The petrochemical industry is a high-risk industry. The materials involved in the production process are highly dangerous, and the probability of fire, explosion, mass death and injury accidents is high; the process technology is complex, the operating conditions are harsh, and sudden catastrophic accidents are prone to occur; large-scale equipment,, large-scale production, strong continuity, individual accidents affect overall situation; technology-intensive installations, capital-intensive, and large property losses due to accidents.

In petrochemical enterprises, the three units of oil refineries (smoke, main fan, air compressor and hydrogen compressor), the five units of fertilizer plants (air compressor, synthesis gas, ammonia compressor, CO2, raw gas or nitrogen pressure) and the three units (pyrolysis gas, ethylene, and propylene) of the ethylene plant are customarily called large units or key units.

The above-mentioned large units have the characteristics of high speed, high power, intensive technology, high price, no standby machine, and long maintenance period. In the event of equipment failure and shutdown for maintenance, the entire production plant will be completely shut down (or a substantial reduction in production), and the economic loss of the enterprise will be very serious. Usually, the direct economic loss of a large equipment accident is about one million yuan or more, and the indirect economic loss (loss of device output and loss of prevention and control of starting and stopping) is about tens of millions of yuan. Pre-judging the possible failures of the above equipment can help petrochemical companies avoid economic losses and reduce safety production risks.