Abstract
This paper describes a total maintenance model which consists of the fewer full complement (Ms) on board with a propelling interval (Ts) and the more home port relief manpower (Mp) at land with a home port one (Tp) .
This model has to keep an allowable inventory of a limited length (Lc) of waiting lines corresponding to the accumulated maintenance man-hour (ΔMH) s left untreated during Ts.
The following three queuing length modes are proposed whether the residual man-hour (ΔMH) p of Mp during Tp is able to counterbalance (ΔMH) s or not;
(A) absolute stable mode (a) ΔLp > LG-LM
(B) temporary stable mode (b) : ΔLp = LG-LM
(C) absolute unstable mode (c) : ΔLp= LG-LN <LG-LM
where LG; a length waiting lines of arrival at home port, LG < LC
LM, LN; ones of departure from home port <LG
ΔLp ; one corresponding to (ΔMH) p
Utilization ηj and queuing length rate QLR lj are defined as follows;
ηj= (4Σi=1Tjmhi0/d⋅Ti0) / (M⋅D) j=4Σi=1 (Tj/Ti⋅Hij/Dj)
lj=dLj/dt=Lj/Tj=λj-μj=(ΔMI) j/mhj
where Tj; each interval of voyage, Dj; duty time of Tj, α; up ratio of reliability
Ti0, mhi0; representative values of mean time between maintenance and mean man-hour per occurrence
λj, μj, Hij; failure rate and maintenance rate and time of each interval Tj, and of each maintenance Pi
The temporary stable mode (b) requires the following conditions for each interval Ts, Tp, Tv (Ts +Tp = a period interval) ;
(1) necessary condition: ηs>1.0, Lc>LG=Ls=ls⋅Ts = (λs-μs) ⋅Ts>0
ηp<1.0, -Lc<Lp=lp⋅Tp= (λp-μp) ⋅Tp<0
(2) sufficient one: ηv≤1.0, Ls+Lp = [(1-δ) ⋅ls+δ⋅lp] ⋅Tv<0
where δ; home port service interval rate = (Tp /Tv)
From the output informations of GPSS digital simulation for 8 hours maintenance model (MODEL II) which is able to give occurring rate λ, over time Ho and length of waiting lines L, some useful relationships among the above many variables.
