K55 L80 Oilfield Casing And Tubing OCTG API Casing Pipe

OCTG Tubing pipe standard

Same as casing pipe standard, OCTG tubing in API 5CT is also in the same material grades (J55/K55, N80, L80, P110 etc), but the tubing’s diameters are up to 4 1/2”, and it ends in various types such as BTC, EUE, NUE, and premium. Most commonly, thickened connections EUE.

API 5CT is standard technical specifications for steel casing and tubing pipes used for oil wells in petroleum and natural gas industries.

Besides casing and tubing, it also includes pup joints, coupling stock, coupling material, and accessory materials, and establishes requirements for three product specification levels (PSL-1, PSL-2, and PSL-3). The requirements for PSL-1 are the basis of this standard.

Common Grades

• J55/K55
• N80/N80Q/L80
• C90
• R95/T95
• P110/C110
• Q125

Connections

API 5CT is applicable to the following connections which comply with API SPEC 5B:
• SC: Short round thread casing
• LC: Long round thread casing
• BC: Buttress thread casing
• NU: Non-upset tubing
• EU: External upset tubing
• IJ: Integral tubing connections

4 Groups of Grade

• Group 1: All casing and tubing in Grades with H, J, K, N and R
• Group 2: All casing and tubing in Grades with C, L, M and T
• Group 3: All casing and tubing in Grade P
• Group 4: All casing in Grade Q

Manufacture

General

According to API 5CT standard, steel material used for making the pipe billet shall undergo grain refining treatment. This steel shall contain one or more grain refining elements, such as a certain amount of aluminum, niobium, vanadium or titanium, so that the austenite grains of the steel Grain refinement.

• Pipes supplied shall be manufactured in seamless type or EW type.
• Couplings, coupling stock and coupling materials shall be seamless.
• Cold-drawn tubing pipe shall be properly heat treated, otherwise it is not acceptable.
• Casing and tubing attachment materials shall be seamless pipes unless other types are stated on the order.

Heat Treatment

Heat treatment methods for API 5CT casing and tubing are a key factor to differ in each grade. Products requiring heat treatment shall be subjected to full-body and full-length heat treatment. The heat-treated upsetting product should be heat-treated in terms of its full body and full length after upsetting.

A separately heat-treated coupling blank is acceptable. If the finishing temperature is higher than the upper critical temperature of the treated steel and the pipe is air-cooled, it shall be normalized.

in the case of welding type, weld seam shall be heat treated to a minimum temperature of 540 ℃(1000°F), or a certain treatment method shall be used to make the no untempered martensite structure in the weld.

N80 Type 1 and Type Q

Steel grade N80 type 1 products shall be normalized or normalized and tempered at the option of the manufacturer.
N80Q steel grade products shall be quenched and tempered.

R95

R95 steel grade shall be quenched and tempered.

L80

When tempered at temperatures below 620 ℃(1150°F), grade L80 grade 13 Cr may be embrittled.

Straightening

R95

R95 casing and tubing shall not be stretched or expanded cold working after final tempering, except for cold working which is necessary for normal straightening and not more than 3% of compression cold working.

M65 and L80

Except for the cold working required for normal straightening, steel grade M65 and L80 products shall not be cold worked after final heat treatment.

C90 and T95

C90 and T95 products can be cold-rotated straightened, but the pipe must be heated to a minimum temperature of 480 ℃(1000°F) degrees for stress relief after straightening. If necessary, light gag straightening for steel grade C90 and T95 products is allowed.

C110

If necessary, the product shall be cold-rotated straightened and subsequently stress-relieved at temperatures between 30℃to 55℃ (50°F to 100 °F) below the final specified tempering temperature, or hot-rotated straightened at temperatures not more than 165℃ (300°F) below the final specified tempering temperature. If necessary, it is allowed to do light gag straightening.

Q125

Gag-press straightening or hot-rotating straightening can be performed for straightening, but the temperature at the end of the rotary straightening should not be less than 400 ℃ (750°F) (unless a higher temperature minimum is specified on the order). If the hot rotary straightening method cannot be used, the product can also be cold-rotated straightened, but the stress relief must be performed at 510 ℃ (950°F) after straightening. The product cannot be subjected to stress relief after cold rotary straightening only by agreement between the purchaser and the manufacturer.

Products ends

Flat-end pipe

Flat-end pipe is a pipe supplied with unmachined threads, and it may be, or not be upset, in whichever case, it shall comply with all requirements of a specific steel grade in this standard.

Product with API Threads

Steel grade H40, J55, K55 or M65 casings are available in short or long threads. However, if the purchaser requests a long-threaded casing, it should be specified in the order.

Rounded Nose

The “round” or “bullet-nose” type of pipe end may be provided by the manufacturer or specified by the purchaser to replace the conventional corner breaks on the threaded ends of external upset tubing. The improved end should be rounded so that the coating is applied and the inner and outer surfaces are rounded and smooth, without sharp corners, or burrs.

Threading

Product threading, gauging practice, and thread inspection shall be in accordance with API Spec 5B. The product end shall not be hammered but may be slightly shaped to meet the requirements of thread machining. For steel grades of C90 and higher strength, such forming shall only be carried out with the consent of the purchaser.

Workmanship of ends

All product ends shall be free of burrs on the inside and outside edges. And sandblasting shall be applied to both male and female threads of C110 steel grade.

Defects

All pipes and fittings made of pipes shall not have the following defects:
a. Any quenching crack
b. Any arc burn
c. Any surface cracking defect that reduces the net effective wall thickness to less than 87.5% of the specified wall thickness can be confirmed.
d. When non-destructive inspection is specified in this standard or on an order, any non-surface cracking defects on the outer surface having an area greater than 260 mm2 (0.41 in2) are detected.
e. Any non-surface cracking defect that reduces the effective wall thickness to less than 87.5% of the specified wall thickness can be confirmed within 1.6 mm (1/16 in) of both sides of the weld.
f. Any internal upset structure on all upset products may have any sharp corners or drastic change of sections that can cause the 90 ° hook type tool to hang up.
g. Any non-linear surface cracking defects on the inner surface of the external threaded part of the sanitary tube with a depth greater than 10% of the specified wall thickness.

CHEMICAL COMPOSITION

The product shall comply with the requirements specified in the chemical composition table for the specified steel grade and type. For the C110 steel grade, the manufacturer shall report when the purchaser asks for the lowest and highest ratios of all elements intentionally added to each batch (regardless of the purpose of its addition).

MECHANICAL PROPERTIES

The product shall meet the tensile performance requirements specified in this standard. The tensile properties of the upset casing and tubing (except for elongation) shall be consistent with the requirements of the pipe body. In case of any dispute, the properties of the upset area (except for the elongation) shall be determined by cutting the specimen from the upset.