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Hydraulic Pumps: Comparison between Direct and Indirect Valves ben lee

Electric motors are often used by designers and engineers to power hydraulic pumps. Some situations demand the use of a direct drive configuration between motor and pump, and others an indirect. Here’s what you need to know about each one:

Direct drives. A simple arrangement that is basically just a shaft connecting between pump and motor. They are low cost, easy to install and have the benefit of being able to eradicate pump bearing side loads. However, it’s not every situation that is going to be right for the direct drive. They will only work on a relatively small number of applications. This is because it’s essential that both the pump and motor are firmly and precisely mounted to ensure accurate alignment between the shafts of pump and motor. It may be necessary to add to the mounting pad a pilot surface with a pilot bore. Whatever the case, alignment is key in this option.

On occasion there could be a flexible coupling used. This is known as a direct coupled drive. This makes is unnecessary to use a precise shaft alignment and is one of the most often used methods of driving a pump.

Indirect drives. A far more complex approach in that this type of drive uses pulleys, chains or gears to negate the motor shaft away from the shaft turning the pump. This means that it’s possible to adjust the rpm or speed of the pump shaft. This type of drive can be set up to give almost any pump/motor speed ratio. So a pump can be driven at a speed that is most unusual by a standard motor. Alternatively, a shaft can be adapted, even though it’s turning at an unusual speed to pump-drive duties.

On the negative side, the indirect drive approach uses many more components which introduces complexity plus the associated financial outlay. This system also requires more space and it can put needless side loads onto the pump shaft.

So in summary, you have two very different approaches to hydraulic pumps. They both offer benefits and by making the right choice, you can avoid mechanical issues and expense later on down the line. 

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