5.2.2.2. Perhitungan MTTF Komponen Gear Coupling
Berdasarkan hasil perhitungan index of fit, selang waktu antar kerusakan pada komponen gear coupling adalah berdistribusi lognormal. Perhitungan MTTF
dapat dilakukan secara manual dan dengan bantuan software. Hasil perhitungan secara manual dapat dilihat pada Tabel 5.17.
Tabel 5.17. Perhitungan MTTF Komponen Gear Coupling
I Ti
ln ti U
ln ti-u
2
1 16
2.7726 3.7827
1.0203 2
20 2.9957
3.7827 0.6193
3 25
3.2189 3.7827
0.3179 4
28 3.3322
3.7827 0.2029
5 30
3.4012 3.7827
0.1455 6
32 3.4657
3.7827 0.1005
7 45
3.8067 3.7827
0.0006 8
52 3.9512
3.7827 0.0284
9 81
4.3944 3.7827
0.3742 10
103 4.6347
3.7827 0.7260
11 110
4.7005 3.7827
0.8423 12
112 4.7185
3.7827 0.8757
Total 654
45.3924 5.2537
Sumber : Pengolahan Data
- µ
= 3.7827
12 3924
. 45
ln
1
= =
∑
=
n ti
n i
- t
med
= e
µ
= e
3.7827
= 43.9345
- s
2
= 0.4378
12 2537
. 5
ln
1 2
= =
−
∑
=
n ti
n i
µ
- s
=
6617 .
4378 .
2
= =
s
- MTTF =
54.6858 9345
. 43
2 4378
. 2
2
= =
e e
t
s med
Perhitungan MTTF komponen gear coupling dengan bantuan software dapat dilihat sebagai berikut:
Universitas Sumatera Utara
Distribution Analysis: Gear Coupling
Censoring Information Count Uncensored value 12
Distribution: Lognormal
Parameter Estimates Standard 95.0 Normal CI
Parameter Estimate Error Lower Upper Location 3.78270 0.209325 3.37243 4.19297
Scale 0.725122 0.171030 0.456713 1.15127
Log-Likelihood = -57.559 Goodness-of-Fit
Correlation Coefficient = 0.970 Characteristics of Distribution
Standard 95.0 Normal CI Estimate Error Lower Upper
MeanMTTF 57.1455 13.9038 35.4716 92.0626 Standard Deviation 47.5310 22.6160 18.7052 120.779
Median 43.9345 9.19658 29.1493 66.2191 First QuartileQ1 26.9400 6.43885 16.8638 43.0369
Third QuartileQ3 71.6496 17.1247 44.8508 114.461 Interquartile RangeIQR 44.7096 14.7287 23.4417 85.2731
Maka diperoleh nilai MTTF komponen gear coupling sebesar 57.1455.
5.2.3. Perhitungan Cost of Failure dan Cost of Preventive 5.2.3.1. Perhitungan Cost of Failure
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