Bottom

Module from the Storage Tank Engineering Curriculum curriculum.

Module 4 - Bottom Design · Learning Objectives · 1. Specify annular plate (sketch plates) at shell-to-bottom (1/4 in min or per Table 5-2) · 2. Apply 3-plate lap welded bottom with 1/4 in typical thickness · 3. Design slope: cone-up (1:120) or cone-down (1:60) for drainage · 4. Apply cathodic protection per IPE-EP-10-3-6 for external CP · 5. Monitor bottom corrosion via MFL floor scan during API 653 internal · Tank Bottom Corrosion Mechanisms

Mechanism	Location	Cause	Mitigation	Detection	Note
Underside corrosion	Bottom-to-soil	Groundwater, MIC	Cathodic protection	MFL, VT from above	Often severe
Topside corrosion	Bottom inside	Water bottom layer	Dewater sump	UT, MFL	Draw-off, heel
Shell-to-bottom weld	Annular region	Bending stress, settlement	CA + inspection	VT + PT	Per API 653
Pitting internal	Bottom inside	Stagnant water	Mixer, clean out	VT, MFL pit sizing	Crude BS&W
SOHIC / SSC	Welds in sour service	Wet H2S	PWHT, upgrade material	WFMT, SWUT	NACE SP0472

Source: Storage_Tank_Engineering_Curriculum_v1.xlsx · Sheet: Bottom

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