An incident occurred when a manhole cover on an underground drainage system lifted. On investigation it was found that there was a high level in the drain sump, which was hot and steaming and local ground drains had back-flowed.The area was roped off and water lines put into the quench water outfall. This had an immediate cooling affect. Soon after the conditions of the drains were back to normal.The drains and downstream drains levels and temperatures were later checked and found to be normal.The report stated the following conclusions:The design of the oily drains system is such that a 100-200mm layer of hydrocarbons is always present in the sump drains. Hot water from the quench vessel vaporised light hydrocarbons in the drain system.The resultant overpressure pushed liquid back up the sumps, lifting the manhole covers.The water from the quench vessel was hotter that normal due to a dip in the raw water supply pressure.
Lessons
The report stated the following recommendations:1. Fit a pressure gauge to the quench vessel raw water supply to monitor fluctuations in supply pressure during reactor regeneration. Consider fitting a temperature alarm to the outfall.2. Check all vents on the gas separation drains system.3. Remove accumulated hydrocarbons from the gas separation drain sumps.4. Check drain sumps for solid debris and remove. Consider need to clean main drain runs at shutdown.
Source:ICHEME
Lessons
The report stated the following recommendations:1. Fit a pressure gauge to the quench vessel raw water supply to monitor fluctuations in supply pressure during reactor regeneration. Consider fitting a temperature alarm to the outfall.2. Check all vents on the gas separation drains system.3. Remove accumulated hydrocarbons from the gas separation drain sumps.4. Check drain sumps for solid debris and remove. Consider need to clean main drain runs at shutdown.
Source:ICHEME
No comments:
Post a Comment