# Hydraulic calculations?



## JohnDoe (Aug 3, 2010)

Hi!

I'm not too familiar with the hydraulics field. I mean i understand how it works, but I have never done some calculations until now, and since the lack of literature i need some help with it (and/or recomendations on some realy good literature i could learn how to do it from).

I'm working on some paper about running a centrifugal pump using a hydraulic motor.

The hydraulic motor is adjustable, while the pump that runs the system runs with constant rpm.

It's realy a simple system with little count of elements.

The first problem i encountered is the filter. Both the pump and the motor require filtration of the oil with max particles size 5 micrometers)

The pump is normally located next to the oil tank. Since suction filters aren't recomendet and if they are used filtration below 100 micrometers isn't recomendet, having trouble deciding where to put the filter? If i put it in the pressure line it's possible the pump sucks something bigger than 5 micrometers isn't it?

The second question is the tank? I've been searching how to determine the needed size of the tank, and found some formula that sais that the volume is 1,5 * Vc, where the Vc is the volume of all cylinders in the system. Since I don't have any cylinders in the system i thought the Vc would indicate the displacement volume of the hydromotor should be put in instead, but that's not right since i get the needed volume needs to be less than 1 liter.

That's the trouble i have in the moment, there will surely be more, hope I can find answeres here when i stumble on some problem, although I'd like to get a great book recomendet where i can learn how to do the calculations (summed up what i need to calculate is: the filter, the oil tank volume, the cooler, losses and how much it'll get heated, so thanks in advance for the recomendet books and all the help you'll be able to give me)


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## pelaw (Aug 3, 2010)

There are two considerations 1) load (parts of system supplied by the pump), and 2) supply (pump and tank).

I am not sure what you mean by: the pump and motor need 5 um filtration, but then &lt;100 um is not recommended. Not recommended by whom? (also, why would a motor need oil filtration? Is the same oil supplying motor lubrication automatically?)

If the load requires 5 um filtration, and the supply can not operate at suction with &lt;100 um, then you have to find a different pump or put the filters for load on the load side, and size your pump to overcome that pressure drop.

The tank is sized to support the load, whatever the load needs, plus the 50% safety factor apparently (hence 1.5). (to size the tank I would go to manufacturer's catalogs and read about vapors and expansion as well.)

Anyway, the system can have 1) a pump and an oil tank already prefiltered, intended for delivery to load, and 2) return tank (collection tank from load return + new supply) with a transfer pump rated at 5 microns or less, which delivers oil to first tank. See http://redlinepumps.com/.


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