# Sand Removal Mechanism of a High-Speed Roller Bit with Helical Sealing
## 3 Methods
### Experimental Device  
The first test was a uniaxial test without pressure. This study independently developed a horizontal helical sealing test device (as shown in Figures 3 and 4). The helical sealing ring installed in the roller (19) was thin (only 0.8-1.2 mm in thickness) and not strong enough to meet the working conditions; it was thus easily damaged and needed to be replaced frequently. The helical sealing ring and helical shaft sleeve were therefore designed as a whole (26) (as shown in Figure 5). On the one hand, the roller (19) does not need to be frequently replaced, which reduces costs and improves efficiency. On the other hand, the strength of the helical seal is enhanced. The inner part of the helical sleeve (26) is a helical sealing ring (for helical sand removal) and the outer part is a thread (for assembly with the inner hole of the roller). The helical sleeve (26) was printed in three dimensions and was installed on the roller and rotates with it.  
Figure 4: A sectional view of the testing device. 5. Liquid line; 6. valve; 7. liquid line; 11. bottom plate; 12. valve; 14. collection container; 15. bolt; 16. support frame; 17. electromagnetic speed regulating motor; 18. coupling; 19. cone; 20. end cap bolt; 21. bearing end cap; 25. bearing; 26. helical sleeve; 28. rolling bearing; 29. liquid outlet; 30. liquid inlet.  
Figure 5: Helical shaft sleeve.  
Figure 3: The appearance of the testing device. 1. Liquid container; 2. valve; 3. liquid container; 4. valve; 5. liquid line; 6. valve; 7. liquid line; 8. machine base; 9. bolt; 10. liquid tank; 11. bottom plate; 12. valve; 13. pipeline; 14. collection container; 15. bolt; 16. support frame; 17. electromagnetic speed regulating motor; 18. coupling; 19. roller; 20. end cap bolt; 21. bearing end cap; 22. cover; 23. bolt; 24. fixed pin.  
Under the driving action of the roller (19), the helical sleeve (26) rotates at high speed. The rotated helical sleeve (26) generates an axial driving force for the liquid injected into the gap. There is thus a pumping effect, and the liquid in the gap is removed from the roller (19) to achieve the sealing.  
The second test was a pressure medium uniaxial test. As for the actual conditions of the well bottom, as the drilling bit operates, the volume of the bearing volume changes owing to vibration of the bearing system, and the thermal expansion and vapor pressure of grease generated by friction heat increase the pressure difference. The pressure difference between the inside and outside of the sealing cavity is about 0.3-0.7 MPa. The liquid container 3 was replaced by a pump having this pressure difference, and the liquid was pumped to the A and B lines, and the remaining steps were the same as in the first experiment. This experiment was based on the first test device to increase the pressurized pump to simulate the actual working conditions.  
The third test was a uniaxial bit loading test. A special high-speed bearing test was conducted to simulate actual working conditions (as shown in Figure 6). This test can exert axial and radial loads on a bit for testing the sealing performance. As for the device, the position of the drilling bit is shown in Figure 7. Moreover, the drilling bit comprises a roller and bearing. The groove at roller position (1) was applied to the axial and circular locations of the roller. The grooves at bearing positions (2) and (3) were respectively used for the axial and circular locations of the roller. The wear-resistant alloys were machined on the bearing side with a radial load to increase the wear resistance, which is consistent with the actual drilling process.