Introduction of LNG ultra-low temperature stop valve

LNG shut-off valve is a low-temperature shut-off valve used in low-temperature liquefied gas storage and transportation equipment and related pipelines; it mainly includes: valve body, valve cover is installed on the valve body, handwheel is fixedly installed on the valve stem, and the valve stem The valve core is fixed to the lower end of the valve stem through the thread and the valve cover is fixed, the compression nut is matched with the valve stem sleeve through the thread, the compression nut is pressed on the compression sleeve, and the compression sleeve will The "V" type sealing ring is pressed on the retaining ring between the valve stem and the valve stem sleeve; its characteristic is: a spring is arranged between the compression nut and the compression sleeve, and the spring is tightly pressed on the compression sleeve. The use of the low-temperature cut-off valve has better sealing effect.

The price of LNG shut-off valve may rise in the near future

The ultra-low temperature globe valve adopts a conical sealing structure in which the disc is in contact with the valve seat. The sealing pair is designed as a metal-to-metal hard seal. The valve seat is designed on the valve body and forms an integrated structure with the valve body. In order to ensure the reliable sealing of the valve, cemented carbide is spray-welded on the sealing surface of the valve disc and the valve body. After low-temperature test and coating mechanical performance test, it is proved that the hardness increases after spraying, and the low-temperature environment wear resistance is good, which promotes the reliable sealing of the valve in the low-temperature environment.

 After consulting data and experimental application, we used plasma spray welding technology to spray-weld StelliteNo6 alloy on the sealing surface of the valve body, and spray-welded StelliteNo12 alloy on the sealing surface of the valve disc, with a thickness of ≥1mm. After the spray welding process, the hardness of the sealing surface of the disc with StelliteNo12 alloy is greater than the hardness of the sealing surface of the valve body with StelliteNo6 alloy, which is conducive to the sealing effect of the shut-off valve. Since the working condition of the ultra-low temperature globe valve is below -100°C, the valve disc and valve body must be cryogenically treated after spray welding of cemented carbide. Keep it cold in liquid nitrogen at -196°C for 2h, and then take it out for natural treatment. In addition, the main components such as the valve stem, long-neck bonnet, and threaded fasteners are all cryogenically processed before finishing.

J41H American Standard Forged Steel Globe Valve

The valve stem of the ultra-low temperature stop valve drives the valve clack to open and close the valve through linear movement up and down. When designing the valve body, the movement guiding function of the valve disc is added. A cylindrical guide wall is designed in the valve body to make the movement of the disc smooth and the valve open and close reliably. At the same time, in the process of valve production and processing, since the valve disc sealing surface and the valve body sealing surface are spray-welded with Stellite alloy, the hardness is greatly improved, and the processing and grinding of the sealing surface is difficult, and the main sealing surface needs to be accurately ground and matched. In order to effectively seal. The design of the guide wall makes the contact and fit of the valve clack and the sealing surface of the valve body more even, which is beneficial to realize the reliable sealing and processing technology of the stop valve.