What is a casing pipe?

What is a casing pipe?

Casing pipe is a type of steel pipe that is typically used to enclose and surround a carrier pipe, which is installed through the center of this pipe. Steel casing pipe is most often used in underground construction projects to encase or protect utility lines from being damaged. This pipe can be used when boring horizontally or directionally under roads, rivers, lakes, or railroads. In general, steel casing pipe is extremely durable and versatile, and therefore, it can be used in a variety of construction projects as well. Casing Pipe is available in a complete variety of different sizes and diameters as well as in straight seam, spiral-weld, and rolled and welded types of manufacture.

Uses for Casing Pipe

Casing pipe is most often used for underground boring to encase and protect pipe. During horizontal underground boring projects under streets, highways, railroads, rivers, and streams, steel casing pipe can be jacked in segments into an augured hole. The casing pipe segments are then connected together by welding or by using special connections. Another commonly used practice for installing casing pipe is to weld the pipe into a ribbon and then to pull the pipe directionally through a previously drilled hole. This can be used to install casing pipe under highways, railroads, lakes, and rivers.Casing pipe is most often used to protect underground utility lines including water mains, electrical high-voltage lines, natural gas lines, telephone lines, and fiber-optic communication lines. This steel casing protects lines from human activity such as drilling or digging as well as from natural elements. The strength of the steel is a major advantage to the protection of these lines.Because steel casing pipe is extremely durable and available in a variety of sizes, this pipe can also be used in a variety of other applications.

Casing pipe can be used for:

  • Road Bore Casing
  • Water Well Casing
  • Culverts Casing
  • Open Cut Casing
  • Oil and Gas Transmission Pipeline Casing
  • Drilling Casing – Surface Casing – Rathole Casing
  • Tunnel Casing

Characteristic of casing pipe

Casing is important to oil drilling equipment, and its main equipment includes drill, core pipe and casing, drill collars and drilling small diameter steel pipe and so on.

The casing is used to support oil and gas wall of the pipe, to ensure that the drilling and completion of the process of the normal operation of the wells. Depending on the drilling each well depth and geological conditions, to use several layers of casing. Casing cementing go down after using it with tubing, drill pipe are different, can not be reused, a one-time consumable materials. Therefore, the total consumption of the casing is 70% of the oil well pipe. Casing can be divided according to usage: catheter, surface casing, casing and production casing. Casing is a large-diameter pipe, play a fixed oil and gas wells, or wellbore wall effect. The casing is inserted into the well hole, fixed with cement to prevent the formation and borehole spaced borehole collapse and to ensure circulation of the drilling mud to the drilling mined.

Casing is mainly used for drilling oil wells during drilling and after completion of the support wall to ensure that the conduct of the drilling process and completion of the wells after the regular oil casing normal operation. OCTG mainly used for oil and gas well drilling and oil and gas transportation. It includes oil drilling pipe, oil casing, pump tubing. Oil drill pipes are mainly used to connect the drill collar and drill and pass drilling power. Casing is mainly used for drilling and completion of the right wall of the support, to ensure that the conduct and completion of the drilling process after the normal operation of the wells. Pumping wells at the bottom of the tubing will mainly oil, gas transported to the ground.

Casing is to maintain the wells run lifeline. As different geological conditions, underground complex stress state, pulling, pressing, bending, torsional stress acting on the combined effect of the tube, which the casing itself, the quality of the higher requirements. Once the casing itself is damaged for some reason, could lead to the whole production wells, or even scrapped.

API Spec 5CT Casing pipe

API Spec 5CT Casing pipe - What is a 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.

Standard: API SPEC 5CT

API 5CT pipe Size (mm):
  • Outer Dimensions: 6.0mm – 219.0mm
  • Wall Thickness: 1.0mm – 30 mm
  • Length: max 12000mm

Application: gas, water and oil transportation in both oil and natural gas .

The main steel grade of API 5CT:
  • API 5CT J55
  • API 5CT K55
  • API 5CT N80
  • API 5CT L80
  • API 5CT P110

Packing: Bare/bundles/crates/crate protection at the both sides of tubes or as per customers’ requirements .

This International Standard is applicable to the following connections in accordance with ISO 10422 or API Spec 5B:

  • 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).

For such connections, this International Standard specifies the technical delivery conditions for couplings and thread protection.

For pipes covered by this International Standard, the sizes, masses, wall thicknesses, grades and applicable end finishes are defined.

This International Standard may also be applied to tubulars with connections not covered by ISO/API standards.

Chemical Composition of API 5CT
Grade C≤ Si≤ Mn≤ P≤ S≤ Cr≤ Ni≤ Cu≤ Mo≤ V≤ Als≤
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
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
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
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
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)
J55 379-552 ≥517
K55 ≥655 ≥517
N80 552-758 ≥689
L80 552-655 ≥655
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.

How to Deal With Cracks of J55 Casing Pipe
When the carbon content dissolved in the matrix has increased to a certain extent, the matrix of the high vanadium high-speed steel in the J55 casing pipe plant has been transformed into a composite matrix containing mainly martensite and austenite, together with the strengthening effect of carbides. Niobium vanadium high speed steel thus obtains sufficient hardness and certain toughness. This high-vanadium high-speed steel wear resistance is good, the author believes that this should be attributed to the composite matrix containing martensite-based austenite, this composite matrix itself has a certain degree of hardness, can resist the intrusion of foreign objects, In addition, it also provides a strong support for strengthening the carbides of the matrix.
As the carbon content continues to increase, the martensite in the matrix transforms to high-carbon martensite, while the M7C3-type complex carbides, which are dominated by chromium and molybdenum, appear as fish bones at the grain boundaries. Thus, the low-toughness high-carbon martensite occurs. With the addition of fish bone M7C3-type composite carbides to the matrix, the toughness of high-speed vanadium high-speed steel decreases, and cracks in the J55 casing pipe plant are easily generated at the M7C3-type composite carbide. In other words, the M7C3 type complex carbide carbide casing plant mainly based on chrome key is disadvantageous for improving the impact wear performance of high vanadium high speed steel.
In summary, to obtain high-vanadium high-speed steel with better wear resistance, the carbon content must be controlled within a suitable range.
How to Solve the Deformation of J55 Casing Pipe
Non-uniform deformation of J55 casing pipe hoop during metal pressure processing, the distribution of internal deformation and stress of the workpiece is not uniform, which affects both the quality performance of the product and the processing process. The main causes of deformation and stress unevenness are: external friction on the contact surface of the J55 casing pipe hoop, geometric factors in the deformation zone, non-uniformity along the degree of contraction, external end of the deformed object, uneven temperature in the deformed body, and deformation of the metal Nature and so on. Uneven distribution of deformation and stress causes unit deformation force, plasticity to decrease, and product quality to decrease. Then we have encountered how to solve it?
Measures to reduce distortion and uneven distribution of deformation: Correctly select the temperature-velocity system for deformation, minimize the harmful effects of external friction on the contact surface, and ensure the composition and organization of the deformed metal as even as possible. The fractures are different according to the plastic deformation before the fracture. The fractures can be divided into two types of brittle spear fractures. There are no obvious signs of plastic deformation in brittle fractures, and only a few traces of plastic deformation can be found near each fracture in each observation. The rupture and tensile stresses are close to orthogonal. The ductile fracture has undergone considerable plastic deformation before fracture. The main manifestation is the transgranular fracture. The intergranular fracture can only be seen when the high temperature is creeping. The main factors determining the metal fracture are deformation temperature, stress state and material nature. Cooling rate and temperature in the cooling intensity, strip thickness, mill speed, thermal properties, and cooling control temperature decrease greatly, laminar cooling area should be designed long enough, so that the letter can be achieved through a certain cooling rate to achieve the target Coiling temperature. There is a large transmission delay between the thermometer of the J55 casing pipe hoop and the thermometer in front of the coiler.

Heat Treatment Technology of Casing Pipe
27MnCrV steel AC1 = 736 °C, AC3 = 810 °C, sub-temperature quenching heating temperature between 740-810 °C selected. Sub-temperature quenching selection of heating temperature 780 °C, quenching and heating of the holding time 15min; tempering temperature after the selection of 630 °C, tempering heating holding time 50min. Since the sub-temperature quenching is heated in the α+γ two-phase region, quenching is performed in the state where the retained ferrite is partially dissolved, and the toughness is improved while maintaining high strength.
At the same time, the low-temperature quenching is lower than the conventional temperature, reducing the quenching stress, thereby reducing the quenching deformation, thus ensuring the smooth operation of the heat treatment production, and providing a very good raw material for subsequent wire processing and the like.
At present, the process has been applied to the processing plant of Magnon Steel, and the warranty data shows that after heat treatment, the yield strength Rt0.6 of the steel pipe is 820-860MPa, the tensile strength Rm is 910-940MPa, and the impact toughness Akv is 65-85J. , The resistance to destruction is 100% qualified. The data shows that the 27MnCrV steel pipe is a very good high-grade casing pipe, on the other hand, it also shows that the sub-temperature quenching process is an excellent method to avoid high-temperature brittleness in the production of steel products.
Different Temperature in Internal and External Ssurface of J55 Casing Pipe
J55 casing pipe manufacturers talk about the rapid heat treatment of steel induction heating, the steel quickly passes through the inductor by the heat treatment temperature and quickly processed. J55 casing pipe requires accurate measurement of the temperature of the fast-moving target in a very short period of time, not an ordinary temperature measurement method.
The use of continuous heating steel bridging technology applies bridging technology to improve the low temperature of the steel crucible and increase the steel product yield. The use of computers to control the head and tail of steel technology; the use of dual-frequency power to control the temperature of the end of the steel pipe; the use of rotating joints to achieve a great advance, etc. to improve the longitudinal temperature uniformity of the steel. The temperature of the tempering heating is low. According to the temperature curve of the metal force, the temperature of the outer surface of the oil casing is enthalpy at the inner surface temperature during the heating and heating process below the hot spot. With the increase of the frequency of the heating power source, the depth of the current penetrates into the human body, the skin effect is enhanced, the heat loss on the surface of the steel pipe increases, and the decrease in the temperature of the oil pipe end increases. The amount of heat lost at the tip also increases. When the heat loss from the head and tail of the continuous heating pipe to the main end is the same as the normal part, the effect of the frequency of the heating power is no longer displayed by the vertical special guide.

Hydrostatic Pressure Test Casing Pipe
The hydrostatic pressure test of casing pipe is an indispensable part of the production process of the steel pipe. Its role is to test the anti-leakage performance of the steel pipe under standard test pressure and regulation time. Like radiographs, ultrasonics, and other flaw detection techniques, it is an important means of testing the overall quality of steel tubes.
The popular description is to fill the pipe with water and test its ability to maintain the specified pressure without leaking or breaking under pressure. Its operations include three steps: flushing, pressure testing and water control.
API-5CT standard for hydrostatic pressure test
1. The hydrostatic pressure test value of coupling and threaded pipe is the lowest value of the hydrostatic test pressure of the flat end pipe, the maximum hydrostatic pressure test pressure of the coupling, and the internal pressure leakage resistance, but the standard maximum pressure is 69MPa and the pressure is calculated. The value is generally rounded to the nearest 0.5 MPa.
2. According to API requirements, the hydrostatic test pressure measuring device should be calibrated within 4 months before each use.
3. If the customer has special requirements, a higher pressure test pressure can be selected.
4. Hydrostatic pressure test Leakage is the basis for rejection.
5. Except where otherwise agreed between the purchaser and the manufacturer, hydrostatic pressure testing is not required for coupling blanks, coupling materials, nearby materials, or Q125 steel pup joints.

Source: China Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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