Control valves are one of the most important pieces of equipment in process automation. The quality of the control valve is directly related to the commissioning of the DCS control system and the operation of the process equipment.
1. Petrochemical industry
After 60 years of development since the founding of the People's Republic of China, China's oil refining industry has now formed a relatively complete industrial system. Refining enterprises have increased their efforts in structural adjustment, focusing on improving product quality, adjusting layout, adjusting the structure of refining units and products, Energy saving and emission reduction, improving device adaptability, etc. At the same time, through the combination of reconstruction, expansion and new construction to develop large-scale, base-based, and integrated refining and chemical construction, gradually optimize the layout of my country's oil refining industry, change the situation of scattered layout, small scale and low concentration in the past, and realize the value of resource utilization. maximizing progress. The following is a brief introduction to typical applications of control valves.
Atmospheric and vacuum distillation unit
In this part, the main control medium of the control valve is to control crude oil, desalinated water, high-pressure fuel gas, fuel oil, steam, deoxygenated water, and purified water. The maximum operating temperature in the steam pipeline reaches 400 °C, and the temperature of the first and second lines, minus the second and third lines, and some fuel oil and flash bottom oil has reached about 250 °C.
1. Main requirements of control valve
1) Control valve type: straight-through control valve, three-way control valve, equipped with double-acting cylinder piston actuator with handwheel mechanism (imported from original), and equipped with air storage tank.
2) Requirements in the process: the three-way control valve meets the flow capacity, and the adjustment accuracy deviation is controlled within ±5%. Steam lines up to 400°C, fuel oil and flash bottom oil at 250°C require the control valve to operate at medium and high temperatures for a long time without failure.
3) Matters needing attention: When the nominal diameter is large, the output thrust of the required actuator is large, and the response speed is fast. The fast response increases the starting load of the valve, and has high requirements for the overall structure design of the valve. Material selection requirements are high.
4) Material selection and surface treatment: the nominal diameter is large, and the valve trim requires high strength and corrosion resistance, so the parts must be treated with special surface hardening; due to the high sulfur content of the process medium, the valve body and valve parts must be Special anti-sulfur treatment; steam pipelines up to 400°C, fuel oil and flash bottom oil at 250°C require high surface hardness of valve trims, and the surface hardened layer will not fail in long-term operation at medium and high temperature.
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