Use of Design Operating Window (DOW) Violation Monitoring Tool to reduce equipment design violations in a crude oil refinery

摘要

Industry codes and standards advise that operating outside equipment design parameters can lead to equipment failures. Equipment failures result in loss of containment and can escalate to a major process safety incident. Detection and tracking of violations to equipment design windows is essential for quantitative understanding of adherence to operating design parameters of said equipment. This simple yet effective concept was first utilised at SAPREF in 2007. SAPREF is a joint venture between Shell and BP and is the largest crude oil refinery in South Africa processing 24 000 tons of crude per day. A Microsoft Excel based tool was developed to report on Design Operating Window (DOW) violations on a weekly basis. Utilising the refinery PI (Plant Information) system, together with a database of all equipment design pressures and temperatures, the macro based tool was able to compare historised plant data for a chosen time period, against the equipment design limits. A proactive monitoring tool, shift exceedance reports and a weekly assurance report was produced indicating the number of violations as well as the duration of the violation. Equipment pressure violations were further analysed to determine the equipment %overpressure and whether relief valves in the system had lifted. Tank high and high high level limits are also included in the tool to give an indication of potential tank overfill incidents. Key performance indicators (KPIs) were developed for the site based on the DOW violations i.e. no of tags in violation and % time that the tag violated for the week. From the introduction of the KPIs in 2009, the site has managed to reduce the number of tag violations from an average of 30 per week to as low as 10 per week in 2016. The total number of pressure violations for 2013 was 150 and gradually reduced to a total of 32 in 2016. By focusing on the reasons for the DOW violations, the site was able to resolve systemic or design problems that were resulting in the design window violations i.e. operational, maintenance, compliance etc. The tool was later updated to include Integrity Operating Windows (IOWs) and Product Quality (PQ) Window limits. IOW violation monitoring allowed the site to proactively determine if a specific material degradation mechanism was favoured which could result in a loss of containment. PQ windows are utilised to minimise the potential of having an off spec product. Monitoring DOW violations has helped SAPREF focus on the "big issues" by gaining control of the design envelopes and working inward instead of being overwhelmed with trying to control the operating envelope violations. The concept that the DOW monitoring tool is based on can be easily applied to any industry especially since it is Excel based.