A refinery in Thailand was facing a major dilemma operating their 35 year old recycle gas compressor due to their failing steam turbine driver. The API 612 non condensing steam turbine had a rated output of more than 2 MW. The main steam chest, casing, and exhaust was of A216 WCA construction.
During a routine inspection, the maintenance team discovered severe erosion problems on the discharge nozzle of the turbine. After some detailed inspections on the eroded areas, the maintenance team found out that nearly 60% of nozzle thickness had eroded away in certain areas. A quick calculation on the erosion rates revealed that that the body would fail within a period of 2-3 years, a few years before their major 5 year turnaround. The refinery did not have any spare compressor trains nor a spare steam turbine casing. As the old steam turbine was obsolete, there was limited support from OEM.
This was a major problem for the refinery as they risked shutting down a major unit in their refinery if they could not find a solution. The reliability and maintenance team contacted PSS to explore various solutions to the problem. The immediate solution PSS proposed to customer was to weld-repair the discharge nozzle. However this option was quickly rejected by the refinery operators as the repair and subsequent overhaul would take a period of at least 1-2 weeks. The maximum time period for a quick shutdown at the refinery was 2-3 days.
With such a short time period, the only alternative was to replace the entire API steam turbine with a new unit giving the same performance without changing any of the steam pipelines, base plate, lubrication system, etc. Or in other words – a drop-in steam turbine. The refinery team was very interested to explore this option further. The first step in this project was to scan the entire turbine to ensure that original dimensions and footprint can be maintained. The refinery team agreed with our suggestions and allowed us to scan the turbine while still in operation.
PSS utilized the latest generation Handyscan equipment to do this job. This is another example of how PSS has used world class engineering and technology to achieve our stated vision of providing asset management solutions to our valued customers. The entire project was completed within 2 days and marks the first time PSS has scanned a steam turbine in our history. This project is still a work in progress and we are ready to move to the next step of providing a drop in turbine.