ดาวน์โหลด All Proceeding - AS Nida

D(t p )
=
H(t p )Tf
+ Tp
t p + Tp
When, Tf is the mean downtime required to make a failure
replacements, Tp is the mean downtime required to make a preventive
replacement.
This is a model of problem relating replacement interval tp to
total downtime D(tp). 3.5 Implement and Refine the maintenance plan
The maintenance plan developed in section 3.4 is
implemented and the results are reviewed to determine if the plan needs
to be refined or modified to ensure its effectiveness.
Implementation of RCM requires the formation of a
multidisciplinary team with members knowledgeable in day-to-day
operations of the plant and equipment, as well as in the details of the
equipment itself. This demands at least one operator and one
maintainer. Members with knowledge of planning and scheduling and
overall maintenance operations and capabilities are also needed to
ensure that the tasks are truly doable in the plant environment. Thus,
senior-level operations and maintenance representation is also needed.
Finally, detailed equipment design knowledge is important to the team.
This knowledge requirement generates the need for an engineer or
senior technician/technologist from maintenance or production [3].
4. Case Study
4.1 Paper Production System
The sample paper machine is the middle manufacturing that
operates paper production category CA and M (brown paper). There are
paper machines MC1 with capacity 40 tons per day, MC2 with capacity
18 tons per day and MC3 with capacity 85 tons per day. The production
processes of the paper production system are discussed hereunder:
1. Stock (pulp + water) preparation unit
2. Forming unit
3. Press unit
4. Dryer unit
5. Rewinder unit
6. Steam Handling System
7. Power Supply unit
The machine downtime is illustrated as Table 1 below:
(4)
241
Table 1 Production line downtime
Month
Operating Time
(min)
Downtime (%) Availability (%)
MC1 MC2 MC3 MC1 MC2 MC3
Jul-09 43,200 25.84 32.70 15.34 74.16 67.30 84.66
Aug-09 40,320 27.89 32.10 22.86 72.11 67.90 77.14
Sep-09 43,200 25.80 24.29 24.65 74.20 75.71 75.35
Oct-09 43,200 26.57 29.63 19.73 73.43 70.37 80.27
Nov-09 41,760 24.86 36.70 25.88 75.14 63.30 74.12
Dec-09 40,320 26.18 33.92 18.53 73.82 66.08 81.47
Jan-10 41,760 23.28 26.32 28.49 76.72 73.68 71.51
Feb-10 40,320 26.18 35.22 26.93 73.82 64.78 73.07
Mar-10 44,640 20.1 29.96 30.33 79.81 70.04 69.67
Apr-10 40,320 26.60 35.28 24.76 73.40 64.72 75.24
May-10 43,200 25.44 23.15 29.06 74.56 76.85 70.94
Jun-10 41,760 26.94 21.02 20.70 73.06 78.98 79.30
By taking data from machine MC1, MC2 and MC3 to
calculate into average downtime rate are 25.48%, 30.02% and 23.94%
respectively. The rate is exceed from target goal which is 20% and
machine availability rate is 74.52%, 69.98% and 76.06% respectively
which can divide into each process per figure 2.
400000
300000
200000
100000
0
Units STOCK FORMING PRESS STEAM DRYER POWER REWINDER
Count 208442 80185 50471 22156 18677 13717 6279
Percent 52.1 20.1 12.6 5.5 4.7 3.4 1.6
Cum % 52.1 72.2 84.8 90.3 95.0 98.4 100.0
Figure 2 Pareto chart
Figure 2 illustrated the highest downtime is from stock
preparation unit which will be selected to be study. Next is to defined
machines using in stock preparation unit in order to indentify the critical
machine rank.
4.2 Identify the critical machine
Refer section 4.1, stock preparation unit was selected as a
system to research by categorize machine to subsystem production
process as follow figure 3-5:
100
80
60
40
20
0