Pull force and rotary speed is very important specification of hole opener. But it’s very regret that many HDD drilling rigs don’t have instrument to show rotary speed of hole opener.
As drilling tools manufacturer with over decade’s experiences, we have chance to compare roller bits working in different fields. Petroleum drilling, horizontal directional drilling and piling drilling. In different fields and working conditions , the abrasion of roller bits are large difference from starting down the hole to scrap.
Petroleum is very important to nation. So there is some petroleum colleges. They have majors for petroleum drilling. In petroleum drilling, instrument show detailed specifications of drilling bits, fluids etc. HDD fields introduce Many practical technology from oil drilling directly.
As we mention at beginning,many rigs don’t show RPM(Revolutions Per Minute) of hole opener. No-dig drilling rigs still have large space of development. Roller bits hole opener develop from petroleum tricone bit. In petroleum and water well field, the percentage of rubber seal tricone bits is much bigger than metal seal tricone bits, especial in shallow. But in HDD fields, the percentage of metal seal is much higher than rubber seal.
Through market research, we find that many users also don’t pay attention to RPM. If the RPM is higher than suggestion. It may damage rubber seal. Silt may enter into bearings. The lifetime of roller bits will decrease. The rotary speed of metal seal is about two times of metal seal. So rotary speed don’t affect metal seal tools too much. In additional, we also find many hole openers are work on low pull force.
Through above analysis, we suggest users control speed in reasonable range. In order to realize target ROP, lower the speed and increase pull force appropriately.
Following is the chart of pull force and rotary speed:
Notes: The upper limits of force and RPM in the chart should not be used simultaneously.