Help nobody knows what their talking about multi control feed system
Help nobody knows what their talking about multi control feed system
(OP)
Hi
I have a drill rig that has a rotational head
the head moves up and down and holds/raise/lowers the head
the head has varible weight and needs to travel up and down at different rates and also different total pressures
the basics are as follows
10gpm 3000psi gear pump
directional control valve with 3000 max psi relief
dir control goes to 2 5" rams
agian system needs to be able to hold constant pressure in either direction with in 20psi consitency
completely controlable from 250psi to 3000psi
rate infanitly varible from no movement to full flow
if i pic is needed i will supply a basic on
I have asked many hydraulic shops and they give me a blank stare
or say i need a ajustable relief, no da but there is alot more to the sytem as well
PS I will tip the person who best fixes my system if you leave an mailing address at the end
I have a drill rig that has a rotational head
the head moves up and down and holds/raise/lowers the head
the head has varible weight and needs to travel up and down at different rates and also different total pressures
the basics are as follows
10gpm 3000psi gear pump
directional control valve with 3000 max psi relief
dir control goes to 2 5" rams
agian system needs to be able to hold constant pressure in either direction with in 20psi consitency
completely controlable from 250psi to 3000psi
rate infanitly varible from no movement to full flow
if i pic is needed i will supply a basic on
I have asked many hydraulic shops and they give me a blank stare
or say i need a ajustable relief, no da but there is alot more to the sytem as well
PS I will tip the person who best fixes my system if you leave an mailing address at the end





RE: Help nobody knows what their talking about multi control feed system
Providing a rod size and speed of movement will be required to determine what is required.
This may require proportional valves, pressure transducers and a controller to provide the level of control you are asking for. Going this direction may be more expensive and less energy efficient than using a variable displacement piston pump with remote pressure control.
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: Help nobody knows what their talking about multi control feed system
If you want to have only manual control look at the following Parker valves. The problem is it will be near impossible to hold 20psi accuracy (or 0.7%) without having to fuss with the control, especially as the flow changes or oil changes temperature.
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See PRH102 or PRH101 series
ISZ
RE: Help nobody knows what their talking about multi control feed system
the slow feed is for actuall drilling
rod size of 4" stroke 30 ft
but that shouldn't be relavent
can you explain both ways the cheaper one as well as the more acurate way
RE: Help nobody knows what their talking about multi control feed system
There are hydraulic motion/force controllers that are designed to do projects like the one you have. Typically one isn't as concerned about the pressure and more about the force. The reason why is that one must take into account the pressure on the rod side of the piston. Then one computes the net force
NetForce=CapPressure*CapArea-RodPressure*RodArea.
The controller will also allow you to offset the weight of the tooling so the true force applied is accurate.
A PLC may work but they will not respond very quickly. The analog A to D and D to A cards are relatively slow. So are the scan times unless you speed a lot for the controller.
You definitely can do MUCH better than a pressure relief valve. Pressure does not take into account the weights of the tooling and the pressure on the other side of the piston.
PS I will tip the person who best fixes my system if you leave an mailing address at the end
I don't fix hydraulic systems. I bet a good distributor can
if I knew approximately where you are. I make the hydraulic controllers.
http://www.deltamotion.com
This would do the trick.
http://www.deltamotion.com/products/motion/rmc70/
BTW, if your watch the Discovery channel you can see one our controllers in action. This is just position control not force control.
http
For those who want to access the full video..... a download is required.
http://video.discovery.com/
The controller is sophisticated enough to follow just about any force or position profile as long as the hydraulic system is capable.
RE: Help nobody knows what their talking about multi control feed system
ISZ
RE: Help nobody knows what their talking about multi control feed system
i am located in Richland wa
RE: Help nobody knows what their talking about multi control feed system
I will find out who is good in eastern WA. Pacific Fluids in Portland may be your best choice because they are relatively sophisticated. I don't think they sell Vickers valves.
This would work well if you must stay with Vickers.
ht
This may work but wouldn't respond nearly as quickly. If you decide to go with a PLC this may do because the PLC isn't very fast either.
htt
I know you see pressure relief valves in the catalog. They are cheap but as I said before, they only control the pressure on one side of the the valve and don't take into account areas so you have no true indication of pressure. Also, pressure relief valves are dumb. They can control a steady state pressure but they have know idea of how to respond to a pressure rate. The hydraulic motion controller computes the press rates on both sides of the piston to get a net force rate. This in turn is multiplied by a derivative term which causes the controller to be responsive to small errors with high pressure rates.
A lot depends on how tight you need to the force set point.
20 PSI x 2 X 20 sqin is 800 lb. You must also figure that the differential force will always be a little less than indicated due to seal friction. This can be 50-100 lbs for each cylinder.
RE: Help nobody knows what their talking about multi control feed system
These kinds of problems are necessary to get a feel for what is realistically possible.
RE: Help nobody knows what their talking about multi control feed system
Peter,
The pressure change will depend on the amount of air trapped in the oil, bore size of the cylinder, wall thickness of the cylinder and initial fluid pressure on both sides of the piston.
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: Help nobody knows what their talking about multi control feed system
If we assume that the volume outside the cap side of the cylinder is small compared to the volume in side we can divide volume by area and get position.
DeltaPressure=BulkModulusOfOil*DeltaPosition/Position
Assume the BulkModulusOfOil = 200,000 psi
DeltaPosition=0.1 inches
Position-20ft*12inches/ft
83.333=200000*0.1/(20*12) psi
A 10 GPM valve can flow 38.5 cubic inches/sec
The surface area of 2 5 inch diameter cylinders is 39.27 sq inches. That mean max speed is about 1 inche/sec. This means the pressure error can be exceeded in about 25 milliseconds of the drill hits a hard spot and the drill is moving 1 inch per second.
It gets worse. If the pressure on the cap side goes up the pressure on the rod side goes down. However it goes down faster because the volume of oil is smaller.
200000*(-0.1)/(10*12) psi=-166.67 lbf
If we look at the differential force
83.88*CapSideArea-(-166.66)*RodSideArea=2814 lbf, Roughly.
You can see that controlling to 20 psi on one side is a challenge. Keeping tract of how the pressure increases on one side and decreases on the other side will be tricky.
RE: Help nobody knows what their talking about multi control feed system
I'm going to assume this is a rotary drill rig and you are trying to keep from stalling the motor that turns the drill bit by adjusting the feed pressure. We have experimented with a feed modulating valve that uses motor pressure to adjust the feed rate in a wood sawing application. In this application we need to cut as fast as possible through multiple stems that pinch the bar or blade. The valve is a 4 port spool type cartridge valve that has one port connected to the saw motor pressure, one port is from the directional control valve, one port goes to the cylinder and one port goes to tank. When the pressure starts to rise in the motor port the spool shifts to meter the speed of the cylinder but does not reduce the feed force. This can be set up to meter out so the weight of the unit being fed does not affect the metering too much. This can be done electronically with better response time but will cost much more and in a high shock, dirty and wet environment will be less maintenance. If you are interested in trying this valve contact me through www.danzcoinc.com .
Ed Danzer
www.danzcoinc.com
www.dehyds.com
RE: Help nobody knows what their talking about multi control feed system
RE: Help nobody knows what their talking about multi control feed system