27 replies to this topic

[Weld Inc]

I have a chance to pick up a Vickers hydraulic power unit for $250. It has a 3 phase 5 hp motor running at 1730 rpm. the pump is a variable displacement piston ranging from 300 to 3000 psi. It is only 5gpm. Would it be too slow for a hydraulic forging press? I am shooting for a 15 to 30 ton press. This unit comes with a 5" or 6" x 18ish" cylinder (exterior dimensions). No exact specs on the cylinder but I could always get a different cylinder. Thanks!

[ciladog]

If you calculate the area of the cylinder piston and divide that into the gpm it will give you the ram travel per minute.

Example: A 5 inch piston is 19.64 square inches. If it travels 1 inch, it needs 19.64 cubic inches from the pump. A 5 gpm pump puts out 1,155 cubic inches per minute. So the ram will move 59 inches per minute or about 1 inch per second.

Compare that to a 6 inch piston and the ram will only move 40 inches per minute or about 1 inch every 1.5 seconds

[poleframer]

I'd read somewhere (I could be wrong) that pumps are rated at 1200 rpm, you may be getting more than 5 gpm at 1750, might be worth checking the pumps actual displacement too.

[HWHII]

Weld Inc, on 09 September 2010 - 01:27 AM, said:

I have a chance to pick up a Vickers hydraulic power unit for $250. It has a 3 phase 5 hp motor running at 1730 rpm. the pump is a variable displacement piston ranging from 300 to 3000 psi. It is only 5gpm. Would it be too slow for a hydraulic forging press? I am shooting for a 15 to 30 ton press. This unit comes with a 5" or 6" x 18ish" cylinder (exterior dimensions). No exact specs on the cylinder but I could always get a different cylinder. Thanks!

I am not an expert by any means on this and still learning alot on hydraulics. What you do have is a low presure pump. I have a H frame press which was converted with a low press cylinder 4' dia. and a 18' stroke, which is I was told about 13 ton. It is slow but by prepositioning the ram were I want it helps alot. As Grant Sarver says you can do alot with 13 ton and he is absolutely right. I am building a 30 ton C frame high pressure but have not had much time to work on it.

[Weld Inc]

Thanks for the fast responses! How many inches per second is considered fast?

[Jose Gomez]

Im currently building a 100 ton two station forging press using what sounds like the same pump/motor combo. if you post the vickers model number off of the tag on the pump I can tell you what the pumps maximum displacement is (probably 15 GPM). Also I have a bunch of manuals and tuning info for these axial piston pumps that I'll be happy to send you if you give me the pump model.

[Nakedanvil - Grant Sarver]

Hey Jose! My system has a Vickers 25V0 P2A. Can you tell me anything about it?

[Weld Inc]

The power unit has a 5 hp motor 1730 rpm 3 phase. The pump model is PVB5RSY20CC11. I haven't seen the unit first hand yet so hopefully this us accurate. Any more info is greatly appreciated!

[Jose Gomez]

Grant, I have a sneaking suspicition that the o might be a Q which would lead me to think you have a 25VQ P2A, Not too terribly sure, the modle number you gave me is not lining up with any of the literature that im finding, but here are a couple of options for the 25V sieries vane pumps, hopefully one is right.

http://hydraulics.ea...pdfs/i3157s.pdf
http://hydraulics.ea...pdfs/i3158s.pdf
http://www.knighthaw...m/vic25Vdwg.htm
http://hydraulics.ea...9501en0298a.pdf

And here is some info for Weld Inc's PVB5RSY20CC11, Looks like yours is a 5 GPM piston pump.

http://hydraulics.ea...pdfs/i3239s.pdf
http://www.knighthaw...cpistonpfb5.htm

This is all that I have with me here at work, but when I get home I'll put up some more info that I have on flow rate VS pressures for the piston pumps

[Jose Gomez]

Weld Inc, here is more than you ever wanted to know about the PVB 5 pump.

Attached Files

•  vickers pump.pdf   535.85K   39 downloads
•  Vickerspump2.pdf   80.6K   24 downloads

[Weld Inc]

Jose Gomez, on 09 September 2010 - 10:09 PM, said:

Weld Inc, here is more than you ever wanted to know about the PVB 5 pump.

Thanks! Do you think that 5 GPM is to slow for a forging press used for punching and drawing out?

[Jose Gomez]

Welder Inc... 5GPM is not a whole lot. The main issue that your facing is ram speed. In most typical home made forging presses a two stage gear pump is used. In this setup the first stage supplies low pressure high volume (15 or so GPM @ 500 or less PSI). This stage supplies the volume that a moderate sized cylinder capable of providing sufficient forging force needs to move rapidly until the dies contact the workpiece. (4 to 6 inch diameter cylinder developing 24 to 40 tons with 1+ inches per second no load speed). When the dies hit the workpiece the pump shifts to the second stage. In the second stage the average pump will only typically move around 5 GPM at 2000-3000 PSI depending on what the relief valve is set to. Your pump moving 5 GPM maximum will move a small ram at a set speed fast enough for forging, but the problem is that you will end up spending a lot of time waiting for the ram to cycle. The one cool thing about variable displacement piston pumps is that they are capable of moving from near 0 GPM up to there maximum rated output, therefore they are capable of building and *holding* pressures of up to 3000 PSI. In a gear type pump, fluid pressure can not be stored easily due to the fact that the pump must constantly move fluid or they will over heat the fluid and stall the motor driving the pump, therefore most gear pumps idle at about 50 PSI while constantly recycling fluid from, and back to the resivoir. Because of this, you have to wait for a gear pump to build pressure (1-2 seconds). But with a piston pump a system can be charged to 3000 psi and have this pressure immediatly available. Or you can store massive amounts of fluid under pressure (by using an accumulator). This is the direction that I have gone. I am using a 15 GPM variable displacement pump and an 18 gallon accumulator. With this set up I am pushing a 10.25"diameter 18"stroke main cylinder, and a 5.5"diameter 22" stroke fast acting cylinder. The Accumulator should store enough fluid under opperating pressure to allow me to move the ram extremely fast when it is not under load. With the proper sized accumulator you should be able to complete numerous forging operations and have the system recover between forging cycles. The problem is that unless you have found a great place to scrounge it is typically cheaper and easier to set up a two stage gear pump....hope this helps.

[Weld Inc]

Jose Gomez, on 10 September 2010 - 01:37 AM, said:

Welder Inc... 5GPM is not a whole lot. The main issue that your facing is ram speed. In most typical home made forging presses a two stage gear pump is used. In this setup the first stage supplies low pressure high volume (15 or so GPM @ 500 or less PSI). This stage supplies the volume that a moderate sized cylinder capable of providing sufficient forging force needs to move rapidly until the dies contact the workpiece. (4 to 6 inch diameter cylinder developing 24 to 40 tons with 1+ inches per second no load speed). When the dies hit the workpiece the pump shifts to the second stage. In the second stage the average pump will only typically move around 5 GPM at 2000-3000 PSI depending on what the relief valve is set to. Your pump moving 5 GPM maximum will move a small ram at a set speed fast enough for forging, but the problem is that you will end up spending a lot of time waiting for the ram to cycle. The one cool thing about variable displacement piston pumps is that they are capable of moving from near 0 GPM up to there maximum rated output, therefore they are capable of building and *holding* pressures of up to 3000 PSI. In a gear type pump, fluid pressure can not be stored easily due to the fact that the pump must constantly move fluid or they will over heat the fluid and stall the motor driving the pump, therefore most gear pumps idle at about 50 PSI while constantly recycling fluid from, and back to the resivoir. Because of this, you have to wait for a gear pump to build pressure (1-2 seconds). But with a piston pump a system can be charged to 3000 psi and have this pressure immediatly available. Or you can store massive amounts of fluid under pressure (by using an accumulator). This is the direction that I have gone. I am using a 15 GPM variable displacement pump and an 18 gallon accumulator. With this set up I am pushing a 10.25"diameter 18"stroke main cylinder, and a 5.5"diameter 22" stroke fast acting cylinder. The Accumulator should store enough fluid under opperating pressure to allow me to move the ram extremely fast when it is not under load. With the proper sized accumulator you should be able to complete numerous forging operations and have the system recover between forging cycles. The problem is that unless you have found a great place to scrounge it is typically cheaper and easier to set up a two stage gear pump....hope this helps.

Thanks. That helps a lot. I will look into finding an accumulator. I do like the aspects of the variable displacement piston pump and would like to make it work. With an accumulator and the variable displacement is it possible to get the best of both worlds being able to work smaller delicate operations backed off and larger operations full on with the accumulator in function? What type of accumulator would you suggest? I was also considering replacing the motor with a higher rpm motor or having this one rebuilt for higher rpm if possible.. . Thanks for all the help Jose

[NeatGuy]

Jose, I would be interested in how you use the accumulator. I have been planning on the using one and like to hear your comments on my circuit.  hydraulic-circuit.pdf   3.81K   51 downloads

brad

[Weld Inc]

If I am understanding things correctly, a 5gpm pump is adequate for doing the actual work but not efficient practically in terms of getting the ram to and from the work?
I have done some research on valving circuits and discovered the regeneration circuit which in essence can negate the bore size and run a cylinder with less force at the speed of a cylinder with a bore the diameter of the the rod, of course with correspondingly less force. Then it can switch back using the cylinder in a normal fashion at slower speed and higher force.
Here is a link to a very good example, ( and much better explanation!) My link.
Does anyone have any thoughts if this could work and be a good set up? I like the idea of an adjustable displacement pump with on demand pressure explained above. It could also mean I could get this power unit for the $250 i metioned earlier and spend more doe on the frame and dies! Thanks for your opinions!

[Weld Inc]

I was also wondering how important is the retraction speed? Is it important for lessoning work contact time (heat loss or seizing punches etc) or just general practicality?

[Nakedanvil - Grant Sarver]

I ran a regenerative circuit once. Usually only done on a cylinder with a rod 1/2 the area of the piston. My press had an 8" bore and a 5" rod. The idea is that for rapid advance you can put pressure oil to both ends and the net effect is that the ram advances at double speed. I had a 5000psi system at the time. Well it turns out that if you don't have exactly the right valving it's possible to have it act as an intensifier and the 5000 psi in the top can create 10,000 psi in the bottom. If this happens for even a moment, you can blow out the bottom seal (don't ask me how I know).

Retraction speed is just important to speed up the whole cycle. A bigger rod helps to speed up the retraction by taking up some of the space in the bottom end, less oil required to fill it.

[Weld Inc]

Sounds like a scary or at least messy learning curve! Given correct and balanced valving and an appropriate cylinder do you think I could come up with a good forging press for punching and drawing with a 5hp 5 gpm power unit? Not sure why but I am stuck on getting the unit. Seems like a good price and I like the idea of a single stage variable displacement pump. I have calculated that with a four to five inch bore size I could get around an inch per minute ram speed at normal pressure and almost two inches per minute with the regenerative circuit. That's with 15 to 20ish tons pressure if I can get 2500 psi out if the pump. I don't have my calcs with me so that is from my heavily weathererd memory. Thanks for the input!

[Mainely,Bob]

STOP!!!
Unless I`m mistaken,Grant just laid another gem before us!

"A bigger rod helps speed up the retraction",makes sense as it the larger rod cuts the displacement yet the power remains and the larger rod will also be more rigid and less likely to bend under full power.

BRILLIANT!
File that little tidbit away under STOCK.

Sounds like Weld inc can snap up that pump and use it to good effect if he couples it to a cylinder with a large diameter rod.

It`s always the simple stuff that`s right in front of you ain`t it?
Stick that ice cream cone to my forehead for me,would ya.

[ciladog]

Weld Inc,
Nowhere have you said what you intend to use the press for. In some cases ram speed matters and in some it doesn’t. If you want to use the press for pattern welding, the ram moves less than an inch each time. If you will use the press as a process machine knocking out parts, it needs to move fast.

Consider this; a press is not a forging hammer and it will not do what a hammer can do. A hammer on the other hand will do everything that a press can do and much more. You can put forming dies on both.

When I seriously got into smithing the first machine I built was a 30 ton press. I thought a press was a lot easier to build than a hammer and it was in my knowledge set. I put a lot of thought into what the press was going to be used for and designed it accordingly.

So the press was finished and the first thing I needed to do was forge some flat dies for it. Got some 3 inch round H13. I thought this would be a fast process and I would have nice rectangular flat dies in no time. Wrong!!

I got that billet up to heat in the propane forge and put it in the press. I thought with 30 tons of force that I would have to careful not to press too far. Well the heat got sucked out of that billet so fast when the press closed that it didn’t upset like I thought it would. I heated and pressed time and time again. I did finally get it into a rectangle but never got the corners square. And there was so much scale pressed into the steel. I took a lot of time in a surface grinder to get it finished.

I made a bunch of dies for all kinds of processes for the press and soon learned there were things a press will do well and things it will not. I was soon drawing up plans to build a hammer.

When the hammer was built and after getting used to it workings for a few days, I had to try that left over piece of H13. Five heats and I had a nice rectangular die with nice sharp corners and no scale pressed into it.

So my advice is to know what you intend to use the press for and if it is for general smithing, put your money into a hammer.