Assembling

DPAL uses a friction welder to assemble the pipe and the tool joint.

Stress relief and heat treatment bring the mechanical properties to meet modern drill pipe standards in the heat affected zone.

Properties are typically as follows:

Strength

Yield: the weld is 1.1 times stronger than the pipe, as per calculations of API Spec 7, sec 6.4.5.2
Elongation: 13% minimum
Reduction of area: minimum 45%
Fracture position: off the weld line

Toughness

Charpy impact at – 20 C
Minimum single value 32 Joules
Minimum average value 42 Joules

We guarantee the "leak before break" criteria as per NS-1

Hardness:

Through hardness 37HRC maximum
Surface hardness range 20 HRC minimum to 37 HRC maximum

Bend test:

Minimum angle: 180 degrees
Maximum defect size: tearing at edge maximum 2 mm.

2 samples are taken, 1 in clockwise, the second in coiunterclockwise direction.

All other tests are made as per API Spec 7.