The Equipment Preventive Maintenance Strategy of Two-stage Spot Inspection Considering Different Detection Effects

For equipment deterioration state from light to heavy progressive characteristics, based on the theory of three-stage delay time, the preventive maintenance strategy of two-stage point inspection equipment considering different detection effects is proposed. In the first stage, the equipment is detected at period T<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf>. When the equipment is in a mild defect state, the detection is not perfect. If the equipment is found in a mild defect state, imperfect preventive maintenance will be carried out. If a device is found to be in a serious defect state, preventive replacement is required. When the equipment life reaches the threshold MT<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf>, there is still no failure or replacement, then the detection period is shortened to T2. In this stage, the equipment will be replaced regardless of whether it is in mild or serious defect. During the detection interval, if an unexpected fault occurs, the device shall be replaced. Considering all situations, T1, T2 and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$M$</tex> were optimized with the aim of minimizing the maintenance cost per unit time. Compared with the equal-period detection model and the non-threshold model, the proposed two-stage spot-inspection strategy can always reduce the unit time maintenance cost more effectively, which verifies the effectiveness of the model.