The drill collar is processed and made as per Standard API SPEC 7. Thermal treatment is conducted over the whole length of the products to ensure that its mechanic performance can meet the provisions under the Standard API SPEC 7. Its Brinell hardness ranges between 285 and 341. And impact energy of its Charpy V-shaped notch can be 45 ft-lb ~55 ft-lb at a temperature of 20ºC±5ºC 1 inch below the surface of the pipe. During the entire process of the making of a drill collar, complete data from performance tests for the processing of each part including roughcast, thermal treatment and connecting thread will be kept for reference. A separate number will be affixed to each single part. All the drill collars will be tested according to the API Standard. Testing of surface dimensions and ultrasonic wave and magnetic particle testing over the whole length of a product will be included. Cold rolling must be done for the bolt root and elevator recess of a drill collar. Thus, the bearing capacity of the upper radius will be increased via reducing crack diffusion to increase fatigue strength of a drill collar and extend the service life. Phosphating or brass plating will be conducted for all screw threads to increase their corrosion resistance and avoid thread jamming of drilling tools. Our company may, as per users' requirements, provide steel or plastic-steel ring thread protectors (thread protector) for our products.
D d L
in mm in mm ft m mm kg/ kg/ft NC23-31 3-1/8 79.4 1-1/4 31.8 30 9.14 76.2 298 9.93