Page 72 - ASBIRES-2017_Preceedings

Wijayarathna & Appuhamy

Also, it indicates the mean breakdown time
of expeller machines in minutes
Table 1: Best fitted distributions and
their parameters

Ma Estimated Parameters
chi Best Shape Scale Thres
ne Distribution hold
No
3-Parameter
2 1.676 9.652 5.428
Weibull
3-Parameter
3 1.835 11.254 3.708
Weibull
3-Parameter
6 1.444 12.891 4.783
Weibull
3-Parameter
8 1.972 14.143 3.690
Weibull
3-Parameter
9 2.467 11.753 3.901
Weibull
10 Gamma 7.775 2.073

19 Weibull 3.057 16.539
3-Parameter
23 2.368 12.701 4.259
Weibull
3-Parameter
26 2.332 13.869 2.941
Weibull
Figure 3: Histograms of machine
breakdown time of selected expeller 28 3-Parameter 1.956 11.868 3.261
machines Weibull
The above Figure 3 shows the 29 Weibull 3.742 18.559
histograms of machine breakdown time of
selected expeller machines. Distributions 3-Parameter
which follow by the machine no 2, 3, 8, 9, 31 Weibull 2.218 12.366 2.676
10, 23, 26 and 28 are skewed to the right
and non-normal.
According to the Table 2, Machine
Therefore heavy tailed distributions 29 has the highest probability to breakdown.
could be better fit the data. The best fitted Subsequently, machine no 6, 31 and 19 had
distributions for machine breakdown times considerably high chance of breakdown.
of each of these 12 expeller machines and Moreover, the highest mean breakdown time
their estimated parameters were summarized was also recorded in machine no 29. Second
in below Table 1. highest goes to machine no 6. Even though
According to the Table 1, nine the chance of breakdown was low in
expeller machines breakdown time follows machines like 8 and 10 its mean downtimes
3-parameter Weibull distribution with were high.
different values for parameters. Whereas This happened due to lack of
two machines follow Weibull (2-parameter) technicians to repair machines soon after
and one machine follows Gamma. The machines become out of work. The
following Table 2 illustrates the steady state following Table 3 illustrates the production
probabilities that the selected machines loss with respect to the mean down time of
become breakdown state and working state. the selected expeller machines.

62