When can non-destructive testing be omitted for atmospheric pressure vessels?
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The last edit to this post was made by 511948814 on 2023-2-28 at 13:10. NB/T 47003.1-2009 \"Steel Welded Pressure Vessels\" – Section 4.7 Weld Joint Coefficients specifies the weld joint coefficient when no non-destructive testing is performed: 4.7.2 For double-sided welded joints or fully penetrated butt joints that are equivalent to double-sided welded joints, the weld joint coefficient is 0.70 when no non-destructive testing is carried out； 4.7.3 For butt joints with single-sided welding and gussets in close contact with the base metal along the entire length of their root, when no non-destructive testing is performed, the weld joint coefficient shall be 0.65 ； 4.7.4 For single-sided welded butt joints without gussets, when no non-destructive testing is performed, the weld joint coefficient shall be taken as 0.60 ； It is stated in 9.6.1 that, unless otherwise specified, the butt weld joints of containers shall be subject to local radiographic or ultrasonic testing. I would like to ask what is meant by \"there are other regulations here\"? (Not explicitly stated in the standards.) I checked the previous version of the standard for atmospheric pressure vessels, JB/T 4735-1997 \"Steel Welded Atmospheric Pressure Vessels\"; section 15.2.4.1 specifies the situations in which non-destructive testing is required. According to 15.2.4.1, for the butt weld joints of vessels, non-destructive testing using radiation or ultrasound must be carried out if either of the following conditions is met, and the testing length must be at least 10% of the length of each weld joint. Local non-destructive testing should preferably be conducted on T-joint areas: a. Vessels as specified in clause 15.1.3 ； b. High-alloy steel containers ； c. Steel containers with a standard tensile strength of the material > 400 MPa ； d. Containers subjected to airtightness testing ； e. Vessels for which non-destructive testing is required per the specifications. 15.1.3 Welding of the following containers must be carried out by persons holding a qualified welder’s certificate for boilers and pressure vessels, or in accordance with 15. Welders specified in Article 3.4.2 shall be assigned to: a. vessels with a design temperature of less than or equal to -10°C or at 250°C ； b. Containers holding materials with toxic hazards or that are flammable or explosive ； c. Containers whose product of the design pressure p and the nominal volume V is greater than or equal to 0.5 MPa • m3, or whose volume V is greater than or equal to 10 m3 ； d. Vessels with a nominal shell thickness of 8 mm or more. From JB/T 4735-1997 to NB/T 47003.1-2009, the standard removed the explicit requirement for partial non-destructive testing, replacing it with other provisions. Does this mean that the standards have relaxed or tightened the requirements regarding non-destructive testing of pressure vessels at normal pressure? Which units or institutions can establish these other regulations?
According to **standards, ordinary pressure vessels must undergo non-destructive testing within 3 years of their initial installation, and then every 5 years thereafter； However, when it is proven that the container can be safely controlled and monitored while in operation, and that the equipment can remain in good condition, no non-destructive testing is required. -
Is there a source? If so, please provide it. Thank you
Reference: \"Steel Welded Atmospheric Pressure Vessels\" GB/T 18800-2008 -
Regarding non-destructive testing of equipment under normal pressure, I have also encountered questions about whether such testing can be waived. For example, can a bucket manufactured on-site (under no pressure) be exempted from non-destructive testing? From a design perspective alone, in order to avoid complications and ensure compliance with regulations in an easy manner, it’s best to simply opt for 10% RT! It may seem trivial, but it is actually an irresponsible attitude as well. It really needs to be discussed on a case-by-case basis. NB/T 47003.1 partially replaces JB/T 4735; for example, the design of large storage tanks was part of JB/T 4735, but this content has been removed in NB/T 47003.1. My personal guess is that the intended standard is still that storage tanks should comply with the standards applicable to such tanks (namely GB50341). According to the explanatory provisions in standard NB/T 47003.1, there is a statement stating that “NB/T 47003.1 is a supplementary standard to standard GB150.” Based on this statement, we can make some guesses: firstly, it relates to the pressure range (-0.02~0.1); secondly, it concerns the structural design (cylindrical, rectangular shapes, type of supports); and thirdly, the calculation methods (using flanges, reinforcement through openings), etc., are all consistent with those specified in GB150. Therefore, vertical flat-bottomed cylindrical storage tanks indeed fall outside the scope of these supplementary standards, and the deletion of them from the new standard is likely based on this reason! All the above rambling by Rory may seem unrelated to the main topic, but if analyzed from the perspective of being \"compatible\" with GB150, and then we return to the matter of non-destructive testing, it will still be helpful for understanding. Do we need non-destructive testing? Is non-destructive testing absolutely necessary? This ultimately needs to be determined by the designer; for example, if the medium is toxic, explosive, or highly corrosive and thus harmful to human health, then, out of safety considerations, non-destructive testing requirements should be specified ； If it’s just an open 1m bucket, what’s the harm in not testing it? Furthermore, testing is merely a means to assess welding quality; it is the welding quality itself that truly ensures quality. Conversely, if the drawings require non-destructive testing, welders will pay more attention to quality during welding. If the drawings do not specify any testing requirements, then quality control on site may be less stringent; as the saying goes, if you loosen things a little at the top, things will become even looser further down.