Tank Risk-Based Inspection (API RP 580)

Tank Risk-Based Inspection (API RP 580 & API 653 6.4.2.2.2)

Risk-based inspection of a storage tank to API RP 580 and API 653 6.4.2.2.2: probability and consequence of failure for each component and damage mechanism, a risk matrix, the risk register and drivers, the API 653 likelihood and consequence factors, and the internal inspection interval and RBI review dates that follow

New here? Read the User Manual — how probability and consequence are categorised, the matrix, and the API 653 rules.

◉ API RP 580 3RD ED. (FEBRUARY 2016) · API 653 5TH ED. ADD. 4 6.4.2.2.2 · UPGRADE DUE: RP 580 4TH ED. (2023) · NOT A REGULATORY SUBMISSION TOOL

⚠ Edition and method. Built on API RP 580, 3rd edition (February 2016), the text on file, with the tank requirements of API 653 (5th edition, Addendum 4, 2025) 6.4.2.1.2 and 6.4.2.2.2. The 4th edition of RP 580 (2023) is current and has not been compared: the tool will be upgraded when that text is available. RP 580 is a framework, not a calculation: the category scales and the risk matrix here are RP 580’s examples (Tables 2, 3, 5 and Figure 7) and must be set to your company’s risk criteria (11.7). The suggested probability is a Tank Protocol screening aid; your RBI team decides (9.3.2). API 653 requires the assessment to be done by a qualified team and the methodology to be validated (6.4.2.2.2).

Identification

Company

Tank ID

Location

Record Type

Units

Assessment date

Summary

Describe the tank, then add each component and damage mechanism.

1. Tank, Service and Team (RP 580 6, 15; API 653 6.4.2)

Product

Working capacity m³

Release prevention barrier (6.4.2.2.2.2 a)

Service (6.4.2.1.2)

Interval being set

Last internal inspection (or in service since)

Proposed internal interval years

Last RBI review and approval

Team leader (15.2.2)

Inspector / inspection specialist (15.2.3)

Corrosion specialist (15.2.4)

Methodology validated by a reviewer outside the team (6.4.2.2.2) Assessment reviewed and approved by the team

Owner’s acceptable risk (11.7)

2. Consequence of Failure (RP 580 10, Tables 3 and 5; API 653 6.4.2.2.2.2)

Safety and health

Environmental

Economic loss (repair, clean-up, lost use)

Currency

B from

C from

D from

E from

Economic bands default to RP 580 Table 3 (USD 10 k / 100 k / 1 M / 10 M); RP 580 says to adjust them to the size of the company. Each mechanism below can take its own consequence category where its failure mode differs (a slow bottom leak against a shell rupture).

Consequence factors evaluated (API 653 6.4.2.2.2.2)

3. Probability of Failure by Component and Damage Mechanism (RP 580 8, 9)

One row per credible damage mechanism. Enter what you know: the susceptibility or measured rate, the remaining life, and how effective the inspections are. The tool suggests a category from those; set your team’s category in the last column. Corrosion rates must come from high or medium effectiveness inspections (API 653 6.4.2.2.2). Use the API 571 tool to screen mechanisms.

#	Component	Damage mechanism	Susceptibility	Rate mm/yr	Rate source	Remaining life, yr	Inspection effectiveness	Failure mode	Consequence	Suggested	POF used	Risk

Likelihood factors evaluated (API 653 6.4.2.2.2.1)

4. Risk Matrix and Register (RP 580 11, Figure 7)

5. Inspection Strategy, Interval and Review (RP 580 12 – 14; API 653 6.4.2)

Next planned turnaround / out-of-service date

Significant change since the last assessment (process, mechanism, rate or premise, 14.3.1) Mitigation implemented since the last assessment (14.3.3)

RBI Documentation Checklist (RP 580 16)

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