bracket, stop washer, stem nut, butterfly spring plate, Gnan, wear plate and stem packing in turn. Remove the connecting bolts and nuts of the valve body cover, separate the valve cover from the valve body, and remove the valve cover gasket. Make sure that the ball is in the "closed" position, so that it can be easily taken out of the valve body, and then take out the valve seat. Gently push the stem down from the hole of the valve body until it is completely taken out, and then take out the O-ring and packing under the stem. Note: Please be careful to avoid scratching the surface of the valve stem and the sealing part of the stuffing box of the valve body. B) Reassemble, clean and inspect the removed parts. It is strongly recommended to replace seals such as seat and bonnet gasket with spare parts kit. Assemble in the reverse order of disassembly. Cross-lock the flange connecting bolts with the specified torque. Tighten the stem nut with the specified torque. After installing the actuator, the corresponding signal is input, and the valve core is driven to rotate by rotating the valve stem, so as to realize the opening and closing of the valve. If possible, before reassembling the pipeline, please carry out pressure sealing test and performance test on the valve according to relevant standards.
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