How to Calculate Hydraulic Horse Power
Hydraulic pump-motor and cylinder systems allow the application of extremely large forces at low-to-moderate speeds. This is in contrast to pneumatic systems, which provide lower forces at higher speeds. Every hydraulic system must have at least three components: a hydraulic pump, a hydraulic motor, and the interconnecting piping and controls. Calculating the pump horsepower needed for an application requires a knowledge of its operational forces and speeds. Does this Spark an idea?
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Instructions
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Hydraulics used in a machine application. Define the operating parameters of the hydraulic system. As an example, if a hydraulic vehicle lift in an automotive repair facility must be able to lift 8,000-pound vehicles from floor level to a maximum of 8 feet in 20 seconds, you can calculate the required horsepower for the hydraulic pump to drive the cylinder.
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Enormous forces can be applied with hydraulics. Calculate the mechanical work accomplished in one lifting cycle. In the above example, the mechanical work accomplished would be the force times the distance, 8,000 pounds times 8 feet, or 64,000 foot-pounds.
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Compute the rate at which the work is done. Accomplishing the work in a defined period determines power. If the lift accomplishes 64,000 foot-pounds of work in 20 seconds, the rate of performing the work is 64,000 foot-pounds times 60/20 seconds, or 192,000 foot-pounds per minute.
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Hydraulics lift loads easily and precisely. Convert foot-pounds per minute to base horsepower. This is the amount of horsepower required solely to lift the vehicle. Dividing the 192,000 by 33,000 foot-pounds per horsepower results in a base figure of 5.82 horsepower.
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Correct the base figure for the overall hydraulic system. Since the lift plunger itself weighs 800 pounds, and overall frictional and motor losses are about 25 percent, these terms will have to be factored in. Multiply the base horsepower, 5.82, by 1.1 (8,800 pounds/8,000 pounds) and 1.25 (loss correction factor) to yield 8.0 horsepower. Any hydraulic pump motor 8 horsepower or greater will lift the vehicle in the required time of 20 seconds.
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Tips & Warnings
The amount of horsepower required can be proportionately lower if more time is allotted to do the work.
Calculate multiple-user systems based on the gallons-per-minute method of each user, and the highest pressure required.
Hydraulic systems are capable of enormous forces and their use challenges the strongest structural components. Always consult a professional when actually installing overhead lifts, cranes and jacks
References
Resources
- Photo Credit mechanizied car park showing hydraulic cylinder image by Heng kong Chen from Fotolia.com hydraulic machine image by Heng kong Chen from Fotolia.com Hydraulic excavator at work. Shovel bucket against blue sky image by Andrei Merkulov from Fotolia.com bagger (1) image by fuxart from Fotolia.com
