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Overburden Casing System, also named Eccentric Casing System, is suitable for drilling water wells, geothermal wells, short mircopiles, medium mini-type grouting hole of building, and diamond harbour projects.
When drilling, the reamer bit will rotate out to enlarge the hole which is enough for the casing tube to slide down behind the reamer. When the required depth is reached, 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.) | 115mm | 142mm | 171mm | 195mm | 222mm |
| DTH Hammer | DHD35, COP2 | COP44, DHD340 | DHD55, COP54 | COP64, DHD360 | COP64, DHD360 |
| Reaming Diameter | 123mm | 152mm | 185mm | 211mm | 237mm |
| Effective length | 174mm | 174mm | 205mm | 225mm | 250mm |
| Phase A | When drilling starts working, reaming sleeve will open, borehole range will increase to accommodate casing shoe and casing tube. |
| Phase B | When finish drilling in overburden layer, reverse circulation is applied, reaming sleeve circles up, and eccentric bit lifts out. |
| Phase C | The casing can be left in the borehole to prevent collapsing while pulling out pipe and grouting concrete. |
| Phase D | Regular drilling bits can be applied to drill the required depth in the rock stratum. |
