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CONCEPTS OF MODERN MAINTENANCE MANAGEMENT

 

 

 

INTRODUCTION

The human civilization has come a long way from the early agrarian societies. The modern industries with mass production capacities have almost put an end to the cottage industries.Machines have long back taken the place of human hands.These modern industries have given us bulk production for the ever increasing population at economic costs.

The industrial revolution saw the advent of complex machinery each fitted with thousands of different static and moving parts.Simple controls have now developed into fully automated systems run not by humans but by computers. Today the industrial world is highly interdependent and competitive.High cost of production or a day of production lost has a high impact on the company.In this challenging scenario, today the maintenance managers have an unenviable and daunting task of maintaining all the equipments and systems in the best of health to meet the needs of the industry.This is possible only by adopting the best of modern maintenance management techniques.

 

SELECTION OF CORRECT EQUIPMENTS

This is extremely important from the viewpoint of future maintenance.Unless the equipment /system chosen at design stage is suitable for the environment and duty of application, it is bound to give the maintenance team a tough time and recurring problems. It is,therefore,essential to consider all the design parameters while selecting and installing an equipment.

New technologies are being introduced in all products and equipments today to reduce the maintenance requirements or make them maintenance free.For example,earlier we had to check and add water often in our car radiator but today coolant is required to be added only during servicing.Also sealed maintenance free batteries have replaced the old lead-acid battries which required topping up of distilled water regularly.Maintenance free items are designed for a certain service life and are to be replaced after their useful service life.

The concept of Life Cycle Cost (LCC) has also gained ground in the western world and private sector in selecting equipments.Life Cycle Cost means the expected costs to be incurred during the design life of the equipment and consists of initial cost,maintenance cost,running cost etc.Here, instead of only the initial capital cost , the life cycle cost is considered for selecting an equipment.To take a real life example, suppose we want to buy a car,then if we compare cars not only on the basis of initial cost but also give due consideration to fuel efficiency,cost of spare parts etc then our selection is based on the concept of life cycle cost.Unfortunately,this concept is yet to be brought into practice by Indian Public Sector where selection of new equipments are solely based on the lowest capital cost which may not prove to be economical in the long run.

Proper installation and commissioning is also equally important. If an electrical panel is not properly tested or a pump is having high vibration at commissioning stage ,it surely requires corrective action at the beginning instead of waiting for failure.

 

 

 

COSTS INVOLVED

Let us have a look at the various costs involved in the maintenance activity:

Every company/enterprise is basically a business unit and hence it has to analyse all costs and try to minimize them for achieving competitive rates of production.It has ,therefore,to optimize the maintenance costs.The following graph shows :

 

 

 

MAINTENANCE SYSTEMS

The following are the types of maintenance systems in practice around the world :

Breakdown maintenance philosophy is generally adopted by companies for small and non-critical normal equipments where breakdown does not have a significant impact on production and cost of repair is low.

Maintenance service

500 km

2000 km

5000 km

20000 km

40000 km

Water pump drive belt

Adjust

Adjust

Adjust

Adjust

Replace

Engine coolant

Inspect

Inspect

Inspect

Replace

Replace

Engine oil

Inspect

Inspect

Replace

Replace

Replace

Engine oil filter

Inspect

Inspect

Replace

Replace

Replace

Spark plugs

 

 

Clean

Replace

Replace

Here the maintenance costs are quite high which is mainly the cost of maintenance manpower and spares parts consumed. By carefully scheduling and adhering to it the chances of pre-mature failures and major breakdowns can be minimized.This philosophy is mainly adopted for all critical and essential equipments.

For predictive maintenance expensive systems like vibration analysers,temperature monitors ,oil testing apparatus are required and hence this maintenance philosophy is adopted only for critical and some essential equipments. This is better than preventive maintenance as we save on cost of maintenance manhours and spare parts to some extent.This also saves us from sudden failures leading to production loss.Modern techniques such as infrared thermography and partial discharge analysis for HT machines are fast gaining ground. These are on-line non-destructive tests which help in health assessment of electrical systems and allow us to prevent catastrophic failures.

TPM strives to achieve overall equipment effectiveness through a combination of availability,performance efficiency and rate of quality products.

 

CATEGORIZATION OF EQUIPMENTS

As we have seen each type of maintenance philosophy incurs different costs to the enterprise.It is clear that any one type of maintenance philosophy cannot be applied economically to all categories of equipments.Hence,it is necessary to categorize the plant equipments as follows :

·        Critical

·        Essential

·        Important

·        Normal

After categorizing the equipment, a VEIN analysis chart can be plotted between degree of criticality of an equipment and type of maintenance requirements as shown below :

Critical

 

Essential

 

Important

 

Normal

 
 

 

 

 

 

 

 

 


Basically one has to distribute the equipment into a mix of breakdown maintenance (BM) and planned maintenance (PM).The planned maintenance can be further sub-divided into preventive and predictive maintenance systems depending upon the degree of criticality of the equipment.

If we look at the VEIN chart we observe that the Critical equipments have a small percentage of breakdown maintenance ( as breakdowns cannot be totally eliminated) and a high share of planned maintenance (PM).This trend reverses for equipments under the Normal category.The Essential and Important category equipments are in between. This kind of mix has to be decided upon as the direct cost of PM is high but the consequential cost of BM is also high. On this basis an organization can save on unnecessary PM costs and give the plant high serviceability and availability.This has to be continually updated with the feedback received along with the defect analysis and the down time analysis reports.

 

MTBF AND MTTR

These are two important concepts that every maintenance man must understand and analyse.

MTBF(Mean Time Between Failures) is basically the mean time between various breakdowns(failures) of a particular equipment over a certain period of time.A low value of MTBF indicates frequent breakdowns of the equipment.The aim is to achieve a high MTBF.

 

MTTR(Mean Time To Repair) is the mean of  time (calculated over a certain period of time, say one year) for which the said equipment was under repair after breakdown.It gives an idea as to how quickly the equipment could be repaired.A low MTTR value is desirable.

 

 

 

 


A

 

B

 

C

 

D

 

F

 

E

 
           

 

 

The above diagram shows the following sequence of operation for an equipment with respect to time :

Breakdown at Point A

Repair from A to B

In Operation from  B to C

Again Breakdown at C

Repair from C to D

In Operation from D to E

Again Breakdown at E

Repair from E to F

 

From the above we can calculate MTBF and MTTR for a period of time from A to F.

 

SPARE PARTS MANAGEMENT

Spare parts management is an important job parameter for a Maintenance Manager. Cost of spares account for about 60 to 80 % of total maintenance costs hence optimizing the spare parts inventory is of utmost importance. Before the era of computers, techniques like ABC analysis were employed as manually keeping track of each spare part was next to impossible. However, computers are now helping in the field of inventory management in a big way. The following needs to be done in this area of maintenance management :

·        Each spare part must be uniquely identified through some effective coding system

·        Spare parts linked preventive maintenance schedules must be drawn

·        Spare parts must be categorized as

1.      Regular spares: Required for scheduled maintenance after a fixed interval. For example, six monthly replacement of lube oil filters.

2.      One-off spares : These spares will be required mostly if some defect occurs. Most of the electrical and electronics spares fall under this category. For example, if fuses are blown as a result of some short-circuit, new fuses will be required for replacement after attending to the fault.

3.      Insurance spares : These are very high value and low consumption spares which may not be required for quite some time but their stockout cost implications are very high.The company can have some sort of rate contract with the OEM (Original Equipment Manufacturer) for supplying such items on need basis.

 

·        The company can also have some float assemblies like turbines,motors etc., depending on their population, to avoid production loss during scheduled overhauls.

 

THE HUMAN ELEMENT

The maintenance workforce is the most vital element which can decide the success or failure of a well conceived maintenance plan.

In multinational and private sector companies each and every employee has got well defined job responsibilities based on scientific work studies and he/she is well groomed/trained for the job. The Public Sector companies are mostly lacking in this basic area. As downsizing is normally not possible in government/public sector enterprises ,as a minimum the following measures shall be adopted for better productivity :

·        Clear cut job assignments and responsibilities

·        Measurable targets

·        Performance linked promotions and monetary incentives for motivation

·        Proper knowledge and skill training to handle the assignment

·        Building cost consciousness and safety awareness

 

ROLE OF COMPUTERS

Various Computerized Maintenance Management Systems are now available in the market. These vary from SAP like integrated ERP packages to small tailor made softwares and cover all dimensions of modern maintenance management such as

·        Preventive maintenance scheduling

·        Inventory management

·        Equipment availability and history records

·        Maintenance costs

·        Failure analysis (MTBF,MTTR)

 

By proper customization of these software based Maintenance Management Systems and applying modern maintenance management techniques,  the maintenance departments can streamline their operations and serve the industry in a more efficient, productive and cost effective manner.