s of fuel is a coal. The handling of this
fuel is a great job. To handle the fuel i.e. coal, each power station is equipped with a coal
handling plant. Almost all CHP these days implies Reactive Maintenance with support of
preventive maintenance. Under the current business environment, cost competitiveness,
effective maintenance management has been accepted as the key to corporate strategy for
reduced costs. This has led to integration of maintenance management function with
production and business problems, not just equipment problems. The failures of
equipments have led to high maintenance and operation costs.

Implementation of modern
concept of Condition Based Maintenance can appreciably reduce maintenance costs and
enhance reliability of machine performance.


The concept of condition-based maintenance, discussed in this paper for Coal Handling
Plant is to offer significant benefits. The system introduced in this paper will measure and
detects the onset of a degradation mechanism thereby allowing casual stresses to be
eliminated or controlled prior to any significant deterioration in the component physical
state. Guidelines for implementation of CBM in CHP are also discussed in this paper.
2.0 Introduction: -
CBMS or Predictive Maintenance methods are an extension of preventive maintenance
and have been proved to minimize the cost of maintenance, improve operational safety
and reduce the frequency and severity of in-service machine failures. The basic theory of
condition monitoring is to know the deteriorating condition of a machine component,
well in advance of a breakdown.
There are varieties of critical equipments in Coal Handling Plants. These components
require routine inspection to ensure their integrity. The purpose of the inspection is to
identify any degradation in the integrity of the systems during their service life and to
provide an early warning in order that remedial action can be taken before failure occurs.

Assessing the condition is necessary to optimize inspection and maintenance schedules,
of Coal Handling Plant to make decisions and to avoid unplanned outages.

3.0 Importance of CBM for CHP: -
To maintain an efficiently operating unit and avoid failure of critical equipment, it is
necessary to maintain the critical parts of that equipment. The effect of planned
maintenance is depending upon the methods used for maintenance. The combination of
corrective preventative and condition based maintenance will required to apply for
Critical Equipments.

This type of maintenance policy and strategy will improve
performance of CHP through availability of Critical Equipment.
The basic layout of Coal Handling Plant is shown by block diagram. (See Fig. No 1) the
coal is unloaded at unloading station and transported by conveyors to crushing and
screening plant via transfer house. After crushing required quantity of coal is transported
to bunker via transfer house and remaining coal is stored in stockyard. This coal is
reclaimed as per requirement.
There are different streams for transporting of coal. The streams are operated as per
requirement. Some of the CHPs are now days are operating beyond their design lives.
Working conditions in CHP are dusty, dirty and often wet conditions. So there is a
constant quest to improve machine uptime and avoid unplanned maintenance. A plant,
which supply of coal to boilers having capacity of 750 tones per hour failed to fulfill need
will loss generation of 0.6 MU for one hour. This cost 1.20 Core of Rupees.
















Unloading Unit
No 2
























Crushing Unit
No 2
Feeder
No4
Direct coal
from coal
mine by aerial
rope way
Conveyors for

Stream A
Stream B
Stream C
Stream D
Stream E
Feeder No 5
Unloading Plant No 2
Figure No 1
Wagon Tippler No 1
Vibrating screen No1
Crusher No1
Primary Crusher
Vibrating screen
Secondary Crusher
Crushing
Unit No 1
Feeder No1
Feeder No2
Feeder No3
Bunker
Transfer
house 3
Stacking and reclaiming

Transfer house
2
Transfer house 1
Unloading Plant No
1
Crushing and Screening
plant
Transfer
house no 4
Unloading Unit
No 1
4.0 Objectives of CBM: -
The main objectives of CBM for CHP should be as follows
1. Establishing an alarm level based on the variations of a physical parameter like
vibration, power consumption, temperature etc. 2. Prediction of impending failures of critical plant components like Crusher Rotors,
Conveyor Pulley Shafts, in real time resulting in enhanced safety, operational
reliability, availability, and maintainability.
5.0 Condition Monitoring Implementations: -
The steps in implementing CBM are
1. Divide Plant For Ease Of Maintenance
2. Detection Of Physical Parameters
3. In Service Examination By Using NDT
4. Analysis or Fault Diagnosis
5. Correction.
5.1 Divide Plant For Ease Of Maintenance: -
Coal handling plant should be divided into five [1] sections for ease of CBM.
°
Unloading Units
°
Feeding Units
°
Crushing and Screening Units
°
Stacking and Reclaiming Units
°
Bunkers
5.1.1 Unloading Plant: -
These comprise of unloading units. The types of unloading units are depending upon the
transport mode of coal.
The transport mode of coal is as follows.
1. Aerial ropeway
2. Railway
3. Road ways
4. Ship
5.1.2 Feeding Plant: -
This comprises of various types of feeders. The use of dozers and mobile equipments are
done for feeding purpose. The efficient and economical storage, movement and control of
large tonnage coal handling installations, coal car unloading, storage, reclaim system
depend on the proper application of feeders.
The various types of feeders being used in coal handling plant are:
1. Apron feeder
2. Belt feeder
3. Rotary feeders
4. Reciprocating feeders
5. Screw feeders
6. Revolving disc feeders
7. Vibrating feeders
5.1.3 Crushing and Screening Plant: -
This comprises the belt conveyors within the crushing and screening plant, the crushers
and the screens. Coal from the mines varies to great extent in its size. So it is required to
crush upto required size. For this various types of crushers are used. There are four basic
ways to reduce material: by impact, attrition, shear or compression. All crushers employ
one, or a combination of these four methods. These ways are given below
1. Impact
2. Attrition 3. Shear
4. Compression
The coal, which of required size, is not required to crush. To avoid entry of proper size
coal in crusher the screens are used.
5.1.4 Stacking and Reclaiming Plant: -
After unloading of the coal, required quantity of coal is to be bunkered. The remaining
quantity of coal is to be required to store. This store coal can be reclaim as per
requirement.
5.1.5 Bunker: -
Generally bunkers are located in boiler house of the power station. The bunkers are
equipped with bins. These bins are feed by mobile conveyors or travelling tippers. The
bunker slots are secured by grates and are covered with trailing belts.
5.2 Detection Of Physical Parameters: -
The basic theory of condition monitoring is to know the deteriorating condition of a
machine component, well in advance of a breakdown. There are many parameters that
can be measured, trended and analyzed to detect [2] imminent failure or onset of
problems. It involves measuring physical parameters level at marked locations on each
machine on a regularly scheduled basis. The objective is to reveal significant increases in
a machine's parameter level to warn of developing problems Common among them are:
1. Vibration
2. Lube oil analysis including wear debris analysis
3. Additionally, operational characteristics such as Coal flow rates; Conveyor speed and
so on can also be monitored to detect problems.
5.2.1 Vibration Monitoring: -
Each machine in the best of operating condition will have some vibration, which may be
regarded as normal or inherent. Whenever machinery vibration increases beyond safe
limits, the usual reasons are unbalance, misalignment, worn gears or bearings, looseness,
etc.
Mass unbalance, bowed shafts and cracked shafts, these being amongst the most common
rotor-dynamic faults within a rotating machines. Vibration response measurements yield
a great deal of information concerning any faults within a rotating machine. Critical
machines of Coal Handling plant like Crushers can be continuously monitored by
providing of permanently mounted vibration transducers.
5.2.2Temperature Monitoring: -
The temperature limit [3] of a component is defined as the peak temperature where the
material characteristics of a component are still within the range, which allows a full
satisfactory function and structural integrity. Whenever this limit increases, beyond safe
limit, the common reasons are improper bearing lubrication, increase friction in the gear
mesh, in the bearings, at the seals and hydrodynamic friction between the lubricant and
the moving components.
In Coal Handling plant by providing of permanently mounted temperature sensors can
continuously monitor Gear-Box of Critical Conveyor, bearings of Crushers. The use of
infrared cameras or installing thermocouple sensors in the housing of a bearing and
measuri