(112c) High Cost of Quick Turnarounds & Erroneous Procedures

A plant turnaround is always challenging. But with proper planning and reliable procedures in place, last minute time crunches and failures can be prevented. When haste combines with faulty methods, costly problems result.

Case Study #1: A sour water stripper (SWS) is a small unit treating waste water from other units of the refinery. After treatment, the waste water is directed to the sewage system and ultimately to a nearby river. The plant has no spare SWS unit, so in case of failure, the whole refinery must be shut down as untreated water is prohibited from being discharged into the river.

In an emergency, a sour water storage tank may be used with a capacity for five days’ of normal waste water accumulation. So in the event that the SWS is down, it must be repaired and started within the five days, otherwise the whole refinery must be shut down as mentioned before..

In this instance, the SWS performance was decreasing, and treated water could no longer be passed to the river; the SWS had to be cleaned immediately. A five-day turnaround was planned, keeping all refinery units running while sending all sour waters to the five-day storage tank.

Typically, a SWS unit will form pyrophoric iron, which is normally washed with water when unit is put out of operation to keep all internals wet and prevent self-ignition and fire. But due to the winter conditions, this procedure was not applied; the SWS column was not washed with water, but opened under dry conditions. When air entered the column, the pyrophoric iron ignited, resulting in fire damage to the column. With no spare SWS unit, the five-day sour water tank slowly filled with water. There was only five days to fix the problem or find another solution as after that period, the refinery would have to be shut down. A solution was found, and refinery shutdown was avoided. Using new internals provided on an emergency basis, the SWS unit was successfully put into operation after a two weeks’ repair period.

Case Study #2:A refinery was completely shut down for maintenance and cleaning. However, the turnaround was not well managed, causing the employees to rush their work and not follow some procedures properly.

In the case of the LPG plant debutanizer, it should have been cleaned and inspected thoroughly, but was not. Only a part of the column was cleaned, and the inspection was poor. After start-up, the debutanizer under performed as it was partly plugged with debris, but officially it was in perfect shape. This was a “mystery” to the refinery management - just cleaned, but not working!

Should the LPG plant be shut down again for an inspection that was just performed? Management needed a justification due to the expense. Troubleshooter proved that the problem was real and further explained that if the debutanizer is not cleaned correctly, it will eventually stop working, forcing the whole refinery to shut down. A short-term LPG unit closure was expensive but much cheaper than a potential unexpected all-refinery shutdown. This was the justification.

The short-term shutdown of the LPG unit was carried out, keeping the rest of the refinery running at a low capacity and temporarily flaring LPG as there was no spare LPG plant. The debutanizer was indeed found partly plugged with debris, a result of the incomplete cleaning and poor inspection.