Class Notes - Year 4 - 2020-2021
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Year 4

Lesson 416

Preventative Maintenance and Troubleshooting

Troubleshooting Definition

The systematic elimination of the various parts of a system, circuit, or process to locate a malfunctioning part

IEC Manual 416

Abbreviations

PDM - Predictive Maintenance
PM - Preventative Maintenance

EMC5 29-1 Preventative Maintenance Systems

PM is maintenance performed to keep equipment running with little or no downtime
Can be scheduled or unscheduled
Increases efficiency
Reduces cost
Minimizes safety issues

Types of Maintenance Work

Facilities Maintenance

Performed on systems and equipment in hotels, schools, office buildings, hospitals
Work performed on HVAC equipment, fire protection systems, and security systems
Downtime cost is minimal

Industrial Maintenance

Performed on production systems in industrial settings
Performed in food processing, parts manufacturing, foundries, timber and pulp mills, mines
High downtime cost

Work Orders

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CMMS - Computerized Maintenance Management Systems

Work Priority

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Order in which work is done based on importance
Indicated on work order
Typically 3 levels
Safety, downtime, and production efficiency
Periodic maintenance
Long term projects

Unscheduled Maintenance

Unplanned service that includes emergency work and breakdown maintenance
Performed to correct unexpected malfunction
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Breakdown Maintenance

Service on failed equipment that has not received scheduled maintenance
Example - lightbulbs
Only used on equipment that is not expensive and non-critical

Scheduled Maintenance

Work that is planned or scheduled
Minimizes emergency work
Ensures reliable and efficient operation

Periodic Maintenance

Completed at specific time intervals
Inspections
Lubrications
Adjustment

Corrective Work

Repair of known problem before breakdown occurs
Discovered during inspection

Inventory Control

Organization and management of commonly used parts, vendors, and suppliers, and purchasing records in preventative maintenance systems

Logbooks

Book or electronic file that documents all work performed and lists info needed to complete work
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EMC5 29-5 Preventative Maintenance Tests

Can eliminate problems before they occur
Test conductor insulation
Two tools to test insulation
High potential or high voltage tester (hipot)
Measures insulation resistance by measuring leakage current
Apply high test voltage between two different conductos or between conductor and ground and measures the leakage current
Megohmmeter
Applies high test voltage and displays resistance in ohms

Insulation Spot Tests

Checks motor insulation over life of motor
Every 6 months
See text for steps

Dielectric Absorption Tests

Checks absorption characteristics of moist or contaminated insulation
See text for steps

Insulation Step Voltage Tests

Cretes electric stress on internal insulation cracks to reveal aging or damage not found visually
Performed only after insulation spot test
See text for steps

EMC5 30-1 Predictive Maintenance Monitoring

Monitoring of wear conditions and equipment characteristics against predetermined tolerance to predict possible malfunctions or failures
Data is gathered to show trends
Requires substantial training and equipment
Monitoring can be random, scheduled, or continuous
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Visual and Auditory Inspection

Analysis of appearance and sound of operating equipment

Vibration Analysis

Monitoring of equipment vibration characteristics
Worn parts produce increased vibration or noise

Lubricating Oil Analysis

Predictive maintenance technique that detects and analyzes presence of acids, dirt, fuel, and wear particles in lubricating oil
Performed on scheduled basis

Thermography

Use of temperature indicating devices to detect temperature changes in operating equipment

Ultrasonic Analysis

Uses high vibration frequencies to create an image or reading
Similar to vibration analysis
Internal flaws or cracks in metal can be located

Electrical Analysis

Uses electrical monitoring equipment and/or test instruments to evaluate the quality of electrical power delivered to equipment and performance of electrical equipment

416.1 Outline and Explain the Purpose and Methods Utilized for Preventative and Predictive Maintenance Systems

Failures caused by insulation failure
Presence of water degrades insulation
High magnitude shorts and faults can damage insulation
Dust and debris can cause current to “leak” or “track” on surface of non-conductive material
Dry-type xfmrs allow ambient air for cooling
Air can contain contaminants
Visual inspections should monitor dust accumulation
Conductive particles in air can cause shorts
When de-energized, cooling can cause condensation
Noticable changes in sound from transformers should be monitored
Could be loose hardware, defective vibration isolators, overexcitation, or possible damage to insulation
Thermography (visual imaging) is an invaluable tool
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Hot spots at terminations indicate loose connections
Can detect flawed fuses, defective switches, faulty breakers, overloaded or unbalanced circuits

EMC5 3-2 General Use Test Instruments

Continuity testers, receptacle testers, voltage testers, branch circuit identifiers, multimeters, clamp-on ammeters, and oscilloscopes

Continuity Testers

Tests for complete path for current to flow
Only used on de-energized

Troubleshooting Fuses with Continuity Tester

Remove fuse

Receptacle Tester

Voltage Tester

Troubleshooting GFCIs

See video

Branch Circuit Identifiers

2 piece test instrument that includes transmitter and receiver

Analog Multimeters

Can measure 2 or more electrical properties and displays on calibrated scales using a pointer
See video

Digital Multimeters (DMM)

Can measure 2 or more properties and displays as numerical values
Most are auto ranging
See video

DMM Voltage Protection

IEC 1010
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Troubleshooting with DMMs

Resistance measurement
De-energize or remove from circuit
See steps in text
AC Voltage Measurement
See steps in text
Troubleshooting Fuses
See steps in text
Ghost Voltages
Voltage that appears on meter not connected to circuit
Produced by magnetic fields generated by current carrying conductors, fluorescent lighting, other operating equipment
In-Line Current Measurements
See text

EMC5 12-5 Magnetic Motor Starters - Troubleshooting Magnetic Breakers

See steps in text

EMC5 11-4 Troubleshooting Transformers

Measuring input and output Voltages

Check Transformer Resistance

Open Circuits in Coils
Resistance of each coil is checked
If winding is open, infinite resistance will be shown
Short circuits between primary and secondary
Coils shorted to core
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Testing Control Transformers

See steps in text

EMC5 13-6 Troubleshooting DC Motors

See text

EMC5 14-1 AC Motor Types - Three Phase Motors

Induction motor - Has no physical electrical connection to the rotor
Have brushes that wear out or require maintenance
Current is induced by rotating magnetic field of stator

Single-Voltage, 3Ph Motors

Operates at only 1 voltage
Wye
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Delta
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Dual-Voltage, 3Ph Motors

Can connect to either of two voltages
Higher voltage is preferred
Wye
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Delta
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EMC5 14-2 AC Motor Maintenance

Enclosures

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Overcycling

Process of turning motor on and off repeatedly
Most are not meant to start more than 10 times per hour

Heat Problems

Heat destroys motor insulation
Can be caused by:
Incorrect motor type of size for application
Improper cooling (from dirt buildup)
Excessive load
Excessive friction
Electrical problem

Altitude Correction

Above 3,300’

EMC5 14-3 Troubleshooting AC Motors

See text

EMC5 5-5 Control Circuit Troubleshooting

Troubleshooting is the systematic elimination of the various parts of a system, circuit, or process to locate a malfunctioning part
See text

Tie-Down Method

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Troubleshooting Open Circuits

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Troubleshooting Short Circuits

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Troubleshooting Short Circuits

Isolation method
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EMC5 12-7 Troubleshooting Contactors and Motor Starters

Usually the first thing checked
Line, load, and control are all present
Many moving parts
See steps in text
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