Do pipes of GC1 grade require 100% radiographic inspection?

Pipes of GC1 grade must undergo 100% radiographic inspection; for details, refer to Appendix J of the Code GB 50316-2000 (2008 edition), Code for Design of Industrial Metal Piping.

Reply to 2# jintchinssen: It doesn’t seem to refer to GC1 grade either; most of them are just GC1 grade pipes.

The appendix only specifies 100% flaw detection for A1 fluids and those under high temperature and pressure conditions. GB20801 only requires a level of not lower than II, which means that the non-destructive testing rate must be at least 20%. The current task at hand is to determine the inspection ratio, and after discussions with the owner, the contractor, and the supervisor, it was decided to combine 20801 and SH3501 – using the one with the higher value. The project involves exhaust gases containing CO, which are classified into SHB and GC1; the design pressure is 3 MPa.G, and the design temperature is 300 degrees. According to 3501, it should be 10%, and finally, according to GC1, it is set at 20%. It is said that 3501 is also set to be revised, with several standards being brought together. This period coincided with the time when the new standards were being implemented while the old standards had not yet been abolished, which indeed led to many problems in implementation. Everyone is welcome to join the discussion~~~

This post was last edited by jintchinssen on 2010-10-27 at 21:15. SH3501-2002 states clearly in its preamble that the relevant content has been coordinated with GB 50235－97, the Code for Construction and Acceptance of Industrial Metal Piping Projects. GB 50316-2000 (2008 edition) also specifies that non-destructive testing of pipelines shall be carried out in accordance with Appendix J and Code GB 50235－97; therefore, Code GB 50235－97 is more practical for the construction and acceptance of industrial metal piping projects. According to 7.4.3.1 of standard GB50235-1997, the welds of the following pipelines shall undergo 100% radiographic inspection, and their quality must be at least grade II: (1) Pipelines transporting highly toxic fluids ； (2) Pipelines for transporting flammable or toxic fluids with a design pressure of 10 MPa or more, or a design pressure of 4 MPa or more along with a design temperature of 400 °C or more ； (3) Pipelines for non-flammable and non-toxic fluids with a design pressure of 10 MPa or more and a design temperature of 400°C or more ； (4) Design low-temperature pipelines with a design temperature of less than -29°C. (5) Other pipes for which the design documents require 100% radiographic inspection. GB/T 20801-2006 \"Code for pressure pipelines – Industrial pipelines\" establishes a separate classification system for pipelines, and the scope covered by GC1-class pipelines is quite broad. Therefore, it is recommended that the non-destructive testing of GC1-grade pipelines be carried out by combining GB/T 20801 and GB50235-1997.

I checked SH3501 and GB50235 again, and indeed there are differences between the two; my previous statement was incorrect. Now, a comparison between the two is presented: GB50235-〉(1) Piping for transporting highly toxic fluids ； SH3501-〉SHA: The degree of toxicity is classified as a quarterly hazard…… GB50235-〉(2) Pipelines for flammable or toxic fluids with a design pressure of 10 MPa or more, or with a design pressure of 4 MPa or more and a design temperature of 400 °C or more ； SH3501-〉Article 2 of SHA, Article 1 of SHB, Article 1 of SHC; GB50235-〉(3) Pipelines for non-flammable and non-toxic fluids with a design pressure of 10 MPa or higher and a design temperature of 400°C or higher ； SH3501 has no provisions for this. GB50235-〉(4) Low-temperature pipelines with a design temperature of less than -29°C. SH3501-〉SHD also includes the pipelines required in other design documents. The main difference lies in pipelines for non-flammable and non-toxic fluids with a pressure of 10 MPa or higher and a design temperature of 400°C or higher; it should be noted that SH3501 is specifically formulated for toxic and flammable media. Our project also doesn’t have such pipelines; otherwise, it would be a problem according to SH3501.