Subsea HIPS

The consequences of underwater HIPS failures do not concern human aspects but rather the environmental and economic aspects (e g. availability of production). 

It follows that the fault tree is inappropriate for the probability calculations and a dynamic model becomes necessary. As the Markovian approach is veiy quickly limited, behavioral modeling using stochastic Petri nets and the Monte Carlo simulation are used for modeling and calculations of subsea HIPS. 

The pipeline upstream from the valves is sized to hold the pressure while the downstream pipeline is not when the pressure increases beyond a certain threshold, the sensors send signals to the processing automaton, which then generates the order to close the valves. 

Here the number of sensors is increased to six because, for the actual system studied, it is equally important that the HIPS functions when needed (risk of destraction of the expedition pipeline) and that it has no spurious failures (risk of not being able to restart the facihty once stopped). 

Two criteria are therefore necessary a high level of safety integrity (SIL 3) and a minimum acceptable spurious failure frequency. 

---

The CCF mechanisms or of mobilization above do not present any difficulty for being taken into account by the PN but could not be modeled correctly by the fault tree. They correspond to the problems we encounter when studying subsea HIPS for which the PN modehng is particularly effective. 

A simplified example of subsea HIPS is shown in Figure 8.25. It is intended to protect the production system in case of overpressure in the production pipeline. 

Beyond the applications already mentioned, HIP-treated materials can also be found in components and equipment in centrifuges, subsea and offshore equipment, compressors and turbines, and nuclear energy and space applications [7-9]. 

---