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Quality inspection standard of spiral steel pipe before delivery

Spiral steel pipe (SSAW) should be subjected to mechanical performance test, flattening test and flaring test before leaving the factory, and must meet the standard requirements. The quality inspection methods of spiral steel pipes are as follows: 1. Judging from the surface, that is, appearance inspection. The visual inspection of welded joints is a simple and widely used inspection method. This is an important part of finished product inspection, mainly to find defects and dimensional deviations on the welding surface. The inspection is usually carried out with the naked eye with the help of standard templates, gauges and magnifying glasses. If there are defects on the surface of the weld, there may be defects inside the weld.
2. Physical inspection method Physical inspection method is a method of measuring or inspecting using certain physical phenomena. The inspection of internal defects of materials or workpieces usually adopts non-destructive testing methods. Non-destructive testing includes ultrasonic testing, radiographic testing, penetration testing, magnetic testing, etc.
3. In addition to the tightness test of the pressure vessel, the pressure vessel must also be tested for strength. There are two types: hydraulic test and pneumatic test. They can test the weld tightness of vessels and pipes that work under pressure. The air pressure test is more sensitive and faster than the water pressure test, and the product after the test does not need to be emptied, which is especially suitable for products with difficult drainage. But the risk of testing is greater than the risk of hydraulic testing. When testing, you must follow the corresponding safety technical measures to prevent accidents during the test.
4. Density inspection For welded containers that store liquid or gas, the weld defects can be found through the density test, such as penetrating cracks, pores, slag inclusions, incomplete penetration and loose structures. Airtightness test methods include: kerosene test, water-carrying test, washing test, etc.
5. Hydrostatic pressure test Each steel pipe shall be subjected to hydrostatic pressure test and no leakage. Calculate the test pressure by pressing P = 2ST/D, where S- the hydrostatic pressure test pressure Mpa, the hydrostatic pressure test pressure should meet the corresponding steel belt standard. Choose 60% of the lowest output (Q235 is 235Mpa). Stability time: D <508 test pressure holding time not less than 5 seconds; D≥508 test pressure holding time not less than 10 seconds
6. Repair welds of steel pipes, butt welds of steel strips and circumferential welds shall be inspected by non-destructive X-ray or ultrasonic inspection. Steel spiral welds used for flammable ordinary fluids and spiral welds of steel pipes used for water, sewage, air, heating steam and water vapor should be 100% SX-ray or ultrasonic inspection. Other common liquids should be spot-checked by X-ray or ultrasound (20%).
According to the quality inspection results of spiral steel pipes, spiral steel pipes are usually divided into three categories: qualified products, repair products and scrap products. Qualified products refer to the appearance and internal quality of spiral steel pipes that meet the relevant standards or technical requirements for delivery acceptance; repaired products refer to the appearance and internal quality that do not fully meet the standards and acceptance standards, but repairs are allowed and can meet the standards and acceptance after repair Qualified spiral steel pipe; scrap refers to spiral steel pipe whose appearance, internal quality is unqualified, not repaired or does not meet the standard and acceptance conditions after repair.
Waste is divided into internal waste and external waste. Internal waste refers to discarded spiral steel pipes found in foundries or foundries. External waste refers to the waste found after the delivery of the spiral steel pipe, which is usually exposed during mechanical processing, heat treatment or use, and the economic loss caused by it is far greater than the internal waste. In order to reduce external waste, spiral steel pipes produced in batches should be sampled before leaving the factory for experimental heat treatment and rough machining. Potential spiral steel pipe defects should be found in spiral steel pipe factories as much as possible so that necessary remedial measures can be taken as soon as possible.

Post time: Jan-15-2021

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