Hydraulic Pump Motor

[whateg01]

I've searched, but nothing has come up, or it was on the 90th page and I didn't look that far. If it's been asked before, please direct me to the response.

tl;dr - can a pump be run with a lower hp motor?

I picked up a large hydraulic press recently. Calculations based on the pump and cylinder put this at about 20T. Not huge, but should be far faster than my enerpac clone with a manual pump, and the throw is about 24", which is more than most of my needs require, but should eliminate moving the bed often. The cylinder is 5" and the pump is a Dayton labeled version of this one:
https://www.surpluscenter.com/hydra...-in-fenner-2ad50ac-hydraulic-pump-9-10028.axd

The issue is that as good of a deal as it is, the pump is 10 hp 3ph, which is a bit much for me to feed. I have a number of 2-3 hp 3ph motors and a couple of 1ph motors in that range. So, my question is, can I pulley it down to get the same torque to the pump as it gets now, but at a lower speed? Obviously, I lose gpm in doing so, but for a home shop, that's less of a concern and it's still faster than my arm.

 

[matt_i]

Consider the hydraulic pump is a positive displacement which attemps to push a defined volume of fluid for each rotation of the shaft (cu in/rev or something like that), up until the point where the bypass spring opens.

Then your motor is rough sized with pressure * flow which equates to units of power (lbs/in^2 * in^3/sec = in-lb/sec) and drives an electric motor hp.

Bottom line is I believe you are going to lose out on peak pressure if you simply downsize the motor. With the same cu-in/rev rating the motor is going to stall due to lack of torque before you get to full tonnage.

A possibility is to downsize the hydraulic pump itself to a smaller cu-in/rev rating to match your electric motor hp and that will enable you to attaiin peak pressure/peak tonnage, but the tradeoff is that you will move the ram considerably slower.

You mentioned belt reduction, just make sure that your hydraulic pump is setup for an "overhung" aka cantilevered load of the belt drive. Most of the hydraulic setups I've seen are direct-shaft coupled with the electric motor. (and consequently you sometimes get C-face motors and not foot-mounted versions) A possibility is to design your belt drive such that the sheave has its own bearings and then the sheave-shaft directly drives your hydraulic pump's input shaft.

 

[whateg01]

The reduction is so that I don't stall the motor at the rated pressure of the pump. If I go that route, I'll run another shaft set in bearings for the pump to attach to, so the pump will know no different. It'll think it's attached to a motor. I couldn't think of any reason the pump would be damaged by being run slower than rated but figured it better to ask.

 

[brownbagg]

hydraulic pumps are based on pressure and GPM, so the gpm would be rpm of pump, most pump pressure are around 2000 psi. gpm would be speed. 2000 time ram size (diameter) would be force

so what variable would not work

 

[whateg01]

I understand where it all comes from. Just don't want to damage anything. Pumps have a rated rpm. I assume that's just so you know how fast is spinning to get the rated flow, but I wasn't sure if there were other factors in it.

 

[nadogail]

IMHO, you probably could cobble together a drive for that pump, but without the right combination of speed and power your results will most probably disappoint you.

A smaller displacement pump could make the pressure you need, with the smaller motor you have, but not at the flow rate you want.

 

[J king]

You won’t have enough pressure and performance will be poor. It takes a lot of hp to power a pump and get the flow- pressure. Went thru this on my car lift

 

[metlmunchr]

No problems from running at a lower speed. As mentioned, just don't put a side load on the shaft as the bearings in a face mount pump won't be sized for that load.

All gas or diesel powered hydraulic equipment operates its pump(s) at speeds varying from idle to full engine speed with no ill effects, and in many cases where gear type pumps are used, the same pump is used in both mobile equipment and constant speed electric motor driven applications.

The ability of a hydraulic pump to build max pressure is based on available input torque which you can obviously multiply via speed reduction. Horsepower is nothing more than a calculated function of speed and torque. If you need 10 ft lbs and your motor is only capable of 5 ft lbs, then a 2:1 speed reduction will give that 10 ft lbs at the output end of the reduction, with a result of half the rated volume output for the pump.

 

[whateg01]

IMHO, you probably could cobble together a drive for that pump, but without the right combination of speed and power your results will most probably disappoint you.

A smaller displacement pump could make the pressure you need, with the smaller motor you have, but not at the flow rate you want.

I don't know how it would disappoint me. The pressure developed is determined by the load at the other end, system losses to friction in the lines, and any leakage within the pump itself. I don't expect to get the gpm the pump is rated for since I'd be turning it more slowly. But it's still going to be far faster than me pumping a manual pump. If I had been using as it is now for years and then went to a smaller pump, sure, it would seem pretty slow. But that's not the reference I'm starting at.

 

[whateg01]

Thanks all! I'll get to work adapting to a different motor. I'd like to get this in the shop and get the manual one gone. With a little luck, I'll about break even on the upgrade!

 

[Oilguy]

HP required can be calculated this way:

HP = GPM x Pressure x .000583
A rule of thumb estimate is 1HP for 1 GPM at 1500 PSI.
If you cut the flow in half, the HP required is cut in half.

I will add another precaution to the one's stated above. If you have a vane pump, they have a minimum RPM. usually around 500-600.

If you know the pressure required, you can purchase units like SPX/Stone, etc. from companies like Grainger, Applied Industrial, Motion Industries. Same design as on car hoists. The pump is direct drive off the motor and no side load stresses.

 

[Bert_]

Original post is not clear whether you have three phase. Almost sounds like you do since you mention having 2-3hp 3ph motors?

 

[whateg01]

Original post is not clear whether you have three phase. Almost sounds like you do since you mention having 2-3hp 3ph motors?

I only have 1ph but use VFDs for other machines. However, it's obviously easier to wire in a 1ph motor than to go that route.

Also, I realize I can buy another pump. There are countless options out there. But, I have this pump on hand. I have the materials to mount the pump on another shaft and drive it with a motor. I'll have another look at the pumps that are out there and see what it'd cost to replace the whole thing, but no matter what, I will probably have to mount the pump differently. None of the motors I have are c-face, so machining a new end bell or buying yet another motor isn't appealing right now, anymore so than buying a new pump. Call me cheap if you want to.

 

[66cj225]

You need more friends in industrial scrap yards.

 

[whateg01]

You need more friends in industrial scrap yards.

The lack of space in my shop says otherwise! That's how I've ended up with some of the stuff I have. The welding shop I buy most of my steel through also has a scrap yard. They had a big Cincinatti shaper out there for awhile. When it was put there, it was clean metal. I asked about it and he said the shop he got it from had moved and they didn't have room for it. I could have bought it for scrap price, but it was as big as my car!

Dave

 

[66cj225]

The lack of space in my shop says otherwise!

Ok, now you need to get beyond the wow factor and find the needed hydraulic power pac and motor(s). It is not uncommon for press to have 2, one high volume low pressure and the other high pressure low volume or a double stack if you don't mind.

 

[Oilguy]

The pump on the link you posted would require approximately 15 HP at 1500 PSI, 1750 RPM. Slow it down to 1/2 speed and HP would be 7.5. If pressure is 3000 PSI, HP required would be 30 at 1750 RPM. Not sure how much side load the shaft and bushing could withstand if belt driven without a jackshaft.

 

[Oilguy]

One more piece of dribble. To get 20T on a 5" bore would require 2037 PSI.
F= P x A. The area of a 5" bore is 19.635 sq. in.

 

[whateg01]

The pump on the link you posted would require approximately 15 HP at 1500 PSI, 1750 RPM. Slow it down to 1/2 speed and HP would be 7.5. If pressure is 3000 PSI, HP required would be 30 at 1750 RPM. Not sure how much side load the shaft and bushing could withstand if belt driven without a jackshaft.

Interesting. I didn't do the math, assuming that the motor was mated to the pump by the manufacturer and they would match all of the specs. So, this 10 hp motor was never utilizing the pump's full potential. Good to know when I start sizing pulleys, etc. In the end, I may end up buying a pump to better match the motor, but unless the one c-face motor I have is suitable, I will still need to find a way to mount the pump. I guess that could just be a big L-bracket, though. Thanks for that info!

 

[Oilguy]

The pump you linked to would require an SAE size A foot bracket for mounting which is readily available from several sources. Or build a bracket with a 3 1/4" hole. Try Northern Hydraulics for example for a foot mount.
Another piece of dribble, the tension on the pump's drive pulley should be installed so that the belt is trying to pull the pump shaft toward the inlet. That will help counteract the forces developed in the pump when the high pressure side tries to push the gears and shaft toward the low pressure side and creates internal wear and affects the life of the shaft bushing.

 

[whateg01]

The pump you linked to would require an SAE size A foot bracket for mounting which is readily available from several sources. Or build a bracket with a 3 1/4" hole. Try Northern Hydraulics for example for a foot mount.
Another piece of dribble, the tension on the pump's drive pulley should be installed so that the belt is trying to pull the pump shaft toward the inlet. That will help counteract the forces developed in the pump when the high pressure side tries to push the gears and shaft toward the low pressure side and creates internal wear and affects the life of the shaft bushing.

If I use this pump, it'll be with a jackshaft in place of the motor, so all of the belt tension will be on that shaft's bearings. With that in mind, and considering the pulleys that I'll need to make or buy, I am now looking at a different pump. Last time I checked, I thought I remembered the pumps being more expensive, but they seem more reasonable. Could be a product of timing, or maybe I was just poorer then than now.

 

[whateg01]

ready-made car lift power units are starting to look pretty appealing now. Thanks all who mentioned them for reminding me that they exist!

 

[Oilguy]

With a 5 x 24 cylinder, the volume required to extend is 471 cubic inches. That is the equivalent of 2 gallons. Make sure the tank on your new unit has that capacity in storage. Most of those small units are designed for single-acting cylinders with spring or gravity return and require some additional work for a double-acting application.

 

[whateg01]

The one that I'm looking at has a tank capacity of 10 l or 2.6 gallons. It's a steel tank so I guess if I really get concerned about it I could go ahead and make it bigger before I put it into use. I doubt I will though

 

[firebirdparts]

So, my question is, can I pulley it down to get the same torque to the pump as it gets now, but at a lower speed? Obviously, I lose gpm in doing so, but for a home shop, that's less of a concern and it's still faster than my arm.

You are correct.

 

[whateg01]

The lift pump might not work. They seem to be single acting, which makes sense since a lift will have weight to push it back down. Back to the drawing board...

 

[Oilguy]

SPX makes units with an optional manifold (KB11) that mounts to the valve plate between the motor and pump which will allow you to mount a 4-way directional valve for double acting cylinders. Look at their website. I built quite a few of them for an OEM customer. You can get a manual control valve to mount to the manifold, size D03.

 

[whateg01]

Thanks. I'll have a look at it that.