This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Centrifugal Pumps”.
1. The ___________ is the piece that rotates inside the casing to effect pumping. The input of the pump is at the eye and the liquid enters perpendicular to the plane of the ________ in the volute or spiral design.
Explanation: Impellers are usually short cylinders with an open inlet to accept incoming fluid, vanes to push the fluid radially, and a splined, keyed, or threaded bore to accept a drive-shaft.
2. Another type of dynamic pump, the _________ pump, utilizes an inline input and output inside a tube shaped houtlising.
Explanation: These are also known as propeller pump. These pumps develop most of their pressure by the propelling or lifting action of the vanes on the liquid.
3. Centrifugal pump action is characterized by the pump performance curve.
Explanation: Centrifugal pump action is characterized by the pump performance curve, upper curve of the graph on the right. The maximum pressure that could be achieved is usually sufficiently low such that a pressure relief valve isn’t required.
4. The maximum pressure that could be achieved is usually sufficiently high such that a pressure relief valve is not required.
Explanation: Centrifugal pump action is characterized by the pump performance curve upper curve of the graph on the right. The maximum pressure that could be achieved is usually sufficiently low such that a pressure relief valve is not required.
5. The _________ is a function of the height to which the liquid is pumped; the frictional resistance of the pipes, valves, and bends; and the velocity head, the energy required to accelerate the fluid.
a) Pump response
b) System response
c) Pump efficiency
d) System efficiency
Explanation: The static head, which is constant with flow rate; the frictional resistance of the pipes, valves, and bends; and the velocity head, the energy required to accelerate the fluid (the kinetic energy is equal to 0.5 mv2).
6. N.P.S.H. requirements could be _________ by utilizing an inducer, a low head, axial flow impeller utilized in front of the impeller of a centrifugal pump.
c) Barely meet
d) Never be meet
Explanation: N.P.S.H. is particularly relevant inside centrifugal pumps and turbines, which are parts of a hydraulic system that are most vulnerable to cavitation. If cavitation occurs, the drag coefficient of the impeller vanes would increase drastically – possibly stopping flow altogether – and prolonged exposure would damage the impeller.
7. In pulp and paper, flow rates are traditionally controlled by utilize of a pump operating at full power and a _________ valve to impede the flow as necessary.
Explanation: Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal confusion. This has an opening that forms a seat onto which a movable plug could be screwed in to close the valve. The plug is also known as a disc or disk.
8. Variable speed motors especially N.E.M.A. B squirrel cage A.C. induction motors might be operated by __.
a) Variable frequency drive
b) Direct current
c) 2 horsepower
d) 756 horsepower
Explanation: V.F.Ds are utilised in applications ranging from small appliances to the largest of mine mill drives and compressors. However, around 25% of the world’s electrical energy is consumed by electric motors in industrial applications, which are especially conducive for energy savings utilizing V.F.Ds in centrifugal load service, and V.F.Ds’ global market penetration for all applications is still relatively small.
9. The pump _________ is proportional to propeller diameter for a given rotational speed or the square of the peripheral speed.
Explanation: The power consumption varies as the cube of the peripheral speed or propeller diameter for a given rotational speed. Hydraulic pump capacity could be calculated as.
q = 0.26 A s / t
where q = pump output capacity (gpm).
A = area of cylinder in square inches.
s = piston stroke in inches.
t = required time for full stroke.
1 gpm =6.30888×10-5 m3/s
Explanation: When impellers are cut, both the vanes and the shroud should be cut to decrease losses from disk losses, which are proportional to the fifth power of the impeller diameter. The diameter should be selected to ensure that the pressure (head) is not excessive, and the power consumed to provide the required coverage for the anticipated flow range, but not excessively high to overload the motor.
Sanfoundry Global Education & Learning Series – Pulp and Paper.
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