Chlorine tonner incident

Thanks to Mr Harbhajan Singh Seghal for sending this incident:
INCIDENT
In one of the chlorine consuming industry two persons were affected with chlorine while the operator disconnected the tonner from the process due to hard valve operation of the tonner.
DETAILS OF INCIDENT
· The consumer withdraws liquid chlorine from the chlorine tonner and consumes gas after evaporation.
· As per practice, the consumer keeps the tonner in line to withdraw maximum chlorine from the tonner.
· On the specific day of the incident, the operator tried to isolate the tonner at 1.0kg/cm2 pressure when about 40-50 kgs liquid chlorine was left in the tonner and there was ice formation at the bottom of the tonner.
· He could not close the valve fully. The spindle of the valve damaged due to excessive force.
· The operator decided to cut off the tonner by wearing SCBA.
· This action resulted in heavy gas leakage and affected two persons in the surrounding area.
ACTION TAKEN
· The tonner brought to the works.(of the chlorine supplier)
· It was depressurized and the valve was dismantled
· Iron chloride rust and greenish color sludge was observed in the threading of the valve.
· Damaged valve replaced with new valve.
ROOT CAUSE
· Liquid chlorine withdrawal rate is 180 kgs/hr. Maximum liquid chlorine is used up in 4-5 hrs operation at this rate. Some quantity (40-50) kgs remains in the tonner at the bottom.
· Some consumers try to recover this 40-50 kg liquid chlorine as gas by keeping the tonner in line for more time.
· The left over liquid chlorine evaporates at 5-6 kgs/hr as gas and lowers the temperature of the tonner/pipe lines due to fall in pressure till the remaining liquid chlorine is exhausted.
· 1.0 kg/cm2 pressure can lead to about -20 degree C and takes 8-10 hrs to completely empty the tonner.
· Normally chlorine in the tonner is dry. But under such conditions (-200) the same chlorine becomes wet.
· Water in the chlorine separates out and freezes in the spindle of the chlorine valve. It makes the valve hard to operate at that time.
· After attaining normal temperature, chlorine evaporates first and water later. This chlorinated water reacts with the sprindle and makes the chlorine spindle greenish.
· The evaporators which do not have backflow prevention system (from evaporator to chlorine tonner) results carry over of iron chloride rust to valve spindle and makes the valve hard in operation.
LESSONS LEARNT
· The tonners containing some quantity of liquid chlorine (40-50 Kg) are not to be cut off at 1.0kg/cm2. The tonner is to be depressurized by releasing the chlorine to neutralization system through header or evaporator.
· After depressurizing, check that no chlorine gas comes from the upper valve of the tonner, and also check that no ice formation appears on tonner or pipe lines before the tonner is disconnected.
· Chlorine header and evaporator must have chlorine release facility connected to neutralization system.
· Chlorine evaporator must have liquid chlorine flow control interlocked with temperature and outlet pressure to avoid the back flow of chlorine
· Evaporator should have emergency release system with rupture disc and safety valve.
· Temperature of evaporator should be maintained between 80-85 degree C to avoid formation of rust as Fecl3 in the evaporator.
· Dry air (-40 degree) dew point is to be utilized for evaporator maintenance.
· Glass wool filter is to be utilized in gas line to avoid carry over of Fecl3 to main products and choking in chlorine system.
· Tonners can be kept in tilted position forming 20-30 degree angle to withdraw maximum liquid chlorine from the tonner.
MOST IMPORTANT LESSONS
· No chance should be taken with liquid chlorine system. Help of the filler (chlorine supplier) must be taken in such cases. One volume of liquid chlorine expands to 460 times
· Chlorine neutralization system must be effective and checked from time to time.
· Single person should never take this type of emergency job.
· Always stand by person ready with safety equipments should be present during such operations.

Process safety - Seeing and managing

A typical day for today's plant manager is like this: Punch in....login......read emails and answer......collect data for the meetings scheduled......firefight today's issues.......go back home late in the evening! I was just comparing the daily routine i used to do many years ago in the same position: Punch in....go around the plant for at least one hour.......read the log book.....write relevant instructions in the instruction book.....attend the daily plant meeting for discussing and resolving issues....discuss and take instructions from my boss....communicate these instructions to the plant......go back home peacefully, on time! Note: There were no ISO9000,ISO14000,OHSAS18001,PSM,TQM,Six sigma etc in those days! Managing process safety needs management by seeing, hearing and understanding. Unfortunately today's plant managers do not have the time to see the plant.....this is a dangerous trend. Also competency for managing process safety is lacking. Somewhere we seem to have lost our way!

Awards and Accidents

Further to the refinery accident during hot work which I had mentioned in my previous blog entry, an article in the Hindu lists out other accidents that occurred in the same refinery in 2009. It also mentions that the refinery won safety awards in 2009 and 2010. There is a disconnect here! Read the article in this link.
While awards are a good way to motivate people, the onus lies on management to sustain and improve process safety performance.Long ago, I had audited an organization that had been granted a prestigious award by an international organization for their safety management system. I visited the plant 6 months after this award. Their safety management was in shambles and I had mentioned to them that the sword is now hanging over your heads.
If everyone goes back home safely everyday and this is maintained, then your process safety management system is working well! Period.

Worker killed in explosion during hot work

An accident at a SRU at a refinery has killed a worker. Read the article in this link. Please see my earlier posts under safe work practices. Hot work should be done with proper precautions and it is sad that repeated accidents are occuring. 

Process Safety and Risk management in the high speed age

A good article called "Black swans turn grey -The transformation of risk" by Price Waterhouse Coopers highlights the following:

1. The boards of big organisations do not fully understand the risks that they are running
2. In the Internet age, speed and prejudice are all
3. Checks and balances at board level are critical.
4. Leadership and culture shape an organisation’s attitude to risk.

I think in a chemical industry "operational risk" is of greater importance that financial and strategic risks. As long as there are human beings involved in making decisions, there is a possibility of a process safety incident that has serious implications for the business. That's why I agree totally with the Baker Panel report suggesting that a person competent to understand process safety be on the board of Directors for Chemical Industries.
Read the article by PWC in this link.