Drill Collars (Slick and Spiral) are processed from AISI 4145 H Chromium Molybdenum Alloy Steel and are fully heat treated to a Brinell Hardness range of 285-341 BHN and have a minimum Charpy V-notch Impact strength of 40 ft-lbs. at 70° F and a minimum elongation of 13%. The mechanical properties meet or exceed API 7-1 requirements. The physical properties are guaranteed one inch below the surface at ambient room temperature.
Drill Collars are precision trepanned to close bore tolerance and all bores are drifted to API 7-1. The connections are cut on CNC Machines. All API connections comply with dimensional requirements specified in API 7-1 and guidelines presented in API RP 7G.
Spiral Drill Collars:
To avoid differential pressure sticking in the hole, the surface of drill collars can be provided with three spiral grooves reducing the contact area with the wall of the hole. The spiral grooves let mud circulate freely around the Drill Collar to equalize pressure and prevent a seal from forming. Loss of weight is approximately 4%, compared to Slick Drill Collars.
API Stress Relief Features and API Bore Back Box decrease the frequency of fatigue failures by improving the bending strength of pin and box connections, thereby, reducing high stress concentrations. Stress relief features are machined in compliance with API 7-1. Connections NC23, NC 26 (2 3/8 IF) and NC 31 (2 7/8 IF) do not have sufficient metal to accommodate stress relief features. Slip and Elevator recesses improve handling efficiency and safety. The upper radius of the elevator recess is cold-rolled. Slip and Elevator recesses can be used together or separately. Slip and Elevator Recesses are machined in compliance with API RP 7G guidelines.
On enquiries and orders, please specify:
Outside Diameter, Bore, Length, Connection Size and Type, API Stress Relief Features on Pin and Box ends, Slick or Spiral, Hard banding (band location and width), Slip or Elevator Recesses, Pressed or Cast Steel Thread Protectors, and any special features.
Drill Collars are inspected to comply with API standards. The inspections include visual dimensional checks as well as Ultrasonic Inspection on each bar over its full length and section.
Thread Profile, Lead, Taper, Pitch and Gage Standoff are 100% inspected on each Drill Collar to all applicable API Specifications and recorded.