Help need with design of hydraulic control - drill rig

[crystallattice]

Hi Guys,

I'm planning on building a rotary air percussion drill rig for well drilling. I need some help with the hydraulic system design.

The system will have the following:

-High torque rotary head (hydraulic motor with planetary gearbox - ready made by Augertorque) 80-240Bar, 40-85LPM, 42-90RPM
-Hydraulic motor geared down 1:2 with sprocket and chain to drive head up and down mast using chain. 160 RPM, 380NM, 60LPM
-Hydraulic motor for driving wire rope winch, used to lift new section of drill pipe, this will only be used when the head is raised and stationary. 46NM 20LPM

Operation needs to be as follows:

Rotary head needs to be set in motion and stay running with speed control (flow restriction) and possibly also torque control (pressure reduction) These controls must preferably be set and not require a lever to be held in a certain position. The head must also be able to rotate in opposite direction with the speed/torque controls also functional (maybe the torque can be max and the speed controlled with the lever to make the control system easier/cheaper).

Whilst the head is rotating, the head must be lowered by forcing it down, again speed and or torque controlled. At some stage when the drill string weighs more than the downward force required, the head must be pushed up to counter the weight of the drill string but still proceed downwards (a certain size drill bit requires a specific downward thrust to be maintained) Some form of visual feedback would be very useful as to indicate what is happening with the drilling operation.

All the motors are gear motors, the head motor would probably get a motor spool so it can freewheel (will be necessary when using spanners to remove drill string from head ) but the other two(head up/down and winch) will get a normal spool so as to hold their position, will it work or will it require a hydraulic brake?

I have a Kohler 25hp command engine which I'm planning on using for the hydraulic power pack, using a 60 or 80LPM single stage hydraulic gear pump, 200Bar@3500rpm.

I was planning on getting a three lever monoblock valve as they are cheaper than individual valves but not sure if it will give me the freedom to do what I want to do.

I did a back of envelope calc on the max lifting power of the head lifting motor and it worked out to something like 6000Kgs with a 1:1 ratio and a 160NM motor using 120mm sprockets, is this plausible? Sounds like a lot for such a small thing!!

The rotary head will be used at max 30RPM So can I assume that I will also use only a third of the flow(85LPM = 90RPM so 30RPM = 85LPM/3 = 28LPM) Also the head will move down quite slow, so the up/down motor (which will require 60LPM to do about 0.5m/sec, will now require a lot less) So I'm guessing the 60LPM pump will be enough, too a big pump = hot oil.

Your comments, suggestions, warnings and criticisms are welcome...

 

[jenkinsph]

I think I would start with a two section pump. One for the rotary head with properly matched motor and pump sections to fine tune the needed rpm's without flow restrictors. The other section for the draw works and winch operation.

You need a weight indicator for the string that you can read easily from the control station. Depending on how you set up your draw works a hydraulic type which works on the chain tension or cable tension to drive the pressure gauge with weight scale conversion is the simple way to go. Probably the most common way it is done.

Planning the whole system with the correct speeds and torque takes some time. Choosing the correct parts the first time is important too.

 

[crystallattice]

Ok, so NOT a two stage pump (high pressure low volume + low pressure high volume) So you're saying two pumps driven by one engine?

The snag with the cable tension thing proposed is that when you start drilling the drill string is too light and the hydraulics will have to provide some down force, then eventually zero down force then later upward force to cancel drill string weight. I'm thinking a loadcell somewhere in the setup that can read compression + tension but this might become a bit expensive...

I know another guy who also built a rig and he did a lot of things twice, unfortunately my budget hardly allows me to do it once!! Therefore I need as much advice before I start.

 

[aczlan]

I would use two pumps, one to power the drill head that maxes out at your target RPM/torque with a motor speed valve to control the speed (if you need to change speed) and the other pump to run the controls to lift/lower the carriage and the drill stem lift.
To lift/lower the carriage, I would use a double acting cylinder and tee into the hoses going to each side to install a pair of gauges. That will tell you how much up or down pressure you are putting on the carriage and if you use a big enough gauge, you could calculate how much force there is and relable your gauge with the actual force on the carriage.

Aaron Z

 

[bigdeano]

Good advice on the two section pump. Second pump bolts to the back of the first so you just have one drive shaft.

How about a hyd pressure gauge on both ports of the lift motor to show up-down force? Seems like it would work.

If you have to adjust speed I would use an adjustable flow control valve instead of a restrictor. It will probably develop less heat since the pressure is not always maxed out.
Something similar to this. 3/4 NPT HYD FLOW CONTROL VALVE W/RELIEF RDRS175-3

 

[JRobyn]

Good luck! I think there's good reason why all of my B-I-L's drill rigs were many hundred thou USD pieces of equipment! His were all Ingersol-Rand, intended for drilling for blasting so typically only used up to 2"-3" bits, but all the same design criteria applied. Even with the smaller bits, IIRC, his used industrial CAT 6 cylinder diesel engines for power (300+ HP).

 

[crystallattice]

Thanks for the ideas guys!

I like the tandem pump idea, but would it not limit the other circuits of available power/flow if the main circuit is not used? It obviously ensures that everything always works as expected if designed properly, but my untrained eye fails to see all the benefits...

The dual gauge idea seems the simplest, the problem with the suggested flow control is that I would also like to limit the torque to the bit, the motor is capable of developing 3500Nm and this might be a bit extreme in some situations. Maybe a pressure relief valve before the flow control?

JRobyn, yes the figures are adding up very quickly and a 21Bar 950CFM compressor ain't cheap!!!! For interest sake, how deep did they drill with the 2" bits? My idea was to make a rig capable of say 6" hammer + bits but start with a small rental compressor and drill 2"-3" holes until I make enough money to buy a big compressor and suitable DTH hammer, bits and drill rods. This is not a cheap hobby, but seems like there is money to be made!

aczlan, I'm planning on making a sectional mast for easier transport, so cylinder is somewhat out of the question, chain is the next best bet I can think of. The idea of this rig is to be able to go places where the truck mounted ones can't go.

 

[bigdeano]

The large pump section could be used to run the main motor, and when that's not running, to lift the carriage or run the winch to pick up a new pipe. A smaller pump section would be used to supply pressure when drilling to push down or up on carriage as needed. You want low flow here to minimize heat produced because some of the flow will go thru an adjustable pressure relief valve.

The flow control valve I linked to has a pressure relief valve built in. Maybe that could be set to limit the drill bit torque, or you could have another main relief valve.

 

[jenkinsph]

Ok, so NOT a two stage pump (high pressure low volume + low pressure high volume) So you're saying two pumps driven by one engine?

The snag with the cable tension thing proposed is that when you start drilling the drill string is too light and the hydraulics will have to provide some down force, then eventually zero down force then later upward force to cancel drill string weight. I'm thinking a loadcell somewhere in the setup that can read compression + tension but this might become a bit expensive...

I know another guy who also built a rig and he did a lot of things twice, unfortunately my budget hardly allows me to do it once!! Therefore I need as much advice before I start.

This would be one pump with two sections, both sections driven by a common shaft. The two sections should be properly sized for the flow rating needed for the hydraulic motors you select. You should be able to vary the engine speed slightly to fine tune the rotary speed without the need for flow restrictors that would build up a lot of heat and waste fuel. The second section of the pump is for intermittent use and less problematic with restrictors or relief valves causing heating.

If you are using a hydraulic motor/drive sprocket to push or pull on the chain then recognize that you can use a tension measuring devise on each end of the chain. You are either pulling on one end to raise or pulling on the other to add down force, but the chain see tension in either scenario. These work well because they are fixed in place without movement and the fatigue that movement would cause.

 

[jenkinsph]

Hi Guys,

I'm planning on building a rotary air percussion drill rig for well drilling. I need some help with the hydraulic system design.

-Hydraulic motor for driving wire rope winch, used to lift new section of drill pipe, this will only be used when the head is raised and stationary. 46NM 20LPM

Operation needs to be as follows:

Rotary head needs to be set in motion and stay running with speed control (flow restriction) and possibly also torque control (pressure reduction) These controls must preferably be set and not require a lever to be held in a certain position. The head must also be able to rotate in opposite direction with the speed/torque controls also functional (maybe the torque can be max and the speed controlled with the lever to make the control system easier/cheaper).

.All the motors are gear motors, the head motor would probably get a motor spool so it can freewheel (will be necessary when using spanners to remove drill string from head ) but the other two(head up/down and winch) will get a normal spool so as to hold their position, will it work or will it require a hydraulic brake? ...

You might consider adding a manual ball valve between the hoses at the rotary motor to make the rotary easier to turn while making up joints. This would make turning the rotary unit much easier than pushing the fluid in long lines back to the valve. If you can't reach this valve then a remote valve is another work around.

About the winch if you are using a worm drive winch it will hold the load without a brake. If the winch is end driven I would get one with a brake. There are lots of these winched built with two speed planetary drive and hydraulic disc brakes built into the winch drum, Braden comes to mind.

I would not rush to purchase a 3 spool valve you may need a single spool valve for the one section of pump and a two spool valve for the second section.