SY/T5037-2018 departmental standard and GB/T9711-2017 national standard are two common standards for spiral pipes. The prices of the two standards spiral pipes is differ greatly. Even if the material and specifications are the same, the national standard spiral pipes are priced 300-400 RMB higher per ton compared to the departmental standard. Why? Follpw us to analyze it.
Firstly, the production process of national and departmental standard spiral pipes is the same. The difference is in the inspection during the production process. The national standard requires 100% ultrasonic testing for each pipe, while the departmental standard only requires sampling inspection of 20%. Additionally, in X-ray industrial TV inspection, the national standard is also stricter than the departmental standard.
Secondly, in terms of hydraulic testing, the national standard spiral pipes have a minimum specified percentage of yield strength for static hydraulic pressure testing, which is at least 75% and can go up to 90% depending on the material. On the other hand, the departmental standard spiral pipes have a minimum specified percentage of yield strength for static hydraulic pressure testing, which is 60%. Lastly, in terms of geometric dimension inspection, the national standard spiral pipes have stricter tolerances for outer diameter, dents, deviations, weld height, ovality, and more.
The departmental standard spiral pipe is used in general fluid transportation pipelines, while the national standard is a standard for steel pipes used in the petroleum and natural gas industry pipeline transportation system. The acceptance criteria of the standard are stricter than the departmental standard, which is why the prices of national standard spiral pipes are much higher than those of the departmental standard.