REVISION Flashcards
what is predictive maintenance?
Predictive maintenance is a proactive maintenance strategy that uses real-time data and condition monitoring techniques to predict when equipment will fail, allowing maintenance to be performed only when necessary.
what is planned maintenance?
Planned maintenance is a proactive approach to maintaining electrical and mechanical systems by scheduling regular inspections, servicing, and repairs before a failure occurs.
what is reactive maintenance?
Reactive maintenance (also called breakdown maintenance) is a corrective approach where repairs are only carried out after a failure occurs.
what is routine maintenance?
Routine maintenance refers to regularly scheduled maintenance activities carried out to ensure equipment operates efficiently and safely. It typically includes basic inspections, cleaning, lubrication, and minor adjustments that help prevent breakdowns.
what does a circuit breaker protect from when tripping?
overload
short circuit
what is the half split fault finding technique?
The half-split method is a systematic fault-finding approach used in electrical and electronic circuits to quickly locate faults by dividing the circuit into halves and testing each section.
what is unit substitution in reference to fault finding?
Unit substitution is a fault-finding technique where a suspected faulty component or device is temporarily replaced with a known working unit to determine if the original unit is defective.
what is the 6 point technique in reference to fault finding?
1 . Collect Information – Gather details about the problem from operators, maintenance logs, or system indicators (e.g., error codes, alarms).
2 . Understand the Normal Operation – Know how the system should function under normal conditions to identify deviations.
- Identify Possible Causes – List potential causes based on symptoms (e.g., power failure, faulty components, loose connections).
4 .Test to Eliminate Causes – Perform systematic tests (voltage checks, continuity tests, visual inspection) to rule out incorrect assumptions.
- Confirm the Fault – Once a faulty component or issue is found, verify it by replicating the fault or swapping with a known working unit.
- Rectify & Test the System – Fix or replace the faulty component, restore power, and test to ensure the issue is resolved before returning the system to service.
what is the input output method in terms of fault finding?
The Input-Output (I/O) method is a structured troubleshooting technique used to diagnose faults in electrical and control systems by systematically checking the inputs and outputs of a system to identify where the failure occurs.
what is condition based maintenance?
Condition-Based Maintenance (CBM) is a maintenance strategy that involves monitoring the actual condition of equipment in real-time to determine when maintenance is needed. Rather than relying on a fixed schedule (like preventive maintenance), CBM only performs maintenance when specific indicators show signs of potential failure. (vibration monitoring for example)
What is BS7671:2018?
BS 7671:2018 is the British Standard for electrical wiring installations in the UK. It is also known as the IET Wiring Regulations (18th Edition) and sets out the rules for the design, installation, inspection, and testing of electrical systems to ensure safety.
What is the purpose of BS7671:2018?
🔹 Ensures electrical safety in homes, businesses, and industrial settings.
🔹 Provides guidance on wiring, earthing, and protective measures.
🔹 Helps prevent electric shocks, fires, and other electrical hazards.
🔹 Ensures compliance with UK legal and regulatory requirements.
What is BS7671 commonly known as?
IET wiring regulations
18th edition wiring regulations
what is the recommended safe lifting weight for manual handeling ?
25kg for men and 16kg for women.
what is a block diagram?
A block diagram is a simplified graphical representation of a system, process, or concept that uses blocks (rectangles or other shapes) to represent components or functions and arrows to show the flow of signals, power, or information between them.
what is a wiring diagram?
A wiring diagram is a detailed visual representation of an electrical circuit that shows the actual physical connections between components. It includes symbols for wires, electrical devices, and connections, helping electricians and engineers understand how a system is wired.
what is a schematic diagram?
A schematic diagram is a graphical representation of an electrical or electronic circuit that uses standardized symbols to illustrate components and their interconnections. Unlike a wiring diagram, which shows the physical arrangement of wires and components, a schematic diagram focuses on how the circuit functions logically.
what is a visual aid drawing?
A visual aid drawing is any graphical representation used to support communication, explanation, or instruction. It helps simplify complex ideas, making them easier to understand through images, diagrams, or illustrations.
what is the half split technique?
The half-split technique is a systematic troubleshooting method used to diagnose faults in electrical, electronic, or mechanical systems efficiently. It works by dividing a system into two halves and testing the midpoint to quickly determine which half contains the fault. This process is repeated until the exact faulty component or section is identified.
what is condition based maintenance?
proactive maintenance strategy where equipment is monitored in real-time, and maintenance is performed only when necessary based on the actual condition of the machine.
what is scheduled maintenance?
is a planned maintenance strategy where inspections, servicing, and repairs are performed at predetermined intervals, regardless of the equipment’s condition. It is done to prevent failures, ensure reliability, and extend the lifespan of machinery and systems.
what is pre planned maintenance?
Pre-Planned Maintenance (PPM) is a proactive maintenance strategy where all maintenance activities are scheduled in advance based on time, usage, or specific conditions. It ensures that equipment is regularly inspected, serviced, and repaired before potential failures occur.
what is preventative maintenance?
Preventive maintenance (PM) is a proactive approach to maintaining equipment by regularly servicing and inspecting it to prevent unexpected breakdowns and ensure smooth operation. It involves planned, scheduled tasks designed to reduce the likelihood of equipment failure and extend the lifespan of machinery, systems, and components.
what is an MCB?
circuit breaker
How does an MCB work?
An MCB (Miniature Circuit Breaker) works by detecting electrical faults (such as overloads or short circuits) and automatically disconnecting the affected circuit to prevent damage to the wiring and connected equipment
What does a MCB protect From?
overload
short circuit
how does an mcb protect from overload
The overload condition heats up a bimetallic strip inside the MCB. The bimetallic strip bends when it gets too hot (due to excess current), which then triggers the mechanism to disconnect the circuit.
how does an MCB protect from short circuits?
A magnetic coil inside the MCB detects the rapid surge in current. The coil produces a magnetic field that pulls on a lever, which trips the MCB to break the circuit immediately, preventing damage from the high current.
what is an RCD?
(Residual Current Device) is a safety device designed to prevent electric shock and protect against electrical fires caused by earth faults.
How does an RCD work?
It works by continuously monitoring the electrical current flowing through a circuit and quickly disconnecting the power if it detects an imbalance, which indicates that current is leaking to earth—potentially through a person.
what level of imbalance or leakage does an RCD have to see to trip?
30 Milliamps
what is the 6 point fault finding technique?
Collect Information
Gather details about the fault from operators, logbooks, or system indicators.
Understand normal operation and recent changes.
Ask: What is the reported issue? When did it start? Any unusual symptoms?
Analyze the Evidence
Observe the system behavior, warning lights, sounds, or smells.
Check meters, gauges, or software diagnostics.
Compare expected vs. actual performance.
Locate the Fault
Narrow down the faulty section using test equipment (e.g., multimeter, thermal camera).
Use circuit diagrams and manuals for guidance.
Apply isolation techniques to pinpoint the issue.
Determine and Remove the Cause
Identify the root cause (e.g., loose connections, overheating, component failure).
Fix or replace faulty components.
Ensure the issue won’t recur due to external factors.
Rectify the Fault
Make necessary repairs or replacements.
Follow safety procedures and reassemble correctly.
Verify all connections and settings are restored.
Test the System & Restore Service
Power up the system and check for proper operation.
Monitor for any abnormal behavior.
Inform relevant personnel and update maintenance records.
what is the input output method of testing?
testing the inputs / outputs
what does colour of a health and safety sign mean?
Blue
RED
yellow
green
Blue = mandatory
RED = prohibition and fire safety
Yelllow+ warning
Green = safe conditions/emergency routes
what is a earth loop impedance test?
An Earth Loop Impedance Test measures the total impedance (resistance) of the path that fault current would take from a live conductor through to earth in the event of a fault
what test devices are used when testing polarity?
milli-ohm meter
what is the purpose of testing polarity
- ensure all devices are connected to the line conductor
What is the purpose of carrying out a earth loop impedance test?
ensures that the protective devices (e.g., fuses, circuit breakers, or RCDs) will operate quickly enough to disconnect power and prevent electric shock or fire.
why would you use PVC conduit?
used when there is a known risk of damn and corrosion
Why would you use steel conduit?
when strong mechanical protection is needed
Why would you used Flex conduit?
used so that vibrations are not transmitted down/through electrical installations
when would you use steel trunking?
used when damp conditions are encountered
when would you install non-metallic trunking?
in corrosive environments.
what are Steel Wire Armour (SWA) cables and where are they used?
PVC insulated steel wire armour cables are used for wiring underground between buildings, for main supplies to dwellings, rising sub-mains and industrial installations. They are used where some mechanical protection of the cable conductors is required.
What is Mineral Insulated Copper-Clad Cable and where are they used.
This cable has a seamless copper sheath making it waterproof and fire- and corrosion-resistant. This makes it the ideal choice for hazardous or high-temperature installations,
The conductors are embedded in magnesium oxide, which is non-ageing and non-combustible powder, but which is hygroscopic, which means that it readily absorbs moisture from the surrounding air, unless adequately terminated.
What applications does a type b mcb be used for?
domestic and light commercial applications
Explain the electricity at work regulations ?
Is a statutory document that requires people in control of electrical systems to ensure they are safe to use and maintained in a safe condition
What are the 5 injury types the EAWR is intended to prevent?
1- electrical shock
2 electrical burn
3- fires of electrical origin
4- electric arcing
5- explosions
What is a permit to work?
Is a specialised SSOW that ensure the potentially dangerous work is done safely.
Serves as communication between the duty holder and those carrying out the work
What features are present on a permit to work?
- details of who is responsible l
- written by a competent person
- provision of training and instruction in the issue use and closure of permits
- monitoring and auditing
-identification of hazardous work - clear and standardised identification of tasks, risks and control measures
What 9 things should a Permit To Work State?
- serial number
- name of duty holder
- declaration of electrical isolation.
- isolation points
- Caution Notices
-lock location - Description of the work
-drawings and Diagrams - signature, date, time completed by authorised engineer
What is a Risk Assessment ?
Is a careful examination of what in your work could cause harm.
also acts as a record to show sufficient precautions have taken place to prevent harm
What are the 5 steps of carrying out a risk assessment?
1- identify hazard
2-who might be harmed
3- evaluate risks and decide precautions
4- record findings and implement
5-review risk assessment and update when required.
What is a Method Statement?
describes a safe system of work laid out in a logical sequence. A method statement should be clear and uncomplicated and are for the benefit of the person carrying out the work . They include the risks identified in the risk assessment and the measures to control them.
What 4 types of protective devices are used?
1- HRC fuses (high rupturing capacity)
2- cartridge fuses
3- semi-enclosed fuses
4- circuit breakers
What are HRC fuses designed to do?
To rupture at very high currents
What classifications of HRC FUSES THERE?
GG and GM
Circuit breakers have thermal and electromagnetic elements. What do these protect?
Thermal protects overload
Electromagnetic protects from short circuits
What three types of circuit breaker are there?
Type B- domestic general protection
Type C- small inductive loads
Type D- large inductive loads
What are the 3 main types of lighting?
1- incandescent
2- discharge
3- LED
How does a three phase induction motor work?
When a three phase supply is connected to separate windings equally distributing around the stator creating a magnetic flux. Rotating magnetic flux caused by windings causes shaft to rotate
What are the advantages of a three phase induction motor?
-Single construction and cheap to make
- cage construction of the rotor is mechanical so provides strength for its industrial uses
- self starting
-very little maintenance
- high efficiency
- good power factor
What are the limitations of three phase induction motors?
-speed variation is difficult
- always operate under lagging power factor
-during light load conditions they operate with poor PF
- Poor starting Torque
