Kelly is main driver of the whole drill string. It transmits torsional energy from the rotary table through the drill string to the bit at the bottom of the hole, and is a long square or hexagonal, precision machined heavy steel bar that is supported by the swivel through the rotary table and is connected to the first joint of drill pipe in the drill string. Straightness of the kelly is very crucial in the manufacturing process, thus straightness inspections are carried out before, during and after each machining operation. All milling processes are performed on specially designed rigid Kelly mills to ensure tight tolerances and high quality drive sections.

1. Manufactured from AISI 4145H-modified, fully heat-treated alloy steel with a Brinell hardness range of 285-341BHN and a minimum average Charpy impact value of 40 ft-lbs

2. Ends and drive sections, IDs and connections machined and inspected to API and NS-1 specifications

3. Ultrasonic inspection is performed on all sections