Deblinding incident

A flash-back occurred as a blind was being removed from the outlet pass of a furnace, as it was being prepared for recommissioning after steam/air decoking.A crude preheat furnace was shutdown mid-run for decoking. On completion of the Steam-Air decoking procedure a maintenance fitter was deblinding prior to recommissioning.As a precaution, because hydrocarbons could be present, the fitter was instructed to wear a fresh air mask, which was supplied by an air line.Working from the burner platform, the fitter loosened the flange bolts (6" x 300 joint) with an accompanying whistle noise as the nitrogen pressure released from the flange joint. As the fitter lifted the blind (approximately half out) some liquid drained out (most likely condensate from the steam purge which was done when the blind was installed prior to the Steam-Air Decoking).There was an explosion, and a fire ball flashed across the burner platform from the central burners back to the loosened flange. The gas, escaping from the tower side of the blind, had entered the heater through the slots for the air register adjustment lever. The fitter left the platform, fortunately only receiving some singeing to his hair.The source of ignition was a pilot burner the potential hazard of ignition from this source was overlooked during the preparation for removal of the blind. The source of ignition may not have been a hazard had both sides of the blind been purged.
Source:ICHEME
LessonsThe accident investigation report recommended:
1. Positive isolation on both sides eg. at a double block and bleed. "Positive isolation" should be checked by opening the bleed, although care should still be exercised when breaking the flange in case the bleed is plugged, or
2. Positive isolation on one side and show of steam on the other. "Positive isolation" should be checked by carefully breaking of the flange to ensure that the valve is not passing, or
3. Show of steam on both sides

Gas leak at Viskhapatnam

Its very tragic to see the gas leak at LG polymers India Limited, today at Visak, with many people affected. The styrene gas leak reportedly occured from a storage tank. It pains me that we are continuing to have such incidents in the land of Bhopal. The Government did bring out a chemical safety and security rating system in 2013, but it died a natural death. See this article https://www.business-standard.com/content/b2b-chemicals/safety-rating-for-chemical-plants-a-step-in-right-direction-113102400722_1.htmlhttps://www.business-standard.com/content/b2b-chemicals/safety-rating-for-chemical-plants-a-step-in-right-direction-113102400722_1.html
This is what I has posted in my Linkedin account:
Will we ever learn from Bhopal?
It's really tragic to see scenes of people, including children, lying helplessly on the sides of the road in TV footage of the gas leak from LG polymers India Limited, Visakhapatnam. As I had mentioned in earlier posts, the late chair of the CSB, Carolyn Merritt asked me in 2004, the reason why PSM is not mandatory in India. I am still waiting for an answer. Even if PSM is made mandatory in India, the enforcing authorities lack the relevant competence to audit PSM systems. They are also highly understaffed. The ghosts of Bhopal are continuing to haunt us. In the recent COVID 19 deaths in Bhopal, a number of deaths were the victims of the gas leak in 1984, that had already weakened their health.

Be careful of unintended confined spaces

An accident involving 2 employees occurred in asbestos removal in an ethylene oxide unit. In order to remove the asbestos insulation around the system generator safely, the removal company was told to build a plastic tent with a lock round the steam generator.A form was drawn up for this purpose which stated that flanges and valves could not be built in the tent and 'without roof'. An oxygen test was carried out on the tent in four different places on man's height and each time, normal values were measured. Based on this, the foreman gave permission to continue working. Almost immediately of mounting the ladder in the tent, the two workers started to feel sick, became dizzy and everything turned black before their eyes. They managed to stumble outside and report the incident to the foreman.Within 10 minutes of the accident, the oxygen test by the operator was done again which gave normal values. The general foreman carried out another test with another meter and normal values were noticed again. Later inspection showed that the tent was built with a closed roof and a bypass line on the nitrogen line was built in the tent with two locked block valves. Several used spray cans of glue and other substances were found in the tent and it was stated on the cans that they should only be used in ventilation rooms.
The actual cause of the accident is unknown and although nitrogen leaks in the tent cannot be excluded, there is reason to assume that other gases may have caused the symptoms of the 2 workers of feeling sick, throat irritation and breathing difficulties.

Lessons
1. It is now required to enter the tent and carry out the job with two people.
2. In the specific case of tents around ethylene oxide reactors in which nitrogen leaks can never be excluded, the tent must be built with windows of translucent plastic on each wall and entering the tent and execution of works in the tent is exclusively reserved for people carrying fresh air masks.
3. A safety guard will watch the tent for the whole period of the activities equipped with air apparatus and a knife to cut open the tent if necessary. The guard must be trained in using compressed sir apparatuses. A guard must also be provided for each work level.
4. Oxygen tests must be carried out every two hours on different heights.
5. The use of spray cans of glue or polyurethane in closed tents is prohibited unless the roof is open.
6. Asbestos removal personnel will be formally re-instructed about the procedure and that the conditions on the form must be observed
Source:ICHEME

Drainage system explosion

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

Theme for the month - Nitrogen related incident

An air compressor that provided instrument air to an acetylene plant and for breathing air failed. A back-up nitrogen supply from a liquid cylinder was connected to the piping system to replace the function of the air compressor. An operator put on a full respiratory face mask to load Calcium Carbide into the hopper and inhaled nitrogen. He died.

Source:EIGA

Theme for the month - Nitrogen related incident

Employee stepped into a control cubicle where the instrument air was temporarily replaced with N2 during shutdown. The green light outside the door was on indicating safe atmosphere. As soon as he stepped into the cubicle his personal O2 monitor alarmed indicating 18% O2 or less.
After exiting safely he opened the door and when O2 level was OK, checked the fan. The ventilation fan was not running. The light was wrongly wired.

Source:EIGA

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Theme for the month - Nitrogen related incident

An experienced contractor was used to purge a natural gas pipeline, 0.5m diameter 10 km long, with nitrogen before start-up. When one contractor employee and two customer employees entered the remotely located chamber, they were asphyxiated and later found dead in the chamber. Two blind flanges were leaking and the oxygen monitor was not used.
Source:EIGA