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Hydraulic pump/electric motor calculations HELP

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Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Sat Mar 07, 2015 3:48 am

Hi,

Maybe someone here can help me. :roll:

I'm making a hydraulic press for my shop, and I would want to use a hydraulic pump that I have. It's a Sauer Danfoss TFP100 gear pump, size is 2.2CC/REV.

I also have a electric motor, it's three phase 380-420V and 0.25kW, runs 1400r/min.

BUT.. is the motor too small, does it have enough power to run the pump ? I would like to get 200-230bar from the pump. (230bar is max for the pump).

Pump and motor are new.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: jrrdw » Sat Mar 07, 2015 7:35 am

What is the maximum r/min of the pump? If you build a transmission to turn 1:1 with the motor it should pump at max output, (at max rpm of both pump and motor). However as a lifelong mechanic I do not recommend running the pump at it's max rpm's.

I've seen my share of fails hoses, fittings, seals/o-rings, blown pump housings, busted welds and I can go on with more but you get the idea.

It's my advise to run the pump at 75% of max rpm. That will give you the power you need to do your work. You will also have to keep in mind the cylinder specs in respect to what the pump output is.

I have a cheapo Harbor Freight 12 ton hand operated shop press and it has been very usefull but I always respect it's power!
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Sat Mar 07, 2015 7:50 am

jrrdw wrote:What is the maximum r/min of the pump? If you build a transmission to turn 1:1 with the motor it should pump at max output, (at max rpm of both pump and motor). However as a lifelong mechanic I do not recommend running the pump at it's max rpm's.

I've seen my share of fails hoses, fittings, seals/o-rings, blown pump housings, busted welds and I can go on with more but you get the idea.

It's my advise to run the pump at 75% of max rpm. That will give you the power you need to do your work. You will also have to keep in mind the cylinder specs in respect to what the pump output is.

I have a cheapo Harbor Freight 12 ton hand operated shop press and it has been very usefull but I always respect it's power!



Motor rpm is 1400, pump maximum is closer to 3000rpm. So i will be fine with direct drive/1:1. But does the motor have enough torque to run the pump to 200bar ?

I work with hydraulics all the time and at work I use presses with 300 ton force... it's quite big :D

Cylinder is new and it has 250bar max pressure, it's also a very high quality cylinder for industrial use (PMC Polarteknik 2300 series.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: jrrdw » Sat Mar 07, 2015 2:40 pm

3000 on the pump....I don't think you'll have the speed. If you don't mind the press being really slow. Before I say anything else here, what exactly is the press being used for?
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Sat Mar 07, 2015 3:32 pm

jrrdw wrote:3000 on the pump....I don't think you'll have the speed. If you don't mind the press being really slow. Before I say anything else here, what exactly is the press being used for?


Press is used for installing/removing bearings, bushings etc. Very normal use for press.
Cylinder is not big, it's 80mm diameter and 120mm stroke (and 50mm piston rod). I would think that I get ok speed running the pump at 1400rpm, like I said i'm more concerned about the motor size/power, someone said to me that it's too small but I'm not sure :roll:
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: jrrdw » Sat Mar 07, 2015 8:13 pm

What's the HP rating of the motor and what is recomended for the pump? It should be in the paper work.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Sun Mar 08, 2015 9:41 am

jrrdw wrote:What's the HP rating of the motor and what is recomended for the pump? It should be in the paper work.


The motor is 0.25kW (0.33HP). There is no info of needed motor/power in the PDF documents I have from the pump.

There is some online calculators for this, but they all want to know how many litres/min it pumps at 200bar or so... Does that mean that if the pump size is 2.2cc/rev and r/min from the motor is 1400.. it's 2.2cc x 1400r/min = 3080cc/min = 3litres/min ?

If so, then I should have about 1kW (1.34HP) motor for running the pump at 1400r/min.. so 4 times more powerful then what I have now.. :roll:

Calculation I got from here: http://www.hydraulicsonline.com/hydraulic-calculations
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Re: Hydraulic pump/electric motor calculations HELP

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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: jrrdw » Sun Mar 08, 2015 3:35 pm

That motor is for a swimming pool pump l0l I'm glad I ask. I would be looking for a 3hp or better.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: DYI » Sun Mar 08, 2015 8:51 pm

Pump is 2cc/rev, maximum 230atm, motor output is probably about 210W after losses. Pressure work at constant pressure is P∆V. So, the work done in a single pump revolution at 230 bar is 230*100 000*0.0000022=51J. This would imply that you could get 4 rev/s or 240rpm if the motor was geared such that it operated at its most efficient speed while turning the pump at 240 rpm. When you add in mechanical losses from the gearbox, maybe 3 rev/s, at best, or 6cc/s. For an 80mm cylinder at 230 bar, that works out to 1.2 millimetres per second extension speed.

If you're interested, I can do a proper analysis of this problem to tell you what performance curve you can expect out of this, if you can give me actual specs or a model number for the motor.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Mon Mar 09, 2015 5:59 am

Hmm.. I think it's too slow and I would need to get some gears..

How about if I use my Atlas-copco LZB-44 planetary gear air motor ? It runs at 600rpm and has about 25Nm of torque ! (If I remember right). That would give me faster speed to drive the cylinder to work piece and then lower speed when pressure builds up ? This motor should have enogh power for this pump.

I can try to find the PDF document for the air motor and post is here later today..
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: jrrdw » Mon Mar 09, 2015 6:14 am

I don' t think a pneumatic motor will be practical or have the needed power, great for speed but lack power.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Mon Mar 09, 2015 7:15 am

jrrdw wrote:I don' t think a pneumatic motor will be practical or have the needed power, great for speed but lack power.


Actually air motors like this develop far more power relative to size and weight then electric motors. They also produce maximum torque at start up, meaning that I could run the motor/pump only when moving the cylinder, not like electric motor that has to be on all time to pump.
I could even throttle it or limit the maximum power by using regulator for the air motor.

EDIT: I did find an example of air motor hydraulic unit: http://www.directindustry.com/prod/glob ... 14401.html

Atlas-Copco motor like this is really good motor for many uses, the one I have is vane motor with planetary gear, It costs new somewhere between 1500 and 2000euros, so it's not some chinese cheap toy motor :mrgreen:

Anyway I might look for bigger electric motor, used they don't cost much.
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: DYI » Mon Mar 09, 2015 10:36 pm

The air motor sounds like a much better idea, assuming you have a compressor that can keep up. The performance curve is definitely in the right range, although I'm unable to find the LZB 44 in the current catalog. Are you sure it's not actually the 42 or the 46?
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Re: Hydraulic pump/electric motor calculations HELP

Unread postAuthor: matti » Mon Mar 09, 2015 11:18 pm

DYI wrote:The air motor sounds like a much better idea, assuming you have a compressor that can keep up. The performance curve is definitely in the right range, although I'm unable to find the LZB 44 in the current catalog. Are you sure it's not actually the 42 or the 46?



I Had the same problem, it's probably old version, I just looked and it says: LBZ-44 AR0006 11, 600R/MIN

It has 3/8" inlet thrads and 1/2" exhaust. motor is reversible so I can connect it so that it runs the pump in right direction. Motor is little over 200mm long and 60mm diameter, saft seems to be about 20mm diameter.
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