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16 Cards in this Set
- Front
- Back
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sketch and describe a single cylinder, double acting piston pump with uses and limitations |
air damped piston, pressure fluctuations relief valve gland sealing corsshead high positive suction head, removes air from suction line, good for viscous fluids, bilge non turbulent flow, steady output limited capacity(get a second piston) bilge pump |
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sketch and describe a progressive cavity pump, explaining its uses and limitations |
double helix stator, elastomer compound, easy to cast, helps seal single helix rotor, steel, chromium plated universal couplings gland sealing various pressures and flow rates good with viscous fluids/ long life abrassive particles will wear/ less viscous fluids will not effectively lubricate bilge /sludge pump |
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sketch and describe a twin rotor screw type pump |
twin stainless steel screws mild steel pump casing relief valve screws rotate in opposite direction, drawing fluid into cavity space and displacing the fluid towards the discharge as they rotate at speed timing gears bearings seals good for high pressure viscous fluids fuel pump |
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sketch and describe a gear pump |
cast iron casing nitralloy hardened steel shaft and gear white metal bearings as gears separate, they create a suction void, fluid fills void, carried around to discharge, as gears mesh they displace the fluid tight clearances allow for high pressures and viscous fluids boiler fuel pump, turbocharger l.o pump |
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Sketch and describe a Centrifugal pump |
Impellor- Al Bronze - accelerates fluid, radial velocity volute - non ferrous copper alloy - divergant nozzle, wear rings - brass, provides from discharge back to suction - clearance 0.2/0.3 .. 0.8 max bush -plastic - protects shaft wears quicker mechanical seal- ceramic/stainless |
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Why are double entry impellers used on centrifugal pumps? |
reduces the NPSH in poor suction conditions, axially balances the pump, increased capacity |
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What are diffuser rings used for? |
Used for high pressure applications, multistage boiler feed pumps, increases pressure energy of fluid, circular casing |
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Why do we use multistage centrifugal pumps?
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used for higher pressure applications delivery pressure is proportional to energy imparted to the fluid... therefore inc. impellers, increase pressure |
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Why is a centrifugal pump not self priming? |
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Why do they have a poor suction lift? |
theoretical lift is around 10.3m. Reduced to approx 5m when you consider altitude, frictional loses, turbulence, temperature, suspended particles and the inhibility to create a perfect vacuum. |
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What can we do to overcome poor suction? |
1. flood the casing or position pump with a positive suction head 2. keep suction lines short, straight and vertical 3. use a positive displacement pump to remove the air form the system 4. use non return lines to keep suction lines full |
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describe and sketch a liquid ring vaccum pump |
1. |
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Describe the routine overhaul of a centrifugal pump |
1. risk assessment and permit to work 2. isolate pump mechanically and electrically. 3. split the pump and remove the rotating element. 4. inspect casing for corrosion and pitting 5. inspect shaft for corrosion and damage 6. inspect impellor for corrosion and pitting 7. gauge wear rings and measure clearance between wear ring and impeller 0.3 - 0.8 max 8. replace mechanical seal, bush, wear rings if necessary, nut 9. reassemble pump, check free rotation, and alignment with motor shaft |
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what are the advantages and disadvantages between packing and mechanical seal? |
Mechanical seals are more expensive Mechanical seals are 100% sealing Mechanical seals dont damage the shaft Mechanical seals will last between overhauls Mechanical seals are not easily replaced |
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Sketch and describe a constant speed, variable delivery pump |
swash plate pump. |
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central priming system |
insert photo |
