*Maintenance Decision Method Based on Risk Level DOI: http://dx.doi.org/10.5772/intechopen.91913*

failure effect, and failure cause of the three categories of mechanical equipment are determined based on the FMEA method. Then, the MDMETs on the mechanical equipment of the petrochemical industry are established by referencing the logic decision diagram in the reliability centered maintenance (RCM) theory. The MDMETs are shown in detail as follows [18–20]:


**Figure 2.** *MDMET of Class A of mechanical equipment*

**Figure 3.** *MDMET of Class B of mechanical equipment.*

**2.3 Research on maintenance decision-making methods based on the risk level**

According to statistical data about the priority orders of the mechanical equipment from their evaluation risk levels in the previous step, their cumulative frequency can be plotted with a curve chart. Based on the principle of establishing a cumulative frequency curve chart, the percentage of the area on the right side of the curve from the total area can be taken as another representation evaluating the risk level of the mechanical equipment [15]. A larger area percentage is indicating that one mechanical equipment has a higher risk level. According to their different area percentages, namely, the different risk levels among them, the mechanical equipment can be divided into three categories, including Classes A, B, and C. Class A is an area percentage of 0–30% of mechanical equipment. Class B is an area percentage of 30–80% of mechanical equipment. Class C is an area percentage of 80–100%

According to different own characteristics and failure modes of the mechanical

equipment in the petrochemical industry, the existing maintenance methods include Lubrication, Service, Corrective Maintenance, Time-based Maintenance, Hidden Failure Detection, and Condition-based Maintenance. In order to reasonably establish maintenance decisions of mechanical equipment tree (MDMET) and effectively implement the existing maintenance methods above, the failure mode,

**of mechanical equipment**

*Logic block diagram of the Monte Carlo simulation.*

*Operations Management - Emerging Trend in the Digital Era*

**Figure 1.**

**340**

of mechanical equipment [16, 17].

**Figure 4.** *MDMET of Class C of mechanical equipment.*

strategies should be applied, and the failure frequency should be reduced by increasing the maintenance costs with advanced maintenance methods. A MDMET of Class C of mechanical equipment is shown in **Figure 4**, which includes corrective maintenance, time-based maintenance, hidden failure detection, and condition-based maintenance.
