The drill pipe joint is an integral part of the drill pipe, which is divided into a male joint and a female joint, and is connected to both ends of the drill pipe body. In order to enhance the connection strength of the joint, it is necessary to increase the wall thickness of the pipe body at the joint part. According to the thickening method, it can be divided into three forms: internal thickening, external thickening, and internal and external thickening. There are threads (coarse buckles) on the joints, which are used to connect each single drill pipe. The drill pipe joint thread is a tapered pipe thread with a sealing shoulder. The shoulder surface is tightened for sealing, and the thread is only for connection. The thickening method is different, and the screw type of the corresponding joint is also different.
Inner flat type: mainly used for external thickening of drill pipe. Its characteristic is that the drill pipe has the same inner diameter, and the drilling fluid flow resistance is small; but the outer diameter is large, which is easy to wear. Through-hole type: mainly used to thicken drill pipe inside and outside. It is characterized in that the drill pipe has two inner diameters, and the flow resistance of drilling fluid is larger than that of the inner flat type, but its outer diameter is smaller than that of the regular type. Formal type: Mainly used for inner thickening of drill pipes, drill bits and fishing tools. Its characteristics are that the inner diameter of the joint inner diameter is smaller than the inner diameter of the pipe, and the drilling fluid flow resistance is large. 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 all use V-type threads, but the buckle type, distance, taper and size are very different.
Digital (NC) series fittings are American National Standard coarse thread series. It has been adopted as an international standard by API. NC threads are also V-threads, and some NC-type fittings have the same pitch diameter, taper, pitch and thread length as the old API standard fittings and can be used interchangeably.
Oil drill pipe joints are mostly in the form of external thickening or internal and external thickening. The outer diameter of the drill pipe joint is larger than the outer diameter of the pipe. During the drilling process, it constantly contacts and rubs with the well wall or casing, causing wear and tear. In order to avoid the joint wear and tear, the drill will break Drilling accidents such as rods and tripping must be provided with drill pipe joint wear-resistant belts on the drill pipe female joint.
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