To avoid cavitation in centrifugal pumps
A centrifugal pump gives maximum efficiency when its blades are
Backward blades are used for maximum efficiency. It gives better performance over wide range of application where forward blades are used for higher pressure ratio.
Discharge of a double acting reciprocating pump is
L = length of stroke
A = cross-section area of piston
N = speed of crank in RPM
For single acting reciprocating pump discharge
for double acting reciprocating pump discharge get doubled
The flow of water leaving the impeller in a centrifugal pump casing is
Air vessel in a reciprocating pump is used
Function of air vessel in a reciprocating pump
The characteristics of a pump are as shown in the given figure. Based on this figure, match List-I with List-II choose the correct answer using the codes given below the list:
List - I
A. Curve P
B. Curve Q
C. Curve R
List - II
1. Discharge versus head
2. Head versus discharge
3. Power versus discharge
4. Efficiency versus discharge
A B C
(a) 2 4 3
(b) 1 3 2
(c) 1 4 3
(d) 4 3 1
Operating characteristic curve of a centrifugal pump.
A pump running at 1000 rpm consumes 1 kW and generates head of 10 m of water. When it is operated at 2000 rpm. Its power consumption and head generated would be
H2 = 40 m
P2 = 8 kW
Match List-I (Type of pump) with List-ll (Liquid handled) and select the correct answer using the codes given below:
A. Closed impeller pump
B. Semi-open impeller pump
C. Open impeller
1. Sandy water
3. Sewage water
A B C
(a) 1 3 3
(b) 3 1 2
(c) 2 3 1
(d) 1 2 3
Closed impeller provides better guidance for the liquid and most suited when the liquid to be pumped is pure and comparatively free from debris. Hence acids is the suitable candidate. Semi-open type impeller is suitable even if the liquids are charged with some debris. Hence sandy water is the suitable this for semi-open impellers.
Open impellers are useful in the pumping liquids containing suspended solid matter such as paper pulp, sewage and water containing sand or grit. These impellers are less liable to clog when handling liquids charged with a large quantity of debris.
Consider the following statements regarding air vessels provided in reciprocating pump installations
1. The air vessels are fitted both on suction and delivery sides
2. The air vessels are fitted for from the pump cylinder
3. The air vessels save energy by reducing the friction loss
Q. Which of these statements are correct?
An air vessel is a close chamber having an opening at its base through which the liquid may flow into the vessel or it may flow out from the vessel air vessel fitted to suction and delivery pipes of a single-acting pump. The air vessel fulfill following functions.
(i) It continuous supply of provides liquid at a uniform rate.
(ii) It saves considerable amount of work in overcoming the frictional resistance in suction and delivery pipes.
(iii) It facilitates pump to run at a high speed without separation.
Select the most appropriate pump from Group-2 to handle each fluid flow given in Group-1.
Group - 1
P. Highly viscous fluid flow
Q. Fluid containing large amount of abrasive solid
Group - 2
1. Piston pump
2. Gear pump
3. Plunger pump
4. Centrifugal pump
Piston pump will not handle corrosive liquids and slurries containing abrasive solids, since damage is done to the valves and the machined surfaces of the cylinder and piston. Centrifugal pumps are widely unused in the chemical industry because they can be constructed to handle corrosive liquids and suspensions.
Priming is necessary in
Filling the pump casing and the suction pipe with the liquid before it is started is known as priming. Unless the centrifugal pump is primed, it will not start as there is not centrifugal head impressed on the liquid. Positive displacement type reciprocating or rotary pump do not needed priming because the air if any in the cylinder or casing is driven out by the piston or vanes.
When two identical centrifugal pumps are operating in series on a common rising main then
When two pumps operate in series, discharge remains same and head produced is doubled and if they operate in parallel, discharge is doubled and head remains the same.
Match List-I (out-let vane angle β2) with List-II (curves labelled 1, 2 and 3 in the given figure) for a pump and select the correct answer using the codes given below the lists:
A. β2 < 90°
B. β2 = 90°
C. β2 > 90°
A B C
(a) 1 2 3
(b) 1 3 2
(c) 2 1 3
(d) 3 2 1
The correct sequence of the centrifugal pump components through which the fluid flows is
At the eye tip of a centrifugal impeller, blade velocity is 200 m/s. While the uniform velocity at the inlet is 150 m/s. If the sonic velocity is 300 m/s then the inlet mach number of the flow will be