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Quality Inspection Requirements for Spiral Steel Pipes

Mar. 31, 2020
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Spiral steel pipes should be tested for mechanical properties, flattening and flare before leaving the factory, and must meet the requirements of the standard. The quality inspection method of spiral steel pipe is as follows:

1. Judging from the surface, that is appearance inspection. The appearance inspection of welded joints is a simple and widely used inspection method. It is an important part of finished product inspection. It mainly finds defects on the surface of the weld and deviations in size. It is usually inspected with the naked eye and checked with the help of standard templates, gauges and magnifying glasses. If there is a defect on the surface of the weld, there may be a defect inside the weld.

2. Inspection of physical methods: The physical inspection method is a method that uses some physical phenomena for measurement or inspection. The inspection of internal defects of materials or workpieces generally uses non-destructive testing. Non-destructive testing includes ultrasonic testing, ray testing, penetration testing, and magnetic testing.

3. Strength test of the pressure vessel: In addition to the tightness test of the pressure vessel, the strength test is also required. There are two types of water pressure test and air pressure test. They all check the tightness of the welds of vessels and pipes working under pressure. The air pressure test is more sensitive and quicker than the water pressure test. At the same time, the products after the test do not need to be drained, which is especially suitable for products with difficult drainage. But the test is more dangerous than the hydrostatic test. During the test, the corresponding safety technical measures must be observed to prevent accidents during the test.

4. Tightness test: Welding containers that store liquids or gases, and the non-dense defects of the welds, such as penetrating cracks, pores, slag inclusions, unwelded and lose tissues, can be found by density tests. The compactness testing methods are kerosene test, water carrying test, water flush test, etc.

5. Hydrostatic test Each steel pipe should be hydrostatically tested without leakage. The test pressure is calculated by pressing the test P = 2ST / D where S-hydrostatic test stress Mpa, hydrostatic test stress according to The steel strip standard specifies 60% of the minimum yield (Q235 is 235Mpa). Stabilizing time: D <508 test pressure holding time of not less than 5 seconds; D≥508 test pressure holding time of not less than 10 seconds 4 Non-destructive testing of repair welding welds, steel strip butt welds and circumferential seams of steel pipes X-ray or ultrasonic inspection. Spiral welds in the direction of steel used for the transportation of flammable ordinary fluids should be 100% SX-ray or ultrasonic inspection. Spiral welds in steel pipes used for the transport of ordinary fluids such as water, sewage, air, heating steam should be X-ray or Ultrasound inspection (20%).

Spiral Steel Pipe

Spiral Steel Pipe

According to the quality inspection results of oil pipeline spiral steel pipe, spiral steel pipes are usually divided into three categories: qualified products, rework products and scrap products. Qualified products refer to spiral steel pipe standards whose appearance quality and intrinsic quality meet the relevant standards or technical specifications for delivery and acceptance; rework products refer to the appearance and intrinsic quality that do not fully meet the standards and acceptance conditions, but are allowed to be repaired, and the standards and acceptance can be reached after the repair. Condition: Spiral steel pipes; waste products refer to spiral steel pipes whose appearance quality and intrinsic quality are unqualified and are not allowed to be repaired or fail to meet the standards and acceptance conditions after rework.

Waste products are divided into internal waste and external waste. Internal waste refers to the waste spiral steel pipe found in the foundry or foundry; External waste refers to the spiral pipe supplier china believes that waste products found after the delivery of spiral welded pipes are usually machined, heat-treated or used It was revealed during the process that the economic losses caused by it were far greater than internal waste. In order to reduce external waste, batch production of spiral steel pipes is sampled for experimental heat treatment and rough processing before leaving the factory. Potential defects of spiral steel pipes are found in the spiral steel pipe plant as far as possible so that necessary remedial measures can be taken as soon as possible.