summary lecture 1 6 plus formulas
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For Logistics and transportTRANSCRIPT
Summary Lecture 1-6, plus formulas
Introduction Transport and Logistic Engineering (Technische Universiteit Delft)
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Samenvatting Introduction Transport Engineering Study Goals:
College 1 – General Introduction I Transport is the application of exact science to determine the physical principles which govern the conveyance of goods, information and energy from one place to another and the design and development of the equipment required to accomplish the physical transport. Logistics concerns the application of mathematical methods to describe the physical processes behind the transport process and the determinations of the physical actions that are necessary to permit the transport to be accomplished as efficiently and effective as possible. Transportation started to serve people’s needs in first life needs. The wheel was an important finding. Water was a first source of energy.
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Now: ships with 18.000 TEU. Problem is not that we want to transport more, but how to handle it? Three categories of transport goods:
1- Liquids and gasses (geen vorm, alleen volume) (kan vorm krijgen door een ULD) 2- Dry bulk solid materials 3- Goods with unique identifiable form or shape
College 2 – General Introduction II A Unit Load Device (ULD) is a standardized unit, used to load goods (bijv. Container). Because standardization, automation + multimodal transport is possible. Een IKEA box is ook als ULD te zien, want het is standardized in some way. T.E.U. = Twenty Foot Equivalent Unit. Boxes van Ikea are ULD’s in some way, because they’re standardized. Continuous (offers transport capacity continuously in time) and discontinuous (offers transport capacity at discrete moments in time) transport systems. In London, the train comes every 30 seconds at some routes. Makes that the train system there a continuous system? Lopende banden die boxen nodig hebben om het materiaal te vervoeren (en dus ook pas ‘aan’ gaan als er een box op zit), zijn discontinuous transport systems. Als boxen gebruikt worden op een continious conveyor (de conveyor blijft dus bewegen), dan de capacity is offered continiously at discrete times. Vc = Ld / Td = Continious travel velocity (m/s) = Transport distance (m) / Time it takes (s) Cd = Md / Td Capacity (kg/s) = Moving mass / Time Als load Md over hele lengte van transport system (bijv. lopende band) is verspreid: Cd = (M’d x Ld) / Td Rf = Rl Material Flow Rate (1/s) = Loading Rate (1/s) Rf= Vc / Sc Material Flow Rate (1/s) = Continious Travel Velocity / Pitch between two materials on the conveyor (m) Two problems with continuous conveyors using ULD’s:
- The possibility that no empty carriers are immediately available at the loading station when needed.
- The possibility that no loaded carriers are immediately available at the unloading station when needed.
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Volgens Kwo zijn er drie principes waar een continuous conveyor met één loading station en één unloading station aan moet voldoen:
1- Speed Rule. Rf = (Np x Vc) / Sc > Max{Rl,Ru}
2- Capacity constraint. (Np x Vc) / Sc < Rf
3- Uniformity Principle: This principle states that parts (loads) should be uniformly distributed throughout the lengths of the conveyor so that no parts are fully loaded while others are empty.
Moving objects with a relatively small force is only possible by:
1- Converting an available smaller force in a larger force: a. The lever (hefboom) (katrol valt ook onder hefboom) b. The wedge (gaat om hoek) c. The impact force d. The hydraulic transmission (hydraulische pompen)
2- Reducing the frictional resistances, by applying: a. A roll (All transport equipment uses rolls or wheels to reduce friction, except
pneumatic or hydraulic conveyors, screw conveyors and vibratory conveyors) b. A liquid or air layer c. Walking or jumping (We know that walking takes less energy than dragging. If
mechanic contact is lost during transport it reduces friction) (een kind meeslepen kost meer energie, dan wanneer het zelf loopt)
d. Magnetic forces (The repulsion force removes the mechanic contact between transport equipment and its support)
College 3 – General Introduction III Internal Transport: Includes transport within a production shop and between shops. In the mining industry it encompasses underground transport, surface transport and quarry transport. Intrashop industrial transport, an integral part of the production process, is used to move workpieces and assemblies between working areas, sections, and departments within a shop. Intershop transport, which is generally not related to the production process, is used to move materials, semifinished goods, and finished products between shops and warehouses located on the enterprises’ premises or in the same industrial area. External transport brings raw materials, fuel, and equipment to enterprises and carries finished products from their premises either to transfer points linked with main line transportation or directly to the purchaser. You need other infrastructure than your own. During transportation of people, passengers and baggage may be separated. For transportation efficiency passengers and baggage should be separated as late as possible. For convenience, security or safety separation should be done as soon as possible.
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Multimodal Transport is the transportation of goods or people under a single contract, but performed with at least two different transport modes. The carrier responsible for the entire carriage is referred to as a multimodal transport operator (MTO). There are different ways to specify the energy consumption of transport equipment. Bijvoorbeeld nu wordt het energielabel gebruikt. Dit wordt gebruikt door in een sort transport de meest vervuilende vorm op F te zetten en de meest zuinige op A (ookal kan deze dus alsnog niet heel zuinig zijn, maar het gaat dus om de verhoudingen). The Transport Loss Factor: Consider transport over a distance L from A to B. Transport includes transport equipment loaded with payload Fpay. Consider only mechanical energy (differences in efficiency of energy conversion are not yet taken into account). Et = Wt = Fpay x L Transport Performance = Work = Payload x Distance Ed = Fd x L Total Energy required to drive the transport system = Load x Distance Ed = Ep + Em Tot energy required to drive the transport system is partly converted to potential energy (Ep) and party used to overcome frictional or mechanical resistance (Em). Ep = Wp = Fpay x H Em = Wm = Ed – Ep The transport loss factor is defined by Jonkers as the ratio of the mechanical energy required to overcome frictional resistance during transport and the transport performance Ft = Wm / Wt. Een schip heeft een lage loss factor, daarna volgen de trein en een vrachtwagen en een vliegtuig heeft een hoge loss factor. The TLF has to be extended to account for the effect that it is not always true for discontinious transport modes. Er geldt nu: Ed = Fd x L + Ek (Ek=kinetische energie) En: Fd x L + Ek = Em + Ep Ed = Fd x L + Ek = ne x Es Total Drive Energy = Engine Efficiency x Energy Source Primary energy (Ep) is energy that has not been converted by an energy conversion system or upgrading process. Ep = rp x Es (rp is the ratio of the used utilized energy and the used primary energy, (rp electricity NL = 2,2, rp Diesel = 1,2))
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To be able to calculate the mass of the emission output, the specific emission factors of electricity and diesel are required. Using the TLF, Primary energy consumption, CO2 emission, and NO emission, you can decide whether to use a truck or a belt conveyor. College 4 – Belt Conveyors I (No formulas in this summary) A Belt conveyor is a continuous conveyor that consists of two or more pulleys, with a continuous loop of material – the conveyor belt – that rotates about them. At least one of the pulleys is powered, moving the belt and the load on the belt forward. The location and lay-out of the drive system is carefully selected. An induction motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor always operates slower than synchronous speed. The difference, slip s, between actual and synchronous speed varies from about 0,5 to 5% for standard Design B torque curve induction motors. Normally, the rotor mechanical speed cannot be transferred to the drive pulley directly; it is too high. Therefore we need a reducer or gearbox. A gearbox, or transmission, uses gears and gear trains to provide speed and torque conversions from an induction motor to the drive pulley. Normally, the gearbox ratio is standardized. The power supplied to the drive pulley is the same as the power generated by the motor if we neglect the losses in the drive train. The gearbox needs to be able to handle the power supplied by the motor! On the drive pulley the rotational speed of the drive pulley is converted into a longitudinal belt speed v. At the same time the drive torque is converted in a drive force applied on the belt.
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In order to operate a belt conveyor in a reliable manner it is essential that a minimum belt tension is maintained in the belt. There are two main reasons for maintaining a minimum belt tension:
1- To allow transfer of drive power from the drive train into the belt. (schommelingen opvangen)
2- For maintaining a minimum belt tension to ensure that the belt sag does not exceed certain limits (niet te ver doorzakken van belt)
Different take-ups are possible, three main types. Take up is om de spanning te behouden volgens mij.
1- Gravity take-up (je hangt er een gewicht aan) 2- Winch for a take-up (spanning door kabel) 3- Screw take-up (schroeven die 1 kant verder weg duwen)
During steady-state operation (belt speed is constant) the gravity take-up and the winch take-up behave identical. During transient operation (starting and stopping of the belt conveyor) the gravity take-up is able to catch up sudden changes in tension whereas the winch take-up “freezes”, which means that it cannot follow sudden changes in tension. The function of belt covers is to protect the carcass. The function of the carcass is to transfer the drive force through the belt. The required strength of the carcass can be calculated by dividing the maximum force in the belt by belt width (kN/m or N/mm). Qualities of belt covers are:
- Anti-static - Fire resistant (mijnen) - Heat resistant (cement) - Cold resistant - Oil resistant (kunstmest) - Food quality (vaak van pvc en altijd wit)
Idlers are used to carry the belt. They consist of a frame and rolls and can be used to create a trough that increases the load carrying capacity of the belt in case of belt conveyors that transport bulk solid materials. College 5 - Belt Conveyors II (No formulas in this summary) A belt conveyor can normally reach a maximum inclination of 18 degrees. Otherwise you need to contain the material either by a force or form:
- Pouch conveyors - Pipe conveyors - High angle conveyors - Pocket conveyors (kan steilste gaan, 90 graden)
Soms zijn er twee losse belt conveyors in line. Dat kan omdat de maximaal mogelijke lengte van een conveyor is bereikt, of omdat er gestandaardiseerd wordt voor gemak.
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Trajectory is about calculating how stuff will fall on the belt. Dit is afhankelijk van de snelheid, hoek en pulley diameter. In an ideal world, tension in whole belt is constant. Where do we put the take-up and the drive?
1- Ensure the lowest overall tensions 2- Ensure the lowest take-up force
Take-up en drive is bij horizontale conveyors altijd het beste bij head. Als een conveyor omlaag gaat, kan er een equilibrium ontstaan, waardoor er geen drive nodig is. Als er toch nog steeds drive power nodig is, blijf je deze bij de head plaatsen. Als er een equilibrium ontstaat, heb je dus geen drive nodig als de conveyor vol is. Maar als deze leeg is wel, dus plaats altijd nog een drive en bij head. Als je een rem nodig hebt, plaats je deze bij de tail. Soms heb je zowel een rem als een drive nodig. Waar dan? Dat hangt er van af wat je het meeste nodig hebt. Halverwege is geen goede optie, want dan heb je een extra roller nodig en dat wil je altijd voorkomen. College 6- Belt Conveyors III (No formulas in this summary) Belt conveyors have different operational conditions:
1- In rest 2- Steady state running 3- Normal operational start 4- Aborted start 5- Normal operational stop 6- Emergency stop
Drift stop: the drive is shut off (voluntarily or not). The only force on the conveyor belt is the previous drive force. A brake force is required if the drift time exceeds admissible levels. Advantages of closed conveyor systems:
- No ambient dust development, no contamination of bulk material - No bulk material build up underneath conveyor or on components - Small horizontal & vertical curve radii, flexible lay-out - Steep inclination angles (>30 degrees)
Japan invented the pipe conveyors. This is a serious issue, because when a pipe conveyor in NL is broken, you have to wait 3 weeks for maintenance. College – Vibratory Conveyors (No formulas here) Advantages:
- Simple structure, drive system needs consideration - Small build-in height - Excellent feeder control options
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- Fit for very fine materials as well as large lumps - Chute can be lagged enabling transport of hot or abrasive materials - Applicability as feeder under silo or bunker - Combination of functions possible - Closed conveying is possible - Applicability in food industry
Disadvantages:
- Noise - Limited conveying distance (<25m) - Small bed thickness - Easy damage to bulk solid material
Difference in chute:
- Sliding chute (low frequency / high amplitude) (Throw number between 0 and 1) - Throwing chute (high frequency / low amplitude) (Throw number higher then 1)
Als je ziet date r alleen horizontal motion is allowed, sowieso een slide chute. Difference in drive:
- Drive system with crank mechanism - Drive system with unbalance motors - Electromagnetic drives
Drive phenomena can be force or amplitude driven (crank can be amplitude driven)\ Grafiek die je moet gebruiken: X-as: geeft aan: friction coefficent (u) x tan (hoek) Y-as geeft iets aan De lijntjes gaat om het throw number What can be done to change capacity?
- Increase the amplitude (r) - Change the vibratory hoek - Increase the friction coefficient - Increase the chute width B
All Formulas:
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