Application of the pneumatic valve and design at low temperature

Cryogenic pneumatic valve application and design of the


low temperature packing parts of the pneumatic valve is higher, the pneumatic valve stem extension, means can be used under low temperature conditions of the pneumatic valve, the working temperature is below - usually The pneumatic valve is called cryogenic pneumatic valve 40 ℃. Cryogenic pneumatic valve is petroleum chemical industry, air separation, gas and other industrial one of indispensable important equipment, its quality fit and unfit quality determines whether security, economy and continuous production. With the development of modern science and technology, cryogenic pneumatic valve USES more and more wide, demand is also increasing.



low temperature pneumatic valve, the general design requirements for



low temperature pneumatic valve working conditions are harsh, most of the working medium for inflammable, explosive, porous material, the lowest working temperature can reach - 269 ℃, the highest working pressure up to 10 mpa. Therefore, low temperature air valve design, fabrication, inspection has the very big difference compared with the general pneumatic valves. In general, according to the low temperature working condition of the use of pneumatic valves, the design work put forward the following requirements:



( 1) Pneumatic valve and its assembly in the medium at low temperature and ambient temperature should have the ability to work long hours, Generally for 10 years or 3500-5000 - cycle) ；

（ 2) Pneumatic valve relative to the low temperature medium, should not become a significant source of heat, this is because the heat flow will reduce the thermal efficiency, and the heat flow into the overmuch, may also to the low temperature medium evaporation, pneumatic valve, produce abnormal booster, dangerous;

（ 3) Low temperature medium should not hand wheel operation performance and packing seal performance harmful effects;

（ 4) Directly in contact with the medium and low temperature structure of the pneumatic valve assembly shall be in conformity with the requirement of explosion protection and fire prevention;

（ 5) Work under low temperature state of the pneumatic valve assembly cannot lubrication, so you need to take measures to prevent friction parts were bruises.



the above requirements shall, throughout the course of the pneumatic valve design process of low temperature also should notice the above requirement is for low temperature characteristic of the pneumatic valve requirements, in the process of the design of the cryogenic pneumatic valves shall comply with the requirement of general pneumatic valve.






low temperature evaluation index of the technical level of the pneumatic valve



in the process of low temperature air valve design, in addition to the need to consider the flow capacity of pneumatic valves and flow resistance at low temperature and other general requirements, also need to consider some other indicators, in order to better evaluate the pneumatic valve technology at low temperature. Usually by measuring energy consumption is reasonable to evaluate the pneumatic valve technology at low temperature, the main evaluation index has the following several.



1. Low-temperature adiabatic performance of pneumatic valves



can use pneumatic valve into the heat flow of low temperature medium flow Q1 and quality ratio of low temperature medium through which the low temperature thermal insulation ability of pneumatic valve. But in the medium type constant, only the velocity changes, its value will change, so in this way as evaluation index of low temperature adiabatic pneumatic valve capacity is clearly not appropriate. Can use indicators KT unified compared.



2. Low temperature cooling performance of the pneumatic valve



low temperature cooling performance of the pneumatic valve pneumatic valve is refers to the low temperature from room temperature cooled to working temperature. This performance can take advantage of the consumed energy in the process of the pneumatic valve, namely in the process of the pneumatic valve to the low temperature medium heat Q2 to measure. For periodic work of cryogenic pneumatic valve cooling performance has very important significance. But only measured by Q2 pneumatic valve cooling performance at low temperature is not enough.



3. Pneumatic valve opening and closing seal performance at low temperature



under the condition of low temperature, the seal performance is often destroyed, in order to realize the reliable seal, must adopt the reasonable structure of seal or increase the sealing pressure ratio. Parameters related to the leakage can be used to measure the sealing ability of cryogenic pneumatic valves.



4. Pneumatic valve surface not icy conditions at low temperature



the pneumatic valve operation of low temperature and the surface should not be condensation, more should not be frozen. Pneumatic valve outside surface are frozen first depends on the ambient air temperature and the parts surface temperature difference between & Delta; T1, secondly depends on the air dew point temperature. In fact, in all weather conditions, eliminate condensation is difficult. But if & Delta; T1 to satisfy certain conditions, the possibility of ice could be greatly reduced, the pneumatic valve surface not icy conditions for & Delta; T1≤ 5℃。


information: cryogenic pneumatic valve principle