What is the standard length of pup joint?

Pup joints are essential components in industrial pipeline connections, typically used to help adjust the length of the pipe string and compatible with various sizes and connection types. Based on the connection type, pup joints can be classified into threaded and flanged types, with threaded pup joints further divided into double-male thread, single-male thread, and flat-end thread types. Additionally, pup joints can be categorized by their function into tubing pup joints and casing pup joints, widely utilized in oil, natural gas, and other industrial pipeline connections. Baowi Steel offers various sizes of tubing pup joints, both flat-end and externally thickened, with steel grades including J, N, and L to meet different operational requirements.

A pup joint is a casing or tubing with the same threaded connection but with a shorter length than the standard range, typically used to adjust pipe string length to precise specifications. Compared to tubing, pup joints differ only in length, with material and connection types similar to conventional tubing. Pup joints are made from modified alloy steels, such as AISI 4145H or 4140H, with heat treatment to achieve a Brinell hardness of 285-341, and a minimum impact strength of 40 ft-lbs at 70°F (at a depth of one inch below the surface). With a minimum yield strength of 110,000 PSI, these joints are phosphate-coated on the surface to prevent wear during initial assembly. Standard lengths are typically 5', 10', 15', and 20', with custom lengths also available upon request.

Pup joints can be classified into tubing pup joints and casing pup joints based on application scenarios. Specifications for each type are as follows:

Outer Diameter: 4 ½" – 13 3/8"

Typical Lengths: 1, 2, 3, 4, 6, 8, 10, 12 feet

Steel Grades: H40, J55, K55, N80, L80, T95, C110, P110

Connection Types: SC, LC, BC, semi-premium, and premium

Sizes: 2 ⅜" – 4 ½"

Typical Lengths: 1, 2, 3, 4, 6, 8, 10, 12 feet

Steel Grades: J-55, N-80, L-80, P-110

Connection Types: EU (externally thickened) and NU (non-upset)

Pup joints can be subdivided into several types to meet various connection requirements, including:

Pin x Pin (with coupling)

Loose coupling

Box x Pin (with coupling)

Hand-tight coupling

According to relevant standards, the length of pup joints should be proportional to their diameter; as the diameter increases, the length should also increase. The typical lengths for pup joints are 150mm, 200mm, and 250mm, with custom design available as needed.

Pup Joint Length Standards in Pipeline Applications

China's national standard GB/T12771-2008, "Stainless Steel Welded Pipeline Technical Specifications," specifies pup joint lengths as follows for different pipe diameters:

DN15~DN100 pipeline pup joints: 150mm

DN125~DN200 pipeline pup joints: 200mm

DN250~DN400 pipeline pup joints: 250mm

DN450 and above pipeline pup joints: 300mm

Applications of Different Specifications of Pup Joints

3 1/2" EUE Pup Joint

Frequently used in intermediate casing strings for shallow to mid-depth wells, its diameter provides sufficient strength and wear resistance. This specification optimizes fluid circulation, ideal for space adjustment scenarios within the well. Commonly manufactured from API casing steel grades like J55, K55, and N80.

2 7/8" EUE Pup Joint

Widely applied in production tubing, this size allows control over the depth of downhole equipment installation. The flat-threaded 2 7/8" EUE pup joint minimizes friction loss in well operations, typically made from corrosion-resistant steel grades like J55 or L80 to enhance durability.

13 3/8" Seamless Pup Joint

This larger diameter is suitable for wide-borehole segments, providing high-strength seamless structure, often used in applications demanding wall thickness and wide-span support. Manufactured with thick-walled seamless construction and API threading, this pup joint offers excellent load-bearing capacity and connection reliability.

20" Seamless Pup Joint

One of the largest diameter sizes in well construction, the 20" seamless pup joint features threaded connections ensuring high strength and compressive performance. The thick-wall design allows it to bear significant pipe string loads, commonly used in conductor stages and deep well drilling where large diameter support is essential.

As a critical component in industrial pipeline connections, pup joints provide various specifications and connection types to meet the demands of different well conditions in industries like oil and gas. Baowi Steel offers high-quality pup joints that meet API standards, using advanced heat treatment and surface anti-corrosion processes to ensure durability and reliability in demanding construction environments.