Question about hydraulic pumps 1

[TheDudeAbidess]

Im going to preface this with a little background. I am a maintenance electrician with a company in the forging industry. I don't just do electrical work, I often find myself repairing hydraulic and pneumatic circuits as well. I have spent 12 years in the electrical trade. 11 of those years in construction. Only recently have a I decided to give maintenance a try.

With that said, we have a hydraulic circuit that is run by two 10hp motors. Each motor services a Rexroth AA10VSO pump. Both pumps feed into a distribution block and combines pressure into one hose, 2 in 1 out essentially. The pumps feed pressure to two benders in parallel. When one bender runs the other bender stutters. We can all agree what kind of safety issue this is. 1st question: Can we maintain the setup we have and eliminate the back pressure? If so, how? It was suggested that I tee off one of the pumps before the distribution block and goto the smaller of the two benders but I fail to see how this will change anything at all. 2nd question: On the Rexroth pumps there are two ports. I am assuming that one is a case drain, to keep the fluid out of the catch pan, and the other is a pressure relief when the pump isn't in the middle of a cycle. Am I assuming correct?

Any help or guidance that can be forwarded my way would be greatly appreciated. I am new to hydraulics and fluid power but am extremely interested in learning as much as I can.

 

[itsmoked]

Do you have a fluid schematic you can post?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Compositepro]

The flow will take the path of least resistance. Each bender should have it's own dedicated supply. If the purpose of connecting the supplies is to provide more peak flow when needed, that can be done by using hydraulic accumulators.

 

[TheDudeAbidess]

Composite: I have been saying each needs it own pump since Ii started working on this project. I think its a money issue just like it is everywhere else in the world.

Keith: I don't. I can draw up something rudimentary but its liable to look more like an electrical drawing than a hydraulic schematic. I will get something by this afternoon.

 

[TimSchrader2]

hello

We use the Rexroth AA10Vs018 pump. The two larger ports are for pressure and one for suction from tank. The smaller line on side of Pump is the case drain. You may not have the pressure compensators or load senses on top of the pump in the front of the pump.

You can use a simple on off valve going to each pump (2 valves) to isolate one pump from the other's pressure. They would need to be installed in those parallel lines.

Or is there no return line on the benders feeding back to the pump? you did not mention the rtn lines? Does it actually dead head the flow on the benders? That would not make sense cause then you would not need 10HP.

 

[TheDudeAbidess]

So, the smaller bender has a 3-1/2'' cylinder and that's the only fluid driven component. The other bender uses 5 of various sizes. the 2 biggest are 2-1/2''. The two pumps are different sizes. 1 is a 45 and the other is a 100. I spoke with an engineer today with one of the vendors we use for parts and service and he suggested that I separate the two pumps. Have the smaller pump run the small bender and the larger to run the one with more cylinders. He said it didn't make sense that we were combining two pumps to just split them in parallel again. Which I have to agree. Does anyone see anything out of the ordinary with that? Essentially the only thing they would share at this point is the filter and reservoir. I will have a small hand drawn schematic shortly.

Tim: I see exactly what you are talking about on the pump. The larger pressure ports on the top, do they just provide a means for the pressure to circulate back to keep pressure off the pump seals?

 

[TimSchrader2]

The two large ports are right next to each other. Your pump may be facing up so they are on top. One port is for pressure to the equipment the other port sucks fluid from the tank.
there should be return lines from the bender cylinders back to tank at the suction filter or before it. Unless they are not two way cylinders and have a spring return inside them