STUDY ON MAINTENANCE PLANNING OF AIR-CONDITIONING SYSTEM USING REPAIRABLE SYSTEM MODEL

Abstract

This study proposes a maintenance plan for air-conditioning system using the repairable system model in reliability analysis. The Weibull process model, which is one of the repairable system models, is applied to clarify the trend of deterioration and failure for the latest periodic inspection data of 5 types air-conditioning equipment (AHP, PUMP, AHU, FCU and HEX). In addition, the cost optimization model for calculating the proper renewal cycle of air-conditioning equipment presented in the previous paper is extended to a model that can take into account the cost of energy and inspection, and an air-conditioning system consisting of multiple equipment, and its theoretical equations are derived. As a result, the proper renewal cycle of air-conditioning equipment and system with the latest data is evaluated by the extended cost optimization model.

 

The followings are main points of this study:

(1)　Repairable system data is created from the periodic inspection data of air-conditioning equipment (AHP, PUMP, AHU, FCU and HEX). The Weibull process model is applied to the repairable system data to obtain the parameter values that indicate the failure tendency of the equipment.

(2)　Two extended theoretical model are proposed based on the cost optimization model with equipment cost 𝐾 and repair cost 𝑟(𝑡) presented in the previous paper: the model that takes into account the operating cost 𝑒(𝑡) and the inspection cost 𝐼, and the model that can be applied to air-conditioning system consisting of multiple equipment.

(3)　The operating cost 𝑒(𝑡) is a model that can take into account the effect of performance degradation due to equipment aging.

(4)　Proper renewal cycles for five types of air-conditioning equipment (AHP, PUMP, AHU, FCU and HEX) and their combined system are clarified by an extended cost optimization model using failure trends obtained from repairable system data based on actual field data.

(5)　The proper renewal cycle of air-conditioning equipment and system varies greatly depending on the value of the performance degradation factor 𝜖. Therefore, it is important to minimize the performance degradation due to aging that affects the operating cost of the equipment. In addition, repairing and continuing to use equipment for which the proper renewal cycle exceeds 30 years contributes to an economically rational maintenance plan for air-conditioning system.

(6)　As a future development of this study, the maintenance planning of air-conditioning equipment by the repairable system model can be used to rationalize and save labor in maintenance work, such as reducing the timing of inspections and inspection items. The approach of this study is also useful for the maintenance planning of building materials and other equipment or devices to be inspected and repaired.