The principle of hemispherical valve

First, the structure uses the eccentric - wedge principle to adjust the valve body and the valve core rotation center (ie the stem axis) and the valve core sealing spherical geometric center offset a radial size, but also with the electric valve seat sealing surface There is an offset dimension on the axis of the valve body channel. The sealing pair is under the action of a metal-metal external force. The pneumatic adjustment valve is self-locked and closed by two eccentricities. The eccentricity is reasonable and the self-locking angle is smaller than the friction angle. The angle selection is too small to close, the opening is extremely difficult, and the angle is selected to be large. Although the opening force is small, the closing moment increases rapidly. It is crucial to determine the two pairs with a reasonable amount of eccentricity and reliable self-locking. Performance ensures tight sealing.

This is the core technology of the hemispherical valve. From the structural principle to achieve the best seal through manufacturing methods, the ball valve, butterfly valve, gate valve, globe valve and so on are indeed inferior.

Second, it is easy to realize and maintain zero-leakage for a long time. The seal between the valve plug and the valve seat is a spherical line contact, and self-locking is realized by eccentricity. The sealing pair does not contact with the entire process of opening and closing. It only comes into contact with the opening and closing moment. And to achieve a zero leakage seal, to ensure that there is no leakage point of the dynamic seal. Fouling or other deposits on the valve seat, the valve core has the ability to remove fouling force in the process of contacting the valve seat. The sealing surface of the gate valve in the frequent reciprocating movement of the opening and closing, the mixed medium fouling precipitated in the lower cavity of the valve body, the closing valve completely relies on the positive pressure to achieve the seal, the scale on the valve seat has no cleaning ability, and both the packing Frequent repeated wear and tear can easily cause internal leakage and leakage of gate valves and globe valves.

Ball valve seal is on the surface of the valve by long-term extrusion, it is sure to wear faster than the hemisphere valve, butterfly valve seal is rubber as an intermediary, it is more than a half-ball valve, ball valve, gate valve metal hard sealing performance far. After long-term use of the half-ball valve, the valve seat will also have a slight amount of wear, which can be adjusted to continue to be used. The stem and the packing only need to be rotated by 90° during the opening and closing process. When there is a sign of leakage, the pressure of the packing gland is compressed. A little bolt, you can achieve no leakage at the packing, and other control valve is still a small leakage, and large leakage change control valve.

Aluminum Corporation of China Guangxi Branch (working medium: red mud slurry, strong alkaline solution) in the use of the report said that ... ... the control valve operation (open, close) easy and convenient, easy maintenance, sealing performance, and ordinary valve Longer than the service life, ... has been used since July 2001 (has worked for nearly three years - the editor) has not found any mechanical problems and leakage problems, and is very popular in terms of labor intensity, energy saving and leakage."

Third, the operation of the extremely light hemispherical valve open and close the whole process, the sealing pair is almost in the state of no damping idling, the external force is only in the opening and closing moments of disengagement or compression, and the stem only need to rotate 90 ° light and fast, of course, easy to operate. In the process of opening and closing, the ball valve is operated under the holding force of the valve seats at both ends. It has larger opening and closing torque than the hemispherical valve. The bigger the nominal diameter is, the more obvious the opening and closing torque difference is, and the opening and closing of the butterfly valve is to overcome the deformation of the rubber. The realization of the moment is greater. The gate valve and globe valve have long operation time and are strenuous.

Fourth, long service life The sealing pair belongs to the bimetal. The alloys used in different applications are surfacing on the mother's body. After special heat treatment, the mechanical properties and physical and chemical indexes of the alloy are optimal to meet different working conditions (strong wear, rapid erosion, etc.) Corrosion serious medium and other needs), valve seat valve hardness slightly lower than the valve core, different materials and different heat treatment process, when necessary, the hardness of the seal can reach more than HRC53, but also resistant to 560 °C high temperature. Practice has proved that its anti-corrosion and anti-biting ability is 6 times that of the stainless steel sealing pair. The regulating valve opens and closes tens of times without failure, prolonging the service life.

Wuhan Iron and Steel Company in the use of the report said: "In the first phase of bituminous coal injection purchase your company's hand, electric, pneumatic half ball valve, there is no dust accumulation during use, the switch is flexible, good sealing performance, which used in the main line Hemispherical valves are well matched with imported foreign equipment, and the prices of various types of regulating valves are only equivalent to 15-20% of the prices of similar foreign equipment. This saves investment for the first stage project of WISCO bituminous coal, and has been used for nearly three years. It is in good condition. , Cost savings, reduced equipment failure, and reduced the labor intensity of workers have been unanimously praised by iron factory leaders and managers."

V. Wide range of applications A wide range of ball valve types are widely used in non-ferrous smelting, gas natural gas, pulverized coal injection and dust removal of steel, power slag, harmful gases (hydrogen sulfide, phosgene, etc.) and oil products (heavy oil, crude oil, Residues, etc.) Smelting and conveying. The reason why it has a wide range of applications is mainly because the seals are separately welded to different alloys to make them bimetals. The main parts such as the valve body and stem are made of the required materials to meet different working conditions and constitute various adjustments of our company. Valve product line.