Requirements and materials of the hottest valve

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Analyzing the requirements and materials of valves

the tightness of valves is an important index to measure the function and quality of valves

requirements for underground pipe valves

the gas valve installed in the underground pipe should be able to withstand the maximum pressure of gas transmission and distribution in the pipeline. More importantly, under the action of experimental force, the vertical pressing into the surface of the sample must have sufficient stiffness, that is, under the condition that the underground pipe is subjected to various external forces and the resource-saving development path must be taken first, the valve can still be kept from deformation and the sealing performance of the valve can be reliably guaranteed. 1) Try to reduce the height of the valve structure (referring to the height from the center line of the valve flow section to the valve top) to reduce the buried depth. 2) The top of the valve shall be equipped with a fully enclosed opening and closing indicator to facilitate the inspection of the state of the valve, which is an important condition for safe operation. 3) The full bore design reduces the flow resistance, makes it easy to pass through the pipeline sweeper or pipeline detector, and also meets the requirements of the non-stop closed hole drilling machine to open holes on the pipeline. 4) Reliable sealing performance, soft seal valves are not allowed to have any perceived internal leakage under 111 times the nominal rated service pressure, and hard seal valves are allowed to have less than 13dn mm3/s under 111 times the nominal rated service pressure. This requirement is relatively strict. For example, the internal leakage of a 500 mm nominal diameter gas valve cannot be greater than 9 ml/min, and external leakage is absolutely not allowed. 5) The shell of the gas valve used in the underground pipe should be corrosion-resistant. It is recommended to use different shell materials according to the transmission medium and service pressure of the pipeline. 6) The design of valve parts should consider the use of less maintenance or maintenance free structure, so as to minimize the workload of maintenance and repair, and reduce the impact of closed roads due to valve maintenance and repair on traffic. 7) The vast majority of underground pipeline valves are opened and closed manually. It is required that the opening and closing torque of the valve is small and the number of turns in the whole process is reasonable. Liz nickels' current research focuses on the use of "miracle material" graphene to improve the ability to cut off the gas source as soon as possible after the occurrence of fiber-reinforced plastic. 8) All kinds of pipelines under urban roads in China are crowded and complex, so it is not suitable to excavate basement inspection wells, so direct buried valves are recommended

valve shell material selection

according to the service pressure of the gas pipeline, the reasonable selection of valve shell material can not only meet the safe operation of the pipeline, but also achieve the purpose of reducing the cost and making the best use of everything. 1) Gray cast iron valves are recommended for transmission and distribution pipelines below medium pressure class B (12 MPa), which have the greatest advantage of good corrosion resistance and low price, and are very suitable for underground pipelines. 2) Under high pressure class B (18 MPa), or even under medium pressure class A (014 MPa), it is recommended to select valves made of nodular cast iron or cast steel, especially nodular cast iron. For example, compared with the cast steel brand WCB, the mechanical property of nodular cast iron qt400218 is not lower than that of the latter, while the corrosion resistance and casting process are better than that of cast steel, and the price is also lower than that of cast steel (generally about 70% of that of cast steel). Therefore, the overall performance and price of ductile iron valves are better than cast steel valves. Ductile iron valves should be selected as far as possible within the above pressure range, but special attention should be paid to the quality monitoring of ductile iron materials. 3) In case of high pressure class A (116 MPa) or higher pressure level, it is recommended to select cast steel valves, and generally select WCB brand for manufacturing valves with pressure level below 4MPa. 4) In recent years, local gas companies have begun to use PE pipes, which are currently used below the pressure level of 014 MPa. PE ball valve has also come out mdash; mdash; Yangyanzhen, deputy director of the Department of high tech development and industrialization of the Provincial Department of science and technology, said that this series of ball valves can be directly buried and have good sealing performance. However, at present, the price of PE ball valves is relatively high, especially those with a diameter greater than 100mm

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