The spiral steel pipe shall be subjected to mechanical performance test, flattening test and flare test before leaving the factory, and shall meet the requirements specified in the standard. The quality inspection method of spiral steel pipe is as follows:
1. Judging from the surface, that is, in appearance inspection
The appearance inspection of welded joints is a simple and widely used inspection method, which is an important part of the inspection of finished products, mainly to find defects and dimensional deviations on the surface of the weld. It is generally inspected by the naked eye and by means of tools such as standard templates, gauges and magnifiers. If there is a defect on the surface of the weld, there is a possibility of defects inside the weld.
2. Physical method inspection
The physical inspection method is a method of measuring or testing using some physical phenomena. Inspection of the internal defects of materials or workpieces is generally carried out by means of non-destructive testing. Non-destructive testing includes ultrasonic flaw detection, radio graphic inspection, penetrant inspection, and magnetic flaw detection.
3. Strength test of pressure vessel
In addition to the sealing test, the pressure vessel shall be subjected to a strength test. There are two types of hydraulic pressure test and air pressure test. They both verify the weld density of containers and pipes that work under pressure.
The air pressure test is more sensitive and speedy than the water pressure test, and the tested product does not need to be drained, which is especially suitable for products with difficult drainage. However, the risk of the test is greater than the hydraulic test. When conducting tests, the corresponding safety technical measures must be observed to prevent accidents during the test.
4. Density test
For welding containers that store liquid or gas, the welds are not dense, such as penetrating cracks, pores, slag inclusions, incomplete penetration and loose structures, which can be found by compactness test. The methods of compactness test include: kerosene test, water carrying test, water flushing test, etc.
5. Hydrostatic test
Each steel pipe should be subjected to hydrostatic test without leakage. The test pressure is calculated according to the test. The test stress Mpa of the S-hydrostatic test in the formula P=2ST/D, and the test stress of the hydro static test.
The corresponding steel strip standard specifies 60% of the minimum yield (Q235 is 235Mpa).
D<50 test pressure holding time is not less than 5 seconds; D≥508 test pressure holding time is not less than 10 seconds 4, non-destructive testing steel pipe repair welding seam, steel belt butt weld and hoop seam Perform X-ray or ultrasonic inspection.
For the spiral weld of the steel direction for the transportation of combustible ordinary fluids, 100% SX ray or ultrasonic inspection shall be carried out. X-rays shall be applied to the spiral welds of steel pipes used for the transportation of common fluids such as water, sewage, air and heating steam. Ultrasonic inspection spot check (20%).
According to the quality inspection results of spiral steel pipes, spiral steel pipes are generally divided into three categories: qualified products, repaired products and waste products.
Qualified products refer to spiral steel pipes whose appearance quality and intrinsic quality meet the relevant standard or delivery acceptance technical conditions; the repaired products refer to the appearance quality and internal quality which are not completely in compliance with the standard and acceptance strips, but are allowed to be repaired, and the standard and acceptance conditions can be met after rework.
Spiral steel pipe; scrap refers to spiral steel pipe that is unqualified in appearance quality and internal quality, and does not require standard or acceptance conditions after repair or repair.