Tracerco helped to diagnose the cause of poor tower performance which resulted in a shorter than expected shutdown and eliminated the need to order costly trays. Following a unit power failure, the column was not able to make even marginal specification product at the desired rates. It was thought that the sudden shutdown had damaged the trays in the column. A computer simulation model of the column indicated that, at the prevailing operating conditions, 30% of the trays would have been malfunctioning for this to occur. Since the product was in demand, a shutdown to replace the trays suspected of being damaged was scheduled for 3 weeks after the incident. Ordering the replacement trays on such short notice would demand a premium price from the manufacturer and extra trays would have to be ordered to have on hand as spares, since the true extent of the damage was unknown. A maintenance engineer recommended using the TRU-SCAN®/Tru-Grid™ Scan to identify the extent of the damage.
The 100ft. Scan was completed in approximately 5 hours and a preliminary interpretation was available 30 minutes later. The scan results indicated that no major tray damage had occurred in the column. The separation problem appeared to be caused by a severe vapour related flood condition occurring above the feed tray. A possible cause was plugged trays, since the column handled material that could cause fouling. The decision was made to inspect the column during the shutdown, but not to order any trays. The inspection revealed pluggage on the trays above the feed point. This was probably caused by material solidifying on the trays after the abrupt shutdown. A substantial cost saving was realised by the shortened shutdown and by not ordering replacement trays.