Block replacement models for cables subject to deterioration

System reliability has become a major concern for most of the oil and gas industries. Many petroleum companies have underestimated the importance of adapting an effective and sustainable maintenance policy for critical systems that are subject to continuous deterioration leading to system failure. This paper attempts to model the maintenance policy of cables for a petroleum company in the Sultanate of Oman. The cables from which the data is collected have high breakdown costs associated with the current maintenance policies. This paper starts with an exploratory analysis of the cables failure/replacement data and adequate corresponding probability distribution is fitted to the data. A block replacement model is proposed in terms of the renewal function in order to determine the optimal preventive maintenance/replacement policy for the cables. These policies are optimised in order to minimise the cable system and the cables maintenance costs. An example of the costs of the preventive maintenance policy is then compared with the block replacement policy in order to determine the most appropriate policy for the cable replacement. The model proposed in this paper would assist the maintenance asset manager to develop a rational for selecting appropriate replacement option for cable by considering the costs of block replacement against the cost of continuous maintenance as an optimal cost effective maintenance strategy to ensure reliability and availability of cable assets.