Plant systems and equipment maintenance: Use of fuzzy logic for criticality assessment in NORSOK standard Z-008

The NORSOK standard Z-008 suggests a criticality matrix for use in consequence classification, maintenance planning, inspection planning and for prioritizing work orders. When the criticality assessments are carried out using a criticality matrix, suboptimal classification tends to occur as there are no means to incorporate actual circumstances at the boundary of the input ranges or at the levels of linguistic data and criticality categories. This manuscript suggests a fuzzy inference system (FIS) to overcome the aforementioned. Membership functions and the rule base development have been carried out in alignment with the Z-008 standard recommended guidelines. A rule view and a calculation result have been demonstrated to illustrate the methodology.