knots Posted January 19, 2014 Share Posted January 19, 2014 I am collecting the components for a small ( 27 Ton) metal forming / forging press. I have an new condition unused 5 HP farm duty, 230 volt, 30 amp, Cap start / cap run,1800 RPM rated motor in my existing stock of parts that I would like to use. My problem is that the literature for the two stage hydraulic pumps from which I will be selecting have product data and power curves for pumps being driven only at 3600 RPM. If the formula, Torque = HP x 5252 / RPM , Is applied the result is that a 5HP, !800 RPM electric motor provides the same torque as 10 HP, 3600 RPM motor. This leads me to conclude that the smaller 5 HP, 1800 RPM motor can be used to drive pumps, with direct shaft to shaft coupling, that the product literature recommend be driven by 10 HP, 3600 RPM motors. Note: The lower RPM drive speed will of course result in a corresponding reduction in pump volume capacity. The basic question is: When selecting motors to power positive displacement, 2 stage, hydraulic gear pumps, is torque the governing factor in the ability of the motor to drive the pump at the pump's rated pressure. If torque indeed rules, then my motor may be able to power a 16 GPM pump at the reduced speed to provide 8 GPM . I have called the pump manufacturer's technical support number, and been refered to their local vendors who seem unable to answer this question. Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 19, 2014 Share Posted January 19, 2014 Yes...I ran a 22 GPM two stage pump rated at 10hp 3600RPM off a 5hp 1750 Rpm motor. It makes half the GPM at same pressures. Runs quieter as well. I set the PSI at 2950 and to my knowledge and the gauge..it did peak very close to that the pressure. Ric Quote Link to comment Share on other sites More sharing options...
knots Posted January 20, 2014 Author Share Posted January 20, 2014 Yes...I ran a 22 GPM two stage pump rated at 10hp 3600RPM off a 5hp 1750 Rpm motor. It makes half the GPM at same pressures. Runs quieter as well. I set the PSI at 2950 and to my knowledge and the gauge..it did peak very close to that the pressure. Ric Thanks Ric -- Just what I wanted to hear. Quote Link to comment Share on other sites More sharing options...
monstermetal Posted January 20, 2014 Share Posted January 20, 2014 "real" hydraulic pumps are rated by how many cubic inches they displace per revolution not in GPM, half the revolutions half the volume. Quote Link to comment Share on other sites More sharing options...
yahoo2 Posted January 20, 2014 Share Posted January 20, 2014 That 10 HP rating is for a petrol engine drive. the 3600 rpm is the clue, If your wiring and power supply is up to the job an you don't get to much voltage drop a 6HP electric motor should do the same job. 100% load for 100% of the time. If you go over their 115% service factor for extended periods they will just pull more amps till the heat can not be dissipated and the hot windings fry the insulation. running a pump that is unloaded most of the time the 5HP should do it easy geared to 3450 rpm. If you run it real hard don't be in a hurry to switch it off, the fan needs to be able to cool the motor between jobs for a long and happy life. Quote Link to comment Share on other sites More sharing options...
Steve H Posted January 22, 2014 Share Posted January 22, 2014 You can drive the 16/4 pump with a 3 hp 1800 for 8/2 gpm. Works great on my 35 ton press. Batson's book once again breaks this stuff down better than any other reference I've seen Quote Link to comment Share on other sites More sharing options...
knots Posted January 22, 2014 Author Share Posted January 22, 2014 You can drive the 16/4 pump with a 3 hp 1800 for 8/2 gpm. Works great on my 35 ton press. Batson's book once again breaks this stuff down better than any other reference I've seen Thanks . The 16/4 pump looks like what will use . I actually found a HP/pressure curve for 2 stage pumps that confirms that a 5HP will work . The curve was for a 10 HP 3600 RPM motor which, after applying the torque conversion formula, indiactes that the 5HP x 1750 RPM motor will work. Rick's and your experience have provided a comfort zone. I am currently working on placing an order for the pump, bell, and coupler. Could be the cylinder as well . 3 HP is pushing the limits unless the supply pressure is/has been reduced. No matter if the 3HP fails it is easy enough to go to your local electrical motor service company who will be happy to unload one of their good used ones for cheap. Now that BATSON is back in the picture, and since my press is going to be a relatively low power unit, I have reopened the option that an open frame press may be the way I go. My only concern is throat depth. The Batson open press had a very shallow working depth. Gotta think that one through. I actually have a copy of the Batson book somewhere but it dissappeared with my last move. Guess my next move is to reorder it. Quote Link to comment Share on other sites More sharing options...
yahoo2 Posted January 23, 2014 Share Posted January 23, 2014 this explains the difference between gas and electric better than I can. general rule of thumb is 60% @ 3450. can go lower with intermittent short duration loading halving the speed would mean 3HP would work with a margin. (with a quality motor) Is your motor designed for direct coupling? Some are belt and pulley only. Quote Link to comment Share on other sites More sharing options...
knots Posted January 23, 2014 Author Share Posted January 23, 2014 I have a Teco-Westinghouse 5 HP, 3.7KW,1750 RPM, high torque, farm duty motor The motor frame is 184 TC. The following links are the source of most of the informaton and formulas that I have relied on for my research process. With interpretation, to adjust for motor speed, indicate to me that my 5 HP motor will be rated at or near continuous duty service when used with the 16/4 pump. http://www.concentricab.com/_downloads/Catalogs/HILO_PUMP_US.pdf http://www.reliance.com/mtr/flaclcmn.htm yahoo2 - I can find no indication in the literature of these two sources that make a distinction between electric and gasoline engine HP . I know that some retail sources do give HP requirements for pumps and accessory packages referenced for gasoline motors. I had a look at your link. Thank you for that reference. I can see the basis for your position. Your basic argument seems to indicate that, since the two motor types are rated for HP at different RPM's, a rating/derating factor needs to be appled in order to compare the two. If this is the case then the Concentric power graphs should be presented in two verisons. One for electric motors and one for Gasoline engines. So the question is: Which are they presenting in their literature ? Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 24, 2014 Share Posted January 24, 2014 "real" hydraulic pumps are rated by how many cubic inches they displace per revolution not in GPM, half the revolutions half the volume. Larry is correct and has pointed out in the past that a single displacement pump often produces more flow at the lower flow rate of the hi/low pumps than the hi/low pumps. In short...if you do not need the high flow/low pressure option on the press then go with a single displacement pump maxing out the power of the motor. My next HYD unit will be able to move the 14" cylinder I have at 1" second...which should be fun to use. Still not the power that Larry has on his large press, but.... Ric Quote Link to comment Share on other sites More sharing options...
knots Posted January 24, 2014 Author Share Posted January 24, 2014 Larry is correct and has pointed out in the past that a single displacement pump often produces more flow at the lower flow rate of the hi/low pumps than the hi/low pumps. In short...if you do not need the high flow/low pressure option on the press then go with a single displacement pump maxing out the power of the motor. My next HYD unit will be able to move the 14" cylinder I have at 1" second...which should be fun to use. Still not the power that Larry has on his large press, but.... Ric Thank you for the clarification. I hadn't considered a single flow pump. I'll have a look. Edit: Alas, the use of real pumps require real motors . Since I already have my motor I must use an unreal, 2 stage pump. Thanks for the enlightenment . Quote Link to comment Share on other sites More sharing options...
adamm Posted January 24, 2014 Share Posted January 24, 2014 yahoo2 - I can find no indication in the literature of these two sources that make a distinction between electric and gasoline engine HP . I know that some retail sources do give HP requirements for pumps and accessory packages referenced for gasoline motors. I had a look at your link. Thank you for that reference. I can see the basis for your position. Your basic argument seems to indicate that, since the two motor types are rated for HP at different RPM's, a rating/derating factor needs to be appled in order to compare the two. If this is the case then the Concentric power graphs should be presented in two verisons. One for electric motors and one for Gasoline engines. So the question is: Which are they presenting in their literature ? I think generally, the comparision between "electric hp" and "gasoline hp" is how the rating is determined. In many cases, gasoline engines are rated at their maximum output. Electric motors are rated based on continuous loading, often with a service factor that derates the output. The peak hp output of an electric motor is higher than the rating, but can only sustain that higher output for a limited time before it over heats. The gasoline engine typically can't produce any additional power over its rating. What this all comes down to, is that when you have a spike in load, the electric motor can often bear down and run through the load spike. The gasoline motor doesn't have reserve and will just stall. This means the electric motor can be sized to the nominal load, while the gasoline motor needs to be sized to the larger peak load. As far as pumps are concerned, hp is hp, doesn't matter if their electric or gasoline. The power source may effect the service factor of the pump, but that depends on a lot of factors, and probably only maters to large industrial concerns. Adam Quote Link to comment Share on other sites More sharing options...
yahoo2 Posted January 25, 2014 Share Posted January 25, 2014 There are not many applications that need a two stage pump on an electric motor, 99% sold as a unit are single stage. the one that comes to mind that is the exception is a hydraulic wool press. these are built with either a 3HP or 5HP motor and a two stage pump the ram tube is 88mm Dia and 750mm long (I know because I just replaced the seals in one this year) I dont remember the rated flow. A full cycle with a fully compressed bale is around 14 seconds, but empty or with a few fleeces in it, it is barely 5 seconds (all on first stage). That's ram full extension, bale pinned and full retraction. if the spool valve is adjusted properly they run all day with very little noise but you really hear them grunt just before they hit the second stage and as the pinning is happening with a really tight bale. If you are only moving the ram a couple of inches each stroke with your press, you could possibly trade some speed for extra force with a bigger ram Quote Link to comment Share on other sites More sharing options...
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