“AUDITING FOR MAINTAINANCE IN CEENT INDUSTRY
ABSTRACT In cement industries maintenance cost consumes approximately 20-25% of the tota l production system, which comes in second rank after the energy cost. Performin g a periodic maintenance audit is essential in maintaining a profitable business . A maintenance audit answers the following questions: How effective is your cur rent planned maintenance program? What areas are working? What areas could be im proved? Continuous improvement can be accomplished by developing the necessary t ools for analyzing the audit results .This helps reveal the current maintenance state and identify potential areas for improvement. Therefore ACC cement plant, taken as a case study represents that cement plants are facing big challenges on reducing both energy and maintenance costs. In orde r to improve the maintenance in the ACC plant, auditing of the existing maintena nce system had been conducted, since this step is essential in improving any mai ntenance system. Maintenance types are like condition based, preventive based, planning based and breakdown maintenance. Maintenance modifications were selected from the calcula tions and questionnaire. A quantitative (statistical) method was used in order t o determine the weakness points in the existing maintenance system. Based upon t his auditing several actions and strategies were put in a medium range plan to r esolve the problems and improve the system.
INDEX Contents Certificate…………………………………………………………………….…………….…2 Acknowledgement…………..…………………………………………….……………….…3 Abstract……………….………………………………………………….…………………...4 1. Introduction……..…………………………………………….…………….…………7 2. Literature Survey………………..…………………………….……………………….9 2.1 Total Maintenance Management…………………………………………….…….9 2.2 Types of Maintenance………………………………………………………….....12 2.2.1 Condition Based Maintenance ………………………………...……................12 2.2.2 Preventive Maintenance …………..………………....……………………........14 2.2.3 Planned Maintenance ……..…………………………………………………….16 2.2.4 Breakdown Maintenance …………………………….…………………………17 3. Cement Kiln……………………………………………………………………………..18 4. Raw Mill……………………………………………………………………………….....20 5. Methodology……..………………………………………….……………………….....21 5.1 OEE Concept................................................................. .......................................21 5.2 Downtime Analysis……………………………………………………………….....22
5.3Net Availability Index%...................................................... ................................24 5.4Production Rate Index………………………………………………………………..25 5.5Mean Time Between Failure……………………………………………………....26 6. Data Analysis ……..…………………………………………….…………………….27 6.1 Downtime Analysis for Kiln…………….…….………............................ ..........27 6.1.1Kiln Downtime Analysis for June………............................... .........................31 6.1.2Kiln Downtime Analysis for July……………………………………………….35 6.1.3Kiln Downtime Analysis for August……………………………………...........39 6.1.4Cumulative Downtime Analysis ……………………………………….............43 6.1.5Parreto Chart………………………………………………………………………47 6.2 Downtime Analysis for Raw Mill……………………………………………….48 6.2.1 Raw Mill Downtime Analysis for June………................... ......................48 6.2.2 Raw Mill Downtime Analysis for July……………………………………52 6.2.3 Raw Mill Downtime Analysis for August…………………………………56 6.2.4Cumulative Downtime Analysis …………………………………………..60 6.2.5Parreto Chart………………………………………………………………...64 7. 8. 9.
Benchmarking ……..………………………………………………………. ……….65 Conclusions and future work .……..……………………………………………….66 References. ……...……………………………………………………..……………...67 CHAPTER 1
INTRODUCTION The importance of maintenance functions for maintenance management in commonly i ndustries has growing rapidly. A lot of researches and publications in the field maintenance decision models have been published to improve the effectiveness of maintenance process. Production systems have changed tremendously in recent yea rs. Attention has shifted from economy of scale to economy of scope. Today’s mar ket conditions are characterized by more emphasis on variety, delivery performan ce, and quality. Product life cycles are shrinking. To respond to these new stri ngent requirements, manufacturers are turning to high-tech equipment such as fle xible manufacturing systems. They are also adopting new material control methodo logies such as the just-in-time philosophy which calls for production systems wo rking without inventory at all. Set-up and adjustment times are also reduced to a minimum. All these factors are shifting the focus to maintenance, since unplan ned unavailability of machines will result in serious problems. This new reality explains the renewed interest in maintenance and the increased attention it is receiving from management. Unfortunately, in many organizations maintenance prod uctivity is very low. However, the maintenance function can no longer be neglect ed. In order to meet today’s challenges; companies must constantly strive for ex cellence in maintenance through serious comprehensive maintenance improvement pr ogram. In order to measure the effectiveness of any maintenance system, we need to meas ure its productivity and identify the areas where improvements can be made. Audi ts are used to assess the current status of the maintenance system so that appro priate improvement program can be formulated. Auditing a maintenance system uses the following steps: (1) A survey carried out using a well-designed questionnaire. The questions are aimed at comparing the current practices with what they should be. (2) Analysis of the data gathered in step 1. (3) Formulation of improvement program based on the analysis of the previous ste p.
The importance of Maintenance in Cement Industries The importance of maintenance increases when the grade of automation and mechani zation increases .In cement manufacturing the equipment at the beginning was not so complicated for the technical point of view and more people were t required to keep the cement production lines in operation. The maintenance activity in th e cement industry couldn’t influence the productivity so much. It was important to keep equipment running but the maintenance department couldn’t contribute muc h to productivity because the quality and quantity of cement was to large extent decided by the skill of the workers and his capacity to work fast. In connection with technical development the importance of maintenance was incre ased as high productivity and quality can be achieved by mean of well developed and organized maintenance. Maintenance must be controlled in a way that the equi pment is stopped for maintenance in a planned stoppage schedule. it Is not accep table if equipment stops unplanned .to achieve the right productivity and qualit y of product ,it is important to procure the right equipment from the very begin ning. Maintenance does not start when equipment s delivered and installed, if it starts at an early stage in the projects and the procurement work. There are many reasons why maintenance is becoming increasingly importan t I developing countries India .maintenance problems are rising foe e.g. in the ACC Cement plant barman , half of the production lines have been operating on av erage for more them 25 years and most of hem are fully automatically controlled. Due to the increase in automation, any breakdown will have as serious impact on production and measures to minimize and reduce breakdowns become a must. Theref ore the main aims of the maintenance activities in cement plants are to preserve the equipment and installation. in order to achieve that all maintenance activi ties should be performed and executed to high standard through accurate planning and scheduling for all resources. The main step in doing so is auditing of the existing maintenance system. Actually once the audi t factors are mastered the maintenance can begin to analyze its operations much ore closely .New information becomes available that can use o justify decisions support expansion arguments and provide better service. Maintenance can benefit from these measures because these information’s are valuable when a manager is f ighting battle to get more resources and more investment, or making decisions th at could affect the future production capacity. CHAPTER 2 LITERATURE SURVEY MAINTENANCE: 1) The act of maintaining or the state of being maintained. 2) The work of keeping something in proper condition; upkeep. TOTAL MAINTENANCE MANAGEMENT Total maintenance management (TMM) can be defined as a systematic approach to ma intenance. The maintenance system comprises three subsystems: (1) Maintenance management; (2) Maintenance operations; (3) Equipment management. The main objective of TMM is to provide a methodology or framework for improving maintenance effectiveness continuously. A brief description of each of the subs ystems follows. Maintenance management: In this section we discuss the main maintenance management areas that have a gre
at impact on maintenance productivity. Organization: A well-designed maintenance department organization is essential to a productive maintenance activity. The organization chart should be current and complete and should take into consideration the following important issues.
1) Appropriate ratio of supervisors to workers; 2) Proper number of planners; 3) Necessary support functions; 4) Quick maintenance response. Training and motivation. Training is essential to good quality maintenance work. A positive climate and necessary support (planning, materials, adequate supervi sion) are necessary ingredients for employee motivation and, hence, good perform ance. Planner training. Planning is a key function in a maintenance department. A plan ner should be well trained to carry out the following functions: 1) Determining job content and duration; 2) Determining work plans using appropriate methods; 3) Determining the number and skill of the workers required for the job; 4) Determining spare parts, tools and materials required; 5) Planning and scheduling works orders; 6) Estimating costs. Maintenance control. A thorough maintenance control system is very important for the identification and control of delays. Such a system includes: l information on work order status and estimated time versus actual time; 1) Maintenance productivity reports; 2) Charts and graphs showing backlog, overtime, emergency work. This kind of inf ormation allows better labour and cost control through corrective action based o n facts and the identification of potential improvement areas. Supervision. Better maintenance productivity and improved quality maintenance wo rk can be achieved through effective supervision. A maintenance supervisor shoul d have a planner who relieves him from the planning/scheduling function so that he can concentrate on better maintenance management and more supervision of crew s at job sites. The span of supervision must be optimal or near optimal. Maintenance operations Work measurement. Planning is an important aspect of good maintenance practice. Time standards must be developed so that proper planning can be carried out. Maintenance scheduling. A maintenance-scheduling function combined with the plan ner function deals with day-to-day scheduling of works orders. Besides issuing d aily schedules, this function determines the priority of works orders follows up on their progress and keeps track of backlogs. Appropriate ratio of supervisors to workers; proper number of planners necessary support functions; quick mainte nance response. The works order system :A well-designed works order form and procedures are a mu st for maintenance management. This system provides clear communication between all parties involved in a maintenance job request (requester, planner, superviso r, craftsman, and support unction). It also ensures good documentation of mainte nance work for analysis and appropriate action. Materials and tool control :. The maintenance activity requires that tools and p arts are available so that unnecessary delays are avoided. A computerized invent ory control system must be installed and optimal order quantities must be establ ished. Appropriate interface and co- ordination procedure between maintenance an d warehouse must be developed.
TYPES OF MAINTENANCE SYSTEMS: 1) 2) 3) 4)
Condition Based Maintenance Preventive Maintenance Planned Maintenance Break down Maintenance
CONDITION BASED MAINTENANCE: Condition-based maintenance was introduced to try to maintain the correct equip ment at the right time. CBM is based on using real-time data to prioritize and o ptimize maintenance resources. Observing the state of the system is known as con dition monitoring. Such a system will determine the equipment s health, and act only when maintenance is actually necessary. Developments in recent years have a llowed extensive instrumentation of equipment, and together with better tools fo r analyzing condition data, the maintenance personnel of today are more than eve r able to decide what is the right time to perform maintenance on some piece of equipment. Ideally condition-based maintenance will allow the maintenance person nel to do only the right things, minimizing spare parts cost, system downtime an d time spent on qui maintenance. How does Condition Monitoring work? Condition Monitoring relies on the fact that most failures do not occur instantaneous, but rather over time. At the beginning of a failure, the magnitude may be so small that it is un-detectable. At some point, however, the magnitude reaches a level in which it is mea sureable. Once observed, the equipment can still function as maintenance prepares for correction. If not corrected, the component will fail completely.
P-F Interval:
PREVENTIVE MAINTENACE: To avoid the problems of correcting unfortunate situations that have already ari sen, many try to maintain equipment before it fails. By doing this, the goal is to avoid failure, unnecessary production loss and HSE violation. As you cannot p ossibly maintain your equipment at all times you need some way to decide when it is proper to perform maintenance. Normally this is done by deciding some inspec tion/maintenance intervals, and sticking to this interval more or less affected by what you find during these activities. The result of this is that most of the maintenance performed is unnecessary; it even adds substantial wear to the equi pment. Also, you have no guarantee that the equipment will continue to work even if you are maintaining it according to the maintenance plan. “Cost-effective maintenance tasks carried out at predetermined intervals to chec k the current physical condition, to reduce probability and/or impact of a failu re in operation, or to maintain a desired level of performance of equipment.”
Preventive Maintenance Level Walk by inspections Lubrication Preventive Maintenance Routines (PMRs) 1)
Walk by inspections:
Walk-by inspections use our human senses to monitor the condition of our equipme nt . This inspection is the first ‘line of defense’, in catching many d ifferent types of problems. It is inexpensive only manpower and minor tools r equired. It is simple easily completed by personnel with experience, sound basic knowledge and a good dose of common sense.
2) Lubrication: The purpose of lubrication is: a. reduce friction and wear b. cooling c. save energy d. help to reach the life expectancy of the component under friction e. prevent corrosion f. Lower maintenance costs. Why is lubrication so important? Lubricants are commonly referred to as the “lifeblood” of machines and e quipment If we treat lubricants the same way we do with our blood, we can fix pro blems in the early stages of development before they become worse and cause perm anent equipment damage Problems can be avoided in the first place when we apply the right tools and procedures for lubrication. 3) PMR(PREVENTIVE MAINTENANCE ROUTINE): The maintenance carried out at predetermined intervals and intended to reduce th e probability of failure or the performance degradation of an item. Tasks carried out at fixed frequencies (e.g. hours, days) Ball mill liner thickness measurement every three months Bearing regreasing every 1’000 operating hours
3)PLANNED MAINTENANCE: The Planned Maintenance is a paper /Software based system which allows ship owne rs and/or operators of vessel/ship maintenance in intervals according to manufac turers and class/Classification society requirements. The maintenance, primarily supervised by the on board personnel, is then credited towards inspections requ ired by periodic surveys. The planning and scheduling of the maintenance, as wel l as its documentation, must be made according to a system that is approved by C lassification society like Germanischer Lloyd, Lloyd s Register or Bureau Verita s etc.Which is now mandatory as per ISM (International Safety Management Code). ADVANTAGES OF PLANNED MAINTENANCE: 1. Releases front-line foremen from major planning duties and allows them m ore time to supervise their crews. 2. Provides procedures to plan, execute, monitor and control maintenance re
sources. 3. Reduces delays in waiting for men, material, tools after a job is in pro gress. 4. Provides for systematic collection of materials prior to planned jobs. 5. Provides procedures to implement and continue a PM program. 6. Provides a communication link between maintenance and operations. 7. Provides a daily plan for front-line supervisors. 8. Allows hourly employees to be 100% work loaded. 9. Helps field repairs coordinate work with shop and construction forces. 10. Performance reporting allows upper management to judge maintenance progr ess. 11. Reduces the time required for critical shutdowns or overhauls. 12. Reduces maintenance costs. 13. Provides a tool for operations to assign priorities. 14. Reduces emergency breakdowns. 4)
Break Down Maintenance:
Breakdowns in industrial manufacturing systems can have significant impact on th e profitability of a business. Expensive production equipment is idled, labor is no longer optimized, and the ratio of fixed costs to product output is negative ly affected. Rapid repair of down equipment is critical to business success; the process of addressing equipment breakdowns after occurrence is known as Correct ive Maintenance and exists in some form in all manufacturing companies. However, when equipment breakdowns occur the cost can go well beyond the period of repai r. Often process lines require significant run-time after startup to begin produ cing quality product, and the manufactured goods in process at breakdown as well as the goods manufactured for a period after breakdown may either be unusable o r of less value. Because of the impact both during and beyond the immediate down time, businesses have sought to prevent equipment breakdown by a process known a s Preventative Maintenance. With preventative maintenance equipment is routinely inspected and serviced in an effort to prevent breakdowns from occurring. Such inspections are based on either calendar periods or equipment process time, and generally include recorded data that can be compared over time to determine if n egative shifts indicate an imminent equipment problem. Breakdown maintenance implies that repairs are m ade after the equipment is out of order and it cannot perform its normal functio n any longer, e.g., an electric motor of a machine tool will not start, a belt i s broken, etc. Under such conditions, production department calls on the mainte nance department to rectify the defect. The maintenance department checks into t he fault and makes the necessary repairs. After removing the fault, maintenance engineers do not attend the equipment again until another failure or breakdown occurs. Breakdown maintenance practice is economical for those (non-critical) equipments whose downtime and repair costs are less this way than with any other type of maintenance. Breakdown type of maintenance involves little administrati ve work, few records and a comparative small staff. There is no planned interfer ence with production program. CEMENT KILN Cement kilns are used for the pyroprocessing stage of manufacture of Portland an d other types of hydraulic cement, in which calcium carbonate reacts with silica -bearing minerals to form a mixture of calcium silicates. Over a billion tones o f cement are made per year, and cement kilns are the heart of this production pr ocess: their capacity usually define the capacity of the cement plant. As the ma in energy-consuming and greenhouse-gas–emitting stage of cement manufacture, imp rovement of their efficiency has been the central concern of cement manufacturin gtechnology.
Principle of Operation The kiln is a cylindrical vessel, inclined slightly to the horizontal, which is rotated slowly about its axis. The material to be processed is fed into the uppe r end of the cylinder. As the kiln rotates, material gradually moves down toward s the lower end, and may undergo a certain amount of stirring and mixing. Hot ga ses pass along the kiln, sometimes in the same direction as the process material (co-current), but usually in the opposite direction (counter-current). The hot gases may be generated in an external furnace, or may be generated by a flame in side the kiln. Such a flame is projected from a burner-pipe (or "firing pipe") w hich acts like a large Bunsen burner. The fuel for this may be gas, oil or pulve rized coal. The basic components of a cement kiln are the shell, the refractory lining, supp ort tires and rollers, drive gear and internal heat exchangers.
ROTARY KILN HORIZONTAL RAW MILL:-It is used for grinding raw material. It consists of two chambers separated by a diaphragm. The whole mill is provided with metallic liners. First chamber cont ains spherical balls of large diameter as compared to second chamber, which has balls of different sizes. The material and hot air is fed to the first chamber a nd grounded material, outputted through second chamber is fed to the air separat or through bucket elevator. Here the fines are separated from coarse and are tak en to the blending & storage silo, whereas coarse particles are fed back to the mill. Sensors used are sound pressure level, vibration sensor, RTD for temp. Main parts of Raw Mill: • Grinding Media : → Grinding of coarse particles. Moderate impact and abrasion leads to d shape resu lting in improper grinding • Diaphragm : → Permitting the fine particles.Jamming of chips in slot decrease the permeability of the diaphragm. • Gear Box : → Changes the toque. • Ball Mill lining Plates : → Preventing mill wear. Impact of ball and material leads to wearing out of the li ning material present inside the mill. • Trunion Bearing : → Bear load of ball mill.setting of mud in jackets lead to the improper elliptical movement of the roller material.
CHAPTER 3 METHODOLOGY OEE CONCEPT: In order to maximize the worth of the equipment installed and its function to bu siness requirements, • It must be available & utilized for operation→ Availability Index (AI) • It must be productive to its capacity→ Production Rate Index (PRI)
•
It must produce quality product to accept→ Quality Index (QI) OEE (%) = Availability Index (%) x Production Rate Index (%) x Quality Index (%) OEE measures the effectiveness of an asset (equipment). Availability Index (AI): The indicator purpose is to measure the total time for which the equipme nt could potentially be operated.→ Net Availability Index (NAI) This also measures the actual utilization of the asset related to total calendar time.→ Gross Availability Index (GAI) NAI indicates the operational availability of equipment and it gives the scope for analyzing the planned/unplanned stoppages due to internal causes. If NAI is 80%, availability of equipment for operation is 80% and remaining 20% los s is due to planned/unplanned stoppages due to internal causes. GAI indicates the overall utilization of equipment and it gives scope f or analyzing the planned & unplanned stoppages due to internal and external caus es. If GAI is 60%, utility of equipment is 60% and remaining 40% loss is due to planned/unplanned stoppages due to internal and external causes. Net Availability Index (NAI) and Gross Availability Index (GAI) Calendar time: = Operating Time + Idle Time + Other Downtime = 24 hours x # of days in the period i.e. total time in the period NET AVAILABILITY INDEX = {(Operating time + Idle time) / (Calendar time)} × 100 GROSS AVAILABILITY INDEX = {(Operating time) / (Calendar time)} × 100 [NAI > GAI for any equipment] DOWN TIME ANALYSIS: What is Downtime? - The term downtime is referred to the period when a system is unavailable. The efficiency of a production facility is linked directly to the efficiency of the individual machinery that makes up the facility. When machiner y falters, the facility falters; when machinery fails, the facility fails. In a capital-intensive industry such as mining, where a typical Greenfield site costs over $450million, the cost of downtime is over $1million per day. In high commo dity applications such as bottling plants, an hour downtime can cost the plant a days profitability. Many of these situations are commonly experienced, and the vast majority of them are avoidable, with the appropriate monitoring and analysi s software. Citect’s Downtime Analysis module provides producers with an intuiti ve tool for monitoring and improving plant utilization and efficiency. By automa tically collecting, storing and analyzing events that lead to downtime, plant ma nagers and engineers can proactively and effectively improve plant ROA. TYPES OF DOWNTIME:
As shown in the diagram on previous page , there are many types of downtimes, ra nging from complete production halt, to machinery that is operating below its sp ecified level, to scheduled stoppages for routine maintenance. All of these cons titute Downtime to a manufacturer. All impact production and can be improved in some manner, even if that means simply scheduling maintenance more efficiently. Automated Downtimes are gathered automatically from the control system. Manual D owntimes are entered when there are no electronic means of detecting the failure . Aim of Downtime Analysis: The aim of a Downtime Analysis tool is to identify problems and trends within a facility to minimize the impact of failures for individual machinery, and hence maximize the efficiency of the overall facility. How it Works: Rules, which are sometimes quite complex, are setup in the Downtime Server so th at it can monitor events in the control system. When a rule is met, a Downtime i s triggered, and as much information as is electronically available about the Do wntime is logged to the Downtime database. A Downtime Notification is sent to se lected users to pro-actively notify them of the event.
Distribution of total calendar hours: . 1) Planned and Unplanned stoppages due to internal causes (other downtime). 2) Equipment Operating Time. 3) Planned and Unplanned stoppages due to external cause (Idle time). Criterion for registering time: 1) Operating Time: Requires that the asset is operating and it is fed. 2) Other Downtime: Equipment is not operating and is not in a condition for imme diate start up with feed. 3) Idle Time: Equipment not operating and in a condition for immediate start up with feed. The main criteria whether a stoppage generates idle or other downtime ar e the immediate starting availability (without any further maintenance) of relev ant asset. No idle time can occur during the shutdown/stoppage for maintenance reas on. Critical examples Kiln is stopped due to plant CPP power failure.→ Other downtime Management decision to stop the Kiln to optimize the cost (no maintenanc e)→ Idle time Kiln is stopped for upgrade of ESP to Bag house →Other Downtime Raw mill is down due to kiln shutdowns, and no maintenance on raw mill i s done→Idle time for Raw mill Lack of raw meal for Kiln→Downtime for Kiln due to process/ production failure Natural disasters with impact on the condition of equipment (e.g. floodi ng of the engine room)→ Other downtime Non-availability of spares (maintenance materials)→ Other downtime Heat-up time and cooling time of Kiln (started after and stopped for shu tdown reason respectively) →Part of “other downtime” for which the stoppage is t aken. Net OEE: The indicator corresponds to the potential performance of a kiln taking into account net Availability Index, Production Rate Index and Quality Index. Net OEE (%) = Net Availability Index (%) x Production Rate Index (%) x Quality Index (%) Aggregated Net OEE The aggregated values on plant and sub-segment (Group Reporting Unit) levels ar e calculated by applying the same rule as for a kiln.The Net Availabi lity Index is replaced by the Aggregated Net Availability Index and the Prod uction Rate Index is replaced by the Aggregated Production Rate Index. Aggregated Net OEE Aggregated Aggregated Aggregated [%] = Availability * Productio n rate * Quality index Index [%] in dex [%] [%] Gross OEE The indicator corresponds to the potential performance of a kiln taking into acc ount Gross Availability Index, Production Rate Index and Quality Index. Gross OEE (%) = Gross Availability Index (%) x Production Rate Index (%) x Qua lity Index (%) Aggregated Net Availability Index Aggregation of NAI calculated by weighing the NAIs of the kilns by the c orresponding BDPs
Production Rate Index (PRI) Is the actual production volume, in relation to the theoretically achiev able production with BDP. Calculation The PRI formula can be used to calculate and aggregate over time (e.g. d ifferent BDP’s), over different clinker types (OR cement types) and over differe nt assets (kilns OR mills). Production Rate index – Kilns: It measures the actual production rate over a period, compared to the BDP. Production Rate Index – Example Production rate index (%) = { Production rate (t/day)} / { BDP (t/day)} = { 42’000 (t) / 20 d} / {2’32 0 (t/day) } =90.5% Information: The kiln was operating for 20 days, produced 42’000 t, BDP is 2320 t/day Quality Index (QI): Like any process the kiln may produce products of bad quality, but a «ba d» clinker will ot affect the kiln OEE, indeed all the clinker produced, bad and good, will be used to make cement. It’s just a matter of proportion you will ad apt to make your cement. It is therefore considered that the quality for the kiln will always be 100%. Mean Time between Failure (MTBF): All break downs can be categorized into: • Idle Down time. • Other down time. Other downtime can be categorized as Planned downtime (e.g. Maintenance, Major up gradations) Unplanned downtime (e.g. Equipment, Process failures). The planned stoppages, are categorised as Planned stoppage with maintenance Planned stoppages without maintenance ( Cement silo full , clinker stock management ) The unplanned stoppages, are categorised as Unplanned stoppage due to internal reason. Unplanned stoppage due to external reason ( Power Failure ) Mean Time Between Failure = Operating Time(hr) / Frequency Of Unplanned Stoppage Due To Internal Reason
BENCHMARKING STEPS: Benchmarking may be grouped into five steps: planning; analysis; integration; ac tion; and implementation and results. These steps are briefly described in Figur e below. The continuous improvement is carried out by ensuring that the desired results are attained. These results are based on the goals set at the integratio n stage and can be repeatedly modified to improve performance. CONCLUSION AND FUTURE WORK: A methodology to measure the effectiveness of the current status of maintenance
management has been presented. Downtime analysis was carried out for CEMENT KILN and RAW MILL at ACC Plant, Barmana. Monthly downtime analysis determined the mo stly affected parts and the time required for their repair or replacement. The d ata was collected to calculate the OEE (overall equipment efficiency) of the equ ipments used in raw mill and cement kiln. The OEE determines the effectiveness o f the asset or equipment, which thereby determines the timely attention required for its proper working. Auditing of maintenance for the months June, July, Augu st, September resulted in respective failure and downtimes for the damaged equip ments.This basic aim of the auditing for maintenance is to reduce the maintenanc e cost, by the use of planned maintenance. To be able to achieve a level of worl d-class maintenance effectiveness, benchmarking has been briefly stated. This ap proach, if followed, guarantees to a degree that the followers of the maintenanc e practice of successful companies can themselves become leaders. Future Work: Similar Downtime Analysis will be done in the coming semester for the months: Ja nuary, February, March and April. Based on the the downtime analysis in the 2 se mesters .OEE will be calculated for the assets which will help in identifying th e potential areas of improvement .According to the modified maintenance schedule and the type of maintenance; preferably planned maintenance will be assured for the particular equipment. Based on the audit results, the objective should clea rly define the vision of the improved maintenance activity and the impact it w ill have on the enterprise. REFERENCES [1] Garg, A. and Deshmukh, S.G., Application and Case Studies Maintenance Manage ment: Literature Review and Directions, Journal of Quality in Maintenance Engine ering, Vol. 12, No. 3, 2006, pp. 205-238. [2] Sherwin, D., Review Overall Model for Maintenance Management, Reliability En gineering and System Safety, Vol. 6, No. 4, 2000, pp. 138-164. [3] O. Fernandez, A.W. Labib, R. Malmsey, D.J. Petty, A decision support mainte nance management system development and implementation, International Journal of Quality and Reliability Management 20 (8) [4] M. Kans, On the identification and utilization of relevant data for applying cost-effective maintenance, Thesis for the degree of licentiate, Va¨xjo¨ Univer sity, School of Technology and Design, 2005. [5] L. Swanson, Computerized maintenance management systems: a study of systems design and use, Production and Inventory Management Journal 38 (2) (1997) 11–16. [6] P. Johnson, Towards a holistic understanding of disruptions in operations ma nagement, Journal of Operations Management 18 (2000) 701–718. 7)Boznos, D. (1998), “The use of CMMSs to support team-based maintenance”, MPhil thesis, Cranfield University. [8] J. Dedrick, V. Gurbaxani, K.L. Kraemer, Information technology and economic performance: A critical review of the empirical evidence, ACM Computing Surveys 3 (1) (2003) 1–29. [9] Hartman, E.H., “Maintenance productivity: why it is so low and how to improv e it”, in Hartman, E.H. (Ed.), Maintenance Management, Institute of Industrial E ngineers, Norcross, GA, 1987. [10] Wierman, T., World-class Maintenance, Industrial Press, Inc., New York, NY, 1990. [11] Madu, C.N. (2000), “Competing through maintenance strategies”, Internationa l Journal of Quality & Reliability Management, Vol. 17 No. 9, pp. 937-49.
“AUDITING FOR MAINTAINANCE IN CEENT INDUSTRY
ABSTRACT In cement industries maintenance cost consumes approximately 20-25% of the tota l production system, which comes in second rank after the energy cost. Performin g a periodic maintenance audit is essential in maintaining a profitable business . A maintenance audit answers the following questions: How effective is your cur rent planned maintenance program? What areas are working? What areas could be im proved? Continuous improvement can be accomplished by developing the necessary t ools for analyzing the audit results .This helps reveal the current maintenance state and identify potential areas for improvement. Therefore ACC cement plant, taken as a case study represents that cement plants are facing big challenges on reducing both energy and maintenance costs. In orde r to improve the maintenance in the ACC plant, auditing of the existing maintena nce system had been conducted, since this step is essential in improving any mai ntenance system. Maintenance types are like condition based, preventive based, planning based and breakdown maintenance. Maintenance modifications were selected from the calcula tions and questionnaire. A quantitative (statistical) method was used in order t o determine the weakness points in the existing maintenance system. Based upon t his auditing several actions and strategies were put in a medium range plan to r esolve the problems and improve the system.
INDEX Contents Certificate…………………………………………………………………….…………….…2 Acknowledgement…………..…………………………………………….……………….…3 Abstract……………….………………………………………………….…………………...4 1. Introduction……..…………………………………………….…………….…………7 2. Literature Survey………………..…………………………….……………………….9 2.1 Total Maintenance Management…………………………………………….…….9 2.2 Types of Maintenance………………………………………………………….....12 2.2.1 Condition Based Maintenance ………………………………...……................12 2.2.2 Preventive Maintenance …………..………………....……………………........14 2.2.3 Planned Maintenance ……..…………………………………………………….16 2.2.4 Breakdown Maintenance …………………………….…………………………17 3. Cement Kiln……………………………………………………………………………..18 4. Raw Mill……………………………………………………………………………….....20 5. Methodology……..………………………………………….……………………….....21 5.1 OEE Concept................................................................. .......................................21
5.2 Downtime Analysis……………………………………………………………….....22 5.3Net Availability Index%...................................................... ................................24 5.4Production Rate Index………………………………………………………………..25 5.5Mean Time Between Failure……………………………………………………....26 6. Data Analysis ……..…………………………………………….…………………….27 6.1 Downtime Analysis for Kiln…………….…….………............................ ..........27 6.1.1Kiln Downtime Analysis for June………............................... .........................31 6.1.2Kiln Downtime Analysis for July……………………………………………….35 6.1.3Kiln Downtime Analysis for August……………………………………...........39 6.1.4Cumulative Downtime Analysis ……………………………………….............43 6.1.5Parreto Chart………………………………………………………………………47 6.2 Downtime Analysis for Raw Mill……………………………………………….48 6.2.1 Raw Mill Downtime Analysis for June………................... ......................48 6.2.2 Raw Mill Downtime Analysis for July……………………………………52 6.2.3 Raw Mill Downtime Analysis for August…………………………………56 6.2.4Cumulative Downtime Analysis …………………………………………..60 6.2.5Parreto Chart………………………………………………………………...64 7. 8. 9.
Benchmarking ……..………………………………………………………. ……….65 Conclusions and future work .……..……………………………………………….66 References. ……...……………………………………………………..……………...67 CHAPTER 1
INTRODUCTION The importance of maintenance functions for maintenance management in commonly i ndustries has growing rapidly. A lot of researches and publications in the field maintenance decision models have been published to improve the effectiveness of maintenance process. Production systems have changed tremendously in recent yea rs. Attention has shifted from economy of scale to economy of scope. Today’s mar ket conditions are characterized by more emphasis on variety, delivery performan ce, and quality. Product life cycles are shrinking. To respond to these new stri ngent requirements, manufacturers are turning to high-tech equipment such as fle xible manufacturing systems. They are also adopting new material control methodo logies such as the just-in-time philosophy which calls for production systems wo rking without inventory at all. Set-up and adjustment times are also reduced to a minimum. All these factors are shifting the focus to maintenance, since unplan ned unavailability of machines will result in serious problems. This new reality explains the renewed interest in maintenance and the increased attention it is receiving from management. Unfortunately, in many organizations maintenance prod uctivity is very low. However, the maintenance function can no longer be neglect ed. In order to meet today’s challenges; companies must constantly strive for ex cellence in maintenance through serious comprehensive maintenance improvement pr ogram. In order to measure the effectiveness of any maintenance system, we need to meas ure its productivity and identify the areas where improvements can be made. Audi ts are used to assess the current status of the maintenance system so that appro priate improvement program can be formulated. Auditing a maintenance system uses the following steps: (1) A survey carried out using a well-designed questionnaire. The questions are aimed at comparing the current practices with what they should be. (2) Analysis of the data gathered in step 1. (3) Formulation of improvement program based on the analysis of the previous ste
p. The importance of Maintenance in Cement Industries The importance of maintenance increases when the grade of automation and mechani zation increases .In cement manufacturing the equipment at the beginning was not so complicated for the technical point of view and more people were t required to keep the cement production lines in operation. The maintenance activity in th e cement industry couldn’t influence the productivity so much. It was important to keep equipment running but the maintenance department couldn’t contribute muc h to productivity because the quality and quantity of cement was to large extent decided by the skill of the workers and his capacity to work fast. In connection with technical development the importance of maintenance was incre ased as high productivity and quality can be achieved by mean of well developed and organized maintenance. Maintenance must be controlled in a way that the equi pment is stopped for maintenance in a planned stoppage schedule. it Is not accep table if equipment stops unplanned .to achieve the right productivity and qualit y of product ,it is important to procure the right equipment from the very begin ning. Maintenance does not start when equipment s delivered and installed, if it starts at an early stage in the projects and the procurement work. There are many reasons why maintenance is becoming increasingly importan t I developing countries India .maintenance problems are rising foe e.g. in the ACC Cement plant barman , half of the production lines have been operating on av erage for more them 25 years and most of hem are fully automatically controlled. Due to the increase in automation, any breakdown will have as serious impact on production and measures to minimize and reduce breakdowns become a must. Theref ore the main aims of the maintenance activities in cement plants are to preserve the equipment and installation. in order to achieve that all maintenance activi ties should be performed and executed to high standard through accurate planning and scheduling for all resources. The main step in doing so is auditing of the existing maintenance system. Actually once the audi t factors are mastered the maintenance can begin to analyze its operations much ore closely .New information becomes available that can use o justify decisions support expansion arguments and provide better service. Maintenance can benefit from these measures because these information’s are valuable when a manager is f ighting battle to get more resources and more investment, or making decisions th at could affect the future production capacity. CHAPTER 2 LITERATURE SURVEY MAINTENANCE: 1) The act of maintaining or the state of being maintained. 2) The work of keeping something in proper condition; upkeep. TOTAL MAINTENANCE MANAGEMENT Total maintenance management (TMM) can be defined as a systematic approach to ma intenance. The maintenance system comprises three subsystems: (1) Maintenance management; (2) Maintenance operations; (3) Equipment management. The main objective of TMM is to provide a methodology or framework for improving maintenance effectiveness continuously. A brief description of each of the subs ystems follows. Maintenance management:
In this section we discuss the main maintenance management areas that have a gre at impact on maintenance productivity. Organization: A well-designed maintenance department organization is essential to a productive maintenance activity. The organization chart should be current and complete and should take into consideration the following important issues.
1) Appropriate ratio of supervisors to workers; 2) Proper number of planners; 3) Necessary support functions; 4) Quick maintenance response. Training and motivation. Training is essential to good quality maintenance work. A positive climate and necessary support (planning, materials, adequate supervi sion) are necessary ingredients for employee motivation and, hence, good perform ance. Planner training. Planning is a key function in a maintenance department. A plan ner should be well trained to carry out the following functions: 1) Determining job content and duration; 2) Determining work plans using appropriate methods; 3) Determining the number and skill of the workers required for the job; 4) Determining spare parts, tools and materials required; 5) Planning and scheduling works orders; 6) Estimating costs. Maintenance control. A thorough maintenance control system is very important for the identification and control of delays. Such a system includes: l information on work order status and estimated time versus actual time; 1) Maintenance productivity reports; 2) Charts and graphs showing backlog, overtime, emergency work. This kind of inf ormation allows better labour and cost control through corrective action based o n facts and the identification of potential improvement areas. Supervision. Better maintenance productivity and improved quality maintenance wo rk can be achieved through effective supervision. A maintenance supervisor shoul d have a planner who relieves him from the planning/scheduling function so that he can concentrate on better maintenance management and more supervision of crew s at job sites. The span of supervision must be optimal or near optimal. Maintenance operations Work measurement. Planning is an important aspect of good maintenance practice. Time standards must be developed so that proper planning can be carried out. Maintenance scheduling. A maintenance-scheduling function combined with the plan ner function deals with day-to-day scheduling of works orders. Besides issuing d aily schedules, this function determines the priority of works orders follows up on their progress and keeps track of backlogs. Appropriate ratio of supervisors to workers; proper number of planners necessary support functions; quick mainte nance response. The works order system :A well-designed works order form and procedures are a mu st for maintenance management. This system provides clear communication between all parties involved in a maintenance job request (requester, planner, superviso r, craftsman, and support unction). It also ensures good documentation of mainte nance work for analysis and appropriate action. Materials and tool control :. The maintenance activity requires that tools and p arts are available so that unnecessary delays are avoided. A computerized invent ory control system must be installed and optimal order quantities must be establ ished. Appropriate interface and co- ordination procedure between maintenance an d warehouse must be developed.
TYPES OF MAINTENANCE SYSTEMS: 1) 2) 3) 4)
Condition Based Maintenance Preventive Maintenance Planned Maintenance Break down Maintenance
CONDITION BASED MAINTENANCE: Condition-based maintenance was introduced to try to maintain the correct equip ment at the right time. CBM is based on using real-time data to prioritize and o ptimize maintenance resources. Observing the state of the system is known as con dition monitoring. Such a system will determine the equipment s health, and act only when maintenance is actually necessary. Developments in recent years have a llowed extensive instrumentation of equipment, and together with better tools fo r analyzing condition data, the maintenance personnel of today are more than eve r able to decide what is the right time to perform maintenance on some piece of equipment. Ideally condition-based maintenance will allow the maintenance person nel to do only the right things, minimizing spare parts cost, system downtime an d time spent on qui maintenance. How does Condition Monitoring work? Condition Monitoring relies on the fact that most failures do not occur instantaneous, but rather over time. At the beginning of a failure, the magnitude may be so small that it is un-detectable. At some point, however, the magnitude reaches a level in which it is mea sureable. Once observed, the equipment can still function as maintenance prepares for correction. If not corrected, the component will fail completely.
P-F Interval:
PREVENTIVE MAINTENACE: To avoid the problems of correcting unfortunate situations that have already ari sen, many try to maintain equipment before it fails. By doing this, the goal is to avoid failure, unnecessary production loss and HSE violation. As you cannot p ossibly maintain your equipment at all times you need some way to decide when it is proper to perform maintenance. Normally this is done by deciding some inspec tion/maintenance intervals, and sticking to this interval more or less affected by what you find during these activities. The result of this is that most of the maintenance performed is unnecessary; it even adds substantial wear to the equi pment. Also, you have no guarantee that the equipment will continue to work even if you are maintaining it according to the maintenance plan. “Cost-effective maintenance tasks carried out at predetermined intervals to chec k the current physical condition, to reduce probability and/or impact of a failu
re in operation, or to maintain a desired level of performance of equipment.” Preventive Maintenance Level Walk by inspections Lubrication Preventive Maintenance Routines (PMRs) 1)
Walk by inspections:
Walk-by inspections use our human senses to monitor the condition of our equipme nt . This inspection is the first ‘line of defense’, in catching many d ifferent types of problems. It is inexpensive only manpower and minor tools r equired. It is simple easily completed by personnel with experience, sound basic knowledge and a good dose of common sense.
2) Lubrication: The purpose of lubrication is: a. reduce friction and wear b. cooling c. save energy d. help to reach the life expectancy of the component under friction e. prevent corrosion f. Lower maintenance costs. Why is lubrication so important? Lubricants are commonly referred to as the “lifeblood” of machines and e quipment If we treat lubricants the same way we do with our blood, we can fix pro blems in the early stages of development before they become worse and cause perm anent equipment damage Problems can be avoided in the first place when we apply the right tools and procedures for lubrication. 3) PMR(PREVENTIVE MAINTENANCE ROUTINE): The maintenance carried out at predetermined intervals and intended to reduce th e probability of failure or the performance degradation of an item. Tasks carried out at fixed frequencies (e.g. hours, days) Ball mill liner thickness measurement every three months Bearing regreasing every 1’000 operating hours
3)PLANNED MAINTENANCE: The Planned Maintenance is a paper /Software based system which allows ship owne rs and/or operators of vessel/ship maintenance in intervals according to manufac turers and class/Classification society requirements. The maintenance, primarily supervised by the on board personnel, is then credited towards inspections requ ired by periodic surveys. The planning and scheduling of the maintenance, as wel l as its documentation, must be made according to a system that is approved by C lassification society like Germanischer Lloyd, Lloyd s Register or Bureau Verita s etc.Which is now mandatory as per ISM (International Safety Management Code). ADVANTAGES OF PLANNED MAINTENANCE: 1. Releases front-line foremen from major planning duties and allows them m ore time to supervise their crews.
2. Provides procedures to plan, execute, monitor and control maintenance re sources. 3. Reduces delays in waiting for men, material, tools after a job is in pro gress. 4. Provides for systematic collection of materials prior to planned jobs. 5. Provides procedures to implement and continue a PM program. 6. Provides a communication link between maintenance and operations. 7. Provides a daily plan for front-line supervisors. 8. Allows hourly employees to be 100% work loaded. 9. Helps field repairs coordinate work with shop and construction forces. 10. Performance reporting allows upper management to judge maintenance progr ess. 11. Reduces the time required for critical shutdowns or overhauls. 12. Reduces maintenance costs. 13. Provides a tool for operations to assign priorities. 14. Reduces emergency breakdowns. 4)
Break Down Maintenance:
Breakdowns in industrial manufacturing systems can have significant impact on th e profitability of a business. Expensive production equipment is idled, labor is no longer optimized, and the ratio of fixed costs to product output is negative ly affected. Rapid repair of down equipment is critical to business success; the process of addressing equipment breakdowns after occurrence is known as Correct ive Maintenance and exists in some form in all manufacturing companies. However, when equipment breakdowns occur the cost can go well beyond the period of repai r. Often process lines require significant run-time after startup to begin produ cing quality product, and the manufactured goods in process at breakdown as well as the goods manufactured for a period after breakdown may either be unusable o r of less value. Because of the impact both during and beyond the immediate down time, businesses have sought to prevent equipment breakdown by a process known a s Preventative Maintenance. With preventative maintenance equipment is routinely inspected and serviced in an effort to prevent breakdowns from occurring. Such inspections are based on either calendar periods or equipment process time, and generally include recorded data that can be compared over time to determine if n egative shifts indicate an imminent equipment problem. Breakdown maintenance implies that repairs are m ade after the equipment is out of order and it cannot perform its normal functio n any longer, e.g., an electric motor of a machine tool will not start, a belt i s broken, etc. Under such conditions, production department calls on the mainte nance department to rectify the defect. The maintenance department checks into t he fault and makes the necessary repairs. After removing the fault, maintenance engineers do not attend the equipment again until another failure or breakdown occurs. Breakdown maintenance practice is economical for those (non-critical) equipments whose downtime and repair costs are less this way than with any other type of maintenance. Breakdown type of maintenance involves little administrati ve work, few records and a comparative small staff. There is no planned interfer ence with production program. CEMENT KILN Cement kilns are used for the pyroprocessing stage of manufacture of Portland an d other types of hydraulic cement, in which calcium carbonate reacts with silica -bearing minerals to form a mixture of calcium silicates. Over a billion tones o f cement are made per year, and cement kilns are the heart of this production pr ocess: their capacity usually define the capacity of the cement plant. As the ma in energy-consuming and greenhouse-gas–emitting stage of cement manufacture, imp rovement of their efficiency has been the central concern of cement manufacturin gtechnology.
Principle of Operation The kiln is a cylindrical vessel, inclined slightly to the horizontal, which is rotated slowly about its axis. The material to be processed is fed into the uppe r end of the cylinder. As the kiln rotates, material gradually moves down toward s the lower end, and may undergo a certain amount of stirring and mixing. Hot ga ses pass along the kiln, sometimes in the same direction as the process material (co-current), but usually in the opposite direction (counter-current). The hot gases may be generated in an external furnace, or may be generated by a flame in side the kiln. Such a flame is projected from a burner-pipe (or "firing pipe") w hich acts like a large Bunsen burner. The fuel for this may be gas, oil or pulve rized coal. The basic components of a cement kiln are the shell, the refractory lining, supp ort tires and rollers, drive gear and internal heat exchangers.
ROTARY KILN HORIZONTAL RAW MILL:-It is used for grinding raw material. It consists of two chambers separated by a diaphragm. The whole mill is provided with metallic liners. First chamber cont ains spherical balls of large diameter as compared to second chamber, which has balls of different sizes. The material and hot air is fed to the first chamber a nd grounded material, outputted through second chamber is fed to the air separat or through bucket elevator. Here the fines are separated from coarse and are tak en to the blending & storage silo, whereas coarse particles are fed back to the mill. Sensors used are sound pressure level, vibration sensor, RTD for temp. Main parts of Raw Mill: • Grinding Media : → Grinding of coarse particles. Moderate impact and abrasion leads to d shape resu lting in improper grinding • Diaphragm : → Permitting the fine particles.Jamming of chips in slot decrease the permeability of the diaphragm. • Gear Box : → Changes the toque. • Ball Mill lining Plates : → Preventing mill wear. Impact of ball and material leads to wearing out of the li ning material present inside the mill. • Trunion Bearing : → Bear load of ball mill.setting of mud in jackets lead to the improper elliptical movement of the roller material.
CHAPTER 3 METHODOLOGY OEE CONCEPT: In order to maximize the worth of the equipment installed and its function to bu siness requirements, • It must be available & utilized for operation→ Availability Index (AI)
• •
It must be productive to its capacity→ Production Rate Index (PRI) It must produce quality product to accept→ Quality Index (QI) OEE (%) = Availability Index (%) x Production Rate Index (%) x Quality Index (%) OEE measures the effectiveness of an asset (equipment). Availability Index (AI): The indicator purpose is to measure the total time for which the equipme nt could potentially be operated.→ Net Availability Index (NAI) This also measures the actual utilization of the asset related to total calendar time.→ Gross Availability Index (GAI) NAI indicates the operational availability of equipment and it gives the scope for analyzing the planned/unplanned stoppages due to internal causes. If NAI is 80%, availability of equipment for operation is 80% and remaining 20% los s is due to planned/unplanned stoppages due to internal causes. GAI indicates the overall utilization of equipment and it gives scope f or analyzing the planned & unplanned stoppages due to internal and external caus es. If GAI is 60%, utility of equipment is 60% and remaining 40% loss is due to planned/unplanned stoppages due to internal and external causes. Net Availability Index (NAI) and Gross Availability Index (GAI) Calendar time: = Operating Time + Idle Time + Other Downtime = 24 hours x # of days in the period i.e. total time in the period NET AVAILABILITY INDEX = {(Operating time + Idle time) / (Calendar time)} × 100 GROSS AVAILABILITY INDEX = {(Operating time) / (Calendar time)} × 100 [NAI > GAI for any equipment] DOWN TIME ANALYSIS: What is Downtime? - The term downtime is referred to the period when a system is unavailable. The efficiency of a production facility is linked directly to the efficiency of the individual machinery that makes up the facility. When machiner y falters, the facility falters; when machinery fails, the facility fails. In a capital-intensive industry such as mining, where a typical Greenfield site costs over $450million, the cost of downtime is over $1million per day. In high commo dity applications such as bottling plants, an hour downtime can cost the plant a days profitability. Many of these situations are commonly experienced, and the vast majority of them are avoidable, with the appropriate monitoring and analysi s software. Citect’s Downtime Analysis module provides producers with an intuiti ve tool for monitoring and improving plant utilization and efficiency. By automa tically collecting, storing and analyzing events that lead to downtime, plant ma nagers and engineers can proactively and effectively improve plant ROA. TYPES OF DOWNTIME:
As shown in the diagram on previous page , there are many types of downtimes, ra nging from complete production halt, to machinery that is operating below its sp ecified level, to scheduled stoppages for routine maintenance. All of these cons titute Downtime to a manufacturer. All impact production and can be improved in some manner, even if that means simply scheduling maintenance more efficiently. Automated Downtimes are gathered automatically from the control system. Manual D owntimes are entered when there are no electronic means of detecting the failure . Aim of Downtime Analysis: The aim of a Downtime Analysis tool is to identify problems and trends within a facility to minimize the impact of failures for individual machinery, and hence maximize the efficiency of the overall facility. How it Works: Rules, which are sometimes quite complex, are setup in the Downtime Server so th at it can monitor events in the control system. When a rule is met, a Downtime i s triggered, and as much information as is electronically available about the Do wntime is logged to the Downtime database. A Downtime Notification is sent to se
lected users to pro-actively notify them of the event. Distribution of total calendar hours: . 1) Planned and Unplanned stoppages due to internal causes (other downtime). 2) Equipment Operating Time. 3) Planned and Unplanned stoppages due to external cause (Idle time). Criterion for registering time: 1) Operating Time: Requires that the asset is operating and it is fed. 2) Other Downtime: Equipment is not operating and is not in a condition for imme diate start up with feed. 3) Idle Time: Equipment not operating and in a condition for immediate start up with feed. The main criteria whether a stoppage generates idle or other downtime ar e the immediate starting availability (without any further maintenance) of relev ant asset. No idle time can occur during the shutdown/stoppage for maintenance reas on. Critical examples Kiln is stopped due to plant CPP power failure.→ Other downtime Management decision to stop the Kiln to optimize the cost (no maintenanc e)→ Idle time Kiln is stopped for upgrade of ESP to Bag house →Other Downtime Raw mill is down due to kiln shutdowns, and no maintenance on raw mill i s done→Idle time for Raw mill Lack of raw meal for Kiln→Downtime for Kiln due to process/ production failure Natural disasters with impact on the condition of equipment (e.g. floodi ng of the engine room)→ Other downtime Non-availability of spares (maintenance materials)→ Other downtime Heat-up time and cooling time of Kiln (started after and stopped for shu tdown reason respectively) →Part of “other downtime” for which the stoppage is t aken. Net OEE: The indicator corresponds to the potential performance of a kiln taking into account net Availability Index, Production Rate Index and Quality Index. Net OEE (%) = Net Availability Index (%) x Production Rate Index (%) x Quality Index (%) Aggregated Net OEE The aggregated values on plant and sub-segment (Group Reporting Unit) levels ar e calculated by applying the same rule as for a kiln.The Net Availabi lity Index is replaced by the Aggregated Net Availability Index and the Prod uction Rate Index is replaced by the Aggregated Production Rate Index. Aggregated Net OEE Aggregated Aggregated Aggregated [%] = Availability * Productio n rate * Quality index Index [%] in dex [%] [%] Gross OEE The indicator corresponds to the potential performance of a kiln taking into acc ount Gross Availability Index, Production Rate Index and Quality Index. Gross OEE (%) = Gross Availability Index (%) x Production Rate Index (%) x Qua lity Index (%) Aggregated Net Availability Index Aggregation of NAI calculated by weighing the NAIs of the kilns by the c orresponding BDPs
Production Rate Index (PRI) Is the actual production volume, in relation to the theoretically achiev able production with BDP. Calculation The PRI formula can be used to calculate and aggregate over time (e.g. d ifferent BDP’s), over different clinker types (OR cement types) and over differe nt assets (kilns OR mills). Production Rate index – Kilns: It measures the actual production rate over a period, compared to the BDP. Production Rate Index – Example Production rate index (%) = { Production rate (t/day)} / { BDP (t/day)} = { 42’000 (t) / 20 d} / {2’32 0 (t/day) } =90.5% Information: The kiln was operating for 20 days, produced 42’000 t, BDP is 2320 t/day Quality Index (QI): Like any process the kiln may produce products of bad quality, but a «ba d» clinker will ot affect the kiln OEE, indeed all the clinker produced, bad and good, will be used to make cement. It’s just a matter of proportion you will ad apt to make your cement. It is therefore considered that the quality for the kiln will always be 100%. Mean Time between Failure (MTBF): All break downs can be categorized into: • Idle Down time. • Other down time. Other downtime can be categorized as Planned downtime (e.g. Maintenance, Major up gradations) Unplanned downtime (e.g. Equipment, Process failures). The planned stoppages, are categorised as Planned stoppage with maintenance Planned stoppages without maintenance ( Cement silo full , clinker stock management ) The unplanned stoppages, are categorised as Unplanned stoppage due to internal reason. Unplanned stoppage due to external reason ( Power Failure ) Mean Time Between Failure = Operating Time(hr) / Frequency Of Unplanned Stoppage Due To Internal Reason
BENCHMARKING STEPS: Benchmarking may be grouped into five steps: planning; analysis; integration; ac tion; and implementation and results. These steps are briefly described in Figur e below. The continuous improvement is carried out by ensuring that the desired results are attained. These results are based on the goals set at the integratio n stage and can be repeatedly modified to improve performance. CONCLUSION AND FUTURE WORK:
A methodology to measure the effectiveness of the current status of maintenance management has been presented. Downtime analysis was carried out for CEMENT KILN and RAW MILL at ACC Plant, Barmana. Monthly downtime analysis determined the mo stly affected parts and the time required for their repair or replacement. The d ata was collected to calculate the OEE (overall equipment efficiency) of the equ ipments used in raw mill and cement kiln. The OEE determines the effectiveness o f the asset or equipment, which thereby determines the timely attention required for its proper working. Auditing of maintenance for the months June, July, Augu st, September resulted in respective failure and downtimes for the damaged equip ments.This basic aim of the auditing for maintenance is to reduce the maintenanc e cost, by the use of planned maintenance. To be able to achieve a level of worl d-class maintenance effectiveness, benchmarking has been briefly stated. This ap proach, if followed, guarantees to a degree that the followers of the maintenanc e practice of successful companies can themselves become leaders. Future Work: Similar Downtime Analysis will be done in the coming semester for the months: Ja nuary, February, March and April. Based on the the downtime analysis in the 2 se mesters .OEE will be calculated for the assets which will help in identifying th e potential areas of improvement .According to the modified maintenance schedule and the type of maintenance; preferably planned maintenance will be assured for the particular equipment. Based on the audit results, the objective should clea rly define the vision of the improved maintenance activity and the impact it w ill have on the enterprise. REFERENCES [1] Garg, A. and Deshmukh, S.G., Application and Case Studies Maintenance Manage ment: Literature Review and Directions, Journal of Quality in Maintenance Engine ering, Vol. 12, No. 3, 2006, pp. 205-238. [2] Sherwin, D., Review Overall Model for Maintenance Management, Reliability En gineering and System Safety, Vol. 6, No. 4, 2000, pp. 138-164. [3] O. Fernandez, A.W. Labib, R. Malmsey, D.J. Petty, A decision support mainte nance management system development and implementation, International Journal of Quality and Reliability Management 20 (8) [4] M. Kans, On the identification and utilization of relevant data for applying cost-effective maintenance, Thesis for the degree of licentiate, Va¨xjo¨ Univer sity, School of Technology and Design, 2005. [5] L. Swanson, Computerized maintenance management systems: a study of systems design and use, Production and Inventory Management Journal 38 (2) (1997) 11–16. [6] P. Johnson, Towards a holistic understanding of disruptions in operations ma nagement, Journal of Operations Management 18 (2000) 701–718. 7)Boznos, D. (1998), “The use of CMMSs to support team-based maintenance”, MPhil thesis, Cranfield University. [8] J. Dedrick, V. Gurbaxani, K.L. Kraemer, Information technology and economic performance: A critical review of the empirical evidence, ACM Computing Surveys 3 (1) (2003) 1–29. [9] Hartman, E.H., “Maintenance productivity: why it is so low and how to improv e it”, in Hartman, E.H. (Ed.), Maintenance Management, Institute of Industrial E ngineers, Norcross, GA, 1987. [10] Wierman, T., World-class Maintenance, Industrial Press, Inc., New York, NY, 1990. [11] Madu, C.N. (2000), “Competing through maintenance strategies”, Internationa l Journal of Quality & Reliability Management, Vol. 17 No. 9, pp. 937-49.
