Risk assessment of solid desiccant dehydration package system using safety integrity level-based safety instrumented system design approach

Abstract

The dehydration package system plays an important role in the stable process operation and production of high-quality liquefied natural gas by removing water, which is essential for natural gas production. However, as this system operates under various conditions with chemicals, there are threats to safety from potential hazards within the system. Therefore, ensuring system safety can significantly impact the reliable operation of process plants. This study aims to assess the risk of the dehydration package system through the safety integrity level (SIL)-based safety instrumented system (SIS) design approach as suggested in the International Electrotechnical Commission (IEC) 61,508/61511 standards. Fourteen major hazards requiring recommendations were identified for improving safety through the hazard and operability study (HAZOP). The three major hazards were valve malfunction and gas heater/cooler control failure. Twenty-one safety instrumented functions (SIFs) in all study nodes were suggested as recommendations to improve safety. Using layers of protection analysis (LOPA), the SIL allocation of the 21 SIFs was performed reasonably with process risks and safeguards. The PDS method was adopted for SIS design and verification, with SIL analysis performed for all the SISs. The results showed that SISs of the dehydration package system satisfied the required SILs.