Higher Level Leaving Certificate Engineering

Revision Notes 2011

(Answer Question 1 - Section A and Section B and four other questions)

Question 1 Section A and Section B are Compulsory

Section A (50 marks – 5 marks per question)

(Short Questions – Summary of the Course, look over past exam papers)

  • Safety symbols, safety with toxic materials, effects of toxic materials, methods of disposal of waste plastic, basic first aid requirements, personal protection, methods of safeguarding machinery, colour code of safety signs, mechanical, electrical and human failures, work space clearances, electrical hazards; principles of protective devices and systems, earthing; single and three phase systems, correct use of equipment, chemical hazards, poisonous, corrosive, combustible and explosive, fire protection methods and equipment

Red (prohibition signs to include danger and fire safety), Yellow (alerts to a caution or possible danger), Green (positive action to safe condition, emergency exit or first aid), Blue (denotes mandatory or information signage)

Highly Flammable / Toxic / Corrosive / Explosive / Harmful / Harmful to the environment
Radiation / Poison / Biohazard / Electrical / General / Laser / Oxidising
Fire Extinguisher / Fire Emergency Telephone / Fire Alarm Call Point / Fire Hose Reel / Fire Ladder / Fire Fighting Equipment
  • Corrosion, mechanisms of corrosion, electrolytic action, influencing factors, minimising corrosion, sacrificial protection, oxidation, electro-chemical corrosion, environment corrosion, protective coatings against corrosion (paint, plastic dipping, lacquer), anodising of aluminium, hot dipping, electro painting, galvanising, design features, environment, anodic and cathodic protection
  • Joining materials with adhesives, preparing materials for joining with adhesives, joint design, types of adhesives, safety hazards when using adhesives, advantages of adhesives
  • Joining Methods – Mechanical Joining (screw fasteners, compression joints, riveting, sheet metal folding), Welding, Bonding (soldering, brazing, adhesive bonding)
  • Manufacturing processes – fabrication, drop forging, calendaring, casting (pattern), sand casting, investment ‘lost wax’ casting, die casting, gravity die casting, pressure die casting, continuous casting, extrusion, drop forging, press forming, blanking, piercing, punching, bending, drawing, deep drawing, thread rolling, rolling, drawing, stamping, profile key cutting
  • Robots in industry – assembly lines, multipurpose capabilities, production with robots, advantages & disadvantages, work envelope, safety, degrees of movement
  • Machining – generating, forming, shaping, turning, milling, grinding
  • Pneumatic symbols –3/2 valve (three port valve), 5/2 valve (five port valve), double & single acting cylinders, push button switch, roller switch, lever switch, plunger switch, solenoid operation, pressure sensitive switch, air supply, exhaust, spring return, reservoir, shuttle valve, flow regulator
  • Forces - torsion, shear, compression, tension, bending
  • Thread forms – buttress, acme, square
  • Electrical symbols – LDR, LED, capacitor, thermistor. Electronic terms – heat sink, breadboard
  • Separation of ores – pyrometallurgy, hydrometallurgy, thermo-electrometallurgy
  • Ore dressing/ore concentration – flotation, magnetic separation, gravity concentration, amalgamation, metal extraction – leaching, electrolysis, smelting & refining, reduction, reduction-oxidation
  • Mining – open cast mining, underground mining, open pit mining, dredging, solution mining
  • Types of materials – polymers, metals, elastomers
  • Properties of materials – tensile strength, shear strength, malleability, creep, hardness, toughness, ductility, elasticity, electrical conductivity, thermal conductivity, thermal expansion, compressive strength, density, proof stress, magnetic characteristics, resistance to corrosion, colour, machinability, melting point
  • Crystal defects (vacant site, substitute defect, interstitial defect), line defects dislocation), covalent bonding, ionic bonding, metallic bonding, crystal patterns - FCC, BCC, CPH, slip in BCC & FCC, crystalline & amorphous structures, dendritic growth, allotropy, crystal structures
  • Computer terms – CPU (central processing unit), DVD (digital versatile disc), CD-RW (compact disc rewriteable) , E-mail (electronic mail), RAM (random access memory), ROM (read only memory), LAN (local area network), ULR (uniform resource locator), HTML (hypertext mark-up language), WWW (world wide web), HTTP (hypertext transfer protocol), ISP (internet service provider), Input Device (keyboard, mouse, joystick, scanner, webcam, microphone, digital camera), Output Device (monitor, printer, speaker, sound card), Hardware (physical parts) & Software (programs)
  • Measuring instruments –limits, tolerance and allowances, limits & fits – (hole & shaft basis of fits), clearance, transition and interference fits

Linear measuring instruments – vernier callipers, micrometer, slip gauges, sine bar, precision cylinders & precision balls, gap gauge, plug gauge, screw thread measuring

  • Mechanisms – cams & follower, gears (rack & pinion, worm & wormwheel, bevel gears, helical gears, spur gear, gear train, idler gear), crank and slider, chain and sprocket, lever, linkage, quick return mechanism, bell crank, pulley, ratchet and pawl
  • Motion – linear, rotary, reciprocating, oscillating
  • PCB (printed circuit board), uPVC (unplasticised polyvinyl chloride), SPST switch (single pole, single throw switch), DPDT (double pole, double throw switch), HSS (high speed steel), CPU (central processing unit), LAN (local area network), IC (integrated circuit), CD-RW (compact disc re-write), VDU (visual display unit), LED (light emitting diode), LDR (light dependant resistor), E-mail (electronic mail), ISP (internet service provider), LCD (liquid crystal display), DOS (disc operating system), RAM (random access memory), ROM (read only memory), HD (high definition)
  • Corrosion of Metals – Oxidation, electro-chemical corrosion, sacrificial/cathodic protection, stress corrosion, protection against corrosion (corrosion resistance, anodising of aluminium, painting, plastic coating, hot dipping, powder cementation, metal spraying, metal cladding, electro-plating), corrosion prevention factors
  • Properties of materials – tensile strength, compressive strength, shear strength, creep, hardness, toughness, brittleness, elasticity, malleability, electrical conductivity, heat conductivity, melting point, resistance to corrosion

Inventors

Albert Fryer / The first incinerators for waste disposal were built in Nottingham by Manlove, Alliott & Co. Ltd. in 1874 to a design patented by Albert Fryer
Joseph-Armand Bombardier / In 1922, he invented his very first snowmobile. He would later go on to invent several other types of snowmobiles, and finally in 1959, he invented the first practical and successful snowmobile.
Heinrich Hertz / Discovered that ultraviolet light altered the lowest voltage capable of causing a spark to jump between two metal electrodes.
John P Holland / Irish engineer who invented some of the first submarines.
Viktor Kaplan / Austrian engineer who invented a water turbine with adjustable blades.
Eli Whitney / US inventor who patented the cotton gin and then manufactured muskets using power-driven tools to produce interchangeable parts.
Igor Sikorsky / Born in Kiev, Russia in May 1889. His most important contributions came in the area of helicopterdesign especially his single rotor design.
Theodore Maiman / He invented the first operable laser. Laser beams are today being used in medicine, industry, electronic data processing & communications.
Dugald Clerk / Born in Glasgow in 1859. He is identified with the internal combustion engine and the two-stroke engine.
Michael Faraday / British physicist and chemist whose discoveries include electromagnetic induction and the laws of electrolysis. The unit of capacitance, the farad, is named after him.
Henry Maundslay / In 1780 he used a revolving cutting tool to mill a slot in a lock. He mounted the tool on an arbour and set it up between centres on a lathe.
Gustaf Dahlen / In 1902 he developed acetylene gas and demonstrated gas welding for the first time.
Simon Stevins / A Flemish mathematician and engineer – he founded the science of hydrostatics, introduced decimal fractions laying the foundations for thedecimal system of weights and measure. He developed methods of stopping invasions by designing sluice openings in dikes which could be opened and therefore flooding the lowlands.
Willhelm Roentgen / In 1895 he produced X-rays in a high voltage discharge tube. The results have significant importance in engineering and medicine.
Chester Carlson / In 1939, he developed the photocopier on a Xerox machine.
Germain Sommeiller / In 1887 invented the compressed air drill, he was also
chief designer for Mont Censis tunnel in the Alps from Italy to France.
Jack Kilby / In 1958, he co-invented the integrated circuit where complete sets of electronic components could be embedded, and connected, to create a complex circuit, ie. the microchip.
Thomas Edison / Tin foil phonograph. A prolific producer, Edison is also known for his work with lightbulbs, electricity, film and audio devices.
Alexander Graham Bell / 1876, at the age of 29, invented his telephone. Among one of his first innovations after the telephone was the "photophone," a device that enabled sound to be transmitted on a beam of light.
John Logie Baird / Mechanical television (an earlier version of television). Baird also patented inventions related to radar and fiber optics.
Henry Ford / improved the "assembly line" for automobile manufacturing, received a patent for a transmission mechanism, and popularized the gas-powered car with the Model-T.
James Dyson / Born in Norfolk in Englandin 1947, he invented the use of cyclone technology in vacuum cleaners. This bagless system does not clog or
lose suction. The Dyson Airblade hand dryer was launched in 2006.
George Atwood / The first accelerometer, originally known as the Atwood machine, was invented by the English physicist George Atwood (1746-1807) in 1783.
Timothy Berners-Lee / Sir Timothy John "Tim" Berners-Lee born 8 June 1955is a British engineer and computer scientistis credited with inventing the World Wide Web, making the first proposal for it in March 1989.
George Eastman / American inventor and philanthropist, who played a leading role in transforming photography. He is the inventor of the first film in roll form in1884 and the Kodak camera in 1888.

Pneumatic Symbols

Section B

Specialist Topic 2011 (50 marks)

“Basic principles and processes in the operation of Incineration Technology”

Incineration (thermal treatment) - disposal of waste by controlled burningSolid, liquid & gaseous wastes are converted into a small amount of ash & a large volume of exhaust gasesGases are cleaned before being released into the atmosphereHeat produced is recovered & used Energy from Waste (EfW) or Waste to Energy (W2E) plants.

Waste Types - Standard domestic rubbish usually called municipal solid waste (MSW)Industrial & chemical wastes Contaminated material from healthcareResidues from animal processing)Small plants handling waste from a single factory or hospitallarge plants processing the waste of entire cities.

Combustion- Combustion or burning is the reaction of a material with oxygenfuel + supply of oxygen + high temperature are needed for combustion

Fuel - The main fuel type in waste is organic material Biological such as paper, timber, food waste and animal fatsPetrochemical such as plastics and solvents.

Oxygen -Combustion is the reaction where a fuel combines with oxygen and is broken into simpler oxide moleculesTo burn properly there must be enough oxygen to react with all the fuel Reaction only occurs when oxygen comes into direct contact with the fuelFor solid and liquids fuels this can only occur at the surface so it is best to break the fuel up into small particles or droplets.

Temperature - Reaction with oxygen will only occur at a high temperature = ignition temp.

Combustion By-Products - If a fuel is burnt completely then:All carbon in it is converted to carbon dioxideAll hydrogen is converted to waterAny sulphur is converted to sulphur dioxide Any nitrogen into nitrous oxides All released as gasesComplete combustion can only take place if: Enough oxygen is suppliedFuel & exhaust gases reach a high enough temperature for a sufficiently long time - called the dwell timeIncomplete combustion of organic material produces solid carbon or soot.

Ash - If fuel contains other elements, such as metals, it will produce a solid residue or ashAmount of ash produced varies with the fuel composition but is usually less than 10% of the weight of the original fuelSome of the ash will be in the form of very fine particles and will remain suspended in the exhaust gases = fly ashDepending on the fuel fly ash may contain a range of heavy metals such as arsenic, cadmium, chromium, mercuryRemainder of the ash is called bottom ashContaminant levels tend to be lower.

Dioxins and Furans -If combustion is incomplete and the fuel contains chlorine then dioxins and furans will be releasedDioxins are produced by the incomplete combustion of any organic materials containing chlorineTo prevent their release very high temperatures must be reached and maintainedBurning of rubbish in bonfires is one of the main sources of dioxinsTemperatures reached are not high enough to give complete combustion.

Incineration Objectives -Achieve complete combustion of the waste:Controls fuel & air supply & temp Maintain required temp & dwell timeExtract as much heat as possible from the exhaust gasesThoroughly clean the exhaust gases to ensure that only minimal amounts of harmful substances are released into the atmosphere.

Waste Supply - Sufficient waste to run the incinerator must be stored at the site  The way it is stored will depend on the waste type Solid wastes are usually stored under negative pressure to minimize the release of odours May be sorted to remove any non-combustibles such as metals Mixed thoroughly to give a consistent fuel It may mechanically processed to reduce the moisture content or to break it into evenly sized pieces for easier handling and burning = Refuse Derived Fuel (RDF) Supply of waste to the combustion chamber is controlled and usually automated.

Combustion Chamber - Key part of the system where the burning actually takes place Different designs depending on the waste type Common Features to ensure complete combustion Adjustable forced supply of air usually sucked in  Too little means incomplete combustion, too much low temperatures  Thorough mixing of the waste and released gases with supplied air Controllable supply of a secondary fuel such as natural gas Used at start up and during operation to achieve required temperature Chamber design ensures exhaust gases have required dwell time.

Flue Gas Cleaning - Flue gas cleaning is done is two or more stages: Scrubbing and particle removal are always done Wet scrubbing sprays a fine mist through the flue gases Active carbon absorbs heavy metals such as cadmium, mercury, arsenic  Water is collected and treated to removed pollutants.

Energy Extraction - Hot exhaust or flue gases are passed through heat exchangers in a boiler to produce high pressure steam This steam can be used to drive a turbine which in turn runs a generator producing electricityEach tonne of MSW produces around 650kWh of electricity and 2MWh of heat and is equivalent to 0.25t of oil or 0.4t of coal  Heat from the steam condenser can be used to supply a local demandIn Europe - used for heating.

Incineration Components

1. Waste Supply2. Combustion Chamber3. Boiler

4. Scrubber5. Fly Ash Filter6. Draft fan

7. Stack with Emissions Monitoring8. Bottom Ash Collection.9. Fly Ash Collection

Static Hearth - Liquid and gaseous wastes which will produce minimal ash are burnt in static hearth incineratorsTypically organic solvents and vapours from chemical or pharmaceutical manufactureSeveral in Ireland e.g. Roche in ClarecastleCombustion chamber is a long cylinderWaste and air fed in by jets to create a swirling flow through the chamberChamber length and swirling ensure sufficient dwell time.

Rotary Kiln -Hazardous solid waste is usually burned in rotary kilns  Combustion chamber is an angled rotating cylindrical drum  Rotation give good mixing of waste with air and flame  Waste fed in at one end  Ash removed Gases released are burnt in a secondary chamber

Moving Grate -MSW is normal burnt in moving grate incinerators Combustion chamber has an inclined moving metal grateair fed up through the grateWaste moves slowly down grate burn as it movesAsh falls off end into bunker.

Particle Removal - Fly ash can be removed by either filters or Electrostatic Precipitators (ESP) Baghouse filters use tightly woven fabrics Same idea as a vacuum cleaner bag Filters are cleaned regularly Up to 99% effective.

Fluidized Bed - Wastes with a uniform composition and high moisture content are burnt on fluidized bed incineratorsSewage sludge is typical burnt this wayFluidized beds are also used in power plants burning high moisture content fuels such as peat and biomass (willow)Instead of a grate there is a bed of sandSuspended on upward blowing jets of airGives thorough mixing and a long dwell timeChamber is a vertical cylinder, sand is reused.

Flue Gas Monitoring - A large number of parameters are monitored continuously to ensure correct operationTotal Organic Carbon (TOC) which is a measure of how much carbon is not fully burntOther more difficult to measure pollutants are measured six monthlyDioxins, furans and heavy metals Strict limits must be met & all data reported to EPA.

Ash Disposal - Bottom Ash and Fly ash are usually treated separatelyBottom Ash is first cooled and then processed to remove any metalsFor MSW bottom ash is then graded into different sizes & used as a construction aggregate Fly Ash & residues from scrubbers can contain highly levels of toxic materials Must be stored long term in a secure landfill to prevent release into the environment.

Role of Incineration -EU landfill directive has firm targets for the reduction of the amount of biodegradable waste going to landfill Currently Ireland landfills ~ 1.5 million tonnes of biodegradable waste Must be reduced to ~ 450,000t by 2016 Landfills cause methane emissions – 25 times more damaging than CO2 Risk of pollutants leaching into water table Incineration is one means of achieving target Reduces volume of material sent to landfill Material landfilled doesn’t decompose Reduces fossil fuel requirement.