Date post: | 12-Jan-2016 |
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Pumps and Lift Pumps and Lift StationsStations
BackgroundBackgroundFluid Moving Equipment
Fluids are moved through flow systems using pumps, fans, blowers, and compressors. Such devices increase the mechanical energy of the fluid. The additional energy can be used to increase
• Velocity (flow rate)• Pressure• Elevation
Why are most water towers 130 feet high?
Because a column of water
2.31 ft high exerts a
pressure of 1 psi, and most
city water systems
operate at 50 to 60 psi
Static Head Difference in height
between source and destination
Independent of flow
destination
source
Statichead
Statichead
Flow
Friction Head Resistance to flow in pipe and fittings
Depends on size, pipes, pipe fittings, flow rate, nature of
liquid
Proportional to square of flow rate
Frictionhead
Flow
The allowable limit to the suction head on a
pump
33 - friction losses through the pipe, elbows, foot valves and other
fittings on the suction side of the pump
Net Positive Suction Net Positive Suction HeadHead
Determine the power required to pump 2000
gpmagainst a head of 14 ft, if the efficiency of the pump
is75% or 50%.
Power Requirement Power Requirement Example Example
Power Power Requirement Requirement
Example Example
Lower efficiency means bigger motor and electrical controls, higher operating costs
DC = 0.375” per dayArea drained = 28 acresLift (from tile outlet in sump todischarge pipe outlet) = 6 ftLength of discharge pipe = 25 ftPump cycles per hour = 5 and 20.
Determine suitable sump size
Sump Sizing Sump Sizing Example Example
Storage Volume (ft3) = 2 x Q (gpm)
n (cycles/hr)
Sump Sizing Sump Sizing Example Example
Area of a Circle = 3.14 x (Diameter)2
4 .
Design Flowrate
Q = 18.9 x DC x A
Q = 18.9 x 0.375 x 28 = 198.5 gpm
Say use Q = 200 gpm
Sump Volume Calculation (5 cycles/hr)
Vol = 2 x Q / n
Vol = 2 x 200 / 5 = 80 ft3
Min Required Volume = 80 ft3
-Try 4 ft diameter well
Area = 3.14 x 42 / 4 = 12.6 ft2
Storage Depth = 80 /12.6 = 6.35 ft
Try 6 ft diameter well
Area = p x 62 / 4 = 28.3 ft2
Storage Depth = 80 /28.3 = 2.83 ft
Flowrate varies with rotational speed:
Q1/Q2 = N1/N2
Head varies with rotational speed squared:
H1/H2 = (N1/N2)2
Power varies with rotational speed cubed:
P1/P2 = (N1/N2)3
AFFINITY LAWSAFFINITY LAWS
A pump with an efficiency of 80%, connected to a diesel engine, pumps 200 gpm against a head of 12 ft. What is the power output of the engine? What will be the flow rate, head and power output if the motor speed is increased from 500 rpm to 600 rpm?
Affinity Laws Affinity Laws Example Example
P =(200 x 12)/(3960 x 0.8) = 0.76 hp
Q2 = 200 x (600/500) = 240 gpm
H2 = 12 x (600/500)2 = 17.3 ft
P2 = 0.76 x (600/500)3 = 1.3 hp
Affinity Laws Affinity Laws Example Example