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LARGE-DIAMETER WELDED PIPELINES - X80 / L555 - X70 / L485

LARGE-DIAMETER PIPES/LINE PIPES

The LONGTAIDI Group is one of the largest global suppliers of large-diameter pipes for oil- and gas pipelines. LONGTAIDI is focused on welded large-diameter steel pipes in lengths of up to 24 meters.

LONGTAIDI is renowned for producing large-diameter pipes used in extreme applications. These pipes withstand the lowest temperatures in arctic environments as well as the extreme pressures to be found in ultra-deep ocean applications.

Our offering consists of pipes in the following dimensions
Longitudinally welded pipes with outside diameters from 610 mm to 1,524 mm and a wall thickness between up to 45 mm.

Spirally welded pipes with outside diameters from 610 mm to 1,422 mm and a wall thickness up to 20 mm.

LONGTAIDI supplies standard products as well as special products for many applications. As an economic solution for transporting gas and oil, LONGTAIDI provides a broad range of customised products: Pipes that are manufactured according to national or international standards (API, EN, ISO) and specifications (NACE, DNV) or according to customer specifications.

Product Range

The tables with our current range of products provides you with an overview of the most important standard solutions.

Large diameter spiral steel pipe production process

Spiral steel pipe is a spiral seam steel pipe which is made of steel coiled coil as raw material, which is often heated and extruded and welded by automatic double-wire double-sided submerged arc welding process. The main production process is as follows:

(1) Raw materials are strip coils, welding wire, flux. Strict physical and chemical testing is required before input.

(2) The steel head and tail are butt jointed, and the single wire or double wire submerged arc welding is used, and the automatic submerged arc welding is used after the steel pipe is rolled.

(3) Before forming, the strip is leveled, trimmed, planed, surface cleaned and pre-bent.

(4) The electric contact pressure gauge is used to control the pressure of the cylinder on both sides of the conveyor to ensure the smooth conveying of the strip.

(5) Adopt external control or internal control roll molding.

(6) The weld gap control device is used to ensure that the weld gap meets the welding requirements, and the pipe diameter, the amount of misalignment and the weld gap are strictly controlled.

(7) Both internal welding and external welding are performed by single-wire or double-wire submerged arc welding by American Lincoln welding machine to obtain stable welding specifications.

(8) The welded seams are all inspected by online continuous ultrasonic automatic injury inspection to ensure the non-destructive testing coverage of 100% spiral welds. If there is a defect, the alarm is automatically alarmed and sprayed, and the production worker adjusts the process parameters at any time to eliminate defects in time.

(9) The steel pipe is cut into individual pieces by an air plasma cutting machine.

(10) After cutting into a single steel pipe, the first three inspections of each batch of steel pipe shall be subjected to a strict first inspection system to check the mechanical properties, chemical composition, fusion condition, surface quality of the steel pipe and non-destructive testing to ensure the pipe making process. Once qualified, it can be officially put into production.

(11) The part of the weld with continuous acoustic flaw detection mark, after manual ultrasonic and X-ray review, if it is defective, after repair, it will pass the non-destructive test again until it is confirmed that the defect has been eliminated.

(12) The tube of the butt weld of the strip and the joint of the butt joint intersecting the spiral weld are all inspected by X-ray television or film.

(13) Each steel pipe is subjected to hydrostatic pressure test and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. The test parameters are automatically printed and recorded.

(14) Pipe end machining, so that the verticality of the end face, the groove angle and the blunt edge are accurately controlled.

Longitudinally welded
high strength up to X100 / L690 | sour service up to X70 / L485 | heavy wall up to 1.770 inch