(143c) You Have SIS Bypassed Right Now and Don't Know It | AIChE

(143c) You Have SIS Bypassed Right Now and Don't Know It


Safety Instrumented Systems (SIS), also known as emergency shutdowns, interlocks, and trips, are very common and critical safeguards protecting process plants. In order to maintain and test these systems, they are usually implemented with well-engineered and controlled bypasses, typically including alarm logging, bypass authorization, and auditing. Even so, there are myriad ways to place an SIS component into bypass, sometimes without even realizing it. Many of these methods occur in the field, away from the watchful eye of the board operator. In many cases, the bypasses occur inadvertently during maintenance or operational activities and are left in place, unmanaged. Common culprits include solenoid valve latches, shutoff valve handwheels, and hand-off-auto switches on pumps and compressors. This paper will explain how some equipment can be inadvertently put into bypass and methods for documenting and verifying that they are not in bypass using advanced mobile computing assisted car-seal list management.