Description
Double-arm drill pipe is also called double-layer drill pipe. It is composed of inner and outer layers of drill pipes (called inner tube and outer tube).
The inner and outer pipes form an annuls, which is a channel for pumping flushing medium to the bottom of the hole during hydraulic rock drilling and center sampling drilling.
The central hole of the inner tube is used to discharge the flushing medium and fixed as a whole, and the threaded buttons of the outer tube are connected between each double-walled drill pipe to ensure the transmission of torque and pressure.
However, the plug-in method is mostly used between the inner pipes, which generally only serve to circulate the flushing medium. Therefore, a sealing device should be installed at the plug-in place.
| Size | Nominal Weight | OD of Pipe Body | Wall Thickness | Grade | Upset Type | Conn. Type | OD of Pin and Box | ID of Pin |
|---|---|---|---|---|---|---|---|---|
| (lb/ft) | (in) | of Pipe Body (in) | (in) | (in) | ||||
| 2 3/8 | 6.65 | 2 3/8 | 0.28 | EXGS | EU | NC26(2 3/8 IF) | 3 3/8 | 1 3/4 |
| 2 7/8 | 10.4 | 2 7/8 | 0.36 | NC31(2 7/8 IF) | 4 1/8 | 2 | ||
| 3 1/2 | 13.3 | 3 1/2 | 0.37 | NC38(3 1/2 IF) | 5 | 2 7/16 | ||
| 3 1/2 | 15.5 | 3 1/2 | 0.45 | NC38(3 1/2 IF) | 5 | 2 1/8 | ||
| 4 | 14 | 4 | 0.33 | NC466(4 IF) | 6 | 3 1/4 | ||
| 4 1/2 | 16.6 | 4 1/2 | 0.34 | IEU | NC40(4 IF) | 6 1/4 | 3 | |
| 4 1/2 | 20 | 4 1/2 | 0.43 | NC46(4 IF) | 6 1/4 | 2 1/2 | ||
| 5 | 19.5 | 5 | 0.36 | NC50(4 1/2 IF) | 6 5/8 | 3 1/4 | ||
| 5 | 19.5 | 5 | 0.36 | 5 1/2 FH | 7 | 3 3/4 | ||
| 5 | 25.6 | 5 | 0.5 | NC50(4 1/2 IF) | 6 5/8 | 2 3/4 | ||
| 5 | 25.6 | 5 | 0.5 | 5 1/2FH | 7 1/4 | 3 1/4 | ||
| 5 1/2 | 21.9 | 5 1/2 | 0.36 | 5 1/2 FH | 7 1/4 | 3 1/2 | ||
| 5 1/2 | 24.7 | 5 1/2 | 0.42 | 5 1/2 FH | 7 1/4 | 3 1/2 | ||
| 6 5/8 | 25.2 | 6 5/8 | 0.33 | 6 5/8 FH | 8 1/4 | 4 3/4 | ||
| 6 5/8 | 27.7 | Aug-65 | 0.36 | 6 5/8 FH | 8 1/4 | 4 3/4 |
