Tubing, Casing and Line Pipes

Tubing and casing strings designed for the specific requirements for conveying gaseous media and combustible liquids or solids.

All wells drilled for the purpose of oil or gas production (or injecting materials into underground formations) must be cased with material with sufficient strength and functionality.

API5L Steel pipe for pipeline transportation system

Peotroleum and natureal gas industies - Steel pipe for pipeline transportation system.
API5L Steel pipe for pipeline transportation system
API Spec 5CT Casing pipe

API Spec 5CT Casing pipe

API Spec 5CT – Specification 5CT/ISO 11960, Specification for Casing and Tubing, Eighth Edition, Petroleum and natural gas industries-Steel pipes for use as casing or tubing for wells.

API 5CT Steel pipes for use as Casing and Tubing

API5CT Peotroleum and natureal gas industies - Steel pipes for use as casing or tubing for wells.

Mill Test Certificate: EN 10204/3.1B 

API5L Steel pipe for pipeline transportation system
Drill Pipes with Welded-on Tool-Joints/ Threaded End

Tubing with Threaded Non-Upset/Upset End and Coupling

Offshore Pipeline

Offshore Pipeline

Geological Drilling Pipe

Geological tube is steel pipe that using core drilling for the geological department, which a hollow cross section, surrounded by long geological drilling joints with steel pipes.

Oil Country Tubular Goods (OCTG)

Oil country tubular goods (OCTG) is a family of seamless rolled products consisting of drill pipe, casing and tubing subjected to loading conditions according to their specific application.

Oil Country Tubular Goods (OCTG)
Select differences between PSL 1 and PSL 2

This is summarized information from API Specification 5L.

 Data PSL1 PSL2
CVN impact (Charpy) testing None required Required for all grades
Nondestructive inspection of seamless Only when purchaser specifies   SR4 SR4 mandatory
Certification Certificates when specified per SR15 Certificates (SR 15.1) mandatory
Traceability Traceable only until all tests are passed, unless SR15 is specified Traceable after completion of tests (SR 15.2) mandatory
Hydrostatic Test Required     Required

Note: Please refer to the specific Standard or Specification or contact us for more details.

API Spec 5CT

API Spec 5CT – Specification 5CT/ISO 11960, Specification for Casing and Tubing, Eighth Edition, Petroleum and natural gas industries-Steel pipes for use as casing or tubing for wells.

The main steel grade of API 5CT:

  • API 5CT J55
  • API 5CT K55
  • API 5CT N80
  • API 5CT L80
  • API 5CT P110

Chemical Composition

Grade C≤ Si≤ Mn≤ P≤ S≤ Cr≤ Ni≤ Cu≤ Mo≤ V≤ Als≤
API 5CT J55 0.34-0.39 0.20-0.35 1.25-1.50 0.020 0.015 0.15 0.20 0.20 / / 0.020
API 5CT  K55 0.34-0.39 0.20-0.35 1.25-1.50 0.020 0.015 0.15 0.20 0.20 / / 0.020
API 5CT N80 0.34-0.38 0.20-0.35 1.45-1.70 0.020 0.015 0.15 / / / 0.11-0.16 0.020
API 5CT  L80 0.15-0.22 1.00 0.25-1.00 0.020 0.010 12.0-14.0 0.20 0.20 / / 0.020
API 5CT J P110 0.26-035 0.17-0.37 0.40-0.70 0.020 0.010 0.80-1.10 0.20 0.20 0.15-0.25 0.08 0.020

Mechanical Properties of API 5CT

Steel Grade Yield Strength (Mpa) Tensile Strength (Mpa)
API 5CT J55 379-552 ≥517
API 5CT K55 ≥655 ≥517
API 5CT N80 552-758 ≥689
API 5CT L80 552-655 ≥655
API 5CT P110 758-965 ≥862

API Spec 5CT standard replaced by:

  • API Spec 5CT – Specification 5CT/ISO 11960, Specification for Casing and Tubing, Eighth Edition, Petroleum and natural gas industries-Steel pipes for use as casing or tubing for wells
  • This product references:
  • API Spec 5B – Specification for Threading, Gauging, and Thread Inspection of Casing, Tubing, and Line Pipe Threads (US Customary Units) (Includes March 2004 Addendum)
  • ISO 10422:1993 – Petroleum and natural gas-industries; threading, gauging, and thread inspection of casing, tubing and line pipe threads; specification
  • This product replaces:
  • API 5CT – Specification for Casing and Tubing (U.S. Customary Units)
  • ISO 11960 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 5, Casing, tubing and drill pipe.

Seamless steel tubes for oil casing and tubing in oil wells

Model N0.of steel tubes:

J55, N80, L80, P110 etc.

  • short round thread casing (STC);
  • long round thread casing (LC);
  • buttress thread casing (BC);
  • extreme-line casing (XC);
  • non-upset tubing (NU);
  • external upset tubing (EU);
  • integral joint tubing (IJ).

This International Standard specifies the technical delivery conditions for steel pipes (casing, tubing, plain end casing liners and pup-joints) and accessories.

PSL C, a    Mna P        S  Si V Nb


Other CEIIW CEpcm
1 0.24 1.40 0.025 0.015 0.45 0.10 0.05 0.04 b,c .043 0.025
2 0.28 1.40 0.03 0.03 - b b b - - -

API SPEC 5L is a international standard specifies requirements for the manufacture of two product specification levels (PSL 1 and PSL 2) of welded steel pipes for use in pipeline transportation systems in the petroleum and natural gas industries.

Characteristics of seamless casing and tubing

Seamless oil casing, oil and gas exploration in the largest amount of a pipe, it relies on male and female buckle buckle which is screwed inside and outside, will a series deep underground steel pipe work. Oil well casing is the lifeline of its quality directly affects the success of drilling operations and the service life of oil and gas wells, related to the oil fields and the manufacturer's economic benefits.

Seamless Oil casing failure is one of the main problems encountered for each oil field, particularly among the most serious failure of the threaded joint. According to statistics, the oil casing failure occurs in about 64% of accidents threaded connections, the domestic this figure is as high as 86%, securing oil casing threaded joints are the weak link in the oil casing string, therefore, increase the thread connection quality is a key factor in ensuring the quality of the column. Oil casing threaded connections used in the stress distribution directly determines the strength of the connection string. Stress distribution of the parts of the study, not only for manufacturers optimize oil casing thread design, casing and tubing used for predicting the performance provide the basis, but also to guide the proper selection and use of oilfield tubing and casing also has a certain reference value.

The plastic casing and tubing nipple

Seamless oil casing joints is externally threaded male buckle and belt buckle female threaded screw together composed of male and female buckle buckle the contact surface, which is a helical surface, and the oil tube fitting force is more complex. Apart screwed contact pressure generated torque, but also by tension (self-weight of the oil casing), pressure (by the oil, gas or other media caused by) the role of such loads. Oil casing the joint force analysis involves material nonlinearity, geometric nonlinearity and complexity of the contact friction conditions and other nonlinear problems establish a complete and accurate mathematical model, an analytical solution is very difficult.

Tech & Service of Seamless pipe

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.

How to make seamless pipe(seamless pipe process)?
Hot Piercing Workshop
Piercing process
The cross roll piercing and pilger rolling process in the size range from approx. 250 to 660 mm outside diameter.
Precision cold drawn steel tube production process
Pipe weld cracks
often follow different mechanisms can be divided into two types of thermal cracking and cold cracking.
How to calculate a steel pipe and tube theoretic weight
Calculate a steel pipe?
Pipe fittings are necessary to join together pipes, or to change the direction of an existing pipe.
Pipe beveling
Pipe beveling is the process where an angle is formed between the edge of the end of a pipe or tube and a plane perpendicular to the surface.
Steel pipe cutting machine
Pipe cutting
Cutting tools have a grinding wheel piece cutting machine (also known as toothless saw), hand saw, cutter and other hand tools.
How to calculate a steel pipe and tube theoretic weight
Packing the steel pipes
There are probably hundreds of different methods for packing a pipe, and most of them have merit, but there are two principles that are vital for any method.
Condition on delivery:

It refers to the state of final plastic deformation or final heat treatment of the delivered product. The hot-rolled or cold drawn (rolled) state or manufacturing state generally delivered without heat treatment; the heat-treated state after heat treatment delivery, or the normalizing, tempering, solid solution, annealing according to the type of heat treatment status.

Delivery status Abbreviation Description

(cold-finished as-drawn)

BK No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.
(lightly cold-worked)
BKW After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
Annealed GBK After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
Normalized NBK The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

Delivery according to actual weight or delivery according to theoretical weight

  • Actual weight - at the time of delivery, the weight of its product is delivered according to the weighing (weighing) weight;
  • Theoretical weight - The weight of the product at the time of delivery is calculated from the nominal size of the steel.


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