You might consider tandem pumps rather than a flow divider.

Ted

I agree about that, but in this particular case we already have a pump and just need to divide that flow equally.

Instead of buying a flow divider, buy a split pump.
For example: https://royalhydraulics.com/index.php/45-products/...

Ted

Something like this?
Simple but should work..

https://www.jotek.se/product/fordelningsblock-4-va...

Best regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

I seem to remember that gear-type flow dividers can in certain instances turn into pressure intensifiers. I can't remember the specifics though and its too late for me to look into it.

And a purely mechanical option is what they use to lift buildings. I have never seen a detailed drawing but from what I understand it is a large area piston driving many smaller pistons. You have to have equal flow even if the smaller cylinders have unequal pressure.

2RedSnake - on that link is just a dividing manifold with needle valves, that can't do the trick.
2IceStationZebra - That's what I do need, a divider that will send equal flow regardless of counter-force being applied on cylinder rod.

It would be easier to help if you explained what the function of the machine will be/is ?
And why the pressure must be 700 bar?

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

Quote:

I seem to remember that gear-type flow dividers can in certain instances turn into pressure intensifiers. I can't remember the specifics though and its too late for me to look into it.

Yes, if one of the out put ports go to the load and the other to tank then the pressure at the load output is doubled minus some inefficiencies. Basically the energy in is equal to thee energy out.

I once consulted on a dam project. Each end of the dam gate was lifted by a pump. The gates were long and about 100 tons. There were crude position sensors. Should one end of the gate be higher than the other by some amount then some of the oil from the high cylinder was dumped to tank till it was even with the lower cylinder. Simple.

The question I have is why not make the cylinder areas twice as big so a more reasonable 350 bar can be used.
Then the flow dividers wouldn't be needed. Still use the simple technique of relieving oil from any cylinder that is too high.

Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/
IFPE Hall of Fame Member

That was acctually my next suggestion/question..

The reason why there are so few hydraulic components with higher pressures than 350 - 420 bar ..
Is that cost end the risk assessment increases exponentially with the pressure increase.
So it is better to stick to "as low" pressures as possible as long as the force can be maintained.
The risk assessment for the force you need to do anyway..

But it is difficult to give good edvice, when one does not know the end purpose/functionality ..

Best regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

PNachtwey or someone..
I have a question about nozzels to reduce the hydraulic flow, is that something you can help me with?
Do not really know in which forum I should put the question there are too many to choose from..

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

On this exact application we are talking about system for lifting bridges etc, one high-pressure hydraulic pump flow has to be equally divided to 4 ÷ 8 hydraulic lifting cylinders. System uses 700 bars because of compact design.

A asume they need to lift with the same hight and speed at all times so the bridge is allways level?
Or do you need the posibility ta adjust the cylinders into diffrent hights?

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

Quote:

On this exact application we are talking about system for lifting bridges etc

The doubling the pressure trick will not work then. Get a gear type flow divider that will have one input and 4 outputs.
Use the trick I mention about relieving some oil on any cylinder that is higher than the others. It has worked for dams.
Feedback will be required.
The Emsworth dams below Pittsburgh work this way.

Ditto Redsnakes' concerns about the higher pressure when the diameter of the cylinder only increase roughly by 1.41 times.
@Redsnake, you should start a new thread rather than distracting this one.

Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/
IFPE Hall of Fame Member

For this system, pump can easely provide 700 bars. Components in system are rated for maximum 700 bar. No higher pressure is needed. Theoretically, if I could fine a gear type flow divider with one common shaft, it would be perfect. Level of precision would work for me with this setup. But as it seems that there is not this kind of flow distributor for 700 bar, we will turn into different direction. We will try 4/3 solenoid powered flow valves together with deblocking-check valves, together with fixed orifices. Power for all 4 solenoids will be turned ON in same time, so I think we will have satisfying precision. However, this does not include same oil flow to all cylinders, but this system depends on counter force applied on cylinder rods. But on controller you will be able to choose which solenoid valves to engage at same time, and which ones to be left in central neutral position.
This is not perfect but it will give us some control. Simplicity and cost effectivness the goal.

Quote (PNachtwey)

@Redsnake, you should start a new thread rather than distracting this one.

I am not shore where the distraction lies?
If you meen the nozzle problem, I did.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

2RedSnake> both of these functions (equal travelling for all cylinders, and also possibility to adjust some of them independently) would be the best, if that could be done.

Mechanically, what are you trying to do?

When multiple cylinders are being used to raise a load, I've found only two approaches that work:

(1) Make the mechanism linking the cylinders sufficiently rigid so that a lagging cylinder will be dragged along without jamming.

(2) Make the mechanism so flexible that any one cylinder can deflect to full stroke without depending on the others moving at all.

In-between is asking for trouble.

In the case of, for example, raising a platform, (1) could include: A structure sufficiently rigid that it can't jam against its guides, e.g. the "platform" is shaped like a cube as opposed to a piece of paper, (2) a rack-and-pinion mechanism at each corner with the pinions connected by shafts, (3) a ball-screw or similar device at each corner linked by timing-belt or sprocket-and-chain drives, etc.

Raising a bridge
Okey, like a car bridge _/ \_ or _/ or ↑-↑ or do you mean something that is used to raise a bridge under construction ?

Best regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

Use a common gear-type flow splitter. Use pressure intensifiers downstream to provide high pressure to the cylinders.

Ted

Leo,

A gear type flow divider is rated for low pressure because of the bearing loads and contamination caused by the high pressure acting on one side of the gear.
A sufficiently high pressure will cause the gear to deflect and run against the metal of the housing, which in turn will cause the internals of the housing to be damaged.
That will introduce contamination in the system and probably cause failures in other components.
Any type of bearing (Journal or Ball) will not be happy with the deflection either, which in turn will wear out the bearings very quickly and generate more contamination.

All that is to say that I do not think that you will find any gear type flow divider with a 700 BAR pressure rating.
Not to mention the potential lockup issues and other application details, like partially independent control, that may mess with the flow divider function.

700 BAR is a high pressure.
If you still want to use a gear type flow divider I would, as others have suggested, try to reduce the pressure by increasing the area of your cylinders.
If you have small cylinders, then this probably would not increase their diameter much (1" to 1.5" bore cylinder area ratio is 2.25, which is sufficient to bring the final required pressure to under 350 BAR, assuming you are using the blind end of the cylinders for the 700 BAR load).

If you want the cylinders to move together, but also be independently controllable, then the easiest way to do so (at 700 BAR) is with electronically controlled valves, a programmed controller, and some position feedback sensors.
It is possible to do so with hydraulically piloted valves, but it will not be as compact, flexible, or accurate as an electronically controlled valve w/ a controller.