Help nobody knows what their talking about multi control feed system

[Drilldesigner]

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

 

[EdDanzer]

Two 5” cylinders with only 10 GPM will be slow for moving a drill head won’t it?

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

http://www.danzcoinc.com

http://www.dehyds.com

 

[IceStationZebra]

I have a similar need, but in a completely different application. I will be using a pilot operated relief valve, with the pilot pressure metered by proportional solenoid controlled with a variable analog voltage. I don't have the part numbers at home, but I can get them tomorrow.

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.

http://www.parker.com/literature/Literature Files/IHD/PCsec1.pdf

See PRH102 or PRH101 series

ISZ

 

[Drilldesigner]

the 10 gpm is the slow feed a rapid feed pump of 100 gpm is used to get to the bottom or top
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

 

[PNachtwey]

if i pic is needed i will supply a basic on
I have asked many hydraulic shops and they give me a blank stare

I believe it. You are just talking to the wrong distributors.

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://dsc.discovery.com/video/play...711172&lineupId=1815835836&titleId=1825926513

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.

 

[IceStationZebra]

I thought about a controller but I assumed this was for a mobile rig, so the controller would take a beating with vibration and dirt. If this application is not mobile than an electronic controller would definitely be the best bet. It will not be the cheapest - but it will be the only way to guarantee the accuracy you want.

ISZ

 

[Drilldesigner]

i do run vickers ele cntrol valves on other systems on my rig what valve where you thinking about?
i am located in Richland wa

 

[PNachtwey]

You mount the controller in a J Box. You would need to do the same with a PLC or any other electronics. One of these controllers just go installed on a mobile rock crusher in Canada. It is used to crush rock, obviously, in that contain oil or is with the oil sands.

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.

http://www.eatonhydraulics.com/products/pdfs/651.pdf

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.

http://www.eatonhydraulics.com/products/pdfs/V-VLPO-MC008-E.pdf

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.

 

[PNachtwey]

BTW, here is a brain teaser for the forum. How does the pressure change when the actuator hits a rock that rolls and pushes the actuator to back 0.1 of an inch. Assume the piston is 20 ft from the cap end.

These kinds of problems are necessary to get a feel for what is realistically possible.

 

[EdDanzer]

The rod size will have an impact on design choices. Are you trying to control feed force and feed speed or just feed force? I agree with Peter that you probably need a very fast controller and 30 gallon valves to provide low enough pressure drops to maintain accuracy at low pressures on the blind end side. A meter out system will provide better speed control but if speed is important then some form of position feedback will be required. PHT in Auburn Washington may be able to help is a slower system will work.

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

http://www.danzcoinc.com

http://www.dehyds.com

 

[PNachtwey]

DeltaPressure=BulkModulusOfOil*DeltaVolume/Volume

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.

 

[EdDanzer]

Drilldesigner,
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

http://www.danzcoinc.com

.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[Newmanite]

Why not run a pressure compensated variable piston pump with an adjustable bleed off line from the compensator.This system would require it to be closed loop and a small cooling valve.When you are operating the pump to come onto stroke the variable restrictor would be wide OPEN.And when you needed to increase the pressure (or force applied to the bit) the electrically controlled variable restrictor would get smaller until shut off thus running at pressure setting set by the comensator e.g from 750psi through to 3500psi.

 

[hydroguy1]

Stay away from the parker prh101 and 102 pressure reducing valves. We have been battling with these valve on a supplied parker HPU units for 7 years. Problems have ranged from zero pressure, to low pressure, and fluxuating pressures and hammering. Contact with vendors,results in huge lead times for replacement or spares.Contact with parker tech service has proven useless. After finally securing some replacements through our vender,three brand new units, direct from parker, displayed problems. The prh 102 was swapped into a know properly operating machine, and the problem followed all three of the new valves. A fourth unit worked like it was supposed to, for three days. It then started to occilate it's regulated pressure 150 psi, up and down constantly. With parkers unwillingness to help, and huge lead times for replacements, we are currently working to get rid of this problematic part. Parkers unwillingness, and difficulty to help, has led us to look to other manufactures for future projects.