What is a Casing Nipple?

What is a casing nipple?

The oil casing nipple is used to fix the wellhead of the drilling well and connect the wellhead casing string. It is used to support the gravity of the technical casing and oil layer casing, seal the annular space between the various layers of pipes, and is used for installing blowout preventers and tubing heads. , the production tree provides a transitional connection, and through the two side ports on the casing nipple body, construction operations such as mud replenishment, monitoring and balancing fluid filling can be carried out.

Typically, oil casing nipple are threaded on both ends and made from straight pipe. These are considered important categories of pipe fittings. Additionally, these fittings allow pipes to be connected to heaters or other types of pipes.

Structure of casing nipple:

The casing nipple is generally made of 35 or 42 chromium-molybdenum high-quality alloy structural steel. A casing hanger is also installed in the casing nipple to hang casing strings of corresponding specifications and seal the annular gap. A blowout preventer group should be installed on it. After the oil well is completed, a Christmas tree is installed on the casing head. A Christmas tree is a wellhead device used to extract oil, such as self-injection wells and mechanical production wells. It is the main equipment at the top of the oil and gas well to control and regulate oil and gas production. It is mainly composed of three parts: casing head, tubing head, and oil (gas) tree body.

Casing nipple abbreviations and meaning:

N.P.S. – Nominal Pipe Size
D.N. – Diameter Nominal

NPS
Nominal Pipe Size is an international standard from North America that designates the thickness and diameter of a pipe.  It uses inches in measuring.

DN

Diameter Nominal is a European standard equivalent to NPS. It uses millimeters in measuring.

Function of casing nipple:

When drilling on land or offshore, in order to support and fix the casing string lowered into the well, the blowout preventer group and other wellhead devices are installed, and the screws or flanges are connected to the top of the casing string and are located on the outer casing. A special short joint for pipe.

Advantages of casing nipple:

Opting for casing nipple offers a lot of advantages. These fittings make a pipe permanently leak-proof which increases the efficiency of the entire system. Also, there is a decrease in turbulence and pressure as the inner surface of the pipe is smooth. These fittings are known to use space more efficiently in contrast with other connecting procedures.

Casing nipple production process:
The production of casing nipples generally has the following process:
1. Casting billet, casting the material into a workpiece blank.
2. Rough cutting, preliminary cutting of the workpiece blank.
3. Fine turning: use a lathe to process the rough-cut workpiece to the designed accuracy.
4. Boring diameter, use a boring machine to boring out the designed inner diameter.
5. Drill holes, use a drill press, and drill out the holes for the external connecting bolts.
6. Heat treatment: perform quenching and tempering heat treatment on the workpiece.

7. Inspection and testing: The casing nipple that has completed the processing process will be inspected and non-destructively inspected for geometric dimensions, hardness, roughness and internal and external defects.

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