1. Current status and analysis of
Plug Valve sealing
Cast stone Plug Valve is an ideal opening and closing device in ash and slag pipelines. The quality and service life of the seal directly affect the quality and service life of the valve. In the past, the O-shaped rubber seal structure was used, that is, an O-shaped sealing ring was placed in the annular groove machined on the shaft, and then assembled into the hole machined on the sleeve parts to form a seal between the shaft and the hole. This kind of The sealing performance of the structure depends on the interference amount during design, that is, the compression amount of the O-ring and the machining accuracy of the hole and shaft parts. If the interference amount is too small, the sealing performance will be poor. If the interference amount is too large, the O-ring will be easily squeezed during assembly, causing the seal to fail.
The sealing structure is simple and easy to assemble. However, if the machining accuracy of shafts and holes is not high or it is difficult to improve the machining accuracy, in addition to the difficulty in ensuring the basic sealing performance or difficulty in further improving the accuracy, the main disadvantage lies in the sealing material. This sealing structure is still used in cylinders and liquid cylinders. It is very applicable. It is difficult to ensure the sealing performance of cast stone Plug Valve used in ash and slag water. The reason is that the switch of the Plug Valve is a partial rotation type and often requires a 90° switch. Since there is a certain gap between the
Valve Stem and the valve body, the huge thrust of the medium acting on the ball when the valve is opening and closing will inevitably cause the valve stem to tilt to a certain extent. If the force of the valve stem is biased to one side, that side will be seriously worn. , and the ash water contains a large amount of suspended matter that corrodes the sealing ring. As a result, the life cycle of the O-ring seal in the valve stem area is short, leakage occurs frequently, and it also has a certain impact on the site environment. Therefore, it was decided to improve the seal structure and materials. The main starting point after the improvement was to make it fit in the shaft and hole. It can be adjusted by the amount of compression, and effective sealing can be ensured without greatly improving the machining accuracy of the shaft and hole.
2. Plug Valve structure improvement and grinding tool design
①X-shaped sealing ring structure
There are sealing surfaces all around the X-shaped sealing ring, and there are lubrication grooves inside and outside the sealing ring. This structure is better than the O-shaped sealing ring. It has low installation accuracy, good use reliability, no maintenance, low price, and can also be used with gaskets. Adjusting the compression amount is now widely used in the sealing of cast stone valves of various pressure levels, which can effectively prevent leakage, greatly extend the service life of the valve, and improve the reliability of the valve.
②X-shaped sealing ring material
The X-shaped sealing material is made of polyurethane (CPU) material, which can effectively solve the problems existing in the traditional O-shaped sealing ring. Casting polyurethane is a relatively accepted sealing material in the world. It has a large elastic modulus, good physical and mechanical properties, and can withstand large impact loads. Polyurethane has basically solved the problem of hydrolysis resistance, and its temperature resistance level is also Continuous improvement has greatly expanded the application fields of polyurethane. Using cast polyurethane to produce X-shaped sealing rings has a simple process and low manufacturing cost. Its pressure resistance level can reach 60MPa or even higher, the pressure maintaining effect is also quite good, and it can basically achieve zero leakage.
③Plug Valve sealing principle
Its working principle: When the bolt is tightened, the packing gland moves downward to compress the adjusting gasket. Through the extrusion of the V-shaped packing gasket, the inner lip and outer lip of the X-shaped sealing ring are pressed against the sealing surface of the shaft and hole at the same time. The main sealing performance of a reliable seal depends on the tightening force of the bolts during assembly and has little to do with the dimensional accuracy of the shaft and hole.
④Abrasive tool design
Ensure that the product usage requirements meet the design requirements. It is easy to demould and clean the mold, convenient to operate, and has low manufacturing cost. The abrasive material is suitable for 45 steel. The shrinkage rate is designed according to 1.5%~1.7%. There is no flash when positioned at a 10° slope. The product The accuracy is guaranteed and the yield is high. The grinding tool consists of an upper mold, an inner mold and an outer mold.
⑤Packing cavity size
The number of seasonings in the stuffing cavity is determined based on the Plug Valve pressure and diameter, and the width is determined by the size of the shaft. For pressures below 0.6~2.5MPa and DN250mm, one X-shaped sealing ring is required, and for pressures above 2.5~10MPa and DN300, two X-shaped sealing rings are required. The size and depth of the packing cavity are determined by the height of the seasoning pad, pressure transmission ring, and X-shaped sealing ring.
⑥Pressure transmission ring
The pressure transmission ring is installed at high pressure and large diameter. It is installed between two sets of X-shaped sealing rings. Its main function is to transmit the pressure above, change the stress state of the X-shaped sealing ring, and make the X-shaped sealing ring stressed. And deform radially to achieve sealing performance.
⑦Finite element analysis of X-shaped sealing ring
The X-shaped sealing ring is a lip-shaped sealing ring that is used in combination with a pressure ring (packing gland) and a support ring (packing pad). It can effectively prevent medium leakage.
⑧Stress analysis of X-shaped sealing ring
The force on the X-shaped sealing ring is transmitted to the X-shaped sealing ring through the pressure of the pressure ring (packing gland). There is a support ring (packing pad) at the bottom of the sealing ring to apply force at three points. The sealing surface between the shaft and the valve hole The force is evenly distributed and a better sealing effect can be obtained.
3. Summary on Plug Valve sealing
Through improvements, the valve structure is more reasonable, sealing is more reliable, raw materials are saved, costs are reduced, service life is increased, modification is fast, investment is low, and the needs of users are met.
