Standards for thickness measurement of pressure vessels
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Recently, one of our company’s gas storage tanks underwent a regular inspection. Using a thickness gauge to measure the thickness of the tank’s head, the reading was 7.8–7.9 mm, whereas the actual thickness of the material used in this equipment is 8.5 mm. We would like to ask experts familiar with pressure vessel equipment whether this value is acceptable What are the standards for this? For example, what percentage of the designed material thickness determines that it is considered scrapped?
First, it is necessary to determine what the minimum thickness required by the design specifications is Assuming the minimum thickness required by the design is 8.6 mm, if you use a plate with a thickness of 8.5 mm, the actual measured thickness will be 9.0 mm, which is also not acceptable; the inspection authorities will not approve it. The thickness of the plate you use must be at least equal to the minimum thickness specified in the design in order to meet the requirements.
The rounded areas on a head after processing are naturally thinner than the thickness of the material before cutting. This is usually taken into account during design, by specifying the minimum thickness of the head after it has been formed; this value is also indicated on the as-built drawings, so one can check those drawings to see whether the thickness is below the minimum required for formation
So, exactly how much is considered to meet the standards? Are there any regulations on this topic that I can refer to?
On the design drawing. . :L:L:L:L:L
There is a minimum thickness specified during the design process; if it isn’t indicated, then the calculation documents need to be consulted. It is also necessary to consider the difference between the calculated thickness, the nominal thickness, and the corrosion allowance. However, the final decision lies with the design department
This post was last edited by SDHZZXM on 2015-8-18 at 11:57. The minimum required forming thickness is usually indicated on the as-built drawings, while the calculated thickness is specified in the design calculations... The thickness to be checked regularly should be greater than the calculated thickness...
I think a comprehensive verification of this tank should be carried out based on its design parameters (pressure, temperature, wind, earthquakes, etc.); if it meets the requirements at the current thickness, it can be used further.
The thickness of the head measured during periodic inspections shall be not less than the calculated thickness plus the corrosion allowance.
If it is a container, the as-built drawings, that is, the blueprint, will show the specifications and thickness in the section related to the head. In the thickness field, the nominal thickness and the minimum thickness permitted for head compression are indicated. For example, EHA1200*6(4.86) means that the nominal thickness is 6 MM, while the value inside the parentheses represents the minimum thickness allowed for head compression. Check the drawings of that container to see if there is such a section; if it is present, then as long as the actual measured thickness is greater than the value in the parentheses, it is considered acceptable.
Thank you all, experts; it’s been solved now.