Low temperature valve with long neck valve cover reasons for low temperature valve selection inquiry order matters needing attention

Low temperature valve with long neck valve cover reasons for low temperature valve selection inquiry order matters needing attention

Low temperature valves include low temperature emergency cut-off valve, low temperature cut-off valve, low temperature check valve, LNG low temperature valve, NG** low temperature valve, etc., mainly used in 300,000 tons of ethylene, liquefied natural gas and other chemical plant. The output liquid low-temperature medium such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc., is not only flammable and explosive, but also gasification when heating up. When gasification, the volume expands hundreds of times.
Reasons for long neck cover for low temperature valves
Suitable for medium temperature of -40℃ ~ -196℃ valve is called low temperature valve, and this kind of valve generally use long neck valve cover.
The low-temperature valve includes low-temperature emergency cut-off valve, low-temperature cut-off valve, low-temperature check valve, LNG low-temperature valve, NG low-temperature valve, etc., mainly used in 300,000 tons of ethylene, liquefied natural gas and other chemical plant. The output liquid low-temperature medium such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc., is not only flammable and explosive, but also gasification when heating up. When gasification, the volume expands hundreds of times
The long neck cover is specified because:
(1) The long neck valve cover has the function of protecting the low temperature valve packing box, because the sealing of the packing box is one of the key of the low temperature valve. If the stuffing box leaks, it will reduce the cooling effect and lead to the gasification of liquefied gas. At low temperature, with the decrease of temperature, the elasticity of packing gradually disappears, and the leak-proof performance decreases. Due to the media leakage, the packing and the valve stem are frozen, which affects the normal operation of the valve stem. At the same time, the pulp packing is scratch due to the movement of the valve stem up and down, causing serious leakage. Therefore, it is necessary to ensure that the temperature of the filler base is above 8℃.
(2) The long neck valve cover structure is easy to wrap the cold retaining material to prevent the cold energy loss of the low temperature valve.
(3) The long neck structure of low temperature valve facilitates the quick replacement of the main valve parts through the valve cover removal. Since the process pipes and valves in the cold section of the equipment are often installed in the ‘cold box’, the long neck valve cover can be extended through the ‘cold box’ wall. To REPLACE THE VALVE MAIN component, simply remove through the valve cover, without removing the body. The valve body and the pipeline are welded into one, as far as possible to reduce the leakage of the cold box, to ensure the sealing of the valve.
Low temperature valve selection inquiry order matters needing attention
Low temperature valve refers to the valve that can be used under low temperature condition. Usually, the valve whose working temperature is lower than -40℃ is called low temperature valve. Low temperature valve is one of the indispensable important equipment in petrochemical industry, air separation, natural gas and other industries. Its quality determines whether it can be produced safely, economically and sustainably. With the development of modern technology, the use of low temperature valve is more and more wide, the demand is also more and more large.
For temperature higher than -50℃, generally do not use the long neck structure, for temperature below -50℃ ball valve, neck length T according to the design and calculation of Yijie valve company. Low temperature ball valve is mainly used for the output of liquid low temperature media such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc., not only flammable and explosive, but also in heating to gasification, gasification, volume expansion hundreds of times.
The material of liquefied natural gas valve is very important, the material is not qualified, will cause the shell and sealing surface leakage or leakage; The comprehensive mechanical properties, strength and steel of the parts can not meet the requirements of use or even fracture. Resulting in liquefied natural gas medium leakage. Therefore, in the process of developing, designing and developing liquefied natural gas valves, the material is the first and key issue. The valve body and cover adopt: LCB(-46℃), LC3(-101℃), CF8(304)(-196℃).
Low temperature valve needs to use a long neck valve cover structure, its day is to reduce the external incoming heat in the device; Ensure that the temperature of the packing box is above 0℃, so that the packing can work normally; Prevent frosting or freezing of the stem and the upper part of the bonnet at the stuffing box part due to the stuffing box part being overcooled.
The design of the long neck valve cover is mainly the design of the neck length L, L refers to the distance from the bottom of the stuffing box to the upper surface of the sealing seat, it is related to the thermal conductivity of the material, the thermal conductivity area and the surface heat dissipation coefficient, the heat dissipation area and other factors, the calculation is more complicated, generally obtained by the experimental method.
The working conditions of the low-temperature valve are harsh. Most of the working media are inflammable, explosive and permeable substances. The low working temperature can reach -269℃ and the maximum working pressure can reach 10MPa. Therefore, the design, manufacture and inspection of low temperature valves are very different from universal valves.
A lot of people, just put the valve material is low temperature steel is directly considered cryogenic valves, actually otherwise, it’s only a cryogenic valves of semi-finished products, because it didn’t after cryogenic treatment at low temperature, and low-temperature cryogenic treatment is the nods eyeball pen of cryogenic valves, cryogenic valves in cryogenic treatment is key, so as to ensure that all parameters of the cryogenic valves meet the requirements, Especially the expansion coefficient, will not lead to a variety of valve stuck in use. Sometimes in consideration of the price of the problem, also need to consider the quality of the valve. Low temperature valve is a special valve.
Now domestic most cryogenic valves is not actually after cryogenic treatment at low temperature, the cost would be expensive, here I can give you a rough work, if your set of cryogenic equipment cost is high, the cryogenic equipment is expensive, and cryogenic liquid nitrogen in addition to the necessary material and is a bad storage medium, and consumed a valve in the processing of liquid nitrogen is very much, And liquid nitrogen are not cheap. The low temperature valve produced by the special low temperature treatment, rough machining parts in the cooling medium for a few hours (2-8 hours), to release the stress, ensure the low temperature performance of the material, ensure the finishing size, to prevent the valve in the low temperature condition, due to temperature changes caused by deformation caused by the leakage of low temperature valve.
Low temperature valve selection inquiry order matters needing attention:
In order to make the cryogenic valve better meet the customer’s use requirements, if you need the cryogenic valve, please provide the specific parameters you know
1. Name of low temperature medium;
2. Temperature of low temperature medium;
3. You need to customize the length of the long neck of the low temperature valve, which is not provided according to the standard of the valve;
4. Material of low temperature valve (can be customized according to customer requirements);
5. Low temperature valve pressure;
6. Low temperature valve seal (soft seal or hard seal);
7. Connection mode (flange connection or welding);
8. Drive mode (manual, pneumatic, electric).