On large-diameter pipelines, the cost of using a shut-off valve is very high and zero leakage cannot be achieved. In the case of emergency shutdown, a shut-off valve must be installed beside the shut-off valve. Although the V-shaped ball valve can also achieve cut-off (zero leakage) and adjustment, the cost is also much higher than that of the triple eccentric butterfly valve.
At present, Chinese butterfly valves above DN300 mm have gradually replaced gate valves. Compared with gate valves, butterfly valves have the characteristics of short opening and closing time, small operating torque, small installation space and light weight. Taking DN1000mm as an example, the butterfly valve is about 2,t and the gate valve is about 3.5,t, and the butterfly valve is easy to combine with various driving devices, and has good durability and reliability. Because triple eccentric butterfly valve has significant advantages compared with globe valve, ball valve and gate valve, triple eccentric butterfly valve has been successfully applied in many occasions in petrochemical industry.
The triple eccentric butterfly valve integrates adjustment and shut-off (to achieve zero leakage), and has been successfully used in polyethylene plants. The reactor cooling water temperature regulation loop of the polyethylene plant is the most important part of the plant. Whether the temperature regulation loop can run smoothly or not directly determines whether the entire polyethylene plant can run safely and smoothly.
The temperature-adjusting water pipeline is of large diameter (above DN450 mm). Under normal working conditions, the triple-eccentric butterfly valve is used as a control valve because of its high control ratio, which is more stable and reliable than the ordinary control valve. When the chain occurs, the triple-eccentric butterfly valve It can also act as a cut-off and is completely cut-off (zero leakage).
From the actual application situation, not only the investment cost is saved, but also the control is particularly stable.
The coke cleaning valve at the outlet of the cracking furnace of the ethylene plant is a kind of valve with harsh operating conditions in the petrochemical industry. Carbon particles in the process medium may accumulate on the sealing surface of the valve, causing the sealing surface to bite, so that the valve cannot be opened normally, or even shortened. service life of the valve. Compared with other types of valves in fire fighting system or types of valves for water supply system, triple eccentric butterfly valve is the most ideal choice due to its unique structural characteristics.
Cut off and adjust the inlet pipeline of the flue gas turbine of the catalytic cracking unit in each refinery. Due to the large diameter of the process pipeline and the high temperature flue gas (up to 750℃) as the process medium, the valves used are mainly triple eccentric butterfly valves. The valve size of the Chinese plant is the largest. It has reached DN1800 mm, and the hydraulic actuator is equipped with a closing time of less than 0.5s; others such as the inlet and outlet pipes of the main fan and the vent valve, the inlet and outlet pipes of the air compressor, the vent valve to the torch, the inlet and outlet of the oil slurry pump, and various high, medium and low pressure steam pipelines. A large number of triple-eccentric butterfly valves are also used for adjustment and cut-off.
Liquefied petroleum gas is very easy to leak. To meet the large flow capacity and avoid leakage, it is more reliable to use a triple eccentric butterfly valve on the main line of the inlet and outlet of the storage tank. In addition, in the sulfur recovery device, the liquid sulfur that needs to be transported in a molten state is currently a triple-eccentric butterfly valve with a steam jacket.