Hydraulic pumps
are used to move all sorts of liquids through pipes and hoses.
Hydraulic pumps move fluids. To do so efficiently, they must have sufficient power to keep the motor running at peak flow. The power requirements are affected by the speed at which the pump must operate, the volume of fluid that must be pumped and the pressure that develops in the pipes or hoses through which the fluid is pumped. Over the useful lifetime of a hydraulic pump, the cost of fuel to run it will vastly exceed the equipment cost, so you want a pump that will provide enough power without using more fuel than necessary to run it efficiently.
Power Calculation
The standard formula to determine how much horsepower you need is the sum of the flow in gallons per minute times the pressure expressed in lbs. per square inch divided by the sum of 1,714 times the pump's mechanical efficiency. This formula can be simply used for any electrically powered hydraulic pump that works in a constant flow system. If the needs of the flow run on a cycle with different requirements during the cycle, using the same calculation for the peak flow will work, but may involve more energy costs than you actually need. As long as the pull-up torque is sufficient to keep the motor running during the peak of the cycle, you have enough motor for the job, even though it will run more slowly during the cycle peak. You will find the motor's efficiency rating in the manufacturer's specifications packet included with each motor.
Electric Motors
Electric pumps are always a straightforward calculation because their start-up torque requirements are always much greater than the running torque. Since the horsepower is sufficient to cover the large start-up torque, you never have to worry that you will not have sufficient power to maintain torque in operation. This makes it easy to get the right pump for a fixed location simply by calculating how much power is needed and running electricity to the motor. The concern with an electric motor is to not oversize it, increasing electric costs beyond what is needed for efficient and continuous operation.
Gasoline and Diesel Pumps
Hydraulic pumps are often needed for spot work in areas where electricity is not conveniently available. Gasoline and diesel-powered pumps offer a superior portability that can handle spot jobs, but the torque-speed curve works much differently than in electric motors. It is much flatter and torque increases as it speeds up, so the horsepower needed for an electric motor may not be sufficient to properly operate a liquid-fuel powered pump. The rule of thumb is to get two and a half times as much horsepower in a liquid-fueled pump as in an electric pump to do the same job.
