TRAINING CENTRE : Monday, April 18, 2011
Maintenance Management
Major Causes of 100 Large Failures
%
38
26
12
107 3 4
Mech Failure
Operator Error
Unknown/Misc
Process Upset
Natural Hezard
Subotage
Design
Equipment Malfunctions
Equipment malfunctions have a direct impact on:– Production capacity– Production costs– Product and service quality– Employee or customer safety– Customer satisfaction
The Maintenance Challenge
Maintenance Strategy Model
Asset Performance Management
Sources Of Unreliability
Performance and Practice- The Current Position
Reduces ReducesMaintenance Policy Frequency
SeverityEmphasize preventive maintenance X XProvide extra machines XReplace machine parts early XInvolve operators in maintenance X XOverdesign machines XDesign machines for maintainability XEnhance maint. dept.’s capability X X
Maintenance Policies that ReduceFrequency and Severity of Malfunctions
11
Bathtub CurveH
azar
d ra
te
Time
Infant mortality
Wear out failures of good items
Failure of weak items
Useful life Wear out period
Failure of manufacturing defective parts, substandard parts
Overall objective of Maintenance
Increased plant availability andReduction of maintenance Cost
3 generation of maintenance
Breakdown Preventive Predictive
First Generation
• Fix It when it broke.
• Maintenance means Repair.
BREAK DOWN MAINTENANCE
BREAK DOWN MAINTENANCE
Second generation
• Higher Plant Availability • Longer Equipment Life• High Cost
PREVENTIVE MAINTENANCE
Reasons for a PM Program
Reduce the frequency and severity of interruptions due to malfunctions
Extend the useful life of equipment Reduce the total cost of maintenance by
substituting PM costs for repair costs Provide a safe working environment Improve product quality by keeping equipment
in proper adjustment
Tradeoff Between Repairs and PMA
nnua
l Cos
t A
nnua
l Cos
t
Degree of Preventive MaintenanceDegree of Preventive Maintenance
Minimum TotalMinimum TotalMaintenance CostMaintenance Cost
PreventivePreventiveMaintenanceMaintenance
CostCostBreakdownBreakdownand Repairand Repair
CostCost
Total Total MaintenanceMaintenance
CostsCostsMinimumMinimumLevel ofLevel of
PreventivePreventiveMaintenanceMaintenance
Third generation
Higher Plant Availability & Reliability Greater SafetyBetter product quality Longer Equipment lifeGreater cost effectivenessMaintenance means Care
PREDICTIVE MAINTENANCE
Evolution of Maintenance Strategy
BREAK DOWN PREVENTIVE PREDICTIVERepair or break down Calendar / schedule On condition of machine No warning Planned Early indication of faultLost production Minimizes break down Failure predication
Machine damage Part may be replaced unnecessarily
Maximum production
High cost High cost Reduced maintenance Cost
OPPORTUNITY MAINTENANCE
In opportunity maintenance, timing of maintenance is determined by the procedure adopted for some other item in the same unit or plant .
DESIGN-OUT MAINTENANCE
In design out maintenance, the aim is to minimize the effect of failures and in fact eliminates the cause of maintenance. The equipment with design-out maintenance are so designed that they perform their useful economic life without any maintenance need. This is also called “Run to Destruction”.
SOME OTHER MAINTENANCE PHILOSOPHIES
PROACTIVE MAINTENANCE:- Identify as to What can go wrong. i.e monitor the parameters that can cause failure.
RCM [Reliability Centered maintenance)- the type of maintenance is chosen with reliability of the system in consideration, i.e. system functions, failures relating to those functions and effects of the dominant functional system failures. This strategy in the beginning was applied to critical systems such as aircrafts, nuclear and space applications. At present, this is being extended to critical systems in the plant.
TPM:- Total Productive Maintenance :-TPM, a Japanese concept, involves total participation of all concerned. The aim is to have overall effectiveness of the equipment with participation of all concerned using productive maintenance system.
Following are the major functions of a maintenance department Maintenance of installed equipment and facilities Installations of new equipment and facilities PM tasks – Inspection and lubrication of existing equipment CM tasks – monitoring of faults and failures using appropriate
techniques Modifications of already installed equipment and facilities Management of inventory Supervision of manpower Keeping records
An effective maintenance system includes the following elements
Maintenance Policy Control of materials Preventive Maintenance Condition Monitoring Work Order Job planning Priority and backlog control Data recording system Performance measurement measures or indices
Core Philosophy
Measurable Targets:-What gets measured get done
Focus on vital few :- Follow 80:20 rule Precision Maintenance Continual Improvement :- Small but
sustainable improvement Documentation :- Do what you write and write
what you do
How to approach
Empower people through maximizing usage of system
Revisit processes in line with latest technology development
Extensive use of statistical tools Maximize use of machine language
ERP System
Define & Monitor PM back-log i.e. No of man days
Develop equipment tree & develop standard code for spares
Implement fault code & follow discipline at all level
Perform RCA & monitor effectiveness Measure crew efficiency
Material (Spares)
Monitor inventory / turn over ratio against bench mark figures
Develop extensive storage and handling system Check for non moving / obsolescence Monitor availability Extra care for Insurance spares e.g. Periodic
checking ensure smooth movement of moving part
Documentation
Follow standard document format Document shall be specific & clear to third party Use more pictures for illustration SOP & SMP shall be treated as living document
and shall be reviewed periodically (once a year) Implement document control system
PM Database Requirements
Detailed records, or an ongoing history, must be maintained on each machine
– Dates and frequency of breakdowns– Descriptions of malfunctions– Costs of repairs
Machine specifications/checklists for PM inspection Computers generally used to maintain a database Also, data can be kept in plastic pocket on a
machine
Modern Approaches to PM
PM at the source - workers have the fundamental responsibility for preventing machine breakdowns by conducting PM on their own machines
Workers listen for indications of potential equipment malfunction
Maintenance-related records maintained by workers
Use of quality circles
Precision Maintenance
Contamination Control Alignment Lubrication Control Vibration Analysis Workmanship & skill development (Introduce
Certification System)
Reliability Maintenance
Monitor OEE Monitor MTBF Measure MTTR Focus on RCA & its effectiveness
OEE Monitoring
Examining The Losses- OEE
Energy Efficiency
Large conveyor belt offers a good opportunity– Set current limit for each motor for corrective action
Check possibility of introducing VFD in large fan where flow is controlled using damper
VFD for large pump Maximum demand control (observed PLF < 0.7) Plan production to take advantage of day & night tariff
Maintenance Excellence Model
Maintenance KPI’s
TRAINING
Knowledge –Skill Gap Analysis Developing Training Modules Competency Test.
Repair Programs
Objectives– Get equipment back into operation as quickly as
possible.– Control cost of repairs crews.– Control cost of the operation of repair shops.– Control the investment in replacement spare parts.– Control the investment in standby or backup
machines.– Perform the appropriate amount of repairs at each
malfunction.
How Speedy Should Repairs Be?CostCost
Speed of Making RepairsSpeed of Making Repairs00
MinimumMinimumTotal CostTotal Costof Repairsof Repairs
Cost of RepairCost of RepairCrews & Shops,Crews & Shops,Spare Parts, andSpare Parts, and
Standby MachinesStandby MachinesCost ofCost of
Interruptions toInterruptions toProductionProduction
Total CostsTotal Costsof Repairsof Repairs
SlowSlow FastFast
Cost of repair as a function of MTTR
Breakdowns TriggerRepairs and Corrective Actions
An equipment breakdown should trigger two actions: Fast repair of the malfunction equipment Development of a program to eliminate cause of the
malfunction and need for such repairs in the future– Modification/redesign of malfunctioning machine– Modification/redesign of part or product being processed– Training of operators to improve machine care– More frequent preventive maintenance/inspection
Advantages of Letting WorkersRepair Their Own Machines
Greater variety may make job more satisfying May be more sensitive to potential
malfunctions Increase flexibility Can make minor repairs faster Can avoid minor repairs by cleaning,
lubricating, adjusting and servicing machines Operate machines more carefully
RELIABILITY CENTERED MAINTENANCE
49
Evolution of Asset Mangement Strategy
ReliabilityAvailability
MTBFProduction
Safety
Maintenance Costdowntime
No. of failures MTTR
Break-down Maintenance
Preventive Maintenance
Predictive Maintenance
Total Productive Maintenance(TPM)
Reliability Centered Maintenance(RCM)
Introduction to Reliability
Definition:
The probability that an item will perform a required function without failure under stated conditions for a stated period of time.
Why Reliability: When you can measure what you are speaking about and express it in
numbers, you know something about it; but when you cannot measure it, when you cannot express it with numbers, your knowledge is of a meager and unsatisfactory kind. -- Lord Kelvin, 1883, May 3
A study, in the 80’s, showed that when a customer is satisfied with a product he might tell 8 other people, whereas, a dissatisfied customer will tell 22 people.
Various Terms Used in Reliability
MTTR (Mean Time To Repair)
MTBF (Mean Time Between Failure)
Availability
Hazard Rate =
Repair Rate =
221 RRMTTR
3321 TTTMTBF
MTTRMTBF
MTBFtyAvailabili
MTBF1
MTTR1
T1 R1 T2 R2 T3
[No of Failures per Unit time]
[ No of repairs per unit time ]
52
Capability: Item’s ability to satisfy functional needs.
Efficiency: Item’s ability to effectively utilized the energy supplied
Quality: Item’s Fitness to a particular purpose
Reliability: The item’s ability to start or continue to operate.
Maintainability: The item’s ability to quickly start following its failure.
Understanding Few Related Key Concepts
53
System Reliability
The main objective of system reliability is the construction of a model (life distribution) that represents the times-to-failure of the entire system based on the life distributions of the components
R1 R2
R
Series System
R2
R1 R
Parallel System- Standby2121 RRRRR 21 RRR
System failure = Failure of any component
At least one of the units must succeed for the system to succeed
REPAIR OR REPLACE ?
REPAIR OR REPLACE
The question as “How long to Repair “ an equipment and “When” to “REPLACE” it has quizzed the maintenance personnel since ever.
Given below are a few guidelines .
REPAIR OR REPLACE
In modern day business environment where the impetus is placed on reduction of manufacturing cost and improving overall plant efficiency and reliability , thus directly affecting the profitability and customer’s satisfaction.
REPAIR OR REPLACE
To know when an equipment is reaching its useful life cycle, the key is not its age but its condition. Plant equipments may be old but most of equipments are continually upgraded and maintained in order to keep up with evolving manufacturing and production requirements. However a few considerations applicable are as follows.
SAFETY
If the equipment presents an un-acceptable safety risk to Plant , Plant Personnel, and Environment –Replace it.
In worst case scenario there could be loss of life or an environmental accident , causing huge financial loss , loss of Customer and public Confidence.
However before replacing , give consideration of possibility of Upgrading the equipment to achieve acceptable safety standard.
EXTERNALLY IMPOSED FORCES
GOVERNMENT LEGISLATIONS:- Externally imposed changes such as those required by Govt. Legislations (Stack Emission, Noise Pollution , Waste Disposal etc) are sometimes the major reason for replacement of equipments /processes.
Example :- Open Hearth Furnaces for Steel Making. MARKET FORCES:- If the present equipment is not able to
produce to the quality standards required by the market , there is no point in producing the goods which can’t be marketed. In such condition replacement of equipment becomes imperative to meet the market demand.
*******************************************
MAINTENANCE COST
Maintenance cost associated with maintaining the equipment to acceptable reliability level may be far too expensive.
Availability of spare parts could become un-acceptable from business stand-point.
TECHNOLOGICAL OBSCELENCE
As each organisation looks for ways and means to reduce cost ,and if the present equipment can not meet production requirement in Quantity and Quality , then it needs to be replaced. However before new equipment is bought , detailed study of life-cycle cost and reliability to be done and strategy developed.