Spiral welded pipe manufacturing process

Spiral pipe (SSAW) is also called spiral steel pipe or spiral welded pipe. It is made by rolling a low-carbon structural steel or low-alloy structural steel strip into a tube blank at a certain helical angle (called a forming angle), and then welding the tube seams. It can produce large diameter pipes from narrower strips. 

Spiral welded pipes are mainly used for oil and natural gas transmission pipelines, and their specifications are expressed by outer diameter * wall thickness. There are single-sided welding and double-sided welding of the spiral pipe. The welded pipe should ensure that the hydraulic test, the tensile strength of the weld and the cold bending performance meet the regulations.

The manufacturing process of spiral welded pipe:

(1) The raw materials are strip coil, welding wire and flux. They must undergo strict physical and chemical inspections before being put into use.
(2) The head and tail of the strip are butted by single-wire or double-wire submerged arc welding, and automatic submerged arc welding is used for repair welding after rolling into a steel pipe.
(3) Before forming, the strip is leveled, trimmed, planed, surface cleaned and conveyed and pre-bending.

(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 forming.
(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 used for single-wire or double-wire submerged arc welding by the American Lincoln welding machine, so as to obtain stable welding specifications.
(8) The welded seams are all inspected by an online continuous ultrasonic automatic flaw tester, which ensures 100% non-destructive testing coverage of the 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 accordingly to eliminate the defect in time.
(9) Use an air plasma cutting machine to cut the steel pipe into single pieces.

(10) After cutting into a single steel pipe, each batch of steel pipes must 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 non-destructive testing to ensure that the pipe-making process is qualified Only then can it be officially put into production.
(11) The parts with continuous sonic flaw detection marks on the welds shall be re-examined by manual ultrasonic wave and X-ray. If they are indeed defective, after repairing, they shall undergo non-destructive inspection again until it is confirmed that the defects have been eliminated.
(12) The tube where the strip butt weld and the T-joint intersecting with the spiral weld are all inspected by X-ray television or filming.

(13) Each steel pipe undergoes a 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) The pipe end is machined so that the verticality of the end face, the bevel angle and the blunt edge are accurately controlled.

The main process characteristics of spiral steel pipe:
a. During the forming process, the deformation of the steel plate is uniform, the residual stress is small, and the surface does not produce scratches. The processed spiral steel pipe has greater flexibility in the size and specification range of diameter and wall thickness, especially in the production of high-grade thick-walled pipes, especially small and medium-diameter thick-walled pipes.
b. Using advanced double-sided submerged arc welding technology, welding can be realized at the best position, and it is not easy to have defects such as misalignment, welding deviation and incomplete penetration, and it is easy to control the welding quality.
c. Carry out 100% quality inspection of steel pipes, so that the whole process of steel pipe production is under effective inspection and monitoring, effectively ensuring product quality.
d. All the equipment of the entire production line has the function of networking with the computer data acquisition system to realize real-time data transmission, and the technical parameters in the production process are checked by the central control room.

The stacking principles of spiral steel pipes require:
1. The principle requirement of spiral steel pipe stacking is to stack according to varieties and specifications under the premise of stable stacking and ensuring safety. Different types of materials should be stacked separately to prevent confusion and mutual erosion;
2. It is forbidden to store items that corrode steel around the stack of spiral steel pipes;
3. The bottom of the spiral steel pipe pile should be high, firm and flat to prevent the material from being damp or deformed;
4. The same material is stacked separately according to the order of storage;
5. For the spiral steel pipe sections stacked in the open air, there must be wooden pads or stone strips underneath, and the stacking surface is slightly inclined to facilitate drainage, and attention should be paid to placing the materials straight to prevent bending deformation;
6. The stacking height of spiral steel pipes shall not exceed 1.2m for manual work, 1.5m for mechanical work, and the stack width shall not exceed 2.5m;
7. There should be a certain channel between the stacks. The inspection channel is generally 0.5m, and the access channel depends on the size of the material and the transport machinery, generally 1.5-2.0m;
8. The angle steel and channel steel should be stacked in the open air, that is, the mouth should face downward, and the I-beam should be placed vertically. The I-channel surface of the steel should not face upward, so as to avoid water accumulation and rust;
9. The bottom of the stack is raised. If the warehouse is on a sunny concrete floor, it can be raised by 0.1m; if it is a mud floor, it must be raised by 0.2-0.5m. If it is an open field, the concrete floor shall be cushioned with a height of 0.3-0.5m, and the sand and mud surface shall be cushioned with a height of 0.5-0.7m.

Hunan Standard Steel Co., Ltd is a leading manufacturer and supplier of carbon steel pipes (seamless and welded), supplying many types, grades, diameters and lengths of pipe to a variety of industries.