The Expanding Sulfuric Acid Drum

Keeping with the recent theme of chemical safety in plants, I offer another true story.

One of my accounts was feeding sulfuric acid from a 55 gallon drum to control pH in an evaporative condenser system for ammonia refrigeration. The plant had a very good safety record over the years because of conscientious and well trained operators.

However one day, the day shift operator was unable to prime the acid pump after changing out the acid drum. He looked at the suction tubing and found it to be cracked and decided not to use the tubing as it was old. It was also seriously discolored making it difficult to see the liquid level in the suction hose.

He soon discovered there was no new tubing in stores and decided to install a used hose and foot valve that had previously been used to feed an unknown chemical. He had to lean over the drum to install the ‘slightly used’ tubing and was able to successfully prime the chemical pump. As he was leaning against the drum, he noticed the drum was beginning to get hot – very hot. After stepping back, he noticed the drum was beginning to swell! He quickly grabbed a fire hose and began spraying the drum with cold water. He continued to douse the drum as if he were putting out a fire and finally the drum began to cool and return to normal size.

The consequences of what might have happened had the drum burst are scary. First of all, the operator was alone in the equipment room and could have been hit by several gallons of concentrated acid. There was a safety shower nearby but if he were hit in the eyes, he may not have been able to find it. Secondly, there were several ammonia compressors nearby that could have been damaged by the acid. If the electrical components, had been shorted out, they could have lost several hundred dollars worth of poultry products. As it turned out, there was no damage to either man or machine or food product.

The used tubing and foot valve may have contained caustic soda or KOH that reacted with the concentrated acid in the drum releasing a tremendous amount of heat. The operator was a very religious man and told me he prayed during the crisis. God answered his prayers that day.