Low temperature valve category and product structure

Low temperature valves include low-temperature ball valves, low-temperature gate valves, low-temperature globe valves, low-temperature safety valves, low-temperature check valves, low-temperature butterfly valves, low-temperature needle valves, low-temperature throttle valves, low-temperature pressure reducing valves, etc. They are mainly used in ethylene, liquefied natural gas plants, natural gas LPG LNG storage tanks, receiving bases and satellite stations, air separation equipment, petrochemical tail gas separation equipment, liquid oxygen, liquid nitrogen, liquid argon, carbon dioxide low-temperature storage tanks and tank trucks, pressure swing adsorption oxygen production and other devices. The output liquid low-temperature media such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc. are not only flammable and explosive, but also require gasification when heated, and the volume expands hundreds of times during gasification. The application of doors controls temperature and prevents hidden dangers such as explosions and leaks. The material of liquefied natural gas valves is very important. If the material is not qualified, it will cause external or internal leakage of the shell and sealing surface; The comprehensive mechanical properties, strength, and rigidity of the components cannot meet the requirements for use and may even fracture. Causing explosion due to leakage of liquefied natural gas medium. Valves suitable for medium temperatures ranging from -40 ℃ to -196 ℃ are called doors.

Product specifications and design parameters:

1. Pressure rating: 150, 300, 600Lb, 900LB, 1500LB (45MPa).

2. Valve diameter: 15-1200mm (1/2-48 ").

3. Connection forms: flange type, welded type, threaded.

4. Valve material: LCB、LC3、CF8。

5. Working temperature:- 46 ℃- 101 ℃- 196 ℃- 253 ℃.

6. Applicable media: liquefied natural gas, ethylene, propylene, etc.

7. Drive mode: manual, bevel gear transmission, electric.

Low temperature standards and product structure:

1. Design: API6D、JB/T7749

2. Routine inspection and testing of valves: in accordance with API598 standard.

3. Valve low-temperature inspection and testing: According to JB/T7749.

4. Drive modes: manual, bevel gear transmission, and electric drive device.

5. Valve seat form: The valve seat adopts a welded structure, and the sealing surface is welded with cobalt based hard alloy to ensure the sealing performance of the valve.

6. The gate adopts an elastic structure and a pressure relief hole is designed at the inlet end.

7. The valve body of a one-way sealed valve is marked with a flow direction symbol.

8. Low temperature ball valves, gate valves, globe valves, and butterfly valves adopt a long neck structure to protect the packing.

9. Standard for ultra-low temperature ball valves: JB/T8861-2004。

Low temperature material selection:

1. The valve body and cover are made of LCB (-46 ℃), LC3 (-101 ℃), CF8 (304) (-196 ℃).

2. Gate plate: Stainless steel overlay cobalt based hard alloy.

3. Valve seat: Stainless steel overlay cobalt based hard alloy.

4. Valve stem: 0Cr18Ni9.

Low temperature manufacturing and testing:

Strict manufacturing processes and equipment have been established for the doors produced, and strict quality control has been implemented for the processing of parts. After special low-temperature treatment, the rough machined parts are placed in a cooling medium for several hours (2-6 hours) to release stress, ensure the low-temperature performance of the material, guarantee the precision machining size, and prevent leakage caused by deformation of the valve due to temperature changes under low-temperature conditions. The assembly of valves is also different from ordinary valves, and the parts need to be strictly cleaned to remove any oil stains to ensure their performance.

Reference method for low temperature test of valves:

1. Preparation before the experiment

Remove oil stains from valve components, wipe them clean, and assemble the valve in a clean, dust-free, and oil free environment;

Tighten the bolts to the predetermined torque and tension values, and record the values;

Connect the valve with a suitable thermocouple to monitor the temperature of the valve throughout the entire testing process.

2. Experiment

Install the valve in the test container and connect it properly, ensuring that the valve packing is located at the top of the container where there is no vaporized gas

Conduct an initial system validation test at room temperature using a specified medium gas at the maximum valve seat test pressure to ensure that the valve is in the appropriate state, and then begin the test

Immerse the valve in liquid nitrogen for cooling, with the liquid level at least covering the connection between the valve body and the valve cover, and provide helium gas to the valve throughout the entire cooling process. During the cooling process, use thermocouples installed in appropriate positions to monitor the temperature of the valve.