Rotary Head Solutions
In a market where efficiency, productivity and multi-functionality are key drivers in the development of drilling rigs, SAI offers a unique solution to optimize drill head performance.
Continuous power transmission without gears or clutches
In drill heads, the rotational speed can vary depending on the tool used or the ground conditions. Conventional designs have addressed this wide speed range by combining variable displacement axial piston motors coupled with gearboxes with mechanical gears to decrease the gear ratio to achieve maximum output speed.
Another solution is to use a larger number of engines, excluding some of them through clutches or freewheeling. However, this discrete variation in displacements creates gaps in transmissible torque, as well as introducing additional mechanical organs, resulting in original equipment costs, maintenance and reduced reliability.
SAI offers variable displacement motors with ratios up to 8:1, enabling the continuous transformation of hydraulic power into mechanical power , from minimum to maximum speed, without the use of gearboxes or clutches.
In Table 3 we find an application benchmark for a 190kNm drill head.
The traditional solution with the axial piston motor requires modifying the mechanical reduction to achieve speeds above 45 rpm, while with the SAI motor, speed can be increased only by decreasing the hydraulic displacement.
|
|
190kNm Rotary Head |
||||
| Axial Piston Motors | SAI Motors | ||||
|
Power available |
270 |
[kW] |
Power available |
270 |
[kW] |
|
Max torque |
190000 |
[Nm] |
Max torque |
190000 |
[Nm] |
|
Max Pressure |
330 |
bar |
Max Pressure |
330 |
bar |
|
Max flow (@max Pressure) |
491 |
l/min |
Max flow (@max Pressure) |
491 |
l/min |
|
Tool speed @ max torque |
14 |
[rpm] |
Tool speed @ max torque |
14 |
[rpm] |
|
Max tool speed on drilling |
45 |
[rpm] |
Max tool speed on drilling |
ANY |
[rpm] |
|
Max discharge speed |
110 |
[rpm] |
Max discharge speed |
110 |
[rpm] |
|
Total reduction ratio DRILLING |
72 |
i |
Total reduction ratio DRILLING |
16 |
i |
|
Total reduction ratio SPIN OFF |
31 |
i |
Total reduction ratio SPIN OFF |
16 |
i |
|
Motor displacement max |
250 |
[cc/rev] |
Motor displacement max |
1100 |
[cc/rev] |
|
Motor displacement min |
75 |
[cc/rev] |
Motor displacement min |
140 |
[cc/rev] |
|
n° of hyd motors |
2 |
n° of hyd motors |
2 |
||
Reducing consumption and temperatures
SAI’s radial piston engine offers maximum starting torque due to its crankshaft and swing cylinder design.
In addition, the change in displacement in the SAI engine is made by changing the eccentricity of the shaft, thus the piston stroke. The contact angle between piston and shaft remains the same as the displacement changes (fig.
In contrast, axial piston engines upon displacement reduction change the angle of force application of the pistons, penalizing the resultant that contributes to torque generation, instead increasing the load on the bearings, reducing overall efficiency.
Finally, the SAI engine delivers power at a speed more suited to the use of the machine. In other words, the SAI engine generally requires one or two fewer reduction stages than an axial piston engine, resulting in efficiency and cost savings.
Higher hydraulic efficiency, less use of mechanical reductions contribute to the reduction of fuel consumption .
Displacement controls for better integration with control systems
The displacement of SAI variable motors can be managed by electrohydraulic control. SAI provides a complete package with CPU, valve, and feedback sensors to adjust displacement. The CPU can be controlled in volts or via CAN BUS.
Alternatively, the motor can be equipped with a fully hydraulic constant pressure (“Constant Pressure”) control, where the displacement is adjusted according to the load while maintaining a set pressure.
Key Points
- Maximum torque and speed range without gears or clutches
- Increased efficiency through SAI radial piston technology and reduced mechanical reduction stages
- Full range of controls for easy integration with machine control systems.
