Scheduling of harbour tugboat services

Pao Yue-kong Library Electronic Theses Database

Scheduling of harbour tugboat services

 

Author: Li, Pok-yan
Title: Scheduling of harbour tugboat services
Degree: M.Sc.
Year: 1998
Subject: Tugboats -- Management -- China -- Hong Kong -- Case studies
Production scheduling -- China -- Hong Kong -- Case studies
Production planning -- China -- Hong Kong -- Case studies
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: vi, 118 leaves : ill. ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1428620
URI: http://theses.lib.polyu.edu.hk/handle/200/1919
Abstract: As the main port for Southern China, Hong Kong has seen a phenomenal growth in its trade with the People's Republic of China and the countries worldwide. All key sectors of Hong Kong's transport system are in expansion mode to facilitate its role as the gateway to China and a leading Asian hub. Yiu Lian Dockyards Limited is a traditional ship repair yard which has tugboats and technical personnel available. Based on a horizontal diversification strategy, a tugboat services strategic unit was established in early 90s' for catering the increasing port activities. The branch out of the company was inevitable. The strategic unit has already grown to be the second largest tugboat fleet in Hong Kong waters operating a fleet of 10 tugboats. The success in increase of business in the company is accompanied with a new issue respecting capacity decisions and routine scheduling of the tugboat services. As a matter of fact, the quantity and timing of expected demand, and the capacity availability which are among the most fundamental of all the design decisions the fleet management are called on to make. To develop a feasible operation plan on an aggregate level that achieves a balance of expected demand and supply, the bulk of the research involves: 1) the using of a feasible model that determines demand. It is aimed to measure the demand level and to predict fluctuating demands from observational data; 2) the design of flexibility into the tugboat scheduling system. It is one of the important issues for absorbing fluctuations originating from uneven demand, breakdown repairs and routine maintenance and crew's rest day, for the sake of maintaining a constant level of output; and, 3) identifying an optimal tugboat operating level. At the ideal level, cost per shift of the tugboat workday is the lowest. Larger or smaller rates or output will result in a higher unit cost. To recapitulate, the objective of the research is to find the combination of tugboats assigned to a workday shift instances with the minimum cost that will meet the demand and the limit on the capacity and flexibility of tugboats available. Widely used approaches are used in the research: 1) qualitative approach - it identifies the characteristic of the sequence of work where vessels are serviced by tugboats, and determines the attributes of the calling population, the service capacity and the queue for application of appropriate queuing model to the problem; and 2) quantitative approach - it develops queuing model and integer programming model to problem solving, and a simulation model for validation test of the queuing model used in the research. The result and implication from the research are of importance for fleet managers and operators in capacity decisions and routine scheduling of tugboat services. On long-term and intermediate-term, possible market demand patterns can be identified by using statistics and forecasting techniques applied on the outputs of the selected queuing model over a time horizon. On short-term, capacity needs can be identified directly using the models developed. It would seem safe to say that a systematic approach to problem solving is established and idle capacity will then be reduced reasonably in day by day operations. And for reasons given above, it will further reveal expected amount of aggregate capacity level to avoid unnecessary initial investment or initial cost tied-up.

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