Short answer
API 580 sets the principles for risk-based inspection of fixed equipment. API 581 gives the quantitative methods to calculate the probability and the consequence of failure. You use API 580 to design the program. You use API 581 to calculate the risk values behind it.
API 580: the framework
API 580 is a recommended practice for risk-based inspection. It states the minimum elements to develop, use and maintain an RBI program. It does not prescribe one calculation method. A qualitative, a semi-quantitative or a quantitative method can meet it.
The elements include the scope, the data, the damage mechanisms, the probability and consequence of failure, the inspection plan and the reassessment. API 580 also covers roles, training and qualifications, and the records to keep.
API 581: the calculation method
API 581 gives the quantitative procedures behind an RBI assessment. The probability of failure is a generic failure frequency, times a damage factor, times a management systems factor. The consequence of failure is an affected area or a financial cost. Risk is the product of the two.
API 581 has damage factors for each damage mechanism, such as thinning, cracking and external damage. It also covers the credit for past inspections and the plan for the next one. It has separate methods for pressure relief devices and heat exchanger bundles.
API 580 and API 581 side by side
| Topic | API 580 | API 581 |
|---|---|---|
| Document type | Recommended practice | Recommended practice |
| Question it answers | What must an RBI program contain? | How do you calculate the risk values? |
| Method | Any method: qualitative, semi-quantitative or quantitative | Quantitative: generic failure frequency, damage factors and consequence area |
| Main users | Program owners, managers and auditors | RBI analysts and the tools that they use |
| Output | A documented RBI program | A risk value and an inspection plan for each asset |
Which one do you need?
Most RBI programs use both. API 580 sets what the program must contain and how you manage it. API 581 is one way to do the risk calculation that API 580 asks for. A plant can meet API 580 with a different calculation method, if it documents that method.
How Reliatic uses them
We designed Reliatic to support API 580 and API 581 workflows. Reliatic records the probability and consequence scores, the risk matrix and the inspection plan for each asset. Reliatic is not certified to either standard.
Questions and answers
Are API 580 and API 581 standards or recommended practices?
API publishes both as recommended practices: API RP 580 and API RP 581. Plants and regulators often refer to them as standards.
Do you need API 581 to meet API 580?
No. API 580 accepts qualitative, semi-quantitative and quantitative methods. API 581 is the quantitative method that API publishes.
Which edition should we use?
Use the edition that your plant procedures name. Check the API catalogue for the current edition before you start a new assessment.
Is Reliatic certified to API 580 or API 581?
No. We designed Reliatic to support API 580 and API 581 workflows. It does not replace a qualified RBI analyst or a certified RBI study.