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Master of Business Administration - MBA Semester 4
“Operations Management” Specialization
OM 0015 – Maintenance Management (4 credits)
(Book ID: B1340)
ASSIGNMENT- Set 1
Note: Each Question carries 10 marks. Answer all the questions.
Q1.a. Describe the three categories of maintenance activities
Answer : The irrigation network is perhaps the most costly element of an irrigation scheme and is designed to last a long time. However, all too often one finds that irrigation schemes not long constructed bear little resemblance to the original construction and design. Silt deposition, weed infestation, malfunctioning of structures and other undesirable situations make it practically impossible to control the flow in these canals. As a result, the system is unable to deliver the necessary water and distribute it equitably. It is not surprising that farmers working in those irrigation schemes sometimes feel frustrated because they know the potential benefits of irrigation and yet cannot realize their expectations.
On the other hand, there are many examples illustrating that with proper maintenance and cooperation among farmers in this task, irrigation systems may last much longer than their original designers or constructors ever envisaged. Irrigation schemes that have been in operation for centuries can be found in Spain, Egypt, Italy, Pakistan and other countries, and are a living testimony that properly maintained irrigation schemes can be of permanent benefit to many generations.
The Maintenance Service is entrusted with the overall responsibility for keeping the irrigation and drainage systems working in a satisfactory manner, within the limitations imposed by the initial design.
Similarly to the Operation Service, the main functions to be undertaken are:
- planning the maintenance activities;
- implementing the maintenance activities planned and those unforeseen;
- monitoring the above mentioned activities.
Planning the activities to be undertaken in the following year is particularly important in countries where government allocations for operation and maintenance are made on the basis of planned expenditure. A good justification of the work to be done and the consequences if it is not undertaken is of foremost importance to obtain financing for maintenance work. Even where this is not the case, planning the activities that can be executed within the limited resources available is a useful exercise.
Maintenance activities can be more easily undertaken in the off-season, as during this period, labour from the farming community is normally plentiful. Furthermore, if farmers are engaged in maintenance work on their own land for their own benefit, they' are more likely to work willingly. Also, operational personnel are more free at that time of the year and can be engaged to supervise or execute part of the maintenance work themselves.
A Maintenance Service requires data for good planning which can be obtained by regular monitoring. Without reliable data on costs for the different units of work and on productivity no realistic planning can be done. Later in this text, productivity data are given for machinery and manpower engaged in maintenance operations. They will be helpful when planning and costing activities if no better data are available, but a project should endeavour to have its own data based on the specific conditions of the area.
Types of maintenance
There are three main types of maintenance, namely:
- routine or normal maintenance which includes all work necessary to keep the irrigation system functioning satisfactorily and is normally done annually;
- special maintenance including repairs of damage caused by major disasters, such as floods, earthquakes and typhoons. The unforeseeable nature of such natural phenomena make it very difficult to take specific preventive action, although general safeguards can be installed in particularly prone areas, e.g. large drainage dykes in flood areas. In irrigation schemes located in places subject to these hazards, a "special reserve fund" or budget allocation should be established for repair work;
- deferred maintenance including any work necessary to regain the lost flow capacity in canals, reservoirs and structures when compared to the original design. It often includes large modifications to the canal system and structures arising from important changes (cropping patterns, drainage problems, etc.) that have occurred in an irrigation scheme. In practice, its difficult to differentiate between so-called 'deferred maintenance' and a 'rehabilitation programme'. The difference is mainly of a financial nature, because 'deferred maintenance' is normally undertaken with funds from the national budget allocated to operation and maintenance while rehabilitation programmes are considered as an investment and the funds come from a different source (loans, national development banks, etc.).
This chapter is mostly concerned with routine maintenance, and to some extent with deferred maintenance.
The maintenance activities for which the Maintenance Service is responsible should be clearly spelled out in the by-laws of the irrigation scheme. While some activities are clearly a responsibility of the Service (silt removal in canals, weed clearing, etc.), there are others not so precisely defined, for instance, rural roads, ancillary works, buildings, the cleaning of the drainage system. Nevertheless, it has 'been decided to include in the text all potential activities that could be the object of maintenance with a brief description of their characteristics and relative importance.
The maintenance activities have been grouped according to the major elements of an irrigation system; they are: (I) dam and reservoir; (ii) irrigation network; (iii) drainage network; (iv) rural road network and flood protection dykes; (v) pump stations; and (vi) ancillary works. They are described below.
1. Dam and reservoir
Maintenance activities in a reservoir itself comprise:
- controlling aquatic weeds,
- removing large debris (e.g. tree trunks) floating in the water that may damage hydraulic works,
- monitoring the water quality: not only from the salt content point of view but also from a biological standpoint in order to detect possible sources of pollution,
- surveying the solid deposition in the bottom of a reservoir.
These activities require little time because they are periodic with the exception of aquatic weed control, which is in any case only likely to be a severe problem in tropical and semi-tropical climates. However, they are extremely important in order to detect promptly the need for corrective action.
The most common water weed in reservoirs in semi-tropical and tropical areas is the water hyacinth (Eichhornia crazies). This plant represents a serious problem because it forms an ideal environment for mosquito larvae and has an evaporation several (2.2 to 13.4) times greater than an open surface of water. The plant has a very fast rate of growth: two plants can produce enough offspring to cover one acre in less than eight months.
Another frequent problem is eutrophication (over-abundance of nutrients in the water bodies) resulting in high production of blue-green algae and the associated phenomenon of lack of dissolved oxygen in the water. This problem, which is very serious if the water is used for urban water supplies, is less important when the water is used for irrigation, the main consequence of the latter being an increase of vegetation in the irrigation canals and greater weed infestation. Injecting compressed air into reservoir water has proved to be a satisfactory solution on several occasions but there are other techniques that can be applied.
The main maintenance activities for an irrigation dam are: lubrication of gates, anti-corrosion treatment, cleaning of debris, control of filters, and some other minor work. Earth dams require greater maintenance, especially the upstream slope where weed control is necessary once or twice a year. The electro-mechanical system of a dam must also receive proper maintenance, particularly electric engines, head gates, and the lighting system. The maintenance of these elements is rather specialized and the manufacturers of the equipment usually provide detailed instructions.
2. Irrigation network
The canals in irrigation networks are generally either of earth or concrete-lined and their maintenance characteristics are quite different.
I. Concrete - lined canals
Concrete-lined canals should require little maintenance, provided that they have been properly constructed and any potential problems studied (sub pressure, gypsum soils, swelling clays, etc.) and adequate technical solutions provided. One of the main reasons for constructing concrete-lined canals is precisely to reduce maintenance operations.
The routine activities include: replacement of joints, replacement of damaged concrete slabs, weed control in joints and on the surface of concrete slabs, control and treatment of filters, control and removal of silt. In the case of concrete flumes, chemical sterilization is also needed around the supporting structures.
Under normal conditions, the silting in concrete-lined canals is not an important problem since water velocity is high and sand traps and silting basins are often provided to reduce the solid content of the water. Heavy rain may cause deposition of solid materials if the berks are not properly formed. Drifting sand may be a serious problem in schemes surrounded by desert or bare land and subjected to strong winds. The most effective way of preventing this type of silting is to install windbreaks or barriers where sand accumulates before reaching the canal.
Removal of silt from concrete-lined canals is an expensive operation because it is mainly manual. Mechanical equipment can be used when specially adapted to avoid damaging the lining. In some irrigation schemes, the technique of flushing "quick water" through the canal is used to remove silt from one place and concentrate it in another where it can be more easily removed or disposed of. For this purpose, the canal should be run at its maximum capacity to reach the highest possible velocity.
Weed control should not be a major problem in lined canals, although aquatic weeds must be periodically removed. Later in the text, guidelines are given for weed control in both lined and earth canals.
The main problem in concrete - lined canals is cracking of the lining and eventual eruption of concrete slabs due to sub pressure. Apart from repairing the damaged lining, corrective action must be taken. Usually the installation of sub pressure valves is enough to relieve the pressure, but this involves major work. An alternative measure can be the construction of a subsurface drainage system to lower the water level.
ii. Earth canals
There are four main problems in earth canals requiring maintenance attention and, although they are closely interrelated, they will be treated separately.
Excessive sedimentation is perhaps the most common problem affecting the performance of earth canals. Mali (1978) identifies the following causes for canal siltation:
1. excessive silt entry at the main canal intake
2. disproportionate withdrawal by branches
3. prolonged heading up at control points
4. drifting sand
5. inadequate transport capacity of channels
6. re-entry of excavated material by rain and wind action
7. malfunctioning of intakes
8. haphazard sediment excavation
9. excessive weed growth
10. wrong channel regulation.
Causes 1 to 5 indicate defective design, 6 to 9 inefficient maintenance, while 10 denotes improper channel operation. Corrective measures for defective design are difficult to implement since they require major physical changes which imply heavy investments. However, the effects of defective design can be reduced by proper maintenance. For example, an erroneous angle between the parent branch and canal may induce the formation of a sand shoal which, if allowed to develop, will accelerate the silting process, thus compounding the consequences. Incorrect operation is also a major cause of silting. Canals carrying a heavy load of material in suspension should not be allowed to run at less than three quarters of their capacity since at lower capacities the velocity decreases inducing silting.
Abrupt shutting of gates, causing rapid changes in flow velocity, may induce bank erosion near the gates.
b. Weed infestation
Weed infestation can seriously impede the flow of canal water not only in tropical conditions but also in semi-arid and arid climates. There are two groups of weeds:
- earth weeds: they root in the soil and their habitat is not the water; they proliferate on the canal slopes and in the banks, benefitting from favourable soil moisture conditions;
- aquatic weeds: they can either root in the water or the earth but their habitat is in the water. Robson (1976) classifies them as follows:
· emergent plants - these are plants growing in the water and whose foliage emerges above the surface, e.g. the common read (Phragmites communes);
· floating leaved plants - there are two sub-groups with floating leaves: in one, the plants are rooted in the mud and their leaves float flat on the surface, in the other, plants are not rooted but free-floating on the surface;
· submerged plants - this group consists of plants whose foliage is totally submerged; a number of them produce flowers which emerge above the surface; one or two plants are free-floating, but most are rooted in the mud;
· algae - this group consists of a variety of algae of various forms, including unicellular algae and the large filamentous forms.
The relevance of the type of weed to the method of control will become apparent when control measures are discussed. Some of these weeds, such as nutgrass (Cyperus rotundus), are not only a problem in the operation of the canals but can become a menace for the farmers when water transports them into fields. There they reproduce rapidly and become a serious problem because of the difficulty of eradicating them.
Another hazard of weed infestation is the shelter and good breeding conditions they offer for vectors (mosquitoes, snails, etc.) of debilitating diseases.
c. Water infiltration
Water leaks through canal banks can be caused by burrowing small crabs and water rats or by rotting plants and roots which were not removed from the canal bank seat during construction. Ants are also known to be a problem even in concrete-lined canals. These leaks can be repaired by following the path of the leak through the bank either by hand digging or hydraulic backhoe if available and once the path has been found, the trench must be carefully backfilled and compacted. Canal leaks, if not repaired in time, can result in major breaches in banks causing far greater inconvenience and most costly repairs.
Water seepage through porous soils may also be a major concern. Seepage through banks can be considerably reduced by trenching them and burying a plastic membrane or thick slurry made from the excavated material. The trench is backfilled with sand after the barrier has been interred.
d. Erosion of banks
Canal banks can be eroded by heavy rainfall or wind, improper canal operation, stock grazing or passage by drinking animals, and the transit of vehicles. Heavy rainfall or wind can cause serious damage to unprotected banks. Seeding of grasses in the unwetted part of the canal is a cheap and effective protective measure. Short growing varieties (e.g. Agropyron riparium (streambank wheat-grass), Psathyrostachys juncea (Russian wildrye), Festuca ovina (sheep fescue) and Phleum bertolonii (dwarf timothy)) give good results.
Abrupt and rapid shutting off of canal water may also contribute to erosion of the banks. The practice of leaving a canal empty during the rainy season will contribute considerably to erosion of canal slopes.
Cattle and sheep damage the channel banks in different ways (Swales 1976). Cattle tend to push the moist bank material at the waterline into the waterway when they drink. Sheep, however, graze the banks bare thereby allowing wind and rain to wash away the bank material.
Erosion of canals can be repaired by mechanical means or manually by re-building the worn canal banks. However, care should be taken to construct a proper join between the old and the new part, otherwise the canal will deteriorate at the same place.
The most effective measures are of a preventive nature: such as seeding grass mentioned earlier, fencing the canals, and constructing special places for animal watering and bathing.
3. Drainage network
The retention in good working order of open drains includes the following operations:
- light deforestation
- weed control in the canal section
- seeding grass in the canal section
- maintenance of flow gauges and other measuring devices
- removal of silt
- maintenance of pumping stations where water cannot be evacuated by gravity.
For practical purposes, the maintenance of open drains is very similar to that of earth irrigation canals. However, all too often drainage networks receive much less attention than the irrigation ones. The result is that during heavy rain, when they are much needed, they do not work as they should.
Drainage maintenance should always be programmed from downstream to upstream, and as far as possible completed within an irrigation season. The intervals in regular maintenance should not exceed periods of 2-3 years between two consecutive cleanings.
Tile drains are subject to two main problems: (a) obstruction due to silting and plant roots, and (b) mineral deposits. The most common is the first. Mineral deposits of iron and manganese occur quite frequently in some irrigation schemes and the time necessary for such depositions varies widely from a few months to 30-40 years, depending on the mineral composition of the soil.
Methods for cleaning the drains are discussed later in this publication.
4. Rural road network and flood protection dykes
Rural roads are of vital importance in irrigation schemes, especially at harvest time. Many post-harvest losses can be avoided and better marketing facilities obtained by having a fully serviceable rural road network. Whether such networks should be maintained by the Project Management or by the local administrative divisions (village, district) is an internal matter than changes from country to country, and the appropriateness of one or the other position will not be discussed here. For comprehensiveness, it is assumed that such maintenance is the responsibility of the Project Management but let it be understood that this is not always the case. The same consideration applies to flood protection dykes constructed along river banks.
I. Types of roads and their upkeep
Maintenance requirements are different for each type of rural road; these are:
a. all-weather roads (paved)
- surfaced with bituminous macadam
- water-bound macadam
b. dust-roads or access tracks
c. berks of canal banks and dykes.
All-weather roads are mostly damaged during the rainy season combined with the action of traffic. Repairs imply removal of loose material, refilling of holes with the base and sub-base material, compaction of the layers and resurfacing. Most of these operations are normally manual except for the compacting which is done with heavy rollers pulled by tractors and the hauling of crushed material by trucks or trailer/tractor units depending on the haulage distance.
Macadam roads are more susceptible to damage than bituminous surfaced roads, but they are also easier to repair with the machinery normally available to maintenance units (scrapers, motor-scrapers). Dust roads deteriorate rapidly in rainy conditions and become unusable without proper maintenance. Unfenced roads can also be damaged by stock using the tracks. Repairs and maintenance can be greatly reduced by keeping the shoulder drains in good condition to evacuate excess water quickly. These tracks are usually graded by mechanical means for long stretches, whereas a small tractor-mounted blade is used for small sections. Grading can only be done when soil moisture conditions are suitable. This entails either waiting long periods before the machinery can be brought to the damaged places or in the other extreme, wetting the surface.
Maintenance of the berks of canal banks or flood protection dykes is similar to that for dust roads. Preventive measures, such as prohibition of traffic on banks and berks which are not supposed to be used by heavy machinery (trucks, tractors, etc.) may considerably reduce the maintenance needs. Flood protection dykes can be badly damaged in severe flood conditions and as such situations cannot be anticipated, their repair must be by so-called special maintenance, for which special budget allocations are needed.
5. Pump stations
Pumping stations for irrigation schemes may be:
a. main irrigation lift-pump stations (surface water or groundwater);
b. booster-pump stations for additional lifts in the main or branch canals;
c. drainage-pump stations.
The first two are usually of medium to high lift, required to pump forecasted quantities of water for long continuous periods. The last is usually for low lift with much larger quantities of water and required to operate intermittently. The irrigation pumps are usually manually controlled whereas the drainage station is frequently float controlled to ensure automatic starting once drainage levels in the scheme begin to rise above a pre-set level. A manual operator should also be on call even with an automatic control.
Operation and maintenance tasks for electric pump stations are comparatively simple, those for diesel operated a little more complex. The operators must be given clear instructions on safety measures, on the methods of starting the pump motors and the way in which they must be brought into full operation. Electric motors sometimes require to be stepped up in speed manually at a strictly controlled rate. Also canals may be damaged if all pumps come rapidly into full operation.
They must also be given a programme of irrigation quantities to be pumped i.e. 1, 2 or 3 etc. pumps to be operating. Where 24 hour pumping is not provided, account must be taken of the rate of rise and fall of canal levels in the irrigated area. It is of little use with a 12 hour pumping schedule if canals do not fill up until late in the morning and still remain full long after dark.
In case of an emergency, there must be some system for easy communication between the pump house operator and the officer in charge - either telephone or signal or runner.
6. Ancillary works
The hydraulic structures in an irrigation scheme include: gates, inlets, spillways, outlets, dividers, siphons, jumps, check dams and other minor structures. Maintenance of such items, when they are constructed in concrete, is restricted to the removal of silt and obstructions. The mechanical elements require periodic greasing. Iron elements require antirust treatment. The same applies to structures in drainage networks (culverts, drainage outlets) and those in road networks (bridges, culverts, crossings, etc.).
Administrative buildings and some other special installations (stores, workshops) require a certain amount of upkeep and should not be overlooked.
b. What are the three stages in the lifecycle management of any machinery?
Q2. What is the difference between MTBF and MTTR? How these to complement for
analysing the maintenance effectiveness.
Q3. For a good maintenance program, what types of requirements are planned?
Q4.a. Explain how breakdown, corrective and remedial maintenance contributes to the
maintenance management of an organisation
b. What are the advantages of Planned Maintenance?
Q5. Replacement of the old equipment with a new one is practiced as a policy to meet
competition. Assess why this issue of replacement is inevitable
Q6. Explain the steps involved in maintenance planning
Get fully solved SMU MBA Assignments
Master of Business Administration - MBA Semester 4
“Operations Management” Specialization
OM 0015 – Maintenance Management (4 credits)
(Book ID: B1340)
ASSIGNMENT- Set 2
Note: Each Question carries 10 marks
Q1. Describe ABC analysis method used for classification for inventory control of
Answer: The ABC analysis is a business term used to define an inventory categorization technique often used in materials management. It is also known as Selective Inventory Control. Policies based on ABC analysis:
· A ITEMS: very tight control and accurate records
· B ITEMS: less tightly controlled and good records
· C ITEMS: simplest controls possible and minimal records
The ABC analysis provides a mechanism for identifying items that will have a significant impact on overall inventory cost, while also providing a mechanism for identifying different categories of stock that will require different management and controls.
The ABC analysis suggests that inventories of an organization are not of equal value. Thus, the inventory is grouped into three categories (A, B, and C) in order of their estimated importance.
'A' items are very important for an organization. Because of the high value of these ‘A’ items, frequent value analysis is required. In addition to that, an organization needs to choose an appropriate order pattern (e.g. ‘Just- in- time’) to avoid excess capacity.
'B' items are important, but of course less important, than ‘A’ items and more important than ‘C’ items. Therefore ‘B’ items are intergroup items.
'C' items are marginally important.
One of the most important considerations of control is the value of annual consumption of inventory items in a year .
Ø Only a small number of inventory items consume a very large share of inventory consumption during the year.
Ø A little larger number of inventory items covers a moderate share of annual inventory consumption.
Ø A very large number of items just cover a very small share of annual inventory consumption.
Ø These acts gave birth to the concept of ABC analysis.
STEPS IN ABC ANALYSIS
The steps in computing ABC analysis are:
a Determine the annual usage in units for each item for the past one-year.
b. Multiply the annual usage quantity with the average unit price of each item to calculate the annual usage in US$ for each item.
c. Item with highest dollar usage annually is ranked first. Then the next lower annual usage item is listed till the lowest item is listed in the last.
d. Table 1 shows ranks of the items according to the annual usage in US$. for 10 items.
e. Arrange the items in the inventory by cumulative annual usage (dollars) and by cumulative percentage. Categorize the items in A, B , and Categories.
Ø It has been observed that in an industrial unit only
Ø 10% of items have 70% of the annual inventory consumption,
Ø 20% of the items have 20% of annual inventory consumption.
Ø 70% of the items have only 10% of the annual inventory consumption.
Ø Since 70% of the annual consumption o inventory is covered by only 10% of the
Ø items in the inventory, these items deserve highest attention and are classified as A ‘items.
Ø Similarly 20% of the items covering 20 % of the inventory investment are B class items
Ø Balance 70% of the inventory items are termed as C class items.
Limitation of ABC analysis
Ø It doesn’t take into account the criticality of an item
Ø It might be possible that item tagged in C category might be crucial for the functioning
Ø So sometimes it is being implemented along withed to overcome this issue
Q2. Why scheduling the maintenance activities is an important process in
management and what benefits will accrue to the organisation?
Q3. What is called as Universal Maintenance standards? What are the techniques
used in UMS system?
Q4. A machine is purchased for Rs.300000. It is expected that this machine will
be used for 12 years, at the end of which it will be sold for Rs.15000.
Calculate the depreciation to be charged for each of the first 3 years of the
machine’s life, using: (I) The straight line method (ii) The reducing balance
method at 30% pa
Q5. Briefly explain eight pillars that support TPM in an organisation?
Q6. a. What are the objectives served to a firm by practicing good craft and
b. What are the objectives served by practicing Autonomous Maintenance
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