Analysis of tests and maintenance

HIPS components are subjected to periodic tests to detect unrevealed failures occurring during a pending period and taking into account the policy applied during testing, which is an important element in SIL calculations. 

Two cases arise regarding the occurrence of a demand during the period when a test is performed  

In the second case, three different situations are considered vis-a-vis the safety function fulfilled by the component tested  

We find ourselves facing many different circumstances  

The safety function can be perfect, improved, degraded, or completely inhibited during testing. It is particularly important to identify potential cases of type 2c) because even if the test time is short, the impact on the SIL can be significant and constitute a key factor for high SILs. 

---