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How reliable is your High Integrity Pressure Protection System (HIPPS) actually?

Keywords: API 521, IEC 61508, IEC 61511, Failure rate data, SIL, SIF, HIPPS

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Abstract:

Engineering contractors are designing the plants, which are being build everywhere in the world. The latest version of the API Standard 521 on pressure relieving and depressurization systems allows the use of a HIPS (High-Integrity Protection System), which is discussed in detail in Annex E of the standard. The more specific term is High Integrity Pressure Protection System (HIPPS). But how high should this high integrity be?

The IEC standards for functional safety IEC-61508 and IEC-61511 provide the guidelines how to apply a SIL assignment. However, they require reliability calculations to confirm the required high integrity levels. How reliable are these calculations for a HIPPS actually?

The objective of this paper is to give the reader a better understanding of the possible pitfalls in the HIPPS reliability calculations. The paper will first introduce the HIPPS concept and discuss its required reliability. Then two common pitfalls in the HIPPS reliability calculations are illustrated in a hypothetical and in a real HIPPS design case. Finally the concluding remarks about HIPPS calculations are presented.

Volume: 2010   Issue: 2

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