Shell Thk

Module from the Storage Tank Engineering Curriculum curriculum.

Module 2 - Shell Thickness · Learning Objectives · 1. Apply 1-Foot Method: t_d = 2.6*D*(H-1)*G/(S_d*E) + CA (in) · 2. Apply Variable-Design Method for tanks > 200 ft diameter (more economical) · 3. Identify minimum nominal thickness by diameter (API 650 Table 5-6) · 4. Apply allowable stress per Table 5-2: S_d = 32/2.6 ksi for SA-516-70 · 5. Include corrosion allowance; typically 1/16 to 1/8 depending on service · API 650 Table 5-6 Minimum Shell Thickness

Tank Diameter (ft)	Min Nominal Thk (in)	Notes	Size Class	Typical Use	Ref
<50	3/16 (0.1875)	Small tanks	Small	Small slop	API 650
50-120	1/4 (0.25)	Medium	Medium	Product	API 650
120-200	5/16 (0.3125)	Large	Large	Crude product	API 650
>200	3/8 (0.375)	Very large	XL	Crude storage	API 650
1-Foot Method Formula and Example (120 ft D, 40 ft H, G=0.9, CA=1/16)
Course 1 (bottom): t_d = 2.6 * 120 * (40-1) * 0.9 / (23200 * 1.0) + 0.0625 = 0.534 in. Round up to 9/16 (0.5625 in). Each higher course decreases H. Course 5 (H_liquid = 8 ft from top): t_d = 2.6 * 120 * (8-1) * 0.9 / (23200) + 0.0625 = 0.158 in - governed by Table 5-6 minimum 5/16 = 0.3125 in.

Source: Storage_Tank_Engineering_Curriculum_v1.xlsx · Sheet: Shell Thk

© 2026 Inflection Point Engineering, LLC. All rights reserved. The content of this page — including calculation methods, reference data, written analysis, interactive tools, and source code — is the intellectual property of Inflection Point Engineering, LLC and is protected under applicable copyright, trademark, and trade secret laws. Unauthorized reproduction, redistribution, modification, or derivative use in whole or in part is prohibited without prior written consent.

Disclaimer. This material is provided for informational and educational purposes only and does not constitute professional engineering advice. Calculations, reference data, and methodologies are based on published standards and accepted engineering practice but are not a substitute for engineering judgment, site-specific analysis, or review by a licensed Professional Engineer. Inflection Point Engineering, LLC makes no warranties, express or implied, regarding the accuracy, completeness, or fitness for a particular purpose of any content presented here, and shall not be liable for any direct, indirect, incidental, or consequential damages arising from its use. Users assume all risk associated with applying this content to real-world design, operations, or decisions.