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Proposed Maintenance Policy and Determining Sparepart Amount Using Reliability Centered Maintenance (RCM) and Reliability Centered Spares (RCS) for Eurosicma E 75 Machine
Tatiara Sanjani1,*, Judi Alhilman2 , and Nurdinintya Athari3
1,2,3Industrial Engineering Department, Faculty of Industrial Engineering, Telkom University, Indonesia
Abstract. PT Konimex produce drug and food. Every year PT Konimex sets a target percentage to be achived in every machine. The achivement of this set goal is based on Technical Availability (TA). TA is the percentage of machines to be ready to use every month. This calculation is adjusted to the amount of downtime and leadtime of the machine. Eurosicma E75 DS (4)/A has the highest number of downtime from January 2017 until October 2017 and the machine only reaches the target once time. The research was conducted using Reliability Centered Maintenance (RCM) method to determine the maintenance method according to the characteristics of machine and Relibility Centered Spares (RCS) method to determine the number of sparepart requirement. Based on the result of data processing using RCM, obtained 11 Scheduled on Condtion Task, four Scheduled Restoration Task, two Scheduled Discard Task and six Run to Failure. The total cost of the proposed maintenance is Rp 237,063,659,829.68 while based on data processing using RCS method, the acquisition of sparepart preparation requirements for each component included in non repairable category.
1 Introduction
PT Konimex is a company that produces various kinds of medical products, food, candy and others. Candy products produced by PT Konimex include Frozz, Hexos, Nano-nano and others. The process of candy through 4 stages. First stage is cooking, then go into stage of
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achivement of this set goal is based on the Techical Availability (TA) data. Technical Availability is the percentage of the machine concerned to be ready for use in every month.
The calculation of TA adjusts to the amount of downtime and leadtime of the machine.
Table 1. Downtime and Target of Eurosicma Machine
Machine Target 2017
The amount of Downtime
(per year)
The amount that reaches the target (per year)
Eurosicma E7 DS (4)/A 100 % 37 1
Eurosicma E7 DS (6)/B 99.90 % 33 1
Eurosicma E7 DS (10)/C 100 % 22 2
Eurosicma E7 DS (1)/A 100 % 12 2
Eurosicma E7 DS (2)/B 99.20 % 27 3
Eurosicma E7 DS (3)/C 99.90 % 26 1
Eurosicma E7 DS (5)/D 0 % 0 0
Eurosicma E7 DS (7)/E 99.20 % 33 4
Eurosicma E7 DS (8)/F 96.80 % 15 8
Eurosicma E7 DS (9)/G 100 % 26 1
Based on Table 1 it can be seen that the Euroscima E75 DS (4)/A machine has 100%
target, the highest number of downtime is 37 and during the perioed of January 2017 to October 2017, the machine only reaches one target. Therefore, the research will focus on Eurosicma E75 DS (4)/A Machine due to the amount of downtime has the highest number and the high value of target that the company wanted. The high value of the target because the machine is always used for production. Therefore, the level of availability is expected to reach 100% for production. The Reliability Centered Maintenance (RCM) method emphasized the reliability characteristics of the system or equipment to avoid the occurrence of functional failure that can impact on company operating cost, as well as the safety of workers and the environtment. The output that will be obtained from RCM calculation is to know which equipment is included in the critical system, and the interval of task according to the fuction. The importance of managing sparepart supply needs can be done using Reliability Centered Spares (RCS) method. The output to be obtained from this RCS calculation is the determination of corresponding number of sparepart on Eurosicma E75 DS (4)/A.
2 Literature Study
2.1 Maintenance Management
Maintenance activities are defined as a combination of all the technical, administrative and managerial measures during the lifecycle of an apparatus to maintain or restore to its original state [1]. In measuring the level of reliability requires an effective and efficient maintenance process for company. Maintenance is divided into two activities namely preventive maintenance which is a maintenance activity before failure occurs and corrective maintenance which is a maintenance activity when failures has occurred.
2.2 Failure Distribution
The distribution used in this research is Normal, Weibull and Exponential. The data used are Time to Failure (TTF), Time to Repair (TTR) and Time Between Failure (TBF). The calculations of MTTF, MTTR and MTBF use formula [2]:
a. Normal Distribution
MTTF/MTTR/MTBF = μ (1)
b. Exponential Distribution
MTTF/MTTR/MTBF = μ (2)
c. Weibull Distribution
MTTF/MTTR/MTBF = η.Г(1 + 1
𝛽).Г(x) (3)
MTTF : Mean Time to Failure (hours) MTTR : Mean Time to Repair (hours) MTBF : Mean Time Between Failure (hours)
2.3 Reliability Centered Maintenance
According to [3], Reliability Centered Maintenance is a systematic process to determine what to do in order for equipment to keep performing its function so that the equipment keeps doing what the operator needs. The purpose of data processing using RCM is as follow [4] :
a. Set priorities related to designs that can support maintenance.
b. Obtain useful information to improve the desin of unreliable components.
c. Develop activities related to preventive maintenance that can restore system reliability.
d. Achieving goals a,b and c with minimum total cost.
In using RCM method, there are steps consisting of seven stages [5]:
1. Selecting of system and information gathering.
2. Definition of system boundary.
3. Sytem description and functional block diagram.
4. Determination of system function and functional failure.
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3 Methodology
Resarch begins with intial input is Candy Plant and then will do an analysis of the amount of failures by looking at historical data. Eurosicma E75 DS(4)/A has the highest number of failure and in 2017 hence the selected Eurosicma E75 DS(4)/A engine dor further study. Next will be selected the most critical subsystem and components using Risk Matrix. Quantitative measurements in this study using input data TBF, TTR and TTF which will be calculated MTBF, MTTR and MTTF. MTBF, MTTR and MTTF distribution values are used as input data of RCM and RCS methods. In this research, two methods used in knowing the right treatment policy with Reliability Centered Maintenance (RCM) method and determine the number of spares requirement with Reliability Centered Spares (RCS) method.
First step in the RCM method is determine the failure function, where in the determination of the failure function requires the identification of the components function so that based in the detaled identification then the fialure function in a component can be known. In the task selection, obtained from the results of Logic Tree Analysis. After the task selection is known, then the next step is to calculate the maintenance interval of selected task along with the total cost proposed from the treatment policy.
The first step in the RCS method is to determine the critical component with ther RCS Worksheet. The results of the RCS Worksheet are critical spares that will be classified into two categories: repairable and non-repairable. After the clasification, the next step is to calculate with poisson process mehod used to determine the level of spareparts requirement so that it can be done sparepart need optimization. Based on sparepart requirement optimization, the sparepart management policy for the critical component of Eurosicma E75 DS(4)/A.
Candy Plant
Eurosicma E 75 DS(4)/A Machine Failure Record
System
Determination of Critical Sub-Sytems Risk Matrix
Lv 1
Determination Functional Failure
TTF
Determination of Critical Spares Risk Matrix
Lv 2
Determination of Critical Components
TTR
MTTF MTTR
Classification Spares RCM Worksheet
Task Selection Repairable Non-Repairable
Poisson Process
The number of spares needs
Effective Maintenance Policy
TBF
MTBF FMEA
LTA
Interval Maintenance Time
Total Cost Proposed Maintenance
RCS Worksheet
Fig. 1. Conseptual Model
4 Discussion
4.1 Selection of Critical Sub-System and Components
Eurosicma E75 DS(4)/A machine has four system: Mechanical, Pneumatic and Electrical.
Risk Matrix conducted based on interviews on the maintenance engineer of PT Konimex.
The result obtained from the interview will be processed usig Risk Matrix. Here is the result of Risk Matrix Susb-System that has been done based on the assessment of factores severity and likelihood.
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Based on Table 2. Risk Matrix of Sub-System, it can be stated that the Mechanics system is in the critical system because sub-system entry in critical areas due to the assesment of the severity factor and the likelihood factor so that the value multication between the two factors is high. Therefore, this research focuses on mechanical subsystem. Mechanical sub-system has eight majot components namely Hopper, Feeding Disk, Motorized Brush, Roller, Reel, Cylinder, Cross Jaws and Main Motor. These eight components will be done Risk Matrix to select the most critical components. Here is the result of Risk Matrix components.
Table 3. Risk Matrix of Components
Likelihood
Severity
Subsistem Minor Major Hazardous Critical
Almost Certain C.Jaws, Cylinder
Likely
Possible Main Motor
Unlikely M.Brush, Hopper
Rare Roller, F.Disc Reel
Based on Table 3. Risk Matrix of Components, it can be stated that the components to be used in the research is the components of Cross Jaws, Cylinder and Main Motor.
4.2 Data Processing using RCM Method 4.2.1 Qualitative Measurement of RCM
Qualitative measurement of RCM is analyzing the functional failure of each subsystem and component then further identified in FMEA. The result of FMEA will be input to LTA. LTA is used to determine the preventive task for each component through the RCM Decision Diagram. This preventive task wll be used to calculate the maintenance interval.
4.2.2 Interval of Maintenance
a. The calculation of maintenance time interval for Schedule on-Condition task is to use ½ P-F intervals equal to the MTTF values calculated using software
b. The calculation of maintenance time intervals for Schedule Restoration and Schedule Discard tasks using MTTF and MTTR taking into account costs such as component costs, loss revenue costs and others. Here is the equation:
𝐶𝑓 = 𝑀𝑇𝑇𝑅 𝑥 (𝐶𝑜 + 𝐶𝑤) + 𝑏𝑖𝑎𝑦𝑎 𝑡𝑜𝑜𝑙𝑠 (4) Cf = Cost of Repair
Co = Cost of Loss Revenue per hour Cw = Labor Cost per hour
Cr = Cost of Component
After getting the Cf value then the next is calculated by the following formula:
𝑇𝑀 = 𝜂 𝑥 (𝐶𝑓 𝑥 (𝛽−1)𝐶𝑚 ) (5)
Table 4. Proposed Maintenance Interval
Komponen Proposed Task Interval
(days)
Cross Jaws
Schedule on condition task 36 Schedule on condition task 36 Schedule on condition task 36
Run-to-Failure 0
Run-to-Failure 0
Schedule discard task 11
Run-to-Failure 0
Schedule on condition task 36 Schedule on condition task 36 Schedule on condition task 36 Schedule restoration task 11
Cylinder
Schedule on condition task 67
Run-to-Failure 0
Run-to-Failure 0
Schedule discard task 20
Run-to-Failure 0
Schedule on condition task 67 Schedule on condition task 67 Schedule on condition task 67 Schedule restoration task 20 Main Motor
Schedule restoration task 6 Schedule restoration task 6 Schedule on condition task 28
c. Calculation of total maintenance cost (TC) using the formula :
𝑇𝐶 = 𝐶𝑚 𝑥 𝐹𝑚 (6)
Based on calculation, the total cost that must be paid by the company based on the existing maintenance policy every year is Rp 582.679.347.884,85 while the maintenance cost of the proposal which must be issued every year is Rp 237.063.659.829,68. The existence of this cost difference due to some tasks that are calculated with RCM done in intervals once a week, but the exixting maintenance policy is done in interval once a month so that the frequency of maintenance is greater.
4.3 Data Processing using RCS Method
4.3.1 Determination of Critical Spares
Determination of Critical Spares using RCS Worksheet which is in the filling according to
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4.3.2 Comparison of Supply Sparepart Proposals and Existing
The calculation of spares need is done for the next 1 year. Spares requirement calculation is done for non-repairable category.
Table 5. Comparison Sparepart Needs
Component Critical Spares Exixting
(unit)
Proposed (unit)
Cross Jaws
Cross Jow Resistance 5 10
Zig-Zag Banked Knife 12 10
Fuse 3 10
Solid State Relay 2 10
Straight Counter Knife 12 10
Cylinder
Cross Jow Resistance 5 6
Fuse 3 6
Solid State Relay 12 6
Main Motor
As Utama 0 8
Pulley 0 8
Toothed Belt 0 8
4 Conclusion
a. Determination of task and maintenance intervals using Reliability Centered Maintenance (RCM), obtained that 11 Scheduled on-Condition Task, four Scheduled Restoration Task, two Scheduled Discard Task and six Run to Failure.
The maintenance interval for Scheduled on-Condition Task on the Cross Jaws component is 1.38 months, Cylinder is 2.56 months and Main Motor is 1.06 months.
The maintenance interval for Scheduled Restoration Task on Cross Jaws component is 0.40 months, Cylincer is 0.74 months and Main Motor is 0.22 month. The maintenance interval for Scheduled Discard Task on Cross Jaws component s 5.78 months and Cylinder is 10.49 months. Components are categorized as run to failure replacement intervals based on when the component is fail.
b. Total cost of the company’s maintenance existing is Rp 582.679.347.884,85 while the total cost of the proposal is Rp 237.063.659.829,68/ The difference between the cost of existing maintenance and the proposal amounted to Rp 345.615.688.055,017.
c. Component calculation using Reliability Centered Spares (RCS) method, it is found that the number of non-repairable component requirement in Cross Jaws critical spares is 10 units, Cylinder is 6 units and Main Motor is 8 units.
References
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2. N. Dhamayanti, D. S., Alhilman, J., & Athari, “Usulan Preventive Maintenance Pada Mesin KOMORI LS440 dengan Menggunakan Metode Reliability Centered Maintenance (RCM II) dan Risk Based Maintenance (RBM) di PT ABC,” J.
Rekayasa Sist. Ind., vol. 3, no. April, pp. 31–37, 2016.
3. J. R. Sifonte and J. V. Reyes-Picknell, Reliability Centered Maintenace- Reengineered : Practical Optimization of the RCM Process with RCM-R. 2012.
4. J. Alhilman and O. F. Safitri, “Preventive Maintenance Program Using Reliability
Centered Maintenance Method and Procurement of Spare Part Based on Reliability ( Study Case : PT . XYZ ),” vol. 4, no. 1, pp. 39–47, 2015.
5. J. Moubray, Reliability-centred Maintenance. London : ButterworthHeinemann, 1997.
6. D. Meilani, I. Kamil, and A. Satria, “Analisis Reliability Centered Maintenance (RCM) Dan Reliability Centered Spares (RCS) Pada Unit Rawmill Pabrik Indarung IV PT. Semen Padang,” J. OptimMeilani, D., Kamil, I., Satria, A. (2008). Anal.
Reliab. Centered Maint. Dan Reliab. Centered Spares Pada Unit Rawmill Pabrik Indarung IV PT. Semen Padang. J. Optimasi Sist. Ind. 8(1), 9–16.asi Sist., vol. 8, no. 1, pp. 9–16, 2008.
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