I have never imagined that a product storage tank overflow incident would happen. And much amount of hazardous chemical contaminated to the environment.
This chemical overflow from a-500 ton storage tank incident happened in last 2014.
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Really, none of us ever thought about this incident. Even, we have not made any emergency procedure for such an emergency condition.
Today, I will share a safety tip of the day about the importance of re-checking storage tank calibration span.
The Root Causes of the Storage Tank Overflow Incident
As the follow up toward the incident, an incident investigation was then carried out.
We found that the root cause was the use of the wrong calibration span.
At the day of the incident, the storage tank LIA (level indicating alarm) shown 88%. The operator thought that the tank would be switched to another storage tank when the level reached 90%.
Unfortunately, the chemical overflew from the tank at LIA of 89%. This made the operator confused. Why it happened?
Then, the operator switched the storage tank immediately to stop the chemical overflow.
After switching he checked the level gauge (in meter). The needle pointed to a value of 12.620 m, which was the same as the actual level of the storage tank (12.620 m).
The operator only relied on the indication of LIA. He ignored the actual level height.
On the other hand, the instrument technician checked the calibration span record. He found that the span was 0-11.232 m. It was lower than the actual tank height.
Safety Tips of the Day: the Lesson
There are several safety lessons we can take from today’s safety tips of the day story. The focus is to prevent the same incident from recurrence.
- Tank level must be monitored by using more than one indicator to get the correct value; Level Indicator Alarm (LIA) and level gauge (LG).
- When two level indicators show different values, it had better take the highest value as the actual value for safety.
- You must compare all the storage tank level calibration span with the actual tank height to avoid using the wrong height reference.
- Keep all the storage tank calibration record for further inspection or re-calibration status