Session Type: Paper
Paths(s): Technician Management Engineer
Conducting a functional safety assessment (FSA), after validation of the safety instrumented system (SIS) and before the introduction of the process hazards, is one of the most inconvenient requirements of ANSI/ISA-84 (IEC61511). It occurs when the project team is stressed to make the start-up date and there are too few hours in the day. But a double check of the systems, especially the systems that prepare the operations team, can catch oversights driven by tight process schedules and limited resources. This paper shares the findings from a series of FSAs and provides some suggestions for improving future SIS projects and startups.
Proof test and inspection serves two primary purposes within the safety lifecycle: to find and repair failures in the system, and validate the failure rate assumptions used in the safety integrity level (SIL) calculations. Many facilities may have robust preventative maintenance systems, but lack sufficient or clear documentation on the failure mechanism to allow classification. There may also be differences in how individual facilities within the same corporation record test results.
It is highly beneficial for a corporation to record and classify failures in a consistent manner so that the instrumentation reliability data can be easily compared and compiled into metrics across multiple facilities or assets.
Challenges with implementing a new or modified approach to testing of Safety Instrumented System (SIS) instruments include issues such as education of participants and stakeholders, integrating the new proof testing procedures with the current maintenance plans and schedule, and documenting failures identified outside of testing. It is critical to create a plan which deals with these challenges ahead of pushing SIS proof testing to facilities.
This paper reviews the technical and management challenges associated with implementing a standard SIS proof testing philosophy and documentation strategy across a multi-facility upstream oil and gas business unit.
This presentation discusses new instrumentation that confirms the isolated state of electrical disconnect switches prior to conducting equipment maintenance. Verification that electrical isolation switches are off is a vital activity when performing equipment Lockout Tagout procedures.
The current methods for verification of electrical isolation are presented. Common methods used by plant operators and maintenance personnel include Test for Dead / Live-Dead-Live Check, Try-Start / Try-out, visible break isolators and mains voltage indicator lamps. Safety hazards and limitations associated with these verification methods are then discussed. An example is presented that demonstrates how Test for Dead / Live-Dead-Live Check may produce unexpected results. In addition, circumstances preventing the use of the Try-Start / Try-out method are presented highlighting practical constraints for its universal use. Challenges associated with mains voltage, indication lamps and the new problems they introduce are also detailed. The limitations of these widely used isolation verification methods open the door for a new approach to address poorly understood safety problems.
Finally a new instrument, DeadEasy, is introduced that aims to provide an unskilled worker with a highly accurate electrical, isolation verification result. The design of the instrument and how it addresses the short comings of existing isolation verification methods and technologies is explained.