NOTES - 12
EQUIPMENT
MANAGEMENT TIPS FOR THE CONSTRUCTION ENGINEERS
AND
PLANT & MACHINERY ENGINEERS
AN
INTRODUCTION TO CONSTRUCTION PLANT AND EQUIPMENT
PREVENTIVE
MAINTENANCE AND REPAIRS
1.0 INTRODUCTION
1.1 All equipment
deteriorates with age or usage. This is more so for construction equipment,
specially the heavy earthmoving equipment which has to work under many rough
conditions, such as extreme temperatures, wet or muddy ground, dust, rocky
strata, altitude, rain and snow. The chances of failure in operation can be
reduced by a proper plan of preventive maintenance; and fall in Production
Capability can be made good through suitable and timely repairs and
replacements.
2.0 Proper maintenance
of plant and machinery and services can make a valuable contribution to the
overall productivity. Spare parts management as a part of a sound policy of
preventive maintenance would go a long way in improving maintenance and
increasing productivity.
3.0 Systematic and
regular maintenance of construction equipment is an essential part of
construction equipment management for smooth, uninterrupted and economical
operation of the equipment.
4.0 OBJECTIVES
4.1 Construction
Industry should have a well organised maintenance department to take charge of
the works connected with the repair, reconditioning and overhauling of the
equipment so as to prolong their life to the extent it is economically
possible. The objective of maintenance would be :
a) To maximize
availability of machinery and facilities needed for smooth production.
b) To minimise
downtime due to breakdown of machinery.
c) To ensure long life
of the machinery to avoid high rate of depreciation of capital.
5.0 FUNCTIONS OF
MAINTENANCE DEPARTMENT
5.1 Maintenance
function is getting more importance in day to day management activity because
of the realisation of its potential in improving over-all productivity. The
various functions of maintenance department can be specified as under :
Equipment Maintenance
This is an important
function of the maintenance department. The maintenance include provision for
all types of maintenance as mentioned below :
a) Break-down
maintenance
This practice allows
the machine to continue in service without much of routine attention till it
actually breaks down. After repairs the machine gets attention only when it
breaks down again. This practice is allowed only for those machines which are
non-critical for production.
b) Scheduled
maintenance
This procedure is
adopted to retard the wear and tear of moving parts to get proper function of
facilities. This involves replacement of fast moving items such as fitters,
seals, bearings, fan belts and periodical lubrication etc. It is found that
about 70% to 80% of the maintenance will con under scheduled maintenance and
the balance will be unscheduled. The advantage of scheduled maintenance is that
there will be minimum down time and required spare parts ordered in advance.
This practice estimates the time, materials and costs involved, assign the jobs
to manpower available.
c) Unscheduled maintenance
The unscheduled
maintenance is to be undertaken due to a major defect found by the operator
which has to be set right immediately or from the break down and accidents.
d) Preventive
maintenance
This preventive
maintenance is precautionary measures taken to retard the expected failure
after certain working hours due to wear and tear of components. This involves
checking, adjustment, routine replacement, lubrication, servicing to avoid
failure due to wear and tear and to ensure availability of machine for
production. This practice renders itself to accurate planning and scheduling
which gives the following benefits :-
i) Less production
down time
ii) Less maintenance
operation cost
iii) Fewer major
repairs
iv) Reduced repair
costs as less manpower and fewer parts are need for planned shutdown than for
breakdowns
v) Efficient spare
parts control with optimum inventory stock
vi) Less stand by
machines reducing capital investment.
vii) Less stand by
machines reducing capital investment.
viii) Improved safety
conditions
Preventive maintenance
is the backbone of the entire maintenance programme. The maintenance work is to
be entrusted to experienced personnel in such works. Normally the deficiencies
in the equipment can be found from operator, regular preventive maintenance
inspections, technical reasons for an unusual breakdown/accident. Most
deficiencies are detected by inspection and can be corrected by scheduling the
repair so that down time is minimised.
e. Overhauling and
reconditioning
The constant use of
machine causes slow wear and tear of components. After certain hours of life,
the machine fails very frequently resulting in higher maintenance costs. At
that stage it becomes necessary to take the machine for major overhaul and
reconditioning. The process consists of complete stopping and examination of
every component of the machine cleaning, adjusting, repairing and replacing the
worn out parts etc.
5.2 Problems of
maintenance
Vehicles and equipment
abuse and misuse are the causes of increased repair costs and non-availability
of equipment. The following are few examples of equipment abuse :-
a. Cannibalization of
parts
b. Tampering with
governors
c. Running engines at
high speeds and beyond normal operating temperatures.
d. Operating equipment
with insufficient oil
e. Overloading
f. Operators,
mechanics not properly trained
g. Use of inferior
quality spares.
Maintenance teams can
prevent such department abuse through preventive maintenance inspections and
surprise checks.
6.0 Inventory
Management
Inventory management
includes standardisation of equipment, Inventory control of spares, numbering
system of equipment, keeping records, storage of equipment and their security.
6.1 Standardisation of
equipment
Standardisation is the
utilisation of identical equipment or equipments with identical/interchangeable
components. A limited degree of standardisation can be achieved by the use of
the same type of engine, similar attachments or components. There are several
advantages in standardisation of equipments which are as follows :
a. Interchangeability
of spare parts-less down time of machine and less inventory cost.
b. Lower maintenance
and labour is simpler.
c. Training of
operators, mechanics is simpler.
d. Owner enjoys better
relationship with his dealer.
The major
disadvantages of standardisation of equipments is the total breakdown of the
entire feet if any major design defect occurs in one equipment.
6.2 Inventory control
of spares
In most developing
countries, plant and machinery have to be used for longer periods far beyond
their normal economical lives. This obviously leads to greater problems in
spare parts management. The consumption of spare parts vary according to the
following factors:
a. Continuity of
operation of equipment
b. Environment
c. Quality of
manufacture of spares
d. The conditions of
machinery and equipment
e. Skill of operators
f. Proper maintenance
of equipment
g. Skill of mechanics
h. Availability of
special maintenance tools and equipment
i. Technological
obsolescence of equipment
j. Determination of
spares due to improper storage
6.2.1. The spare parts
management would include the procurement of spares at right time, right
quantity, at right price and right quality from a right source. The management
should give guidelines for proper preservation of spare parts to avoid
deterioration in stores.
6.2.2. The spare parts
planning will include the purpose of carrying inventory of spares, forecasting,
average demand of previous time periods. While arriving at the stocking levels,
the desired service level, the cost and the procurement lead time should be
taken into account. A continuous monitoring of the inventory becomes an
important part of planning spare parts.
6.2.3. ABC analysis is
well known technique in inventory management. The items are grouped as per the
annual consumption in monetary value to facilitate selective control. About 5%
of the items (called 'A' items) will account for about 75% of the total value
of annual consumption. About 15% of the items (called 'B' items) will account
for 20% of the total value. Balance 80% of the items (called C items) for 5% of
the total value.
6.2.4 Allied to ABC
analysis is the VED analysis where the spares are classified into :
Vital (V)
Essential (E)
Desirable (d)
6.2.5 Vital spare
parts are those which vendor the equipment totally in-operative when out of
stock and consequently must be held in stock at all times. Essential parts
affect the performance of the equipment. These spare parts are essential for
the operation of the equipment but could result in expensive procurement and
stocking. Desirable parts are not functional and do not affect the performance
of the equipment and are not likely to cause major disruption.
6.2.6. A few systems
for better control of inventory are briefly dealt with below :
a. Fixed order
quantity system
Under this system the
quantity of an item ordered is kept constant while the time of placement of the
order varies with fluctuations in usage/demand.
b. Fixed internal
system
The order is placed at
fixed interval of time with quantities ordered varying from time to time.
6.3 Equipment history
A suitable numbering
system for equipments should be adopted to identify each machine. The history
of the machine throughout its working life should be recorded including the following
details.
a. Date of purchase -
ownership charges
b. Hours or working
c. Details of
operators
d. Lubricating oil
change record
e. Details of spares
fitted and life of spares
f. Depreciation
g. Overhauls carried
h. Replacement of
major assemblies
i. Operating costs
j. Battery record -
Recharging, Replacements etc.
k. Tyre record
6.3.1 The history of
the equipment will enable timely replacement of spares/maintenance depending
upon the number of hours/years of usage.
6.4.0 Storage of
equipment
Equipment should be
stored carefully and protected during the ideal period as it will deteriorate
faster. If the equipment is kept for a short term it will normally be left in
open storage yard with a cover. The following measures should be taken during
short term storage :
a. Start equipment
once a week to keep parts lubricated and battery charged.
b. Cover exhaust pipes
during storages.
c. Tyres to be
properly inflated and the position of equipment changed often.
d. Fuel tanks to be
locked.
e. Oil levels should
checked.
f. Avoid dust/dirt
entering the systems. Check wind direction at storage yard.
g. Guard from
pilferages and fire risks.
6.4.1 The equipment
should be protected carefully during long storage. The following are some of
the measures to be taken.
a. Store under a good
covered accommodation
b. Batteries and Tyres
are removed and preserved as per the technical instruction.
c. Seal all entrances
to internal parts of engine, transmission, Hydraulic, lubricating system.
d. Exhaust pipes to be
plugged.
e. All electrical,
rubber components to be preserved.
f. Ensure security and
fire precautions
g. Prevent pilferages
7.0.0 Documentation of
maintenance data and evaluation of maintenance performance.
The proper
documentation of maintenance data should be maintained machine wise regarding:
a. Types of break
downs and frequency of occurrence
b. Parts replaced and
period of service
c. Planned periodic
inspection dates
d. Cost of maintenance
of the machine
e. Display of
maintenance charts, Schedules, aids
7.1.0 The function of
maintenance department is to take corrective action if its performance is not
upto desired level. The performance can be quantified by use of maintenance
indices, some of them are:
a. Percentage machine
down time :
Machine hours lost due
to maintenance
=
--------------------------------------- x 100
Total calendar hours
during that period
b. Percentage
maintenance cost :
Total expenditure in
maintenance x 100
=
----------------------------------------
Total value of output
c. Percentage utilisation
:
Total hours worked
=
------------------------------------- x 100
Total hours available
during that period
d. Inventory Index:
Cost of maintenance
spares used
=
---------------------------------------------
Total cost of
maintenance spare stock in hand
8.0
Modern Maintenance Techniques
The oil and wear
analysis (OWA) method is used to detect excessive wear of lubricated parts
inside the machine that may lead to critical machine trouble. The presence of
metal particles from worn-out parts in the lubricated oil indicate the level of
wear of components inside the machine. When the wear of some components is high
then the amount of metal particles in the oil will be excessive and this
abnormal condition warrants, timely replacement of worn-out parts. Centralised
lubricating points have been developed in modern machines for easy lubrication
of inaccessible parts. Electronic sensing devices are fitted on major
assemblies such as engine, gear box, transmission system to give the operator
early warning of any abnormal wear in the systems.
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