The heat exchanger has two functions: one is that the process temperature of the stream reaches the specified temperature through heat exchange to complete the heating, cooling, evaporation and condensation processes; the second is that the heat source can be effectively utilized, and it is recovered in the waste heat. Etc. has become an indispensable device. However, some heat exchangers work under high temperature and high pressure. For example, the working medium has a pressure of up to 250 MPa and the operating temperature is up to 1000-1500 ° C. Some of the working fluids are flammable and explosive. It is toxic and corrosive, and the chemical and petrochemical production requires a large amount of processing and strong continuity. Therefore, this brings certain difficulties to the normal operation of the heat exchanger. If there is a slight accident, an accident will occur, endangering the lives of the employees. Safety.
The types of accidents in heat exchangers are mainly three types: combustion explosion, severe leakage and tube bundle out of control. Unreasonable design, manufacturing defects, improper material selection, serious corrosion, operational errors and poor maintenance management are the main causes of accidents in heat exchangers.
Cause of the accident:
1.Self-made heat exchanger, blindly change the structure and materials of the equipment, the manufacturing quality is poor, does not meet the pressure vessel specification, and the equipment strength is greatly reduced.
2.The welding quality is poor, especially the welding head is not welded, and the weld flaw inspection and blasting pressure test are not performed, resulting in leakage or fatigue fracture of the welding head, and then a large amount of flammable and explosive fluid medium overflows. explosion occurs.
3.The pressure strength decreases due to corrosion (including stress and intergranular corrosion), causing the tube bundle to fail or cause serious leakage, and an explosion occurs in an open flame.
4.When the heat exchanger is subjected to the airtight pressure test, the flammable refining gas is leak tested by oxygen pressure, causing physical and chemical explosion.
5.operation violations, operational errors, valve closure caused by overpressure explosion.
6.Long-term no sewage discharge, excessive accumulation of flammable and explosive substances (such as nitrogen trichloride), coupled with excessive temperature, causing a violent explosion of heat exchangers (such as liquid chlorine heat exchangers).