Common assembly method of valve Connection mode of electric actuator and valve

Common assembly method of valve Connection mode of electric actuator and valve

Valve assembly methods commonly used
Valve commonly used assembly methods can have three kinds, namely the complete replacement method, repair method and matching method:
(1) complete exchange method: when the valve is assembled by complete exchange method, each part of the valve can be assembled without any dressing and choice, and the product can meet the specified technical requirements after assembly. At this time, the valve parts should be completely processed in accordance with the design requirements to satisfy the dimensional accuracy with the shape and position tolerance request. The advantages of the complete interchange method are: the assembly work is simple, economic, workers do not need a high degree of skill, the production efficiency of the assembly process is high, easy to organize the assembly line and organization of specialized production. However, when complete replacement assembly is adopted, the machining accuracy of the parts is required to be higher. Applied to globe valve, check valve, ball valve and other simple structure of the valve class and small diameter valve.
(2) Matching method: the valve adopts the matching method of assembly, the whole machine can be processed according to economic accuracy, and then select a size with adjustment and compensation effect during assembly, so as to reach the specified assembly accuracy. The principle of the matching method is the same as that of the repair method, only the way of changing the size of the compensation ring is different. The former is to change the compensation ring size by selecting accessories, and the latter is to change the compensation ring size by dressing accessories. For example, the top core and adjusting gasket of the double wedge gate valve of the control valve model, and the adjusting gasket between the two bodies of the open ball valve are selected as compensation parts in the dimension chain related to the assembly accuracy, and the required assembly accuracy is achieved by adjusting the thickness and size of the gasket. In order to ensure that the fixed compensation parts can be selected under different circumstances, it is necessary to make a set of hydraulic control valve models of gasket and sleeve compensation parts with different thickness sizes in advance for selection in assembly.
(3) Repair method: the valve is assembled by repair method. The parts can be processed according to economic accuracy. During assembly, the size of a certain adjustment and compensation effect can be repaired to achieve the specified assembly goal. For example, wedge gate valve gate and valve body, because the processing cost of exchanging requirements is too high, most manufacturers are using repair method technology. That is, when controlling the opening size of the gate sealing face in the rear grinding, the plate should be matched according to the opening size of the valve body sealing face in order to achieve the sealing requirements. This method is added to the plate process, but ** simplifies the dimensional accuracy requirements of the front processing process, the plate process of the person skilled operation, in general will not affect the effectiveness of production. Valve assembly process: THE valve is individually assembled in a fixed site. The assembly of parts and components of the valve is carried out in the assembly workshop, and all the required parts and components are transported to the assembly working site. Usually parts assembly and total assembly distinguish by how many groups of workers at the same time, which not only shorten the assembly cycle, but also facilitate the application of the best assembly tools, the requirements of the workers’ technical level is also relatively low.
Some foreign manufacturers or high technology grade valves also have the use of assembly suspension line or assembly rotary table mode:
(1) Preparatory work before assembly: The valve parts shall remove the burr formed by mechanical processing and welding residue, clean and cut the packing and gasket before assembly.
(2) valve parts cleaning: as a fluid pipe control installation of the valve, the inner cavity must be clean. Especially nuclear power, medicine, food industry valves, in order to ensure the purity of the medium and avoid medium infection, the valve cavity cleanliness requirements are more severe. Clean THE VALVE PARTS BEFORE ASSEMBLY TO REMOVE DEBRIS, RESIDUAL SMOOTH OIL, COOLANT AND BURR, WELDING SLAG AND OTHER DIRT FROM THE PARTS. Valve cleaning is USUALLY DONE BY spraying WATER or HOT WATER with ALKALI (KEROSENE can also BE used FOR cleaning) or in an ultrasonic cleaner. The parts need to be cleaned after grinding and polishing, and the cleaning is usually to brush the sealing surface with gasoline, and then blow dry with compressed air and wipe clean with cloth.
(3) packing and gasket preparation: graphite packing has been widely used because of the advantages of corrosion resistance, good sealing and small friction coefficient. Filler and gasket to prevent media leakage through stem and cover and flange joint face. These fittings should be prepared for cutting and handling prior to valve assembly.
(4) Valve assembly: the valve is usually based on the valve body as the reference parts according to the order and method specified by the process of assembly. Before assembly, the parts and components should be reviewed to avoid undeburred and uncleaned parts entering the final assembly. In the process of assembly, the parts should be handled with care to avoid knocking and scratching the processing personnel. The active parts of the valve (such as valve stem, bearing, etc.) should be coated with industrial butter. The flange of the valve cover and the valve body are connected with bolts. When fastening bolts, the response is said, interwoven, repeatedly and evenly tightened. Otherwise, the joint surface of the valve body and the valve cover will produce leakage of flow control valve due to uneven force around it. The handle used for fastening should not be too long to prevent the preload from affecting the bolt strength. For VALVES WITH severe PRELOAD requirements, torque handles shall be applied to tighten the bolts according to the specified torque requirements. After assembly, the control mechanism should be rotated in order to check whether the activity of the valve opening and closing parts is mobile and whether there is a blockage scene. The VALVE cover, support and other parts of the device direction in accordance with the requirements of the drawings, all reviews have passed the valve can be tested.

The connection mode of the electric actuator and the valve The electric actuator is mostly matched with the valve, which is used in the automatic control system. There are many kinds of electric actuators, which are different in the mode of action. For example, the angular stroke electric actuator is the output angular torque, while the straight stroke electric actuator is the output displacement thrust. The type of electric actuator in the system application should be selected according to the work needs of the valve.
The electric actuator is mostly matched with the valve, which is used in the automatic control system. There are many kinds of electric actuators, which are different in the mode of action. For example, the angular stroke electric actuator is the output angular torque, while the straight stroke electric actuator is the output displacement thrust. The type of electric actuator in the system application should be selected according to the work needs of the valve.
The connection method
I. Flange connection:
This is the most common form of valve connection. According to the shape of the joint surface, it can be divided into the following:
1. Smooth type: used for valves with low pressure. Convenient processing
2, concave and convex type: high working pressure, can be used in the hard washer
3. Tenon and groove type: gasket with larger plastic deformation can be used in corrosive media, and the sealing effect is better.
4, trapezoidal groove: use oval metal ring as washer, used for working pressure ≥64 kg/cm2 valve, or high temperature valve.
5, lens type: the washer is a lens shape, made of metal. For high pressure valves with working pressure ≥100 kg/cm2, or high temperature valves.
6, O ring type: This is a relatively new flange connection form, it is developed with the appearance of various rubber O ring, it is in the sealing effect of the connection form.
Two, thread connection:
This is a simple connection method and is often used with small valves. There are two further cases:
1, direct sealing: internal and external threads directly play the role of sealing. In order to ensure that the joint does not leak, often with lead oil, linoleum and PTFE raw material filled; Ptfe raw material belt, the use of increasing popularity; This material has good corrosion resistance, good sealing effect, easy to use and preserve, disassembly, can be completely removed, because it is a non-viscous film, much better than lead oil, linoleum.
2. Indirect sealing: the force of screw tightening is transferred to the washer between the two planes, so that the washer plays the sealing role.
Three, card sleeve connection:
The connection and sealing principle of the clamping sleeve is that when the nut is tightened, the clamping sleeve is under pressure, so that its edge bites into the outer wall of the pipe, and the clamping sleeve outer cone is close to the joint body cone under pressure, so it can reliably prevent leakage.
The advantages of this form of connection are:
1, small size, light weight, simple structure, easy disassembly;
2, strong connection, wide range of use, can withstand high pressure (1000 kg/cm2), high temperature (650℃) and shock vibration
3, can choose a variety of materials, suitable for corrosion prevention;
4, machining accuracy requirements are not high; Easy to install at high altitude.
The clamping sleeve connection form has been used in some small diameter valve products in China.
Four, clamp connection:
This IS A QUICK CONNECTION METHOD that REQUIRES ONLY TWO BOLTS AND IS SUITABLE FOR frequently removed low PRESSURE VALVES.
Five, internal self-tightening connection:
Above all kinds of connection forms, are the use of external force to offset the pressure of the medium, to achieve sealing. The following describes a form of self-tightening connection using medium pressure. Its sealing ring is installed in the inner cone, with the medium opposite side into a certain Angle, medium pressure to the inner cone, and transferred to the sealing ring, in a certain Angle of the cone surface, produce two components, one parallel to the center line of the valve body outward, the other pressure to the inner wall of the valve body. The latter component is the self-tightening force. The greater the medium pressure, the greater the self-tightening force. So this type of connection is suitable for high pressure valves. It saves a lot of material and labor than flanged connection, but also requires a certain amount of preload, so that the pressure in the valve is not high, reliable use. The valve made of the principle of self tight sealing is generally a high pressure valve.
There are many forms of valve connection, for example, some do not have to remove the small valve, welded together with the pipe; Some non-metallic valves, using socket connection, and so on. Valve users should be treated according to the specific conditions.