Overview of cryogenic valves
Overview of cryogenic valves:
The utility model is suitable for a valve which is suitable for medium temperature -40 DEG C to -196 DEG C and is called a low temperature valve.
Low temperature valve ball valve, gate valve, including low temperature low temperature, low temperature valve safety valve, cryogenic valve, cryogenic valve, cryogenic valve, cryogenic throttle valve, cryogenic valve, mainly for ethylene, liquefied natural gas plant, natural gas storage tank LNG LPG, receiving the base and the WeiXing Railway Station, air separation equipment, petrochemical gas separation equipment, liquid oxygen, liquid nitrogen, liquid argon, carbon dioxide cryogenic tank and tank, pressure swing adsorption device etc.. Output temperature of the liquid medium such as ethylene, oxygen, hydrogen, liquefied natural gas, liquefied petroleum products, not only flammable, but when the temperature gasification, gasification, the volume expansion of hundreds of times.
Liquefied natural gas valve material is very important, the material is not qualified, will cause the shell and sealing surface leakage or leakage; parts of the comprehensive mechanical properties, strength and steel can not meet the use requirements and even fracture. Liquefied natural gas leakage caused explosion. Therefore, in the development, design, development of liquefied natural gas valve process, the material is the first key issue.
After years of manufacturing, has accumulated a wealth of experience, from design, technology to manufacturing matures, and has developed a series of low-temperature valve products.
First, cryogenic valve product specifications and design parameters:
1 pressure level: 150, 300, 600Lb, 900LB, 1500LB (45MPa)
2 valve diameter: 15 ~ 1200 mm (1/2 ~ 48). 3 connection form: flange type, welding type, thread.
4 valve material: LCB, LC3, CF8.
5 working temperature: -46 centigrade, -101, -196 C, -253 C
6 applicable medium: liquefied natural gas, ethylene, propylene, etc..
7 drive: manual, bevel gear transmission, electric.
Two, cryogenic valve standards and product structure:
1 Design: API6D, JB/T7749
2 valve routine inspection and test: according to API598 standard.
3 valve low temperature inspection and test: press JB/T7749.
4 drive: manual, bevel gear transmission and electric drive device.
5 seat form: seat welded structure, sealing surface welding cobalt based carbide, to ensure the sealing performance of the valve.
6 the gate adopts elastic structure and the pressure relief hole is designed at the inlet end.
7 one-way sealed valve body marked with flow mark.
8 low temperature ball valve, globe valve, butterfly valve with long neck structure, in order to protect the filler.
9 ultra low temperature ball valve standard: JB/T8861-2004
Three, cryogenic valve material selection:
1 body, valve cover: LCB (-46 C), LC3 (-101 C), CF8 (304) (-196 C)
2 Gate: stainless steel surfacing cobalt base cemented carbide
3 seat: stainless steel surfacing cobalt base cemented carbide
4 stem: 0Cr18Ni9
Four, cryogenic valve manufacturing and testing:
Former Ze on the production of low temperature valve developed a strict manufacturing process and the use of special equipment, parts processing strict quality control. After low temperature treatment, the cooling medium parts into rough machining in a few hours (2-6 hours), to release the stress, to ensure the low temperature properties of materials, ensure the finishing size, to prevent the valve in the low temperature conditions, due to the temperature change caused by the deformation caused by leakage. Valve assembly and ordinary valves are different, parts need to undergo strict cleaning, remove any oil to ensure the use of performance.
Five, cryogenic valve test equipment:
1 low temperature valve test device
2 liquid nitrogen storage device
3 cryogenic treatment tank
4 low temperature test-bed to ensure the performance of the valve under low temperature conditions
Six, cryogenic valve test and inspection:
Low temperature valve for the main parts and low temperature treatment for each batch of sampling impact test to ensure that the valve does not crack at low temperature conditions, withstand low temperature medium impact.
The following tests are performed on each valve:
1 normal temperature shell strength test;
2 sealing test at normal temperature and low pressure;
3 low temperature and low pressure sealing test;
4 low temperature seal tightness test (with seal);
5 low temperature gas seal test to ensure that the whole cryogenic valve meet the standard requirements;
6 low temperature valve for the main parts and low temperature treatment for each batch of sampling impact test to ensure that the valve at low temperature conditions do not brittle crack, withstand low temperature medium impact;
7 low-temperature (cryogenic) valves were treated for hypothermia and impact test according to the corresponding material specification
8 engage in electrostatic function is more powerful, the valve body and stem or internal parts and the valve between the conduction resistance of less than 1 ohms.
Other parameters of cryogenic valve:
Body light, small size.
In order to reduce the heat loss of the valve body, especially in order to ensure the use of ultra-low temperature valve, specially designed into light weight, small size of the valve body. A low temperature fluid flowing through the valve shaft of the valve, the valve stem long form, can avoid the external heat of the gland is maintained at room temperature, to prevent lower lid seal performance. This length is the best length calculated and tested.