Lec 12 Flashcards
Mechanical device used to transfer fluid from one place to another. The source of fluid is usually of lower elevation than the point of delivery (e.g. wells, rivers, lakes, reservoirs and canals).
Water Pumping Machinery
This is pressure exerted by atmospheric air on the water surface.
Atmospheric pressure
At sea level, atmospheric pressure is?
P = 14.7 psi = 10,200 kg/m2
Atmospheric pressure decreases above sea level and increases below sea level by?
1 bar
At _____, the water surface exerts an equal but opposite pressure on the atmosphere. If a tube is dip into a surface of water and air is drawn out of the tube, the water will rise in the tube to a level where the pressure exerted by the column of water is again equal to atmospheric pressure.
equilibrium
Taking the specific weight of water as ρ = 1000 kg/m3, the rise of water in the tube will be:
h = P/ ρ = (10,200 kg/m2)/(1,000 kg/m3) = 10.2 m
The above rise of water can only be attained when:
- There is a perfect vacuum (no leaks)
- When pure water is used (various liquids have different weights)
- There is no resistance to flow (surface roughness, bends, strainer, and
couplings)
Because of water impurity and frictional losses, most pumps can lift water at less than the amount stated previously. Practical suction lift can only be specified at?
7.62 m = 25 ft
The ratio of the density of a substance to the density of a standard substance such as pure water. The rise of a liquid in a tube under vacuum would be higher if the. specific gravity of the liquid is less than 1.0. The performance of a pump is affected by the specific gravity of
the liquid (e.g. mixture of water and air, mixture of two liquids of different density, liquid with different density that water).
Specific gravity
Force acting on a body moving in a circular path tending to force it away from the axis of rotation. The water is rotated by the rotation of the cylinder with vanes. Water is forced out
against the wall of the can and
moves up. Water near the
center is drawn downward since
a vacuum is created near the
center as the water moves outward.
Centrifugal force
Discharges the same volume of water regardless of the head against which it operates. This type of pump must be powered to meet its discharge head. Because of its small discharge capacity, it is not commonly used for irrigation and drainage. However, it is commonly used for home water supply system and well drilling.
Positive Displacement Pump
Having to-and-fro (motion backward and forward or upward and downward) motion as distinguished from circular or rotary motion.
Reciprocating Pump
Four elements are necessary for reciprocating pump operation these are the following:
• Cylinder
• Piston or plunger
• Inlet or admission valve
• Outlet or discharge valve
Single-acting pump consisting of an open cylinder, piston with built-in bucket valve. When the piston goes up, water is sucked from the
source through the inlet valve and enters the lower chamber.
When the piston goes down, the inlet valve closes and the water is transferred from the lower chamber to the upper
chamber through the bucket valve. Every time the piston goes
up, water that is already in the upper chamber will spill out
from the spout.
Lift Pump
Single-acting or double acting pump consisting of a plunger, inlet valve, and outlet valve. When the plunger goes up, water is sucked
into the cylinder through the inlet valve.
When the plunger goes down, the inlet
valve closes and water is forced out of the
pump through the discharge valve. This pump forces water above
atmospheric pressure as distinguished
from the lift pump.
Force Pump
