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Topics
Definition of Preventive Maintenance (PM)
Reasons for the increased need of PM
Advantages of a PM system
Risks of running a PM system
When to use a PM system
The law of PM
Guide to a successful PM system
Execution process Conclusion
Readings
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What is Preventive Maintenance?
Preventive maintenance is a schedule of
planned maintenance actions aimed atthe prevention of breakdowns andfailures. The primary goal of preventivemaintenance is to prevent the failure of
equipment before it actually occurs. It isdesigned to preserve and enhanceequipment reliability by replacing worn
components before they actually fail.
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Reasons for the need of a PM system
Increased Automation
Business loss due to production delays
Production of a higher quality product
Just-in-time manufacturing
Need for a more organized, planned environment
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Advantages of a PM system
Reduced production downtime, resultingin fewer machine breakdowns.
Better conservation of assets and
increased life expectancy of assets,thereby eliminating prematurereplacement of machinery andequipment.
Timely, routine repairs circumvent fewerlarge-scale repairs.
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Continued -
Reduced cost of repairs by reducing secondary failures. When partsfail in service, they usually damage other parts.
Better quality products
Identification of equipment with excessive maintenance costs
Improved safety and quality conditions.
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Brainstorming Exercise
Are there any risks of running a PM system?
If there are risks when would it be a good time to use PM?
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Potential errors or damage
of a PM system
Damage to an adjacent equipment during a PM task.
Reintroducing equipment mortality by installing new parts ormaterials.
Damage due to an error in reinstalling equipment into its originallocation.
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When Does Preventive Maintenance Make
Sense
This is a logical choice that considers two conditions
- #1. The component in question has an increasing failure rate.
- #2. The overall cost of the preventive maintenance action must be less than theoverall cost of a corrective action.
If both of these conditions are met PM would make sense
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The Law of PM
Higher the value of the plant assets andequipment per square foot of plant, thegreater will be the return on a PM program.
E.g. - downtime in an automobile plant assembly line at one
time cost $10,000 per minute. Relating this to lost productiontime an automobile manufacturer reported that theestablishment of a PM program in their 16 assembly plantsreduced downtime from 300 hours per year to 25 hours peryear. With results such as this no well-managed plant can
afford not to develop a PM program.
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How to determine the optimum age of
replacement?
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How to determine the optimum age of
replacement?
A more technical approach.
Where:
R(t) = reliability at time t.
CP
= cost of planned replacement.
CU= cost of unplanned replacement CPUT(t) = The optimum replacement time
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The key for a successful PM system
Scheduling Should be automated to the maximum extentpossible
Execution Should be done before the actual break downoccurs.
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Execution
The Bath Tub Model Three
stages of new parts1. Infant morality stage
2. A fairly long run stage
3. Wear out stage
Traditional View according toBath Tub Model Replacecomponents just before theyentered wear out stage
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Execution
Traditional view says
Wear out stage = Increased rate of failure.
Point to Ponder
Since, wear out stage represents increased rate of failure,wouldnt it be plausible to execute the PM program at this stage?
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What really should PM focus on?
Cleaning Found through testing Lubrication and inspection
And correcting deficiencies
Predetermined parts replacement
should be minimal and done onlywhere statistical evidence clearlyindicates wear-out characteristics
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In the absence of data
Age exploration programs
Statistical analysis
Cost shouldnt be a primary factor in deciding against data collectionfor a PM
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Motivating Preventive Maintenance
Workers
Training programs most effective
Establish inspection and preventive maintenance as a recognized,
important part of the overall maintenance program.
Assign competent, responsible people to the preventive maintenanceprogram.
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Continued -
Follow-up to assure quality performance and to show everyone that managementdoes care.
Provide training in precision maintenance practices and training in the righttechniques and procedures for preventive maintenance on specific equipment.
Set high standards.
Publicize reduced costs with improved up-time and revenues, which are the resultof effective preventive maintenance
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Summary
PM is not difficult to achieve. It is an essential part for cost reduction
There is an element of risk involved in PM
Careful planning and execution will reduce the risk of PM
The biggest benefits of a PM program occur through painting,lubrication, cleaning and adjusting, and minor componentreplacement to extend the life of equipment and facilities.
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Why and what has to be maintained
on breakers ?
Case
Mechanism
Arc chute
Main contacts Control unit
Connection systems
Auxiliary Devices
Communication system
Example for Breaker Maintenance
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Maintenance of case Function of case :
- isolate the main contacts and protect from arcingeffects
- support the mechanism, tripping device, auxiliarydevices, terminals
- Must withstand the stresses during short circuit
Damaged case is the consequence of
- shocks,
- moisture,
- high short circuit,
- overheating ( loose connection)
Preventive maintenance includes :
- visual inspection of dust, dirt, grease, moisture,cracks, soot,
- cleaning, ( dust, dirt, soot,) with dry cloth, brush orvacuum cleaner
- replacement in case of cracks
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Maintenance of the mechanism
Breaker mechanism
- Spring energy on Masterpact- Tumbler on Compact NS
- operate the contacts to establish and interruptthe circuit
Chassis mechanism
- to rack in and out the breaker, test the breaker
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Jammed mechanism is the consequence of :dust :
shocks : bending of mechanical partcorrosive atmosphere : rust and corrosionof metallic partNo operation for a long time
Preventive maintenance includes :dust removal : vacuum cleanerrecommendedcleaning : dry cloth, brush, solventprohibitedgreasing : only Schneider recommendedgreases, in small quantity
operation of breaker / chassis : to give thespring charged energy and themechanism their original characteristics
Maintenance of the mechanism Contd.
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Maintenance of the arc chute (Power breaker only)
Function of arc chute :- splitters : extinguish the arc and
absorb the energy under normalcondition and electric fault- filter : blow the pressured gas
out , cool down the gas
Arc chute deteriorates- under In : the insulation material
of the arc chamber can perforate- under Icc : the metal part is
vaporised
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Maintenance of main contacts (Power breaker only) Contd.
Arc chute in bad condition may resultin a non interruption of the arc,
decrease of the isolating function andultimately destruction in case of highshort circuit current.
Filters : avoid compound (made ofdust + grease) covering the filter
Preventive maintenance includes :periodic inspection after a fault :splitters should not present holesand be too thin, plastic part shouldnot have holes ( decrease of
insulation level)replacementcleaning of filter
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Maintenance of main contacts (Power breaker only) Function of main contacts :
- To make or break the circuit under normal (
In) or fault conditions (overload and Short-circuit )
Contacts get worn during each mechanicaland electrical open / close operation andafter short circuit ( maxi 2 cycles at Icu)
Worn contacts will result in :
- over heating of the breaker ( increase ofcontact resistance)
- decrease of life expectancy
- measurement of individual pole resistance- replacement
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Worn contacts will result in :over heating of the breaker ( increase of
contact resistance)decrease of life expectancy
Preventive maintenance includes :periodic visual check, control of themechanical contact wear indicator and
electronic wear indicator on Micrologic P &Hmeasurement of individual pole resistancereplacement
Preventive maintenance includes :periodic visual check, control of the
mechanical contact wear indicator andelectronic wear indicator on Micrologic P &H
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Maintenance of electronic control unit
Function of control unit :
- permanently analyse the phase current compare it to the protection set and in case of fault
trips the breaker
Control unit is sensitive to :
- environment : ambient temperature, humidity, corrosive atmosphere,
- operating conditions : vibration, electro-magnetic field,
A malfunctioning of the trip unit will result in :
- a non interruption of the fault current
- damage of equipment and breaker
Preventive maintenance includes :
- periodic push to trip test or trip test- control of the complete tripping channel
- curve adjustment
- saving of log event, settings ( Micrologic P & H)
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Maintenance of thermal-magnetic trip unit
Function of thermal-magnetic trip unit :
- Connected permanently in series with the phase currents
- based on the bending of a bimetal for overload and the movement of a magnet in a strongmagnetic field
Thermal -magnetic trip unit is sensitive to :
- ambient temperature, corrosive atmosphere
A malfunctioning of the trip unit will result in :
- a non interruption of the fault current
- damage of equipment and breaker
Preventive maintenance includes :
- primary injection test to trip the breaker
M i t f ti t
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Maintenance of connection systems Function of connection systems :
- Link together various types of devices by mean of electricaldistribution systems (bus bars, cables, auxiliary wires, ).
Bad connection ( too tight or too loose) will result in :
- Thermal effect leading to destruction of devices
- short circuit or fire
Preventive maintenance includes :
- For fixed connectors : No need of control if done with Schneiderrecommendation . otherwise : check temperature rise, if loose,dismantle and tighten with new screws, bolts & washers
- For sliding connectors : (mainly chassis)
- periodic cleaning and greasing with Schneider
recommended grease
- if corrosive atmosphere ( SO2 / H2S) : clean withspecial solution ( Thioure) and re grease
- Wires : check tightening and the insulation material
i f ili d i
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Maintenance of auxiliary devices
Function of auxiliary devices :
- Shunt trip release, under voltage release, OF contacts,
SD/SDE alarm contacts , electrical motor MCH Malfunctioning of the auxiliary device will result in a wrong
operation of the breaker
the consequences can be :- no safety operation ( emergency)
- wrong operation in the circuit
Preventive maintenance includes :- functional test of auxiliary device at nominal voltage
- replacement
PPM S h d l F T hi (M i P l)
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PPM Schedule For Township(Metering Panel)
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Sl No
Name of the
Cluster
Name of
the block
Date of PPM to
be carried outPPM start time PPM end time
Activity to be carried out
1 A & B 11/5/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
2 C & D 11/6/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
3 E & F 11/7/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
4 G & H 11/8/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
5 J ,K & L 11/9/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
6 M & N 11/10/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
7 O & P 11/12/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel )
cleanning & all Basbas & cable conection check &
tightness
8 Aminety 11/15/2012 9:00 15:00
Electrical Panel Cleaning & all busbar & cable connection
check & tightness
9 A & B 11/16/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel)
cleanning & all Basbas & cable conection check &
tightness
10 C , D & E 11/17/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel)
cleanning & all Basbas & cable conection check &
tightness
11 F & G 11/19/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel)
cleanning & all Basbas & cable conection check &
tightness
12 J & K 11/20/2012 9:00 15:00
All eletrical panel( Metering Panel, Utility Panel)
cleanning & all Basbas & cable conection check &
tightness
13 Aminety 11/21/2012 9:00 15:00
Electrical Panel Cleaning & all busbar & cable connection
check & tightness
Koel
Sankha
PPM Schedule For Township(Substations)
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34
Sl No
Name of the
Cluster
Name of the
block
Date of PPM to be
carried outPPM start t ime PPM end time
Activity to be carried out Efected Area
1 LT Panel # 6 1-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness
SA/SB,SC/SD,WTP,PROJECT
OFFICE,KA/KB,KC/KD/KE,
KF/KG,KH/KJ,KF/KG
2 LT Panel # 7 2-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness
SE/SF,SG/SH,SJ/SK/SL,
SM/SN,SO/SP,COMMERCIAL
LT Panel # 5 3-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness SPARE
3 LT Panel # 3 4-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness
STUDIO/MA/MB,MC/MD/ME,
MF/MG
4 LT Panel # 4 5-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness
MAINGATE/BANGALOW/
HOSTEL
5 LT Panel # 1 6-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness
HATI BLOCK/COMMUNITY
CENTER,TEMPLE,APPOLO
6 LT Panel # 2 7-Mar-13 9:00 15:00
Eletrical Feeder panel cleanning , Breaker Rackout,Rackin
check, Breaker Contact check. All Busbar & cable conection
check & tightness BRAHMANI BLOCK
Substation # 3
Substation # 1
Substation # 2
PPM Schedule For Township(Substations)
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THANK YOU