Test: Hydraulic Pump - 3 - Mechanical Engineering MCQ

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.

For single acting reciprocating pump discharge

for double acting reciprocating pump discharge get doubled
hence

Function of air vessel in a reciprocating pump

• To obtain a continuous supply of liquid at a uniform rate.
• To save a considerable amount of work in overcoming the frictional resistance in suction and delivery pipes.
• To run the pump at a high speed without separation.

Operating characteristic curve of a centrifugal pump.

For head


H₂ = 40 m
For power,

P₂ = 8 kW

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.

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.

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.

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 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.