Tài liệu Thi tuyển Lọc Dầu Nghi Sơn PUMPS SUMARY1

PUMPS SUMARY The moving part of a centrifugal pump is a………… A Impeller B Diffuser C Volute D Suction nozzle Throttling the delivery valve of a pump results in A Increase head B Increase power C Decrease head D Both A and B Installing larger diameter pipe in pumping system results in reduction in A Static head B Frictional head C Both A and B D None of the above What is the impact on flow and pressure when the impeller of a pump is trimmed? A Flow decreases with increased pressure B Both flow and pressure increase C Both flow and pressure decrease D None of the above Friction losses in a pumping system is A Proportional to / Q B Proportional to / Q2 C Proportional to / Q3 D Proportional to / Q4 For high flow requirement, pumps are generally operated in A Parallel B Series C Both A and B D None of the above The operating point in a pumping system is identified by A Point of intersection of system curve and efficiency curve B Point of intersection of pump curve and theoretical power curve C Point of intersection of pump curve and system curve D Cannot be determined by the pump characteristic curves If the speed of a centrifugal pump is doubled, its power consumption increases by _ times A No change B Two C Four D Eight Using the affinity laws in the centrifugal pump, if the speed of a centrifugal pump is doubled, its head increases by _ times A B C D 10 In centrifugal pumps, a change in the diameter of the impeller can reducing the diameter to about of maximum size A 25% B 50% C 75% D None of the above 11 Small by-pass lines are sometimes installed to A Control the flow rate B Control the pump delivery head C Reduce pump power consumption D Prevent the pump from running at zero flow 12 Centrifugal pumps have a minimum operating flow rate, below which the pump should not be run for long periods without sacrificing reliability From the standpoint of long term reliability and operating efficiency, it is the best to operate pumps close to A Maximum head B Maximum flow rate C Minimum flow rate D Their BEP 13 When packing is used to seal the shaft on a centrifugal pump: A the packing will prevent the pump from getting too hot B the packing must be adjusted daily C the packing will wear out quickly D some leakage is necessary along the shaft for good lubrication 14 The capacity of a pump is usually rated: A In GPM B In SCFM C in foot pounds per inch D in metric measure 15 Which of the following measures pump capacity? A Barrels per day B Pounds per square inch C Static head D Standard cubic feet per minute 16 In a centrifugal pump, normally ring packing is lubricated by: A a gravity flow oil system B a drip oil system C a mechanical lubricator D.The liquid being pumped 17 Normally, ring packing is lubricated by: A the liquid being pumped B outside oil systems C mechanical lubricators D hand 18 Which of these will result in an increase in flow from a pump? A Decreasing the impeller diameter B Increasing the RPM of the shaft C Increasing the required NPSH D Increasing the length of the shaft 19 In a centrifugal pump, liquid flows: A from the rim of the impeller to the suction eye of the impeller B from the outlet of the vanes to the suction eye of the impeller C from the suction eye to the inlet piping D From the suction eye to the rim of the impeller 20 Casing wear rings of a centrifugal pump: Answer: must allow no flow from the impeller back to the suction 21 If the liquid level to be pumped by a centrifugal pump is below the pump level: A the pump will not pump B the pump will only pump the liquid to a height equal to the liquid level below the pump C the pump must be primed before start-up D the pump must be lowered so that it is positioned below the liquid to be pumped 22 If the suction head of a pump is feet and the vapor pressure of the liquid in the pump (changed to equivalent head) is feet, the liquid will: A Condense B fill the casing completely C burst the pump casing D vaporize 23 Which of these pump arrangements increases head? A A B B C Neither, since head is not related to pump line-ups 24 Which of the pump line-ups below will create the most head? A A B B C Not enough information is given to make this evaluation D Since two equal sized pumps are used, the head will be the same for both line-ups 25 Which of the following is most likely to cause cavitation? D Both of them 26 27 28 29 30 31 32 33 34 35 A Worn bearings B Worn packing C Insufficient NPSH D Poor pump alignment A multi-staged pump is used: A only for pumping heavy fluids B when you need increased capacity C only for pumping light fluids D only when higher pressure is required Cavitation in a pump: A does little damage if the pump is kept running B means the pump casing has a cavity (or hole) in it C is the continual forming and collapsing of vapor bubbles in the liquid in a pump D is caused by corrosion Cavitation in a pump creates so many undesirable effects out of the following, which is not an undesirable effect created by cavitation? A Decrease in effect B Increase in thrust C Develops noise D Develops high pressure If a centrifugal pump is operated too long with the discharge valve closed: A the pump may overheat, causing a vapor lock B the pump bearings will overheat and begin to wear C the discharge valve is likely to become damaged D the discharge valve will work its way open When the discharge of one pump is fed into another pump's suction: A the pump will soon cavitate B the pumps are in parallel C the pumps are said to be operating in series D an increase in capacity and a decrease in discharge pressure will occur Balancing drums are used on multi-stage pumps: A to reduce weight B to reduce axial thrust C to increase the total flow of liquid through the pump D to balance the speed of the driver to the speed of the pump A multi-stage pump is used when you need: A increased capacity B increased head pressure C both increased capacity and higher head pressure D high velocity and lower pressure Multi-stage centrifugal pumps are generally used for A high head B low head but high discharge C highly viscous liquid D slurries of high solid concentration If the suction level is below the level of the pump, a centrifugal pump: A will not pump B will have to be primed before it will pump C will need to be lowered so that it will pump D None of these A small amount of leakage between the packing and the shaft of a pump: A usually indicates that the wrong packing has been used 36 37 38 39 40 41 42 43 44 45 B should be stopped any leakage at all is too much C is necessary for proper lubrication D is an indication that a mechanical seal is needed The speed of turbine-driven pumps can be controlled decreasing the speed of the pump will: A cause cavitation B increase the discharge pressure C increase the pump’s capacity D have the same effect as installing a smaller impeller If a pump has lost its prime: A it must be replaced B it will need extensive repairs C it must be reprimed before it can be expected to pump again D it must be shut down long enough to cool off If the pumps are taking suction from the same tank and pumping into a common discharge line: A neither pump will pump B they are said to be pumping in parallel C they will overpressure the discharge line D they are said to be pumping in series To help eliminate axial thrust in large, multi-stage pumps, we often use: A sleeve bearings B wear rings C a balancing drum D rubber bumpers The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the ………………… A Discharge B Suction C suction minus vapor pressure of the liquid at suction temperature D discharge minus vapor pressure of the liquid at the discharge temperature Net positive suction head (NPSH) of a centrifugal pump must be A greater than the vapour pressure of the liquid B less than the vapour pressure of the liquid C equal to the vapour pressure of the liquid D less than barometric pressure To prevent pump from losing prime, foot valves provided in pumps are valves A Relief B three/four way C pressure reducing D directional control Head developed by a centrifugal pump depends on its A Speed B impeller diameter C both speed and impeller diameter D neither speed nor impeller diameter What causes cavitation in centrifugal pump? A High suction pressure B Low barometric pressure C Low suction pressure D High suction velocity Answer: Low suction pressure A centrifugal pump loses prime after starting The reason of this trouble may be A incomplete priming B too high a suction lift C low available NPSH and air leaks in the suction pipe D all of these 46 A centrifugal pump designed for handling water (μ = cp) will deliver when pumping a thicker oil (μ = 30 cp) A less head & capacity B more head C more capacity D less head & more capacity 47 When the water is warm, the height to which it can be lifted by a pump A decreases due to reduced viscosity B decreases due to reduced vapour pressure C increases due to increased vapour pressure D decreases due to increased frictional resistance Answer: decreases due to reduced vapour pressure 48 Consider a centrifugal pump having a specific impeller diameter, fixed impeller speed pumping a liquid of constant density at a particular discharge capacity with decrease in the capacity of the pump, the decreases A NPSH required B BHP required by the pump C head of the liquid pumped D all of these 49 Cavitation in a centrifugal pump can be avoided by keeping the A inlet pressure high B outlet pressure low C inlet pressure low D outlet pressure high 50 The phenomenon occurring during pumping of a liquid solution containing dissolved gases, which may come out of the solution giving rise to gas pockets, is termed as A Evaporation B Cavitation C Sublimation D Stripping 51 While starting a centrifugal pump, its delivery valve should be kept A Opened B Closed C either opened or closed ; it does not make any difference D either opened or closed; depending on the fluid viscosity 52 Purpose of relief valve in a reciprocating pump is to A protect the pump against developing excessive pressure B facilitate unidirectional flow of liquid C reduce the discharge pressure D control the rate of discharge 53 Function of air vessel provided in a reciprocating pump is to _ A reduce discharge fluctuation B reduce the danger of cavitation C avoid the necessity of priming D increase the pump efficiency 54 Cavitation occurs in a centrifugal pump when the suction pressure is A less than the vapour pressure of the liquid at that temperature B greater than the vapour pressure of the liquid at that temperature C equal to the vapour pressure D equal to the developed head 55 In centrifugal pumps, cavitation occurs, when pressure of the impeller eye or vane becomes A less than atmospheric pressure B more than liquid vapor pressure C less than liquid vapor pressure D more than atmospheric pressure 56 Cavitation can be prevented by…………… A suitably designing the pump B maintaining the suction head sufficiently greater than the vapour pressure C maintaining suction head = developed head D maintaining suction head lower than the vapour pressure 57 The capacity of a centrifugal pump can be increased by increasing the A impeller diameter or speed B Number of pumps and joining them in series C Number of pumps and joining them in parallel D all of these Answer 58 Look at this drawing to answer questions, what kind of impeller does this pump have? Answer: Open impeller 59 Look at this drawing to answer questions, what kind of impeller does this pump have? Answer: Semi-open impeller 60 Look at this drawing to answer questions What is the name of X? A Total Head B Static Head C Friction Head D Flow rate 61 Look at this drawing to answer questions What is the name of A & C? A Shaft and suction end B Shaft and discharge end C Shaft and casing D Shaft and impeller 62 Look at this drawing to answer questions Which is the centrifugal pump? A A and C B A and B C B and C D None of above 63 In centrifugal pump, where are the stuffing box and mechanical seals placed? A At suction end B At discharge end C Between centrifugal pump and electric motor D None of above 64 The energy placed into the water by a pump can be expressed as an increase in and increase in A Pressure head B Velocity head C Pressure head and velocity head D Pressure head and BEP 65 Look at this drawing to answer questions What is the name of X? A Mechanical seal B Packing seal C Impeller D Volute 66 What are the basic types of maintenance? A Preventive and breakdown maintenance B Preventive and predictive maintenance C Preventive, predictive and breakdown maintenance D Other 67 In centrifugal pump, the Best Efficiency Point (BEP) is defined as A The most stable condition at which the pump can operate B The worst stable condition at which the pump can operate C The unstable condition at which the pump can operate D The most stable condition at which the pump can not operate 68 Consequently most centrifugal pump users will attempt to operate their pumps within a range of A 10% to 30% of the BEP B 30% to 50% of the BEP C 50% to 70% of the BEP D 70% to 120% of the BEP 69 Look at this drawing to answer questions, what number indicates the discharge line of this pump? A B C D 70 Look at this drawing to answer questions, what number indicates the wear rings on this pump? A B C D What number indicates the wear rings on this pump? 71 Look at this drawing to answer questions, what kind of impeller does this pump have? A Open B Close C Partially open D Turbine 72 Look at this drawing to answer Questions, The packing on this pump: A is a mechanical seal B is indicated by the number C is indicated by the number D is not shown in this drawing 73 Look at this drawing to answer Questions, The centrifugal pump shown here is: A a double suction pump B a double volute pump C a multi-stage pump D a single-stage pump 74 The specific gravity of a fluid is a comparison of the weight of a specific volume of the liquid with an equal volume of: A oil at 60 °F B Hydrogen C Water D 30 wt oil 75 What is the total head produced by this pump? A 30 B 20 C 10 76 The 43 PSIG in this drawing measures: D 40 A the pressure produced by liquid head B the pressure added by atmospheric pressure on the liquid C atmospheric pressure D the total force on the bottom of the tank 77 What is the absolute pressure on the tank pictured below? A 57.7 psia B 43.7 psia C 54.7 psig D 14.7 psia 78 High vapor pressure will be more of a problem in which of these pumps? A A B B C The problem is identical for both D.Neither Vapor pressure will not affect the pumps, only the tanks 79 A lantern ring is: A a ring through which light passes to show flow B a metal cage about the size of a packing ring in the packing box C a rubber ring used to seal the casing head of a pump D Several light beams in a circle used to measure the level in a tank 80 Which of those drawings illustrates the principle of the centrifugal pump? A A B B C C D None of these 81 Vapors need energy to escape from liquid this energy comes from A Heat B Radiation C pumping action D Electricity 82 Potential energy is: A energy of motion B electrical energy C stored energy D nuclear energy 83 Which of the pumps pictured below is a centrifugal pump? A A B B C C D None of these 84 If an electric driver for a centrifugal pump persistently kicks out or trips off: 85 86 87 88 89 90 91 92 A the pump will burn up B it usually means the motor is overloaded C it will have to be replaced D the pump has an obstruction in it and must be turned over by hand till the obstruction is cleared Design of the casing of centrifugal pump should be such as to minimize the A back flow through impeller B loss of kinetic head C loss of static head D none of these Propeller type centrifugal pumps are most suitable for A high capacity at high heads B high capacity at low heads C Low capacity at high heads D low capacity at low heads a pump is a machine used Answer: to move liquid through a piping system and to raise the pressure of the liquid A pump can be further defined as a machine that uses several energy transformations Answer: to increase the pressure of a liquid The energy input into the pump is typically ……………… This is electricity used to power an electric motor Answer: the energy source used to power the driver ……………… is the driving force responsible for the movement of the fluid Answer: Pressure ………………… is the force that slows down fluid particles Answer: Friction ………………… is the amount of volume that is displaced per unit time Answer: Flow rate