Towards Plant Instrumentation Safety Instrumented Function Asset Mgmt Excellence - Case Study of 1oo2 ASO voting implementation

摘要

Reliability of Plant Instrumentation, in particular, Safety Instrumented Function (SIF) at PP(T)SB {PETRONAS Penapisan (Terengganu) Sdn Bhd} , a refinery situated East Coast of West Malaysia is critical. The challenges encountered here is ability for the existing SIF instrumentation to meet the Safety Integrity Level (SIL) as calculated and reported in the SIF Study conducted in Year 2008 to 2010 - taking into account the aging plant and inherently non-robust plant design, and with lean maintenance organization with the unfavourable oil prices. Among focus areas is to be innovative in coming up the implementation strategy of the SIF Report Recommendation. Issues encountered by PPTSB being a brown field plant is the lack of cables spares to install additional initiators to meet the SIL 2 and SIL 3 required. The allocated CAPEX is also a challenge to implement the 2oo3 initiators/transmitters configuration to meet the SIL 3. Toward this end, PP(T)SB has embarked on using the unorthodox 1oo2 voting with 1 hour Automatic Sensor Override (ASO) for its transmitters, instead of the conventional 2oo3 voting for about 80 nos of safeguarding tags in compliance with the IEC standard. The project was completed in 2011 and 2012 for PC aromatics and Refinery respectively. As part of the continuous improvement, the 1oo2 with ASO logic was further modified in 2012 to ensure all failure modes of the transmitters are captured and sent to DCS for Operators further action. In 2014, we have identified 27 tags with 1oo2 with ASO configuration which have control or indicating transmitters to be further upgraded to 2oo3 voting. The cost of conversion is very minimum since we are utilizing the indicating or the control transmitters as the 3rd safeguarding transmitters to form a 2oo3 voting. For the shutdown Valves, the strategy is to have procedure and philosophy in place to ensure good maintenance of the shutdown valves which begins from completeness of shutdown valve database which serves as central repository for easy access and depository of critical information of all shutdown valves assets datasheet, photos, Bill of Materials, construction drawings etc. With the implementation of Systematic Shutdown Valves Philosophy, any potential dangerous failures of the shutdown valves are kept to the very minimum.