In chemical process safety, Safety Instrumented Systems (SIS) are employed to reduce the risk of critical scenarios. Conventional methods for SIL allocation have been specified in the IEC 61508 and IEC 61511. In addition, several methods derived by the researchers. In this study, Layer of Protection Analysis (LOPA), Risk Graph, Improved Risk Graph, and the SPW method were applied to determine the Safety Integrity Level of a sorbitol reaction section under the overpressure and overtemperature scenarios. The analysis showed that the SIL value determined by the LOPA method was lower than those obtained from the other methods. Furthermore, the Risk Graph method resulted in a SIL 3, whereas the Improved Risk Graph and SPW methods resulted in a SIL 2. The Improved Risk Graph and SPW methods, which were developed to develop the Risk Graph method, calculated results similar to the Risk Graph. This is despite the fact that the developers of these methods claimed that their approaches reduce the conservative nature of the Risk Graph method. According to the analysis, producing different SIL values for various scenarios using the proposed methods is predictable. In the case study of the sorbitol reactor, the application of these methods resulted in differences in the SIL values between the LOPA method and the other three methods for both the overpressure and overtemperature scenarios.