23 May 2020

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  1. RAMCO INSTITUTE OF TECHNOLOGY Mr.M.LAKSHMANAN Assistant Professor (Senior Grade) Department of Mechanical Engineering
  2. UNIT II MAINTENANCE POLICIES – PREVENTIVE MAINTENANCE Maintenance categories – Comparative merits of each category – Preventive maintenance, maintenance schedules, repair cycle - Principles and methods of lubrication – TPM.
  3. Maintenance Approach Planned Maintenance Preventive Maintenance Corrective Maintenance Predictive Maintenance Condition Based Maintenance Reliability Central Maintenance Breakdown Maintenance
  4. Breakdown / Reactive Maintenance • The equipment is allowed to operate till no failure occurs. No maintenance work is carried out in advance to prevent the failure. • The people wait till equipment fails and repair. • Its ineffective and extremely expensive. • Poor planning and incomplete repair will be contributed for high maintenance cost.
  5. Limitations of Reactive Maintenance • Most repairs are poorly planned due to time constraint caused by production and plant management. • This approach focus only on repair or the symptoms of failure and not on the root cause of failure.
  6. Planned Maintenance • Corrective Maintenance: Its focused on regular planned tasks that will maintain all critical machinery and system in optimum operating conditions. Main Objectives: 1. Eliminate breakdowns 2. Eliminate deviations from optimum operating conditions. 3. Eliminate unnecessary repairs 4. Optimize all critical plant systems.
  7. • Corrective maintenance can be defined as a maintenance task performed to identify, isolate, and rectify a fault so that the failed equipment, machine, or asset can be restored to an operational condition within the tolerances • Corrective maintenance is maintenance which is carried out after failure detection and is aimed at restoring an asset to a condition in which it can perform its intended function.
  8. Preventive Maintenance • It is the maintenance program which is committed to the elimination or prevention of corrective and break down maintenance. • It involves periodical evaluation of critical equipment, machinery to detect problem and schedule maintenance task to avoid degradation in operating conditions. • Its designed for day to day maintenance like cleaning, inspection, lubricating, retightening etc., to retain the healthy condition of equipment.
  9. Benefits of Preventive Maintenance • It maintains the equipment in good condition to preventing them from bigger problems. • Prolongs the effective life of the equipment. • Detect the problem at earlier stages. • Minimize / eliminates the rework. • Reduces unplanned downtime.
  10. Predictive Maintenance • It is a management technique that uses regular evaluation of the actual operating conditions of plant equipment, production systems and total plant operation. • Predictive maintenance as regard to maintenance management, based on need, will provide necessary data for scheduling of preventive and corrective maintenance tasks.
  11. • Predictive maintenance (PdM) techniques are designed to help determine the condition of in- service equipment in order to predict when maintenance should be performed. This approach promises cost savings over routine or time-based preventive maintenance, because tasks are performed only when warranted.
  12. Its helps to improve/increase, • The production capacity • Product quality • Overall effectiveness of production function. Benefits of predictive Maintenance: • Reduced breakdown losses • Reduction of Quality defects • Increased net operating profit • Reduced maintenance cost
  13. Condition Based Maintenance • Condition-based maintenance (CBM), shortly described, is maintenance when need arises. This maintenance is performed after one or more indicators show that equipment is going to fail or that equipment performance is deteriorating.
  14. Condition Based Maintenance Techniques • Vibration Monitoring: Determines the actual condition of equipment/machines by studying the noise or vibration produced during functioning. • Thermography: Determines the condition of plant machinery, system etc. by studying the emission of infra red energy ( Temperature)
  15. • Tribology: Determines the dynamic condition of bearing lubrication, rotor support structure of machinery etc. by adopting any one of the techniques like lubricating oil analysis and wear particle analysis. • Electrical motor Analysis Determines the problem within motors and other equipments. • Visual inspection: Determines the conditions of working elements visually based on the experience.
  16. Reliability Centered Maintenance (RCM) • RCM is one of the well established systematic and a step by step instructional tool for selecting applicable and appropriate maintenance operation types. • It helps in how to analyze all failure modes in a system and define how to prevent or find those failures early.
  17. The rough process of RCM is as follows: • Target products or systems of maintenance should be clearly identified, and necessary data should be collected. • All possible failures and their effect on target products or systems are systematically analyzed.
  18. Applications of RCM • When designing, selecting and installing new systems in a plant • When setting up preventive maintenance for complex equipment and systems for which are not clear on how they work.
  19. Total Productive Maintenance (TPM) • In industry, total productive maintenance (TPM) is a system of maintaining and improving the integrity of production and quality systems through the machines, equipment, processes, and employees that add business value to an organization. • It’s a maintenance program which involves a newly defined concept of maintaining plants and equipments.
  20. • To increase the production, at the same time increasing employee morale and job satisfaction. • To maximize plant and equipment effectiveness to achieve optimum life cycle cost of equipment. Goal of TPM
  21. Evolution of TPM • Dr.W.Edward Deming – Japanese Industry • Nippon Denso of Toyoto groups – Quality circle, Involving employees participation
  22. Implementation of TPM Stage I Initialization (Preparatory) Stage II Introduction on TPM (Take off phase) Stage III Implementation Stage IV Institutionalization (Stabilization Phase)
  23. Stage I Initialization (Preparatory Phase) • Discussions with workers union representatives • Establish basic TPM policies and goals – Analyze the existing condition • Preparation and formulation of master plan
  24. Stage II Introduction on TPM (Take off phase) • Formal presentation by top executive with all employees attending. • To get the full support of all employees. • Also invite our external customers, suppliers, contractors and affiliated companies to get their supports.
  25. Stage III Implementation • 5’S Principle • Autonomous Maintenance (JISHU HOZEN) • KAIZEN • Planned Maintenance • Quality Maintenance • Training • Office TPM • Safety, Health and Environment
  26. Stage IV Institutionalization (Stabilization Phase) • Once TPM has been implemented, it should be properly monitored and evaluated and some reward system can be introduced for further encouragement. • The Japanese institute for productive maintenance runs an annual PM Excellence Award.
  27. TPM Objectives Objectives of TPM Zero Defect Zero breakdown Involvement of people from various levels Reliable maintenance policy
  28. Benefits of TPM • Enhanced/ improved productivity and overall efficiency • Reduction of manufacturing cost. • Customer satisfaction by delivering right quantity at right time with expected quality. • Minimization of accidents. • High confidence level among employees.
  29. Category TQM TPM Objective To have quality output To have reliable equipment Means of achieving Through systematized management Through active participation of employees Target Minimized defective through planned preventive maintenance Elimination losses and wastes
  30. Pillar -1: 5S Principle
  31. Pillar -2: Jishu Hozen(JH) • Training employees • Initial cleanup of machines • Taking counter measures • Fixing tentative JH standards • General Inspection • Autonomous inspection • Standardization • Autonomous management
  32. Pillar -3: KAIZEN
  33. Elements of KAIZEN
  34. Motorola’s steps for continuous improvement
  35. Major losses in an organization • Equipment efficiency based losses 1. Failure/Breakdown losses 2. Setup/adjustment losses 3. Minor stoppage/ idling loss 4. Speed loss-Operating at low speeds 5. Defect/Rework loss 6. Scheduled downtime loss • Human work efficiency based losses 1. Management loss 2. Operating motion loss 3. Line organization loss 4. Measurement and Adjustment loss
  36. • Effective use of Production Resources 1. Energy loss 2. Die, Jig and Tool breakage loss 3. Yield loss
  37. Pillar -4: Planned Maintenance(PM) 1. Preventive Maintenance 2. Corrective Maintenance 3. Predictive Maintenance 4. Condition Based Maintenance 5. Reliability Centered Maintenance
  38. Pillar -5: Quality Maintenance(QM) 1. Its aimed towards customer delight by getting them the highest quality through defect free manufacturing. 2. Its focused on eliminating non conformances in a systematic manner. 3. Understanding of what parts of the equipment affect product quality and begin to move potential quality concerns.
  39. Pillar -6: Training  Its aimed to have multi skilled employees whose morale is high and who are eager to work and perform all the required functions independently and effectively.  Its not sufficient to know only “Know-How” but they should also learn “Know-Why”.
  40. Target:  Achieve and sustain downtime at zero on critical machines.  Achieve and sustain zero losses due to lack of knowledge/skills/techniques.  Aim for 100% participation in suggestion scheme.
  41. Pillar -7: Office TPM • To improve productivity, efficiency in the administrative functions and identify- eliminate losses. • Analyzing processes and procedures towards increased office automation.
  42. Office TPM Major Losses • Processing loss. • Cost loss (Accounts, Marketing, Sales) • Communication loss • Idle loss • Set-up loss • Accuracy loss • Office equipment breakdown • Communication channel breakdown(Telephone, Fax Lines) • Non availability of correct on line stock status • Customer complaints due to logistics
  43. Benefits of Office TPM • Involvement of all people in support functions for focusing on better plant performance. • Better utilized work area • Reduce repetitive work • Reduced inventory levels in all parts of the supply chain. • Reduced administrative cost • Reduction in number of files • Reduced manpower • Clean and pleasant work environment
  44. Pillar -8: Safety, Health and Environment • Zero accident • Zero health damage • Zero fires
  45. Maintenance Scheduling • Maintenance scheduling is a joint maintenance operations activity in which maintenance agrees to make the resources available at a specific time when the unit can also be made available by operations.
  46. Stakeholders of maintenance scheduling Planner Scheduler Maintenance Supervisors Craftsman Store’s In charge Operation Superinten dent Operator
  47. 1. Planner He/She should ensure that the work is properly planned with respect to customer requirements, Stores material, directly purchased materials, etc. also work to be carried out with line of safety requirements should be described.
  48. 2. Scheduler He/She should ensure that, • Trades are available to conduct the work during the schedule duration. • Materials and service availability. • Communicating the details of the above to person involved in maintenance and operation.
  49. 3. Maintenance Supervisor He/She will be responsible for the day to day activities comprised in weekly schedule and also determine the business availability. 4. Craftman: He/She execute the assigned task and keep informing the maintenance team, the outcome as well as any practical difficulty in their part, for any further analysis.
  50. 5. Storeroom personnel: They maintain the records of receipt of goods and notify if any damage exists. 6. Operation Superintendent: He must be kept informed in advance about the equipment condition. 7. Operator: He is the person responsible for securing the equipment and report back to maintenance personnel if any deviation is observed.
  51. Maintenance Scheduling Principles Schedules are important job priorities are important Schedule from forecast of highest skills available Schedule for every workhour available Crew leader handles current day’s work (Daily schedules) Measures performance by analysis of schedule compliance Plans with lowest required skill level
  52. Repair • To restore to a good or sound condition after decay or damage. • Inspection(I) • Minor Repair (R1) • Major Repair(R2) • Overhauling(O)
  53. Repair Cycle • The repeated performance of all/some of the above mentioned activities in sequence between successive overhauling is termed as Repair Cycle.
  54. O I R1 R2 I R1 I R2
  55. Lubrication • To reduce wear and heat between contacting surfaces in relative motion. • Coefficient of friction could be reduced and inturn heat and wear of the surfaces. • Lubrication also aids to 1. Reduce oxidation and rust formation 2. Transmit mechanical power in hydro fluid power systems. 3. Seal against dust, dirt and water.
  56. Lubricants • Any materials used to reduce friction between wearing surfaces with high coefficient of friction, by establishing low viscous film are called lubricants. Methods of Lubrication: • Hydrostatic Lubrication • Hydrodynamic/ Fluid film Lubrication • Boundary Lubrication • Elasto hydrodynamic Lubrication (EHD) • Extreme pressure Lubrication (EPL)
  57. Method of lubrication is based on: Mean fluid film thickness R = Surface Roughness Where, R is less than or equal to 1 for Boundary/Hydrostatic Lubrication R is in between 5 and less than or equal to 100 for mixed lubrication or EHD/EPL R is between 1 and 5 for fluid film lubrication
  58. 1. Hydrostatic Lubrication A thin film of lubrication is created between the journal and the bearing by supplying lubricant under pressure with an external source like pump.
  59. 2. Hydrodynamic/ Fluid film Lubrication In heavy loaded bearing such a thrust bearings and horizontal journal bearings apart from viscosity of fluid, higher fluid pressure is also required to support the load. In hydrodynamic lubrication a fluid wedge is formed by the relative surface motion of the journals over their bearing surfaces.
  60. Ex: Cylindrical Journal Bearing & Connecting rods
  61. 3. Boundary Lubrication When a full fluid film is not developed between rubbing surfaces, the thickness of film may be reduced so that dry contact is formed at high points of mating surfaces. Ex: Gear Teeth
  62. 4. Elasto hydrodynamic Lubrication (EHD) • The lubrication principle is applicable to rolling bodies such as ball or roller bearings. • Elastic deformation of the contacting bodies under load and hydrodynamic effects forcing the lubricant to separate the contacting surfaces while the pressure of the load is deforming them. • Ex: Ball bearings
  63. 5. Extreme pressure Lubrication (EPL) In heavy loading applications, oil temperature raises beyond the anti wear protection. Under this situation lubricants containing additives that protect against extreme pressure (EP) lubricants are used. EPL can be achieved by chemical compounds of boron, phosphorus, sulphur, chloride or combination of these.