series of LNG cryogenic valves is introduced, A)

LNG series valve is mainly applied to - 162 ℃ low temperature of liquefied natural gas, LNG transport, LNG storage and LNG regasification and other fields, including LNG LNG LNG butterfly valve, gate valve, globe valve, LNG LNG LNG safety valve, ball valve, check valve, series of LNG throttle valve and belong to the multiphase flow with phase change temperature control equipment, high pressure process for liquefaction process, greatly different, appearance design is different, have different purposes.

in the field of traditional low temperature fluid control, complete set of processes that is commonly used in process control valves are numerous, such as the main cut-off valve, gate valve, ball valve on-off valves, one of the advantages of small flow resistance, may transport gas liquid two phase flow, the valve is not easy to jam, control characteristics such as large flow, gate valve, ball valve has a two-way sealed and two-way on and off, easy control, etc, is indispensable to the main equipment of complete sets of processing equipment, and flanged or threaded connections are generally adopted in the pipeline. Sealing surface, because of the large traditional exists control valve sealing surface, blind area, easy to leak and other characteristics, cannot be applied to cryogenic flammable fluid, and other fields, especially - 162 ℃ LNG field.

first, gate valve, ball valve, for example, the traditional gate Industrial Valves, ball valve opening or closing will form a two-way seal, valve cavity have blind spots. Normally LNG for saturated liquid or gas liquid two phase flow in low temperature, blind area in the LNG after the valve opened or closed, due to the existence environment of heat, blind area in LNG gasification quickly, temperature rising rapidly, the pressure increases rapidly, lead to multiple sealing the upper and the lower part of the main sealing surface is easily damaged, and the valve such as blasting more serious hidden trouble. To solve this problem, the traditional gate at low temperature, low temperature ball valve used for LNG, increase pipeline through outside the body, connected to blind the outlet structure of ball valve, cryogenic fluid was derived, but this method leads to blind area and valve connected at one end, and damaged the gate valve, ball valve sealing surface two-way sealing, double check, the advantages of two-way control valve, ball valve, can only use one main sealing surface, cannot have the effect of two-way sealing. In addition, due to the pipe ends of LNG gasification extremely easily, the valve co. , LTD. , LNG is easy to reverse flow, the requirement of LNG gate, LNG ball valves have double check, two-way sealing effect, therefore, plus catheter connected on one side can not solve the problem of the double check. At the same time, and conduit leakage due to reasons such as intensity is easy to damage, and there is the body of the lateral is not easy to be insulated, the body appearance such as asymmetric faults.

second, because of the LNG gasification for flammable and explosive gas, after the main component of CH 4, traditional cryogenic valves due to more seal, easy to cause the CH 4 leak, such as two-way between primary seal, valve body and valve cover multiple seal and seal pipe flange connection, etc. , especially in the - 162 ℃ low temperature condition, sealing gaskets and sealing surface tend to direct contact with the LNG, sealing material low temperature brittle fracture, appear easily leak sealing surface often appear, there is a big security hidden danger. In addition, due to the LNG valve and temperature difference is bigger, cut-off valve, gate valve, for example, the body contact with LNG, stem rotary actuator, valve body and the upper stem parts contact with external atmospheric environment, there are around 200 ℃ temperature difference on both ends of the valve, causing part within the large temperature difference stress, especially on the valve stem and valve body. Because of LNG generally made of cast steel body heat transfer rate faster, need a long delay on the Industrial Valves body and Industrial Valves stem heat transfer, in order to prevent the rotating actuator components, such as the temperature is too low, can't work normally, or prevent frostbite, etc. , so top extended to general requirements stem not for frost to. In addition, because the body USES the steel casting, valve stem adopts steel forgings, the thermal expansion coefficient is large, there is a big difference in temperature stress under different temperature conditions, after contact with each other, low temperature and strain is easy to cause the body craze, deformation of the stem, the primary damage, LNG can't deadline and so on. So, the traditional cryogenic valves used in the domain of LNG, request a longer stem in order to reduce the local temperature difference strain, make whole valve size is bigger, to adapt to the cold contraction and solve the problem of large temperature difference stress, etc. Finally, the LNG cryogenic fluid, pipeline pressure generally lower than 0. 2 mpa, in saturated condition or overheating and conveying outside will be flowing through the valve and pipe provides heat for LNG, lead to LNG gasification, a two phase flow. Two-phase flow encountered a sudden time remaining LNG is easy to cause the pipe pressure surge and critical. When pressure is more than critical pressure 4 quickly. - 6 mpa, the temperature is more than critical temperature 82. After 59 ℃, can cause great security hidden danger to the whole transportation system security, so the general of LNG valve or LNG system design pressure is greater than 6 mpa, make whole LNG increase difficulty of system design, equipment heavy and bulky.

The use and installation of rising stem gate valve is compared with most other systems for managing the cast iron gate valve effectively and no doubt double flanged gate valve have won the race so many times.
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