Purpose– This paper aims to revisit

Purpose
– This paper aims to revisit the preventive maintenance scheduling literature. The problem to be solved is the simultaneous scheduling of resource‐constrained preventive maintenance and operations. In particular, the expression that defines the period‐dependent cost function for a preventive maintenance scheduling activity is redefined. A case study is presented from the shipping industry.

Design/methodology/approach
– In this paper a mathematical theory of differential calculus known as three‐dimensional wave equation is applied. The methodology involves transforming the preventive maintenance cost function that is expressed in terms of several variables into a more precise framework. The motivation for the work is the need to measure the total preventive maintenance scheduling cost more precisely than with the use of the existing linear cost structure.

Findings
– In this paper the findings from the analysis carried out found evidence that validates the claim of the feasibility of analyzing preventive maintenance cost using the approach proposed.

Research limitations/implications
– The paper shows that, in practice, maintenance managers strive to reduce the cost of preventive maintenance activities in order to achieve low cost production of goods. This would encourage a high patronage of customers and prevent decisions being made on wrong data. The approach presented here aims at correcting this weakness by revealing a more precise and reliable method of preventive maintenance scheduling cost computation. This is a scientific tool that should be of immense benefit to maintenance planners, particularly those actively engaged in scheduling functions.

Originality/value
– The work in this paper is new, since a novel framework is presented in a way that has not been documented earlier.