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Classification of drill pipe joints
Feb 02, 2019
Integral Drill Rod.jpg

The drill pipe joint is an integral part of the drill pipe, and the male and female joints are connected at both ends of the drill pipe body. In order to enhance the joint strength of the joint, it is necessary to increase the wall thickness of the pipe body at the joint portion, and can be divided into three types: inner thickening, outer thickening, and inner and outer thickening. The joint is threaded (rough buckle) to connect the single drill pipe. The thread of the drill pipe joint is a taper pipe thread with a sealing shoulder. The shoulder surface is tightened to seal, and the thread only serves as a joint. Different ways of thickening, the corresponding threaded type of the joint is also different.

There are four types according to the threaded type drill pipe joints: inner flat (IF), through eye (FH), regular (REG); digital (NC).

Buckle connection condition

The three conditions that must be met by the buckle connection:

1 equal in size;

2 thread types are the same;

3 male and female buckles match.

Drill pipe joint buckle type

Inner flat type: mainly used for outer thickening drill pipe. The characteristic is that the inner diameter of the drill pipe is the same, and the flow resistance of the drilling fluid is small; but the outer diameter is large and easy to wear. Through-eye type: mainly used for thickening drill rods inside and outside. It is characterized in that the drill pipe has two inner diameters, and the drilling fluid flow resistance is greater than the inner flat type, but the outer diameter is smaller than the regular type. Regular type: mainly used for inner thickening drill pipe and drill bit, fishing tools. The characteristic is that the inner diameter of the joint inner diameter is smaller than the inner diameter of the pipe body, and the drilling fluid has large flow resistance, and the relative flow resistance is the largest among the three buckle types, but the outer diameter is the smallest and the strength is large. The above three types of joints are all V-shaped threads, but the buckle type, the buckle length, the taper and the size are all very different.

The digital (NC) series connector is a US national standard coarse thread series. It has been adopted as an international standard by the API. NC threads are also V-threaded, and some NC-type joints have the same pitch diameter, taper, pitch and thread length as the old API standard joints and can be used interchangeably.

Most of the oil drill pipe joints are in the form of outer thickening or inner and outer thickening. The outer diameter of the drill pipe joint is larger than the outer diameter of the pipe body. During the drilling process, the inner wall or the casing is in constant contact with the friction, resulting in wear and tear, so as to avoid broken joints. For drilling accidents such as poles and trips, drill pipe joint wear belts must be provided on the drill pipe female joint.

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