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Analysis of Full Welded Ball Valve Sealing Surface Processing Technology

June 1, 2018

It is necessary to study the processing technology of the full welded ball valve sealing surface. The ball valve itself has certain structural characteristics: the valve body structure is welded, has a standard diameter, and has a certain pressure test value when the ball valve is used. There are many difficulties in Welding ball valve processing technology. Therefore, SINOVAL studies the welding ball valve processing, and then provide production experience for the ball valve processing. 

1 Difficulties in Process of Welding Ball Valve Sealing Surface

For the technicians, in the process of welding the ball valve structure and its overall ball valve, not only are the welding difficult, but also there are many difficulties in the ball valve cover processing. The difficulty in welding the cover of the ball valve mainly includes the following two aspects: the guarantee of the coaxial height of the sealing surface between the valve body and the core and whether the sealing surface of the valve body cover can be at the same height before and after welding. 

2 Analysis of Difficulties in Process of Welding Ball Valve Sealing Surface

In the process of welding the sealing surface of the ball valve, it is necessary to compare and analyze the sealing surfaces of the ball valve with different structures and properties, so as to obtain the problem that the welding ball valve is difficult to solve in the process of processing, and then put forward a countermeasure to solve. In order to ensure that the coaxiality of the welded ball valve core and the ball valve body’s sealing surface after processing can still meet the requirements of the previous drawings. In the process of sealing the surface of the valve body and the ball core, it is necessary to ensure that the sealing surface of the valve body and the ball core meets the requirements of the coaxiality. In the part of the ball valve, in addition to the ball valve structure, the overall welding work of the structural ball valve is also required. In the welded structure ball valve, the heat treatment of the valve body joint surface before and after the welding is required. At this time, there will be a large deformation of the valve body, and the coaxiality of the valve body upstream or downstream may not be guaranteed. At this time, the coaxiality cannot be viewed as a reference for the positioning of the sealing surfaces of the valve body and the core. If the following method is used to solve the problem of the sealing surface of the welded ball valve, the concentricity of the valve body and the sealing surface of the ball core can be guaranteed within a reasonable range. In the production process, it is necessary to apply the principle of conversion and exchange, and carry out in-depth analysis to effectively solve the sealing surface of the valve body and the ball core of the welded ball valve. 

3 Solutions for Difficulties in Process of Welding Ball Valve Sealing Surface 

3.1 Coaxiality Guarantee of Valve body Sealing Surface Before And After Welding

In the processing of the welded ball valve sealing surface, the most important thing is to ensure the coaxiality of the sealing surface before welding and after welding. First of all, prior to assembly of ball core machining ball valve, a separate processing step of the ball core is required to ensure the cylindricity of the ball face, and it is also beneficial to determine the relative position of the ball core face and the sealing surfaces of both ends of the ball core. Second, to ensure the following two aspects, that is,  the coaxiality of the sealing surface of the valve body before welding and the coaxiality of the sealing surface of the valve body after welding. On the one hand, after the process of assembly and welding of the valve body and the ball core, the entire process flow of the sealing surface of the valve body before welding is mainly the following. Firstly, the core should be rotated to the fully open state and the core should be the size of the flow-through in-plane circle is used as a reference, and the downstream and upstream of the valve body are adjusted at the same time to keep the uniformity as uniform as possible. At the same time, it is necessary to ensure that the inner circle of the ball flow surface is basically concentric, and then the inner circle of the valve body and the ball core are over-flowed. The inner circle of the surface is welded to make it fixed firmly. Finally, the upstream side of the valve body is placed upwards, and then the correct position is found through the size of the inner circle of the flow surface of the core, thereby ensuring the coaxiality of the valve body up to standard. On the other hand,  the coaxiality of the sealing surface of the valve body after welding is ensured. Under normal circumstances, the sealing surface of the valve body may be deformed due to welding, and at the same time, the valve body sealing surface cannot be deeply processed due to the absence of the original machining reference. In order to ensure that the coaxiality of both ends of the valve body sealing surface reaches the pre-accuracy standard after surfacing of the valve body, it is necessary to continue processing using the ball core over-flow surface, and the machining process is similar to the production processing of the valve body sealing surface before welding, that is, the core needs to be turned to the fully open state, and the upstream adjustment of the valve body and the deep processing of the inner circle on the downstream side are performed at the same time. 

3.2 Coaxiality Guarantee of Sealing Surface of Valve Body and Core

In the above-mentioned research solutions, the core needs to be processed to find a benchmark, and then transferred to the cover on both ends of the valve body, so as to ensure the coaxial accuracy between the sealing surface of the ball core and the rear valve. The process flow of the ball core and the valve body sealing surface mainly includes the following steps. First, the ball core is rotated to the fully closed state, and at the same time, the coaxiality between the valve body circle and the outer circle of the sealing surface of the ball core is adjusted to make them parallel to each other, and then use the positioning block to effectively fix the valve body and the ball core. The next step is to calibrate the coaxiality based on the inner circle of the valve body so as to make the dimensions of the valve body inner circle and the sealing surface of the ball core meet the requirements of the drawings. The valve body and the ball core are further fixed by using the machining positioning block. At the same time, in turn, the reference surface is found according to the sealing surface of the valve body, so that the sealing surface of the ball core and the valve body on the other side meet the requirements of the drawing design. If the following method is used to solve the problem of the sealing surface of the welded ball valve, the coaxiality of the valve body and the sealing surface of the ball core can be guaranteed within a reasonable range. In the processing, it is necessary to apply the principle of conversion and exchange, in-depth analysis, and effectively solve the welded ball valve body and the ball core sealing surface. According to the improved method mentioned above, that is, the research on the processing technology of the coaxial seal surface of the valve body and the ball core, this can ensure the coaxiality of the valve body and the sealing surface of the ball core in the welding process. 

4 Conclusion

According to the research on the full welded ball valve sealing surface processing technology, currently it basically meets the qualified standards in processing and assembly, but the most important thing is to meet the standards of the owner acceptance. The full weld ball valve sealing surface processing technology research provides the production experience for the full welded ball valve and helps to improve the quality of the valve.


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