High-speed Roller Cone Drill Bit Seal Study

The service life of cone bits which play an important role in breaking rock of the bottom of a well is almost directly decided by the life of bit bearing, which depends a large extent to the life of their seals. The recent development trend of cone bits is to realize their high speed. Faster the speed of bit is, the more weak of common bearing seals worked under the rough environment is. Therefore, we should not neglect the study and improvement for the service life of bearing while researching cone bits.To enhance the reliability of bearing seal of cone bit, this paper plans to adopt face-radial combination sealing structures; that is to say, end-face and radial seal are arranged in one bit simultaneously. The nonlinear finite element method is applied to analyze and optimize the design of sealing structures. The dishing ring seals belong the end face sealing parts, and act as sealing by some axial compression. Because of different distribution of internal pressure and temperature, the friction inside the end-face is also different at all area. In order to improve the friction between the outer diameter of dishing ring and cone, and prevent any contaminant, such as slurry and ect. from coming, the outside diameter may be curved upward. The length and open of the curved may be determined by the analogue to the actual condition. The innovative dishing ring not only possesses end -face sealing capacity, but also has some radial seal and clean function.The most common sealing ring of bit bearing is single O-ring, which is made of rubber. It has basically matched with low speed sealing bearing bit, but it cannot avoid its fault. Therefore, the common rectangular groove seals are often be changed into the curved groove with some arc degree. When the O-ring acted as sealing function is placed in the curve groove with suitable design, its stress, strain and friction are all improved so as to lengthen the service life of sealing.The finite element method has guide meaning to analyze and design of structure. By comparing between the rectangular groove and curved groove, we find that two high stress area of rectangular groove O-ring occurs during the sealing period, and the wearing on the both inside and outside diameter surfaces; the high stress area only happens at the part area of cone shaft, and the distribution of stress is more even than the former, and the wearing is on the inside diameter surface, the improvement of its distortions makes the service life of sealing lengthen.According to achievements in research, using face-radial sealing structures can adapt to the developing trend of increasing rotary speed of cone bit to a certain extent in lubricating system of bearing seal, which is cramp to bit service life.