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Case Studies

TRACERCO Diagnostics™ Tower Scan

Tracerco Asia was invited to carry out the TRACERCO Diagnostics™ Tower scan technique to inspect the condensate tower on a major operator’s plant in Malaysia. The objective was to investigate the flooding condition in the tower that was affecting the column parameters and leading to discolouration and contamination of the condensate naphtha stream.

The condensate tower was scanned in three sections. The top section (Trays 1-9) was scanned using scan lines along two chords at an orientation 90° - 270° (Scans T1 and T2). These passed through the active areas of the trays, avoiding the side and centre downcomers. The middle section (Trays 10 - 20) was scanned along the 0° -180° diameter, avoiding the side downcomer (Scan C). The bottom section (Trays 21 – 30) was scanned along two chords at the same orientations as for the scans of the top section (Scans B1 and B2).

From Tray 21 down to Tray 25, the column was completely flooded: although no flooding was observed below Tray 25. This suggested that there was probably a restriction in the Tray 25 downcomer. However, an alternative possibility is that the flooding was a result of restrictions in the hole-sizes on the active tray areas, caused by the lay down of deposits.

On the North side of the tower, the tray appeared to be operating satisfactorily, while on the South side the profile of Tray 28 was irregular. It appeared to be holding very little liquid, which indicated that this side of the tray was dry, or partly damaged.
Trays 29 and 30 looked normal with clearly defined vapour spaces and liquid levels. The liquid level on the North side of the tower (200mm) appeared to be greater than that observed on the South side (100mm), The condensate tower was experiencing severe flooding conditions at the time at which the scans were performed. The flooding extended from Tray 25 up to the top tangent line. In the first scan, Trays 1-4 appeared to be in position and functioning satisfactorily.

Tracerco Asia’s engineers’ recommendation detailed in their preliminary report that a scan should be done at a lower rate, or after the column had been flushed and cleaned, to check the condition of the trays. The column was then opened and cleaned and has been brought back on line and is operating under normal conditions. Tracerco Asia’s techniques were able to investigate and clarify the flooding conditions within the tower, minimizing shutdown time and helping the plant to effect speedy repairs and a rapid return to full production of high quality product.

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