Get fully solved SMU MBA Assignments
(May 2012)
Master of Business Administration - MBA Semester 4
“Operations Management” Specialization
OM 0015 – Maintenance Management (4 credits)
(Book ID: B1340)
ASSIGNMENT- Set 1
Marks 60
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.
Main functions
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.
Maintenance activities
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.
a. Silting
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
(May 2012)
Master of Business Administration - MBA Semester 4
“Operations Management” Specialization
OM 0015 – Maintenance Management (4 credits)
(Book ID: B1340)
ASSIGNMENT- Set 2
Marks 60
Note: Each Question
carries 10 marks
Q1. Describe ABC
analysis method used for classification for inventory control of
spare parts.
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.
Quantitative analysis
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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