Regarding the selection of steel supporting structure steel pipe, which material is better for straight seam steel pipe and spiral steel pipe?
The following analysis gives an introduction from the comparison of the production process and price of the two steel pipes, which can give the practical user an intuitive understanding of the attributes and characteristics of the two steel pipes:
- Comparison of production and manufacturing processes with materials:
Straight seam steel pipe process
- Plate inspection: After the steel plate used to manufacture large-diameter LSAW steel pipe enters the production line, the whole plate is first subjected to ultrasonic inspection;
- Edge milling: double-sided milling of the two edges of the steel plate with a milling machine to achieve the required plate width, plate edge parallelism and bevel shape;
- Pre-bending: Use a pre-bending machine to pre-bend the edge of the board so that the edge of the board has a curvature that meets the requirements;
- Forming: On the JCO forming machine, first half of the pre-bent steel plate is pressed into a "J" shape by multiple stepping and pressing, and then the other half of the steel plate is also bent and pressed into a "C" shape to form an open "O" shape
- Pre-welding: Join the formed longitudinally welded steel pipe and use gas shielded welding (MAG) for continuous welding;
- Inner welding: longitudinal multi-wire submerged arc welding is used to weld the inner side of the longitudinal steel pipe;
- External welding: Use longitudinal multi-wire submerged arc welding to weld on the outside of the LSAW steel pipe:
- Ultrasonic inspection I: 100% inspection of the inner and outer welds of the longitudinally welded steel pipe and the base materials on both sides of the weld;
- X-ray inspection ?: 100% radiographic industrial TV inspection of the inner and outer welds, using an image processing system to ensure the sensitivity of flaw detection;
- Diameter expansion: expand the total length of the LSAW steel pipe to improve the dimensional accuracy of the steel pipe and improve the distribution of the internal stress of the steel pipe;
- Hydraulic test: The expanded steel pipes are inspected one by one on the hydraulic testing machine to ensure that the steel pipe meets the test pressure required by the standard. The machine has automatic recording and storage functions;
- Chamfering: Process the pipe ends of the qualified steel pipes to meet the required pipe end groove size;
- Ultrasonic inspection II: Ultrasonic inspection is carried out again one by one to check the possible defects of the longitudinally welded steel pipe after diameter expansion and water pressure;
- X-ray inspection ?: Carry out radiographic industrial television inspection and filming of pipe end welds on the steel pipe after the expansion and hydraulic test;
- Tube end magnetic particle inspection: carry out this inspection to find tube end defects;
- Anti-corrosion and coating: The qualified steel pipe is anti-corrosion and coating according to user requirements.
Spiral steel pipe forming process:
- The raw materials are strip coils, welding wires, and fluxes. Strict physical and chemical tests are required before investment.
- The strip head and tail joints are welded by single-wire or double-wire submerged arc welding, and automatic submerged arc welding is used for repair welding after coiling into steel pipe.
- Before forming, the strip undergoes leveling, edge trimming, edge planing, surface cleaning and conveying, and pre-bending treatment.
- The electric contact pressure gauge is used to control the pressure of the cylinders on both sides of the conveyor to ensure the smooth transportation of the strip.
- Adopt external control or internal control roll forming.
- 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.
- Both internal welding and external welding adopt American Lincoln electric welding machine for single-wire or double-wire submerged arc welding to obtain stable welding specifications.
- The welded seams are all inspected by an online continuous ultrasonic automatic flaw instrument, which guarantees 100% non-destructive testing coverage of spiral welds. If there is a defect, it will automatically alarm and spray the mark, and the production workers can adjust the process parameters at any time to eliminate the defect in time.
- Use an air plasma cutting machine to cut the steel pipe into individual pieces.
- After cutting into single steel pipes, the first three of each batch of steel pipes shall undergo a strict first inspection system to check the mechanical properties, chemical composition, fusion status of the welds, the surface quality of the steel pipes and pass non-destructive inspections to ensure that the pipe manufacturing process is qualified Later, it can be officially put into production.
- The parts with continuous sonic flaw detection marks on the weld are re-examined by manual ultrasonic and X-ray. If there is a defect, after repairing, it will go through non-destructive inspection again until it is confirmed that the defect has been eliminated.
- The pipes where the strip butt welding seam and the D-shaped joint intersecting the spiral welding seam are all inspected by X-ray television or filming.
- Each steel pipe undergoes hydrostatic pressure test, and the pressure adopts radial seal. The test pressure and time are strictly controlled by the steel pipe hydraulic microcomputer detection device. The test parameters are automatically printed and recorded.
- The pipe end is machined to accurately control the verticality of the end surface, the bevel angle and the obtuse edge.
Product price comparison:
In terms of price, the straight seam steel pipe is slightly higher than the spiral steel pipe. The reason lies in the use of the raw materials of the two. The straight seam steel pipe is directly rolled in a large steel mill with a limited size of plate width and length. , So the price is higher than spiral steel pipe. The raw materials used for spiral steel pipes are strip steel or coiled plates, which can produce larger diameter steel pipes with narrower and various sizes of plate surface.
In the above two forming processes, it is not difficult to see that the welds of the straight seam steel pipes are expressed in a straight line on the steel pipes; the welds of the spiral steel pipes are expressed in a spiral shape on the surface of the steel pipe. There is no difference in the welding process, but the length of the welded seam is much longer than that of the straight seam steel pipe; their stress points are also not the same. The force of the straight seam steel pipe is uniform, and the force of the spiral steel pipe It spreads over the entire pipe body, so the strength of the straight seam steel pipe should be better than the spiral steel pipe.
In addition, the straight seam steel pipe is better than the spiral steel pipe in terms of the beautiful appearance of the steel pipe, because the weld seam of the straight seam steel pipe can achieve the appearance of a seamless steel pipe after the seamless treatment.
Tips: In Oil and Gas, ASTM A53 steel pipe are used in the structural and non-critical applications. They are not used in hydrocarbon services or any services that involve pressure and temperature.