Valve is an important pressure pipe element in the oil chemical plant, which has the function of cutting off, adjusting, guiding, preventing backflow, stabilizing pressure, diversion or overflow, pressure relief, etc..
Varieties and specifications of the valve is very wide, according to the function and the structure of the valve opening and closing parts, the valve can be divided into gate valve, globe valve, throttle valve, ball valve, butterfly valve, butterfly valve, check valve, pressure reducing valve, diaphragm valve, steam trap, safety valve, etc.. Valve opening and closing can be used in a variety of control methods, such as manual, electric, pneumatic, hydraulic, electric - gas or electric - hydraulic linkage and electromagnetic drive, etc., can also be in the role of pressure, temperature or other forms of sensing signal, according to the predetermined requirements of action, or simply open or close.
Valve is widely used, in all kinds of petrochemical and chemical plant, pipeline material costs accounted for about 15% of the total investment of the project is to 20%, and the investment cost of the valve and accounted for about more than 50% of the total cost of the piping and the proportion of various types of valves are not the same, the unit in refinery as an example, the various types of valves in the device accounted for the proportion of the total number of valves respectively: 80% of the valve, the cut-off valve, 8% check valves 6%, the three valve in petrochemical plant is used most of the valve, 6% other valves, valve device investment accounted for 5% ~ 8%. To 2500000 tons / year of atmospheric pressure relief device and 1400000 tons / year catalytic cracking unit, for example, the valve size of the total number of valves:
DN = 4003%
DN150 ~ 35012%
DN50 ~ 10025%
DN = 4060%
Valve material mainly carbon steel, alloy steel and stainless steel. Several different types of oil refining unit valves are used in the table below.
Device name
Valve
Remarks
Carbon steel
Stainless steel
Taiwan
Weight /t
Taiwan
Weight /t
2500000 tons / year atmospheric vacuum distillation unit
2166
114.8
91
15.4
1400000 tons / year catalytic reforming unit
3454
226.06
428
9.28
300000 tons / year catalytic reforming unit
3522
150
43
0.78
1000000 / delayed coking unit
2390
92.15
117
9.26
800000 tons / year diesel hydrogenation unit
996
12
600000 tons / year, 1000000 tons / year reforming and hydrogenation unit
1959
27
Not including foreign orders
2000000 tons / year atmospheric heavy oil hydrogenation unit
3837
433
Aromatics combination unit
6597
Due to the special nature of petrochemical industry, operating conditions are often high temperature and high pressure, toxic and harmful, flammable and explosive, chain long, continuous operation. And device of the valve and like circuit switching, dotted all over the whole length, kept open and close to regulate all of the production process. Therefore, the reliability of the valve proposed higher requirements, factory "run, run, drip, leak," phenomenon that occurs in the valve, caused by fire, poisoning, burns, equipment corrosion increasing material and consumption, environmental pollution and shutdown shutdown accidents happen frequently, caused irreparable losses to safety, civilization, long production cycle, directly affect the economic efficiency of enterprises. Especially with China's accession to the WTO, the petrochemical industry is gradually with the foreign petrochemical enterprise management mode, the implementation of the green plant, no pollution, health, safety, environmental protection (HSE) management system, also on the use of the valve performance. Therefore, combined with the production process operating conditions and equipment requirements, the selection of suitable valves, the right to install on the equipment and process piping, safe operation, careful maintenance, to extend the service life of the valve, for the design, procurement, construction and production management is very important.