Low temperature tank manufacturers speak about tanks

Introduction of cryogenic storage tanks:

The cryogenic storage tank is used for storing liquid oxygen, nitrogen, argon, carbon dioxide and other media. It is a vertical or horizontal double-layer vacuum insulated storage tank. The inner tank is made of austenitic stainless steel or 16MnDR. The outer container material is different according to the user's area. According to the national regulations, it is selected as Q235-B, Q245R or 345R. The inner and outer containers are filled with insulating materials such as pearl sand or aluminum foil, heat-insulating cotton and vacuum. The product is on-site inspection by the State Bureau of Technical Supervision and issued a pressure vessel supervision inspection certificate. The product specifications are 5-500 cubic meters and the working pressure is 0.8/3.5Mpa. Nitrogen is the main raw material for the nitrogen fertilizer industry. Nitrogen is mainly used as a protective gas in the metallurgical industry. For example, steel rolling, galvanizing, chrome-plating, heat treatment, continuous casting, etc. are used as protective gas. In addition, by blowing nitrogen into the blast furnace, the quality of the iron can be improved. Widely used in the electronics industry, chemical industry, petroleum industry and glass industry.

The structure and type of cryogenic storage tanks have become more and more prosperous in recent years. The sales of liquid oxygen, liquid argon, liquid nitrogen, liquid carbon dioxide and LNG natural gas have increased significantly. Therefore, the profit of oxygen generator by-products is very impressive, and it has become a non-ferrous steel enterprise. An important part of steel product revenue. The production, storage and transportation of cryogenic liquids are inseparable from the thermal insulation storage tanks, and they are installed and used in large quantities.

   Low-temperature storage tanks are divided into vacuum powder insulation type and atmospheric pressure powder insulation type, powder insulation, using low thermal conductivity powder, fiber or foam to reduce heat transfer. It is divided into two forms: one is to apply ordinary powder insulation (accumulation heat insulation) under atmospheric pressure, the insulation layer is thick, and it is filled with dry nitrogen to maintain positive pressure to prevent moisture from entering and condensing, and low time is suitable for liquid nitrogen temperature. Another kind of vacuum powder insulation, that is, vacuuming the space for filling the powder, reduces the heat transfer of the gas, and the powder particles also weaken the radiation heat transfer, so that the heat insulation effect is better.

   The vacuum powder storage tank is a double-layered cylindrical structure, the inner cylinder and its piping are made of austenitic stainless steel, the outer casing is made of carbon steel, and the interlayer is filled with expanded perlite (also known as pearl sand) and a specially treated adsorbent is provided. It is pumped to a high vacuum (0.5 to 6 Pa) and has a capacity of 200 m3 or less. The working pressure is high (the working pressure of the two storage tanks in the four workshops is 2.0 Mpa), and there is a gasifier outside the tank, which can make the pressure boost in the tank easy to charge, and can directly send the pressure gas. According to the application, it can be divided into fixed type and transport type. The fixed type is mainly used for the storage of cryogenic liquids. It is installed at the place of production, use point or supply station of cryogenic liquid; transport type transports cryogenic liquid from the place of production or supply station to The point of use, often in the form of land transport, water transport, etc., they are called tank trucks, trailers and tankers.

Maintenance of cryogenic liquid storage tanks:

   Analysis and treatment of common problems: The maintenance of vacuum in the sandwich tank of low temperature storage tanks guarantees the thermal insulation performance of low temperature storage tanks, and is the fundamental guarantee for the normal operation of low temperature storage tanks. After the cryogenic storage tank is put into use, the common problem is often related to the degree of vacuum maintenance.

(1) There is a clear large area of “sweating” and “frosting” outside the cryogenic storage tank. This may be caused by leaking pipes in the sandwich of the low temperature storage tank, unfilled pearl sand or other factors causing damage to the interlayer vacuum. This requires inspection and repair, or leak detection, or supplemented with pearl sand, which can be re-vacuum.

(2) The pressure in the inner cylinder of the low temperature storage tank is abnormally increased, and the safety valve takes off. This may be due to three reasons:

a. The vacuum of the low temperature storage tank interlayer is destroyed;

b. The inner cylinder booster valve fails, and the booster valve needs to be repaired or replaced;

c. The leakage leaking part of the lower part of the interface is located at the joint of stainless steel and carbon steel shell, or the joint of copper tube and stainless steel inner tube, that is, the heterogeneous welded joint, which mainly forms electrochemical corrosion at the heterogeneous welded joint.

(3) The amount of evaporation becomes large, and the degree of vacuum becomes small. It may be due to the deflation of pearl sand. Pearl sand has certain grain size and temperature requirements when filling. When the particle size and temperature of the pearl sand are not suitable, after running for a period of time, the pearl sand will release water vapor, which will reduce the vacuum and increase the evaporation.

(4) The top of the outer cylinder of the cryogenic storage tank “sweating”. It may be caused by the accumulation of pearl sand in the lower part. After being put into use for a period of time, the pearl sand sinks and forms a space at the top of the container, and the local heat insulation effect is significantly reduced, causing the container to run cold. In this case, if the amount of evaporation is large, the top of the jacket outer cylinder can be dug up and the pearl sand can be added.