For large organization, the focu i uually on improving the maintenance activitie uch that minimum amount of fund are expended (Anily et al., 1999; Alfare, 1999; Burke and mith, 1999a, b).
The high cot of breakdown maintenance could be unbearable uch that the need for preventive maintenance become obviou. The afety of equipment and employee i improved by preventive maintenance ervice. Thi ha ignificant impact on the production proce. Reaching maximum plant availability through minimal delay and breakdown and optimal equipment working condition reduce or eliminate the need for ubcontracting ome apect of the job (Chen and Liao, 2005; Cheung et al., 2005). Thi ha a reducing effect on the uually large maintenance budget of many organization. Maintenance cheduling i uually baed on preventive maintenance activitie (Oke, 2004). In an organization where a large number of equipment are operated, preventive maintenance cheduling offer a mean of achieving continuou indutrial operation without which ytem utenance would be extremely difficult. ince the cot of implementing preventive maintenance cheduling i more economical than that of replacing broken down equipment, in the long term, it i more economical to implement thi maintenance option.
ound maintenance cheduling i indipenable for high maintenance performance, which in turn facilitate the production proce to yield maximum output. Thi i attained when preventive maintenance upport continuou improvement programme. Effective maintenance cheduling require pecific time and labour allocation, knowledge of equipment hitory, pare availability, knowledge of work and facility priority rating, job pecification, etc.
Maintenance cheduling promote effective utilization of both maintenance and production team, notably through minimizing idle time, breakdown and delay (Zhou et al., 2004; Gharbi and Kenne, 2005; Kim et al., 2005). For many year, extenive cientific documentation ha been made on cheduling both maintenance and operational activitie for profit (Yamayee et al., 1998). Recently, the focu of reearcher ha hifted from near optimal olution to the development of optimal olution approache. Thu, the recent work of Charle-Owaba (2002) i important in thi repect. The problem olved i the imultaneou cheduling of reource-contrained operation and maintenance (ee alo Oke and Charle-Owaba, 2005, 2006a, b). The current tudy i an extenion of the novel work of Charle-Owaba (2002).
The remaining part of the paper i organized a follow: the next ection dicue the model formulation. Under thi ection, the notation ued in the model are dicued. In addition, the model aumption relevant to ea veel maintenance and operational activitie are explained. In thi ection, the algorithm governing the original model developed by Charle-Owaba (2002) i preented with detailed tep explained for it practical application. till in thi ection, the model framework i preented with mathematical equation upporting the original tructure preented by Charle-Owaba with ome extenion of the idea. Thee tep are preented in a logical manner peruaive enough for the reader to follow. In particular, the three-dimenional wave equation methodology i adopted. ection three dicue the cae tudy of a hipping company. Thi ection conider apect, which include the cae decription, ome variable affecting cot of hip maintenance and their mathematical repreentation,