This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Pump Basics”.
1. Dynamic pumps usually rely on centrifugal force.
Explanation: These are one category of pumps under which there are many classes, 2 of which are: centrifugal and axial. These pumps operate by developing a high liquid vel. and converting the velocity to pressure in a diffuse flow passage.
2. Centrifugal pumps are the most common type of dynamic pump and the most common type of pump utilized in pulp and paper mills.
Explanation: These are utilized to transport fluids by the conversion of rotational K.E. to the hydrodynamic energy of the fluid flow. The rotational energy is generally utilized from an engine or electric motor.
3. The utilize of an adequate _________ would avoid cavitation . Much difficulty and premature wear encountered in the utilize of pumps are the result of an inadequate _________
b) Partial pressure
c) Vapour pressure
d) Saturation point
Explanation: It’s the minimum pressure required at the suction port of the pump to keep the pump from cavitating. N.P.S.H.A. is a function of your system and must be calculated, whereas N.P.S.H.R. is a function of the pump and must be provided by the pump manufacturer.
4. _________ is aggravated by utilizing liquids at high temperatures where their vapor pressure is high, by utilizing filters with high pressure drops.
Explanation: The physical process of cavitation inception is similar to that of the boiling. The major difference between the 2 is the thermodynamic paths that precede the formation of the vapor. Boiling occurs when the local vapor pressure of the liquid rises above the level of its local ambient pressure and sufficient energy is present to cautilise the phase change to a gas.
5. Cavitation could be alleviated by having a generous geodetic height for the liquid entering the pump; this is accomplished by _________ the pump or raising the reservoir.
Explanation: The faster the blade moves, the lower the pressure around it could become. As it reaches vapor pressure, the fluid vaporizes and forms small bubbles of gas.
6. Inlet pipes and filters with larger inside diameters would _________ the frictional and velocity pressure drops.
Explanation: The proper inlet pipe brings the air from the filter to the compressor with no pressure loss and shouldn’t create operational problems with any type of self-contamination on the inside. It is crucial to realize that the ambient inlet air condition may well dictate the selection of one type of pipe over another.
7. If the flow rate is pulsating with a period less than a few seconds, the utilisation of a _________ system could level the flow rate at the inlet.
Explanation: The rollers are travelling in opp. directions at the point of contact, keeping liquid from flowing through the nip, the point being to decrement or eliminate the excess dampening solution returning from the plate from interacting with the fresh metered solution from the fountain. This helps to more closely control the flow rate of the fountain solution to the plate, as the incoming solution doesn’t interfere with the outgoing solution
8. N.P.S.H. the net positive suction head, is calc. by the absolute suction head _________ the vapor pressure of the liquid being pumped.
Explanation: The calc. of N.P.S.H. in a reaction turbine is different to the calculation of N.P.S.H. in a pump, because the point at which cavitation would first occur is in a diff. place. In a reaction turbine, cavitation would first occur at the outlet of the impeller, at the entrance of the draft tube.
9. N.P.S.H.A. is the net positive suction head available and must be _________ than N.P.S.H.R. the net positive suction head required.
Explanation: Net Positive Suction Head N.P.S.H. could be defined as 2 parts: N.P.S.H. Available (N.P.S.H.A.): The absolute pressure at the suction port of the pump and N.P.S.H. Required (N.P.S.H.R.): The minimum pressure required at the suction port of the pump to keep the pump from cavitating.
10. N.P.S.H. ___________ as the square of the pump flow rate near and above the design flow rate of a pump.
Explanation: The violent collapse of the cavitation bubble creates a shock wave that could carve material from internal pump components and creates noise. The inevitable increment in vibration could cautilise other mechanical faults in the pump and associated equipment.
Sanfoundry Global Education & Learning Series – Pulp and Paper.
To practice all areas of Pulp and Paper, here is complete set of 1000+ Multiple Choice Questions and Answers.
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