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Overburden Casing System, also named Eccentric Casing System, is suitable for drilling water wells, geothermal wells, short micropiles, medium mini-type grouting holes of buildings, and diamond harbor projects.
Economy: Eccentric is the most economical solution because of its ingenious reaming wing. The bit is retrievable and can be used at the next hole.
Working Principle:
When drilling, the reamer bit will rotate out to enlarge the hole enough for the casing tube to slide down behind the reamer. When reached required depth, the drill pipe will drill in the reverse direction and the reamer bit will retract, allowing the whole drilling system to pass through the casing.
| Part | PA90 | PA115 | PA140 | PA165 | PA190 |
|---|---|---|---|---|---|
| Casing Tube(max.O.D.)(mm) | 115 | 142 | 171 | 195 | 222 |
| Casing Tube (min.O.D.) (mm) | 102 | 128 | 155.6 | 182.6 | 205 |
| Guide Sleeve | 174mm | 174mm | 205mm | 225mm | 250mm |
| Drill Pipe Connection | API2 3/8"Reg | API2 3/8"Reg | API2 3/8"Reg | API3 1/2"Reg | API3 1/2"Reg |
| DTH Hammer | DHD35, COP2 | COP44, DHD340 | DHD55, COP54 | COP64, DHD360 | COP64, DHD360 |
| Reaming Diameter | 123mm | 152mm | 185mm | 211mm | 237mm |
Different Shanks:
Different Face Shapes:
Different Buttons Shapes:
| A: When drilling starts working, reaming sleeve will open, borehole range will increase to accommodate casing shoe and tube. |
| B: When finish drilling in overburden layer, reverse circulation causes reaming sleeve to circle up, lifting eccentric bit out. |
| C: Casing can be left in the borehole to prevent collapse during pipe pull-out and concrete grouting. |
| D: Regular drilling bits can then be applied to reach required depth in the rock stratum. |
