Standard: API 5DP
Outer diameter: 2 3/8'-51/2'
Wall thickness: 6.45mm-12.7mm
Length: R1,R2 and R3
End Type: EU, IU and IEU
Drill pipe is hollow, thin-walled, steel or aluminium alloy piping used on drilling rigs.
It is hollow to allow drilling fluid to be pumped down the hole through the bit and back up the annulus.
Modern drill pipe is made from the welding of at least three separate pieces:
box tool joint
pin tool joint
The green tubes are received by the drill pipe manufacturer from the steel mill. The ends of the tubes are then upset to increase the cross sectional area of the ends. The tube end may be externally upset (EU), internally upset (IU), or internally and externally upset (IEU).
The tool joints (connectors) are also received by the manufacturer as green tubes. After a quench and temper heat treat, the tool joints are cut into box (female) and pin (male) threads. Tool joints are commonly 120 ksi SMYS, rather than the 135 ksi of the tube.
Tubes and tool joints are welded using rotary inertia or direct drive friction welding. The tube is held stationary while the tool joint is revolved at high RPMs. The tool joint is the firmly pressed onto the upset end of the tube while the tool joint is rotating. The heat and force during this interaction weld the two together.