Applicables:
The surface of the stratum is mostly covered by loose material, sand
and mud layers, backfill layers (without boulders), etc
1. When drilling starts,the pilot bit drives the casing shoe and casing tube down.
2. When reaching the bedrock, reverse rotation of he tool and pull the pilot bit out.
3. The casing tube can be left in the hole or grouting can be done while the tube is being pulled out.
4. Use normal bit to drill to the desired depth.
| No. | Items | Description |
|---|---|---|
| 1 | Casing tube | a. Threaded casing tube, left hand thread; b. Welding type casing tube |
| 2 | Drill pipe | Thread: API (REFG/IF)/NC |
| 3 | Stabilizer | Thread of stabilizer is same as that of drill pipe |
| 4 | DTH hammer | Thread type: API REG |
| 5 | Casing shoe | a. Threaded casing shoe, left hand thread; b. Welding casing shoe |
| 6 | Concentric casing system with blocks | See the forms for specs |
| D | t | H | C | G | ||||
|---|---|---|---|---|---|---|---|---|
| Model | OD of casing tube（mm） | Thickness(mm) | Max dia. of guide device (mm) | Reamed diameter (mm) | Max OD of normal bit (mm) | Qty of blocks | Bit shank | Weight（kg） |
| T115 | 140 | 6 | 126 | 150 | 115 | 2 | DHD340/SD4/QL40 | 17.2 |
| T136 | 168 | 10 | 146 | 182 | 136 | 2 | DHD350/SD5/QL50 | 25 |
| T146 | 178 | 10 | 156 | 192 | 146 | 2 | DHD350/SD5/QL50 | 30 |
| T160 | 194 | 10 | 172 | 212 | 160 | 2 | DHD360/SD6/QL60 | 41.2 |
| T185 | 219 | 10 | 196 | 234 | 185 | 3 | DHD360/SD6/QL60 | 59 |
| T203 | 245 | 12 | 218 | 260 | 203 | 3 | DHD380/SD8/QL80 | 85.5 |
| T240 | 273 | 10 | 251 | 305 | 240 | 3 | DHD380/SD8/QL80 | 105.6 |
| T280 | 325 | 10 | 302 | 346 | 280 | 3 | NUMA100/SD10/DHD380 | 167.2 |
| T305 | 355 | 10 | 332 | 376 | 305 | 3 | DHD112/NUMA120 | 232.5 |
| T330 | 377 | 10 | 354 | 398 | 330 | 3 | DHD112/NUMA120 | 253 |
| T360 | 406 | 11.5 | 380 | 428 | 360 | 4 | DHD112/NUMA120/UNMA125 | 282 |
| T380 | 426 | 11.5 | 400 | 448 | 380 | 4 | DHD112/NUMA120/UNMA125 | 305.8 |
| T412 | 460 | 11.5 | 434 | 485 | 412 | 4 | NUMA125/TH14 | 383 |
| T432 | 480 | 12.7 | 450 | 505 | 432 | 4 | NUMA125/TH14 | 426.6 |
| T457 | 508 | 12.7 | 479 | 534 | 457 | 4 | NUMA180/TK18/TH14 | 590 |
| T510 | 560 | 12.7 | 530 | 590 | 510 | 4 | NUMA180/TK18 | 735 |
| T551 | 610 | 12.7 | 582 | 639 | 551 | 4 | NUMA180/TK18 | 922 |
| T600 | 660 | 14 | 628 | 684 | 600 | 4 | NUMA240/NUMA180 | 1192 |
| T645 | 711 | 16 | 675 | 741 | 645 | 4 | NUMA240/TK24 | 1340 |
| T694 | 762 | 16 | 726 | 800 | 694 | 4 | NUMA240/TK24 | 1603 |
| T750 | 813 | 16 | 776 | 845 | 750 | 5 | NUMA240/TK24 | 1790 |
| T794 | 862 | 16 | 824 | 900 | 794 | 5 | TK24/TK28 | 2009 |
| T846 | 914 | 16 | 876 | 960 | 846 | 5 | TK28/QL300 | 2345 |
| T892 | 960 | 16 | 922 | 1000 | 892 | 5 | TK28/QL300 | 2536 |
| T950 | 1016 | 16 | 980 | 1060 | 950 | 6 | TK28/QL300 | 2965 |
