Hydraulic Pump Question

It depends on exactly what is happening. If the press is driven by two cylinders, the pump may be a duplex one that supplies equal oil to each cylinder. In that case, a single pump with a simple tee would not work; it would also require a precision flow divider.

Hi there Tornado,

I see your thinking, i will have to check this out but i would almost be sure you are right. Thanks for your valued input.

I would have to agree with Tornado, But there is also possibly another reason that there are 2 outlets from the hydraulic pump, that being to allow maximum flow to both cylinders when the press is traveling at the fast speed.

Depending on the control system though, it may be possible. You would have to look at how the control system operates, IE how the system compensates for an imballance in the travel of the hydraulic rams.

Cheers

Joe

Most press brakes have a proportional valve fitted to keep the same pressure in both rams when pressing depending on how the press is plumbed this can be through two seperate lines going to the valve block or done internally in the valve block, if you dont have a hydraulically adjustable table camber i dont know what else two lines would be for. Are their any other hydraulics on the press? You could Physically follow them out from the valve block to see where they go. I cant see any reason you cant tee the lines going into the valve block.

I think in press brake a dual pump is used to reduced the HP of a motor. This pump haves two cartridges one with high volume low pressure & another is low volume high pressue.

During operation for fast approch a high volume pump is used, & for pressing a low volume pump is used. And these pumps are connected with unloading circuit in power pack, So as per my knowledge you may not get the results by just joining a single pump with "T" joint

Hi there , Thanks again to you all for your input.

I don't think the pump is a dual cartridge due to the fact that both ports are in the end plate and opposite each other. the inlet is at the bottom at the front.

Where do the two visible tubes actually go?

These two tubes go to a valve block , bolted above the hydraulic tank. To be honest from there i have no idea as it means taking the press brake out of service to remove all the safety barriers and interlocks.

From what the customer tells me someone else came in and tested the pump pressures and said they were well down. it cant even bend a 6mm (1/4") mild steel plate 4ft long.

It runs out of steam as soon as it contacts the plate.

The general idea i have is to replace the electric motor and pump with a new updated set up(150bar/2175psi), remove the steel pipework and fit in new hydraulic hoses along with a precision flow divider as per your suggestion and also with a pair of 6000psi gauges inline so that we can see at a glance whats going on.

If you are sure your pump is faulty & developing sufficient pressure, you can replace this pump, After seeiing the photograph this looks to be a simple vane pump which readily available in market either of YUKEN, ETON, Rexroth make.

Looking at the photo the pump is a single vane pump ( vickers V10 /V20) with possible a priority or flow control end cover. You should be able to get a new cam ring assembly and fix your existing pump.

Check the oil return and safety relief valve. Maybe the second line serve as the return or recycle line to maintain the pressure in the system. Check also the monifold ports direction for above function.

If you want to replace the pump just make you understand the system or make a flow diagram so that you will see the other modification requirement of the system.

On the pump itself, or on a relief valve elsewhere in the system, there may be a pressure adjusting screw/spring that has vibrated loose. If so, you can remove an access cap and perhaps find a screw that can be turned clockwise to increase the pressure. (This is only a maybe, but it is a fairly common item.)

Thanks very much once again for all your inputs, i also though along the lines that it would be a simple vane pump. As i think the customer has his heart set on a new pump and electric motor and seems quite prepared to pay for it.

It is also good that you have got various suggestions as to the issues that it may be having, but have to hear it when it tries to press.. The motor just runs down and totally looses steam. I would be inlinced to thing it is more likely the electric motor is tired more than the pump itself. But as he has been told that the pressure is just not there( Motor tired maybe) it maybe be a good thing to replace the whole setup with a new more effecient unit and fit a prcision divider into the circuit.

There is no such thing as a 'Motor tired'.

You can check the motor rpm, Amps as per the nameplate. If the rpm is going down as the press is contacting the part to be bent, then the amps should be also going up. If this is the case, then the pump will be trying to do its job but somewhere else in the system you are loosing the pressure: You might have to check the Cylinders seals or the hydraulic valves seals... There would be a lot of oil returning back to the tank after the press has contacted the part and stopped moving! This will not be the case if the seals are all OK.

Check also the hydraulic system relief valve.

If the Electric Motor is running at full rpm and the current (Amps) are relatively low, then you might suspect that the pump internals are worn and maybe needing replacement.

Thanks for the input, you would think that the motor would keep on running,But it is loosing rpm.As soon as it comes under load. Either motors work or they don't.I also dont thing the motor has lost a Phase or it would be like that all the time.

How would you check the ram seals for bypass with out stripping everything down?

There does'nt seem to be any oil leaking anywhere . So it would have to be internally. Like you say, maybe the valve block seal or rams seals.

But having said that, if the ram or valve block seal were leaking then the motor would not loose rpm. Almost like the load is too much.. A blockage maybe?If there were a blockage then the pump would be loaded all the time.. Everything works like it should except is cant bend plate like it should.Which points to a ram seal bypassing but surely that would not cause the motor to run down?

Hi taurus66

I agree with your logic "a ram seal bypassing but surely that would not cause the motor to run down"

The problem with hydraulic circuits you invariably have to "get down and dirty" to identify problems.

There are so many possible reasons for your fault, "bad" electric motor, pump, relief valve, etc.etc.etc. you could spend a lot of time and money before solving it.

Take the advice of the forum members who have responded and check as much as you can before spending money on parts you might not have needed to change.

Best of luck with your endevours.

John

Hi John ,

Thanks for your comment, i agree with you about the getting down and dirty. The issue is how far does one go to rectify the fault.. I also have just started up my business coming off a Hose replacement service van (8 1/2 years) and i don't want to start of with a bad reputation of not solving the problem.

I enjoy what i do, but this is somewhat doing my head in..I have to say i am used to diesel driven pumps and motors, hoses and the such like and when a digger is down , it is down and until i have fixed it..., but this is a customer i have not dealt with before and i came recommended by another customer. I don't want to have to say to him sorry mate , shut the rest of your business down while i try and find this fault.

I am not convinced that it is a valve or ram bypassing nor a stuck or blocked componant as surely some of the functions would not work in theory. And as everything seems to work as it should until it comes to pressing thats when the fault pops up. Basically a lack of power, but like someone said earlier if it were the pump the motor would not loose rpm. and even if it were bypassing the motor should still stay at its design rpm.

Would a releif valve have this effect in that it is not set correctly or to low a setting or too high , but if too high the press would bend the material. too low and the motor would not show any loss of rpm..

Do the basic troubleshooting, install a good pressure gauge in the system and set the relief valve to the desired working pressure. Run the hydrualic pump and monitor the motor load as it reach the set relief pressure. If the motor load is okay but you cannot build a pressure close the return line manually and try again. if you cant reach the set pressure then the pump have a problem. Gear pump usually have bush bearing, check and repalce. this may cause the "lost of rpm" you mentioned because the gear are meshing each other causing more load to the motor.

If you reach the set relief pressure stop the pump and observe if the system can hold maintain the pressure say 5 minutes. if not then check the non-return or check valve.

Check also the monifold seal and solenoid valves if available in the system. Maybe the SV is operating opposite to its required operation.

If you have a three phase check also for loose connection.

Hi Erlo,

Thanks for your advice there, will do all that if and when i can get to do it. However i have yet to suggest that the three phase maybe not working as it should. Although the motor sounds ok when it is running. However like you suggest there maybe a loose connection that when under load it drops a phase and looses rpm.

Thanks.

If you are going to work on hydraulic systems you will need to at least get a couple of books and ask more questions,

Did it stop working suddenly?

is it new to the Plant?

Ask the operator questions...

Is it operating over capacity...

Look for work done by unqualified people...wrong type repairs could be dangerous so be careful.

Some cylinders have both ports hooked together to speed the rod end out then switch pressure to the head side when it comes under load.

hook a pressure gage into the pump pressure side of the pump to check if it is ok when equipment is not moving.

Customer will not be happy if you change motor/pump and valves or seals are the issue. If you don't know find out vickers has excellent books drawings.

From your picture you need to follow lines to valves and cylinders. An electric motor draws more amps when under load you need tees and gages to check things... A single bad check valve can cause all this trouble...

I have years experience and have always solved the problem by thinking system through and knowing all the basic componts. realizing all the possible configuration

will help solve problem.

Hi There ,

The press has not stopped working as such, just can't press 1/4" plate more than a couple of degrees. It is not new to the shop (Trailer repair and body shop)

The operator showed me what it does and thats when i got the story of the pressure had been checked and shown as low... i think personally due to the fact the electric motor looses rpm when it tries to press.

If i am not mistaken this press at 60 tonne should be able top bend a 1/4" plate 8ft long into a 90 Degree angle.

So far , the person that did the original pressure check was from a Hydraulic company not far from me.

I agree with you that the customer will best not be pleased to be paying for something that has not solved the problem.

If anyone has any links to a Hydraulic circuit simulation download that would be useful too. Cheapest i have seen so far is £295.00

By my reckoning it will be something so simple and stupid that will solve the problem.

What is everyones thought on the possibility of a filter being blocked or the suction strainer being blocked. As i have yet to have been given the time to open the machine or check things like the oil condition etc .

I am flying blind on this one i have to be honest.

By the way the Press brake in question is a Cressex Hydrabend 60Tonne. If anyone has experience with this particular machine it would be great to have your input.

Thank you for replying to my comment.

In response: If there is a seal leak inside the rams, there will still be a loading on the motor, but since the leak is there, the oil will not be able to develop enough pressure to bend as usual.

The motor rpm will go down because there is a load ... but not developping the required pressure: The leak is small in volume through the seal lip and the hydraulics will not develop the pressure required.

To Check: This will be messy! Slack the opposite hydraulic connection to the ram when it stops moving under the load. Oil will sqirt out BE CAREFUL under pressure, therefore be protected (eyes etc. ) if the oil coming out slows down (pressure drops quickly) then the internal seal might be OK. BUT if the oil keeps coming out with the same speed or keeping the pressure, then there is definitely a leaking seal.

Hi there ,

Thanks for your update, i know about loosing off fittings under pressure... i learnt a few times from experience...it maybe some time before i actually get around to doing all this testing as it will have to be when the shop is quiet or not working at all.

I think they first thing i will do is get the customer to call in a qualified electrician to test the motor and the possible drop out of a phase under load and the amperage to see if it goes up or down when the motor looses rpm.

So thanks to everyone that have contributed to an altogether interesting session for me. I have made a list of things to check off and trace etc.

Once i get full and proper access and i can update you all then on what the fault was.

Just hang on a minute - what bottom "V" dimension do you expect to bend 1/4 plate with.

8 ft wide might take 1000 tones if it's a 5/8" wide V.

Is it the press not working, or the operators brain?

Look a bit deeper.

Just sayin'

The press is working, but just does not have the power to press 1/4" plate as it should. When a piece was put in it was about 2ft long and 1/4" thick and it would not bend it more than a couple of degrees, and i mean not more than a couple of degrees. It looked like it had hardly bent it at all.

Most of this customers work is aluminium but quite often he has to bend steel and if i am not mistaken this press is designed to press Steel. And as the work involves using both on the same job he has to take out the steel for bending else where at great extra expense.

Put simply - you cant 'break' 1/4 plate in a 1/2" wide V

If your bottom tool is not at least 1 1/2" wide - "6 to 8 t" - you got Buckley's.

So how wide was the bottom tool V?

I have no idea how wide it was , I am not the operator!. And i certainly don't think the v was a 1/2" wide.

I am sure the press operator knew what he was doing. He has been the operator for a few years now on this machine.

Just saying don't ass-u-me - 'look deeper' - before you go all 'spend money'

You should be able to read the model code on the pump and get it identified. Try and get a circuit diagram, there are plenty of Hydrabend machines on sale so someone must have a CD. Do not mess about with the control manifold unless you know what you are doing as it will almost certainly contain some form of synchronization system. Replace the pump and clean the system thoroughly then check it out. Oliver Dunthorne Hydraulic Engineer

Good afternoon Oliver,

Many thanks for your advice, i will look into finding a CD. I am none too keen to go delving into the inner workings of a control block, too many springs and seals, balls and the such like.

If you can do this then get back to me Oliver

Hello again.

If the operator says that he used to bend that sort of job on this machine, and now this is not happening, then maybe it can. But as suggested by others, find out in case it did not bend such jobs before.

On the matter of seal leaks, you can find out if the ram seals are leaking internally by using a stetoscope (like the medics checking the patients breathing...). If you are careful enough and have reasonably good hearing, you should be able to determine at least the moment when a bypass leak happens on the seal...

Good luck.

Hi there ,

Thanks i will do once i get the time to do all this. I used to use a long flat screwdriver when working as a mechanic to hear for rumbling bearings in gearboxs , i should imagine the same will be applicable..

Many thanks for everyones input on this subject..

Pump on this machine is a Vickers V220.8W.OB.J.12.S2. now according to the vickers guy it delivers 8 us Gallons a minute at 1200rpm and 85 bar working pressure. Still have not managed to find a diagram of the flow circuit as yet adn finding specs on the pump on the net is near impossible.

So the thinking is to change it all to a gear type pump with a new motor, change the old cetop 5 directional valve (DG4S4L 010C) to a newer version DG4V5. And change out the relief valve for a new one too., Change out all the hard pipe for flexible hoses and remove all the multitude of adaptors that have been fitted( in one line there is the following.. 1/2" tee, 1/2 fem/fem adaptor,1/2" -3/8" m/m adaptor, 3/8" - 3/8" fem/fem adaptor, 3/8" m/m/f tee, to 3/8" bore hose to ram. Off the last tee there is a 3/8 bore hose about 5' long with a male insert in one end and a 1/4" bsp fem insert the other blanked off.. Why all this i have no idea... and similar on the opposite side.. None of this makes any sense at all..

My theory is to start again from scratch , new pump and motor , cetop and new relief valve and hose work. As i am sure the rams are ok, and then i think we may have a good working press brake for little more than £2000 of work.

Hi,

The information you have given shows the units are somewhat dated, however a Vickers distributor would be able to support all that you have. Today the vane pump is available but the model is now a V20 but it fits on the same mounting and has a better performance. Your pump delivers 25ccs/rev and the V20 has an option at 22.8 or 26,6 ccs/rev The power absorbed at 85bar is 5 kws / 6.7 hp so if you have power to spare go with the bigger pump if not go smaller. If you go on the web to Vickers Hydraulics and look for vane pumps, you should find all the information.Or try hydraulics.eaton.com/products/pdfs/V-PUVN-MC002-E.pdf. Vickers is now part of Eaton Corp. I think your idea of replacing the DGVS4 with the later CETOP 3 valve and relief valve is a good idea. I did try and check out the pump model code but I do not have a catalogue any more and the web site concentrates on the latest models but again a Vickers man at a good distributor will sort that for you just e mail through all your model codes and ask for an up to date equivilent. There is nothing wrong in fitting a gear pump but the mounting face will be different. Do not forget to clean the circuit properly, easier said than done.

As for more information try (a) Going on the web and find out where the Press brakes were orginally made and see if there is not a second hand machinery dealer in the district the chances of him having some old press brakes and therefore some information might be good. (b) Look on the second hand market and see if you can find a similar one for sale and see if they have a hydraulic circuit you might get a copy of. (c) Lastly try and find the Vickers office or local distributor that used to supply them and see what they know.

Good Luck.

Oliver Dunthorne

PS. I am assuming you are in the USA?

Hi oliver, Thanks for your very concise feedback, but no i am in the UK , not far from the portsmouth facility of Eaton.. The fellow i spoke to today is a vickers man.. Very helpful indeed.. Like i said there is not a lot of stuff out there on this age of pump etc.. Even he had trouble as he no longer held catalogues that old anymore.. But i think we will get it sorted.. thanks and the same for your taking the time to reply..

Hi,

I do not have any up to date information on Vickers distributors but you could try a guy by the name of Dave Wilson who used to own South Eastern Hydraulics at Redhill. He sold it but is the technical manager there now. They are Parker people but Dave (a) knows what he is doing and (b) will know the name of the nearest Vickers man who can help you if he cannot. www.seh-ltd.co.uk. You can mention my name and say hello from me.

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Oliver

Hi

I have just thought that as you are in the UK the electric motor will run at 1450 or 960 rpm and therefore th 8W ring will supply 37.7 lpm or 25 lpm. At 85 bar(1232psi) it will absorb 6 kw's or 4 kw's.. If you can find anymore model codes etc send them on and I will try and put more info together. I have found a Vickers catalogue at least 25 years old.

Oliver

Hi there ,

Since i have been stripping out the old pump and motor etc i have been able to get to closer inspecting the pump etc. I scratched off some old paint to find a p and a t stamped into the pump next to the port. I am assuming they denote pressure and tank? Now my theory is now that as this "t" port on the pump must return oil to the tank. Would it be then safe to blank off this port on the base block of the Cetop 5 or would it be advisable to send it straight back to tank..

No, No no! the pump will go bang

Oliver Dunthorne

The port i am referring to is on the base that the new Cetop mounts to, this then is plumbed to the "T" port on the Pump(Old Vickers). What is very confusing is why is there a second port on the pump(As per picture it is the furtherest from the camera), one stamped "P" and the other stamped "T".. Not even the vickers guy can tell me this.

The new Pump is a Gear type unit with an inlet and outlet. Could the port stamped "T" on the pump just be a bypass off the pump and dumps back to the tank?

So far i have come up with absolutely nothing regarding a Hydraulic diagram on this machine. An internet search reveals only a phone number that does not get answered. So can only assume they have gone bust and with no successor. thereby meaning all owners of these brand machines will be left high and dry when it comes to parts and technical help...

Hi,

Alas there is no photo with the comment. Give me a part number or a model code.

It does sound like a drain port but gear pumps don't usually have them but gear motors do! Give me the port sizes, no doubt they are flanged?

Oliver

Vickers V220.8W.OB.J.12.S2

The photos were posted a long while back, if you scroll back throeugh the thrad you will see the pictures

Port sizes on both the outlets is 1/2 npt, the inlet is 1" flange type. but not an SAE type.

Not sure if you can see the diagram properly but all ports are joined in the centre. The pipe in the background comes from the "T" port on the pump. To the right and below that is the pipe that comes from the "P" port on the pump. My thinking is that the pump supplies both sides. The directional control valve then changes the flow when either pressing or returning.

There fore if i fit a tee into the pressure side of the pump and run two flexi hoses to the ports on the above block we should achieve the same effect.

Hi,

You do seem to being having trouble getting to the bottom of this system. CR4 will not let us add phone numbers or E mail addresses to these comments, however if you contact there administration and refer to this comment I am prepared to allow them to pass my e mail address to you and from there we can exchange phone numbers.

The valve shown in your recent photo is the old DG4S4 and is a double solenoid, three position, spring centred unit with all ports open in the centre condition.(P-T-A-B) This is now superceded by a CETOP 3 unit. It is difficult to help you without seeing the set up and/or a circuit diagram. Perhaps you could try and sketch the pipe layout to the various valves and cylinders.

Regards

Oliver Dunthorne

This is a quick sketch, of the circuit as it stands. The Hydro cushion valve (Could not find a relevant symbol) i washed off and found the Plate with that number on it.It also has a 1/4 bypass hose fitted and joined to the return line. What i have done so far is to fit the relief valve right next to the pump. With a 2000psi gauge fitted and a bypass straight back to tank.After that i have fitted a tee piece in to acommadate both hoses similar to the orginal set up on the vickers pump but with a relief valve in line first so as to be able to set the pressure going into the stytem. I hope you can understand the diagram that is as basic as it seems to be.

I am guessing that as the orginal pump had two ports(Vickers V220) feeding to the proportional valve, the valve would open and close taking pressure either to the down stroke or upstroke when required. Hence both feeding direct off the pump so to give the system full pressure both ways. I am also guessing that the proportional valve would decide which way the oil would flow depending on operators use at the time. I hope i am making some sense.

Just wanted to say a very big thankyou to Oliver Dunthorne for his assistance and being Patient with me while i find the fault with this Press. He took the time to do a circuit diagram that i used to check my work. A very invaluable Person to have on here..

Thank you once again.

Hi! I'm now stuck in the same situation with the same model pump in Australia. Did you find out anymore about the P and T ports? I know it was back in 2011 but thought you may remember

Thanks

Josh