Maintenance

MAINTENANCE SUDHIR CHOPADE

INDEX  Definition  Evolution

of maintenance techniques  Expectations  Causes of failure  Aims and objectives of maintenance  Types of maintenance

WHAT IS MAINTENANCE? It is the process of ensuring that physical assets continue to do what their users want them to do. •

Maintenance can be considered as a combination of actions carried out in order to replace repair, service (modify) the components of an industrial plant so that it will continue to operate to a specified availability for a specified time •

In this lecture we will discuss…  What

is maintenance?  Why do we need maintenance?  What are different types of maintenance?  Advantages and disadvantages of different type of maintenance  Changing expectations from maintenance  What are the costs of doing maintenance?  What are the costs of not doing maintenance?  What are the benefits of maintenance?  How can maintenance increase profitability of company?

Evolution of maintenance techniques

Growing expectations of maintenance

Machine failure mechanism/bath tub curve

Causes of ‘Infant Mortality’

Maintenance Objectives  Must

be consistent with the goals of production (cost, quality, delivery, safety)

 Must

be comprehensive specific responsibilities

and

include

Aims and objectives of maintenance of power plant AIMS OF MAINTENANCE :- Achieve budgeted Generation - Achieve Targeted Profit - Improve Plant Availability Factor - Reduces unexpected Break down - Enhance life cycle & efficiency thro quality OBJECTIVE OF MAINTENANCE :- To reduce outages time - Best use of resource - Maintenance work Quality - Low cost of Generation - Improve safety

Types of Maintenance Maintenance may be classified into following categories:  Corrective or Breakdown maintenance  Scheduled maintenance  Preventive maintenance  Predictive (Condition-based) maintenance  Proactive maintenance  Reliability centered maintenance

Corrective or Breakdown Maintenance  Corrective

or Breakdown maintenance implies that repairs are made after the equipment is failed and can not perform its normal function anymore.

 Quite

justified in small factories where: – Down times are non-critical and repair costs are less than other type of maintenance cost – Financial justification for scheduling are not felt

Corrective / Breakdown/crisis Maintenance  Run-to-failure

maintenance is sometimes called "crisis maintenance" for good reason.  This has been the dominant form of maintenance for a long time, and its costs are relatively high because of unplanned downtime, damaged machinery, and overtime expenditure.

Disadvantages of Corrective Maintenance  Breakdown

generally occurs inappropriate times leading to poor and hurried maintenance  Excessive delay in production & reduces output  Faster plant deterioration  Increases chances of accidents and less safety for both workers and machines  More spoil of materials  Direct loss of profit

Preventive Maintenance (PM) Principle

– “Prevention is better than cure” Procedure - Stitch-in-time locates weak spots of machinery and equipments provides them periodic/scheduled inspections and minor repairs to reduce the danger of unanticipated breakdowns

Periodic Preventive Maintenance 

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



From run-to-failure, we progress to periodic preventive maintenance, which is sometimes called "historical" maintenance. This is where the histories of each machine type are analyzed and periodic overhauls are scheduled to occur before the statistically expected problems occur. It has long been known that most groups of similar machines will exhibit failure rates that are somewhat predictable if averaged over a long time. This gives rise to the so-called "Bathtub Curve" which relates failure rate to operating time, as follows:

Scheduled Maintenance Scheduled

maintenance is procedure and incorporates

a

stitch-in-time

• Inspection • Lubrication • Repair and overhaul of equipments If

neglected can result in breakdown  Generally followed for: • • • •

Overhauling of machines Changing of heavy equipment oils Cleaning of water and other tanks etc. Cleaning of machinery and auxilliary

Advantages of PM 

Advantages:        

Reduces break down and thereby down time Less odd-time repair and reduces over time of crews Greater safety of workers Lower maintenance and repair costs Less stand-by equipments and spare parts Better product quality and fewer reworks and scraps Increases plant life Increases chances to get power generation incentive bonus

Predictive (Condition-based) Maintenance In

predictive maintenance, machinery conditions are periodically monitored and this enables the maintenance crews to take timely actions, such as machine adjustment, repair or overhaul

It

makes use of human sense and other sensitive instruments, such as – Audio gauge, vibration analyzer, amplitude meter,

pressure, temperature and resistance strain gauges etc.

Predictive Maintenance (Contd.)  Unusual

sounds coming out of a rotating equipment predicts a trouble  An excessively hot electric cable predicts a trouble  Simple hand touch can point out many unusual equipment conditions and thus predicts a trouble

Predictive Maintenance  



Predictive maintenance allows management to control the machinery and maintenance programs and vice versa. In a plant using predictive maintenance, the overall machinery condition at any time is known, and much more accurate planning is possible. Benefits of Predictive Maintenance – The major benefit of predictive maintenance of mechanical equipment is increased readiness due to greater reliability of the equipment. The trending over time of developing faults in machines can be carefully done so as to plan maintenance operations to coincide with scheduled shutdowns.

Condition-Based Predictive Maintenance    

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Minimize corrective maintenance Minimize costly preventative maintenance which often replaces good equipment and is costly Decisions based on actual condition of equipment Need early fault detection and diagnostic capabilities to minimize likelihood of forced outages and equipment damage Need highly accurate predictive capabilities based on actual equipment condition and status of failure precursors for reliable estimate of time to failure Select the best time to perform maintenance

Benefits of predictive maintenance 

Effective on-line early detection, diagnosis, and prognosis would: –

– – – – – – – –

Provide system engineers and maintenance staff with necessary information to make informed, cost-effective operations and maintenance decisions based on the actual condition of the system/equipment Provide more options to the operations staff to handle the fault and its consequences Allow earlier mitigation or corrective actions Reduce the likelihood of unplanned plant trips or power reductions Reduce challenges to safety systems Reduce equipment damage Reduce likelihood of repetitive failures Support the Maintenance Rule Facilitate the implementation of condition-based predictive maintenance practices

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On-line monitoring addresses the strategic needs for the power industry Need for sensors other than process measurement – Remaining life – Damage accumulation Synergy between wireless technology and on-line monitoring Fleet-based diagnostics/prognostics capabilities Still a lot to do in order to achieve the benefits possible from equipment condition-based predictive maintenance – Requires research, development, and application activities – Collaboration and information sharing needed

Predictive maintenance data collection        

Vibration monitoring Thermographs Acoustic Technology-transformer partial discharge, leak/ corona detection. Lube oil monitoring-for wear/ oil cond. DGA in transformer oil Electrical Tests-Motor current/ IR value Ultra sound- for sub surface defects DPT(Die Penetration Test)-for surface defects

4-PRO-ACTIVE MAINTENANCE: PAM is process of learning from past maintenance. Problems, work and identifying activities to reduce/eliminate future maintenance or improve reliability  PAM based on ROOT CAUSE ANALYSIS to basic reason for corrective actions. It compliments Predictive maintenance.

Proactive Maintenance Technologies  Dynamic

Balancing  Precision Shaft Alignment  Ultrasonic Testing / Air & Steam  Belt / Pulley Alignment  Acceptance Testing  Water / Air Flow balancing & Measuring  Metering

Pro-active Maintenance  Pro-active

maintenance, which uses a variety of technologies to extend the operating lives of machines and to virtually eliminate reactive maintenance.

 The

major part of a pro-active program is root cause failure analysis, which is the determination of the mechanisms and causes of machine faults.

 The

fundamental causes of machine failures can thus be corrected, and the failure mechanisms can be gradually engineered out of each machinery installation.

RELIABILITY CENTERED MAINTENANCE  It is the process which is used to determine what must be done to ensure that any physical asset continues to do what its users want it to do in its present operating context. 

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RCM is approach & not maintenance. Activity that employs reactive, preventive, proactive practices & strategies in integrated manner to increase probability that m/c function in required manner over its life with minimum maintenance at lowest cost.

7 KEY ATTRIBUTES OF RCM 1. Functions – what are standards of performance. 2. Function failure- ways it can fail 3. Failure mode- causes of failures 4. Failure effects- what happens 5. Failure consequences- impact on process. 6. Proactive task- To be done 7. Default action- To be done if 6 fails.

 RCM

to SRCM Simplified or stream lined RCM is to reduce cost also known as a. Maintenance Rationale b. PM basis optimization This process is used in REAP (RISK EVALUATION & PRIORITIZATION ):-

Aims to optimize maintenance cost & risks for given availability.  It is highly data driven. i.e What maintenance jobs are required to be performed on priority in the available funding so as to mitigate maximum risk 

Maintenance Requirement Analysis The determination of maintenance requirement is a significant component in the Logistics Support Analysis (LSA) process 1. Failure Modes, Effects and Criticality Analysis (FMECA) 2. Fault Tree Analysis (FTA) 3. Maintenance Cost Analysis 4. Maintainability Checks 5. Reliability Centered Maintenance (RCM) 6. Reliability and Maintainability Analysis (RMA) 7. Level of Repair Analysis (LORA)

 Along

FAMIS

with many other features, it can be a tool for equipment management and record information source.  Examples of equipment information:  Manufacturer, Model#, Serial#  Sizes, flow rates, age, gpm, cfm, psi  Electrical data: HP, Voltage, FLA

Plant Maintenance Policy  Improve

plant and equipment availability / reliability while ensuring equipment to operate at optimum capability and efficiency  Ensure compliance to statutory, safety and environmental regulations / requirements. Ensure quality of maintenance  Plant set up to be supported by maintenance management cell, contract department, efficiency group and costing group

Plant Maintenance Policy  Maintenance

cost control and proper budgeting in commensurate with generation plans/actual work plans  Effective long term and annual outage planning and execution  Improvement of skills and knowledge of personnel  Modernize documentation and other maintenance functions with the use of IT

Plant Maintenance Policy  Ownership

role to be played by Operation department with maintenance as a service function  Setting up of good maintenance practices  Setting up of maintenance performance indicators  Develop external support functions for maintenance  Recognize major deficient areas for improvements like spare management

DEFNITION OF MAINTENANCE PLANNING

 Maintenance

:- Maintenance is defined as systematic care and attention to keep equipments/machines in good working condition for peak production.  Planning:- A way to work effectively & efficiently in organized way to achieve best quality with optimum time, cost, resources.

AIMS AND OBJECTIVES OF MAINTENANCE PLANNING DEPARTMENT

MAINTENANCE AIM:- Achieve budgeted Generation - Achieve Targeted Profit - Improve Plant Availability Factor - Reduces unexpected Break down - Enhance life cycle & efficiency tro quality

Maintenance Organizational set-up and duties It is recommended to form separate Maintenance Management planning Cell at individual power stations with following responsibilities : -

Duties of Maintenance Planning department 1.

 

Preparation/Planning of work scope/work contracts and manpower Planning of Annual/Capital overhaul based on : Performance of equipment History of past maintenance and failures

Duties of Maintenance Planning Department   2. 3.

4.

Necessary modification/refurbishment to improve efficiency/heat rate Manufacturer’s recommendations Preparation of PERT / BAR chart schedules Planning and procurement of spares required for the listed works and follow-up with OEMs and vendors Planning for special tools & tackles and external transportation

Duties of Maintenance Planning Department Proper mobilization of contractors including requisite skilled manpower and tools 6. Identification and organizing of storage spaces for spares, tools etc. for contractors. Arrangement of accommodation, canteen etc 7. Preparation of Quality Assurance and Quality Control protocols 5.

Duties of Maintenance Planning Department Coordination with external agencies and necessary formalities. Inter-departmental coordination and review of progress. Compilation of overhaul report. Report shall include:  Jobs planned and completed  Major modification / renovation carried out  Cost of overhaul with the break-up department and system/equipment-wise 8.

Duties of Maintenance Planning Department  Performance

before and after overhaul  Deficiencies left and corrective actions needed for future  Broad plan of next outage along with preparation milestones expected

Duties of Maintenance Planning Department Condition monitoring of critical equipment shall be assigned to this cell 10. A Sub Cell may be formed under this maintenance management cell to carry out Quality Assurance or Quality Audit function 11. Equipment history record 12. Long term planning 5/7 year rolling plan 9.

Duties of Maintenance Department 1. 2. 3. 4. 5. 6. 7.

Attend daily maintenance work Trouble-shooting Preventive and Predictive maintenance Management of materials and spares for regular work Execution and supervision of work – During overhaul of plant / equipment Quality control of work execution Maintenance performance indicators

Duties of Maintenance Department Insurance 9. Special maintenance or capital budgets 8.

Cost Factors for Maintenance of Equipment  Down

time cost  Efficiency of machine  Life of machine  Reliability and its effect on business

Work contract groups and service providers Service providers for running plant shall be mainly developed for labour extensive works of one time nature and not of repetitive nature.  Registration of vendor or service provider shall be done in a scientific manner.  Competent vendor is key to ‘low down time and good quality work’.  Longer duration partnerships can help in vendor development 

Work contract group and service provider These service providers shall be developed with good quality conscious background 2. OEM’s internal resources shall be used for machinery requiring precision 3. Work contract should be finalized at least three months before starting the planned jobs 1.

Work contract group and service provider 4.

5.

The maintenance management group should send proposals for the work scope to the Work Contract Cell at least six months before starting the job (major outage) Contract should be mobilized at least a week before shutdown of the units/equipment

Work contract group and service provider 6.

Index of problems encountered after the outage may be related to indications of “Quality of Work”

Proposed norms for the registration of ‘Service provider’ i. ii. iii. iv. v. vi.

Reputation and qualification of staff and adequacy Experience on similar jobs Response time Tools & tackles inventory Financial capacity Familiarization with computerized control and follow up systems

Proposed norms for the registration of ‘Service provider’ vii.

Preference should be given to OEM – OEM generally has fleet of machines and is normally in a better position to advice corrective actions, especially in case of crisis

Spares Parts Management & Vendor Development Spare parts management is vital from the point of view of ‘Down time cost’ and ‘Inventory carrying cost’. Well thought of selection of equipment helps in reducing inventories in addition to the normal criteria of cost, efficiency, duty, material, track record, etc

Equipment selection shall also give attention to:  Vendor’s quality

reputation  Vendor’s response and lead times  Vendor’s engineering backup  Duplication of existing equipment for other plants and processes  Vendor location  Overhaul strategy recommended

Equipment selection shall also give attention to:  Standardization  Readiness

to provide manufacturing drawings and good specific manuals  Inventory shall not exceed around 2.5% of appreciated capital cost  Spares for overhaul shall be managed by ‘Maintenance Management Cell, while for normal O&M, these shall be managed by ‘Maintenance Department’

Equipment selection shall also give attention to:  Computerized

system is a necessity for managing spares  Preparation of specifications is the single top priority, which needs attention by each and every power plant  Philosophy of buying few parts to meet project requirements and build up inventories that will just cover next outage needs review

Spares program shall take care of:  Design

deficiencies  Criticality and related down time  Obsolescence of equipment  Capital cost  Cost of spares  Lead time  Quality  Sufficient essential spares as part of project

Spares program shall take care of:  Development

of quality local vendors for imported or costly spares  Metallurgical Improvements  Off shelve readily available items  Standardization of vendors and certification of their quality from central agency like ISI mark can be an alternative to ensure price competition to OEM and delivery

Budget & Costing Details of the cost and budget involved for planned maintenance are generally not available with the power stations. The reasons being non-existence of the Costing Cell as support cell. It is, therefore, recommended that this Cell may be established for all the power stations. This Cell shall also maintain records and documents in respect of actual expenditure made by the power plant for planned maintenance. The Group should adopt latest IT tools (Information Technology) available and should have networking with the spare parts management group and finance group for acquiring information about the budget and costing

Functions for Budget & Costing cell  Costing

cell shall be calculated per unit of generation  Budget for Planned Overhaul and Regular maintenance to be identified  Capital budget to be prepared

Work Culture Development  Technical

courses and workshops should be provided for every maintenance personal  Manual should be provided for each maintenance personal  Establish a core group of highly skilled staff  Install a culture that encourages, promotes rewards for innovations

Work Culture Development  Install

culture to have operation and maintenance staff work together  Training programs shall ensure that staff remains qualified and competent

Documentation & Reporting Online Computerized Data Management System should be adopted for activities like: a. Defect reports b. Feedback c. History Record d. Spares part management e. Performance monitoring f. Preventive maintenance

Documentation & Reporting Maintenance cost h. Maintenance index i. Maintenance back log j. Work orders g.

Quality Assurance Quality management starts from design, award of contract, manufacturing, transportation, receipt, storage and preservation of the same. All stations should have their own QA Group with trained manpower and modern laboratory.

Maintenance policies for Boiler and Turbine divisions 1. 2. 3. 4. 5.

Fixed time maintenance (individual or group replacement) Condition based maintenance (Continuous or periodic) Operate-to-Failure (Corrective maintenance by repair to replacement Opportunity Maintenance Design-out Maintenance

General Recommendation  Maintenance

Management Cell should forward indents for planned outage jobs to the Material Management Department at least 24 months in advance  Availability of the spares should be ensured at site at least one month before starting the planned jobs  Outage planning shall start 12-18 months in advance except for spares, which have to be taken care of 24 months in advance

General Recommendation  Pre

outage survey shall be carried out 3 months in advance and repeated 15 days in advance  16 hrs. could be planned on critical works. Works like scaffolding, condenser, etc. could be planned round the clock  Mobilization by contractors shall be carried out at least one week in advance  Final report with recommendations for next outage must be prepared with in two months of completion of outage

General Recommendation  Work

contract should be finalized at least three months before starting the planned jobs  The Planning Group should send proposals to the Work Contract Cell at least 6 months before starting the job.Changeover to Availability Based Monitoring  The duration of planned outages as recommended above are from the time unit is taken out of the grid to the time the unit is synchronised back to the grid. As such the time period to be tied up with the service providers/contract services for Capital Maintenance, Boiler Overhaul will be correspondingly less (from barring gear to barring Gear).

Problems in Maintenance  Lack

of management attention to maintenance  Little participation by accounting in analyzing and reporting costs  Difficulties in applying quantitative analysis  Difficulties in obtaining time and cost estimates for maintenance works  Difficulties in measuring performance

Problems Exist Due To:  Failure

to develop written objectives and

policy  Inadequate budgetary control  Inadequate control procedures for work order, service requests etc.  Infrequent use of standards  To control maintenance work  Absence of cost reports to aid maintenance planning and control system

For any type of maintenance/ overhaul, following major points should be consider: NDT test with trained manpower  Boiler tube thickness (QA Personnel should be involved for cross check)  Quality man should witness all critical checks (turbine/boiler/rotary tests) and check sheet should be filled and protocol should be signed 

For any type of maintenance/ overhaul, following major points should be consider: Station QA Group should be equipped with trained manpower and well-equipped laboratory. Training should be given regularly to keep them update  Station has to be vigilant regarding modern technique development for fault detection  Engineering declaration before unit goes out of bar for maintenance/ overhaul 

For any type of maintenance/ overhaul, following major points should be consider:      

Special tools/ tackles list Availability of spares before overhaul Mobilization of Contract before overhaul Availability of lifting tools, welding points and lifts, testing should be done prior to overhaul Pre-outage survey of the unit Scope of work of each section boiler/turbine/Elect. /C&I/off site

For any type of maintenance/ overhaul, following major points should be consider: Formation of outage committee before overhaul  Budget plan with five year rolling plan  Carrying out of efficiency test of Boiler and Turbine before and after overhaul Planned outage period should not increase the scheduled period.  Early and meticulous planning 

For any type of maintenance/ overhaul, following major points should be consider: Frequent review of resources and contracts for overhaul  Re-commissioning of overhauls with approved checklist.  Meticulous monitoring of critical activities 

Maintenance performance indicator  Forced

down time as a percentage of Planned down time  Recurrent jobs to percentage of total jobs  Maintenance index; mean time for attending to a defect  Maintenance cost – Expenditure per kW hr  Productivity – Man – days /man –hours per kWh

Maintenance performance indicator  Technical

Index – number of unsolved problems to number of solved problems  Cost of outage  Cost of spares consumed and inventory level  Maintenance backlog – ratio of ‘jobs attended’ every week to ‘jobs unattended’  Availability – as a percentage – critical equipment and plant

Maintenance performance indicator  Innovation

index – money saved on account of innovations/modification/import substitution to money spent  Safety – man-days lost on account of accidents  Average time of capital overhaul over three outages  Savings due to restoration/improvement in efficiency- absolute and compared to previous year

Maintenance performance indicator  Heat

rate, Aux. Consumption and DM water consumption

Safety Every power utility shall have safety manual of its own. Personnel shall be tested for its knowledge at the time of joining the organization b. Noise pollution from the machinery shall be surveyed and appropriate precautions like use of earplugs in those areas shall be enforced. Noise can be also reduced through isolation of area a.

Safety Use of personal safety appliances like helmets, grinding goggles, safety shoes, breathing filters, and gloves shall be enforced d. Use of electrical tools shall be as per safety procedures. Safety tools shall be yearly checked also e. Defective tools shall either be repaired or replaced c.

Safety All exposed rotating components of machinery shall be isolated through proper guards g. Proper O&M procedures also help in safety h. Lifting tackles, pressure vessels shall be tested as per statutory requirement i. First – Aid training shall be given to all employees f.

Safety Hazardous areas shall have protection implements periodically checked for proper functioning k. Safety culture shall be developed through putting posters at prominent and relevant locations, conducting safety completions, facilitating safety committees l. Any accident shall be thoroughly investigated and corrective actions taken j.

Safety Maintaining cleanliness of plant. All working groups be it maintenance, be it lubrication group, be it operation group, etc. – should clean the area of debris generated by the group n. Operation group shall own the responsibility for keeping the area and machinery clean m.