PSI - Issue 72

Lazar Jeremić et al. / Procedia Structural Integrity 72 (2025) 91–96

95

3. Application of API standards to the integrity of pressure equipment After the NDT inspections, collected data was compared to recommendations from the relevant API standard. The minimum acceptable shell plate thickness was calculated for all nine shell courses according the formula from API 653 standard. Calculations of shell plate thickness for courses 1-9 were shown in table 2, whereas the formula which was used is shown below:   2.6 H-1 DG t,min= SE (1) Values for calculations: D = Nominal tank diameter of: 45 m, Total height of tank, H: 23200 mm, H = Maximum fill height: 22710 mm (Number of courses: 9), G = Specific gravity of contents at 20 °C: material density/water density 794,52 kg/m³ / 998,23 kg/m³ =0.795 = 0.8, Built in 1997 in according Built in 1997 in accordance to basic edition of API 650, 9th Ed, Structural material: A516 GR70/RAEX 500M depending on shell course, E = Joint efficiency, E = 1 (Table 4.2, API 653),Corrosion Allowance - CA = 3mm,

Table 2. Calculations of shell plate thickness for course 1-9 Plate course Height

Plate T- Nom Plate T- Min Corrosion Allowance With Allowance

Material

1 2 3 4 5 6 7 8 9

2930 5860 8790

8.0 mm 8.0 mm 8.0 mm 8.0 mm 8.0 mm 8.0 mm 8.0 mm 8.0 mm 8.0 mm

2.54 2.54 2.54 2.54 2.54 2.54 2.54 2.54 2.54

3.0 mm 3.0 mm 3.0 mm 3.0 mm 3.0 mm 3.0 mm 3.0 mm 3.0 mm 3.0 mm

5.54 5.54 5.54 5.54 5.54 5.54 5.54 5.54 5.54

A516 Gr.70 A516 Gr.70 A516 Gr.70 A516 Gr.70 A516 Gr.70 A516 Gr.70 A516 Gr.70 A516 Gr.70 A516 Gr.70

11720 14650 17580 20380 22176 23176

Through API standards, minimum required thickness for which the pressure equipment in question was obtained. The advanced inspection methods described here are tools that monitor the condition of the material according to the inspection program prescribed by the API standard. 4. Discussion and conclusions As can be seen from the previously shown analyses, there were no issues with either of the tanks. Tanks are in acceptable conditions with no discernible surface corrosion, including all of their components - shell plate, roof and foundation, all in accordance with the API standard. All of this suggested that the pressure equipment which was examined using modern techniques is safe for continued operation. This analysis also emphasises the advantages of the adopted approach - a very detailed and comprehensive consideration of numerous factors and various potentially critical locations in these tanks. The application of advanced tank testing methods makes the job easier and gives much more reliable results that are later used to assess the integrity of tanks, all of which is facilitated by the application of API standards. This approach can be effectively combined with other commonly used methodologies such as numerical methods and fracture mechanics principles. It can be seen that this method was validated by the results presented in this paper. Based on this analysis, following conclusions can be drawn:  The integrity and safety of the tested tanks is not compromised, and this was confirmed in several ways.