Fatality at ammunition factory

A fatal accident at an ammunition factory has even experts "baffled". The article mentions "Mule, a permanent employee, was described as a highly skilled worker. The incident happened around 2.10 pm when he was about to go for lunch. AFK officials said there was a spark and suddenly Mule was on fire. Showing presence of mind, Mule sprinted towards a water tank and doused the fire. Otherwise, the fire could have spread causing much damage, said some of the employees". Maybe static electricity was the cause??
Read the article in this link
Read another article in this link

The dangers of aerosol cans

Yesterday I had been to the birthday party of my friend's eight year old daughter. The kids were playing with an aerosol can which generated foam thread, when pressed. None of the kids were aware of the hazards of the aerosol can and that the gas used as a propellant was flammable! What does this have to do with process safety? We also use aerosol cans for dye checking or lubricating/removing rust etc. Read the warnings on the can before you use them. Propane and butane are often used as propellants and the escaping gas can catch fire if a source of ignition is present. Also do not dispose empty aerosol cans in a fire. They can explode.
Thanks to R.Sriram for sending these tips on aerosol cans:

• Aerosols contain a product and a propellant that are packed under pressure.  
• Many people use aerosols without realizing some of the potential hazards associated with them. 
• Oven cleaners, tile cleaners, pesticides, disinfectants, hair sprays, room deodorizers, paints, and furniture polishes are examples of aerosol products. 
• When the nozzle of an aerosol is pressed, the product and propellant are released from the container in a fine mist. The actual product propelled by the aerosol, such as some oven cleaners, can be corrosive, flammable, or poisonous. Acute symptoms of aerosol exposure include headache, nausea, dizziness, shortness of breath, throat irritation, and skin rash. 
• A misdirected spray can cause eye injury and chemical burns. 
• Never leave or place an aerosol can near high heat sources, such as a heater, direct sunlight, or fire. 
• Keep aerosol cans away from children and pets. 
• Never puncture or subject an aerosol can to sharp impact; a sudden puncture may cause an explosion. 
• Dispose the Aerosols in a proper way.

A water tank kills

A supervisor was killed when he attempted to rescue his fellow worker who had collapsed after entering an empty water tank. Investigation is on to determine what was present inside the water tank. If a water tank can kill, just imagine the hazards you face when you enter a confined space in a chemical factory. Follow your company procedures strictly and don't take any confined space for granted. Read the article about the water tank fatality in this link.

Two killed in pharma factory fire near Hyderabad

A news article mentions that a fire in a pharma factory at Patancheru has killed two people. The article mentions that
"According to police, the fire engulfed the factory after a reactor exploded due to an electrical short-circuit. The fire broke out in the evening, and spread to neighboring factories. Fire-fighting personnel had to battle for five hours to control the flames.This is the second such accident in three days. Four workers of a chemical factory were killed in a reactor blast at Polepalli Special Economic Zone (SEZ) at Jadcherla in Mahabubnagar district near Hyderabad last Friday".
Read the article in this link
See a photo in this link.

The dangers of sewers

Two people were reportedly killed in a factory in Chennai when they entered a sewage tank that was not opened for a long time. Be careful of sewers in your factory and residential colonies. Entry should be done only with proper confined space entry permits

The dangers of water hammer

Many of you would have heard the "banging" noise that a water hammer produces inside a pipeline. We also do not expect a pipeline to be destroyed by water hammer. But it happens. An article by Gregg Basnight mentions the following:
"Contrary to old operating practices to drain and warm up steam lines, "Cracking Open" valves in lines to bleed condensate under steam pressure is NOT safe and has resulted in numerous reported water hammer fatalities.Before admitting steam to any line, the condensate must be removed. Condensate should be assumed to be in all low points and dead legs until proven otherwise by verification of drain or steam trap position and operation. Pressurized dead legs without functioning traps or periodic manual blowdowns will have condensate present. The affected section of piping should be isolated, depressurized and drained before restoring steam to the system".
Read the full article in this link.

Give importance to sight glasses

30 years ago, in the ammonia plant where I worked, the sight glass of a high pressure (200 Kg/cm2) ammonia separator leaked during start up. Luckily we managed to shut the plant down safely with no injury to anyone. The root cause was the wrong torquing procedure used. A good article about sight glasses mentions the following:

"Proper design, installation and maintenance of sight glasses are the keys to their safe and effective use....a sight glass almost always fails in tension rather than compression. This is similar to the case for concrete, because glass is not ductile and cannot stretch like metal. Therefore, tiny imperfections in a sight glass window can create stress concentrations, which are potential failure points. Just the touch of a finger on the window can reduce the tensile strength of a virgin glass element by three orders of magnitude from one million to 1000psi. Although design and manufacturing flaws are important, most sight glasses fail due to improper installation. Mechanical stress is a frequent cause, arising from the over-tightening or uneven torquing of bolts that generate bending loads on the glass. When an existing sight glass window is replaced, trapped debris may become a problem if old gaskets have baked onto the flanges. While this may seem trivial, it is actually very dangerous. Even small contaminant particles or build-up might be enough to scratch, pit or bend the new glass during installation".

Read more: http://www.articlesnatch.com/Article/Sight-Glass-Safety-A-Major-Process-Plant-Concern/1604779#ixzz1gkkBXVxV
Under Creative Commons License: Attribution No Derivatives

Laser scanning - a tool for Management of change and Asset Integrity

The most difficult elements to implement in a PSM program are management of change and asset integrity simply because of the large quantity of data involved and less time available. I was reading an interesting concept of laser scanning in an article in Power magazine. It mentions the following:
"Laser scanning also provides a dimensionally accurate representation of the plant and all its equipment as well as a photographic quality visual representation. The laser scan database can be integrated with a variety of plant design applications to provide comprehensive facility management support".
The concept will be very useful for PHA teams who are analysing changes/modifications as they can virtually "see" the proposed modification. It is also an useful tool for managing your asset integrity as another article mentions.
Read the article on laser scanning in this link
Read the article on Virtual asset integrity management in this link.

US Unions briefing on Process Safety

The USW union of the US has briefed the US Congress about health and safety problems in the oil industry. As per a news article,"USW Health and Safety Specialist Kim Nibarger outlined five fatal flaws at the briefing on where the oil industry needs to improve its health and safety record: process safety, mechanical integrity, management of change, incident investigation and control room alarms and instrumentation. “When things go bad in a refinery, they go really bad and people die,” he told the briefing. “Focusing on personal safety—the wearing of hard hats and safety glasses, slips, trips and falls—says nothing about how safe a refinery is for workers and the surrounding community. BP had a low personal injury rate at its refineries, but the 2005 explosion and fire at its Texas City plant showed it failed miserably in terms of process safety. Fifteen people were killed and 170 were injured in the 2005 accident as a result of this failure. “The oil companies are playing Russian roulette with their equipment,” Nibarger said. “They are doing quick, stopgap fixes, like placing clamps on pipes instead of replacing the pipe. They’re extending the time between unit shutdowns when all the equipment is checked. When there is a shutdown they’re not always repairing or replacing critical equipment. When they do repair equipment they’re not bringing it up to current RAGAGEP (Recognized and Generally Accepted Good Engineering Practices) standards.”
If the above sound familiar to you, take a hard look at your PSM program!
Read the full article in this link.

Adding too much chemical causes an incident

A news report mentions an incident where an orange gas cloud leaked from a manufacturing facility for making ferric sulphate. Apparently, too much nitric acid was added to a batch, resulting in a violent reaction that produced excess amounts of nitrogen dioxide that escaped from the reactor into the air.Nitrogen dioxide is a reddish brown gas and is highly toxic if inhaled and is also corrosive.
Ensure that you have proper controls over addition of chemicals, especially if adding an excess of one chemical can trigger something unwanted. Engineering controls are the best to avoid such mishaps. Depending only on an SOP in such situations may cause an an incident to happen.
Read the article in this link.

Boiler burst kills 4

A boiler of a dyeing unit  burst on Tuesday, killing four persons and injuring 20 others on Tuesday. Inquiries are on to find out the reason for the blast. An official said that the safety valve failed release in time, leading to pressure building up inside the boiler.Read about it in this link.

A change in piping material may overlook something else!

A plant decided to change its sulphuric acid piping from Cast Iron to SS. However, they decided to conduct piping design analysis as per code requirement.The analysis found out that design did not adequately consider the difference in cross-sectional thickness between Cast Iron and SS (Cast iron is very thick compared to stainless steel). Also, the heat transfer rates of CI and SS differ. The piping expert redesigned the piping system to account for the thinner cross-section and thermal expansion properties of stainless steel and thus avoided premature failure. 
Read the article in this link.

Explosion in sulphuric acid tank

An explosion in a sulphuric acid tank has injured four personnel in Japan. There is the danger of presence of hydrogen in sulphuric acid tanks and when you do hot work be aware of the simple precautions like gas testing etc.
Read about the accident in this link. The Chemical Safety Board had earlier brought out a safety bulletin on the Dangers of Hot work, which is worth reading for every plant operation, maintenance and safety personnel. Read it in this link.

Fire in Pharma Plant

A fire in the vacuum dryer area of a pharma plant has reportedly seriously injured three people. As per Company press release, it states "There was a fire incident in a powder processing area at early hours on Nov 28,2011, at unit 11 which is located at Pydibhimavaram, Srikakulam near Vizag, A.P. Three persons were injured and they were taken to the hospital. The powder processing area is isolated from the intermediate block. There was no impact to the operations as well as to the assets".
Another news report indicates that the fire was caused by an explosion due to high pressure in the vacuum dryer.
Read the news reports in these links
Link 1
Link 2
Link 3

Remembering Bhopal............

Please spend December 2nd/3rd as “Process Safety Day” in your organisation. Educate your personnel on the Bhopal Gas tragedy and its lessons. 27 years ago, on the night on December 2nd/3rd, 1984, on a wintry night in Bhopal, thousands of men, women and children died an excruciating death when MIC leaked from the Union Carbide factory. The survivors and the next generation children born to those exposed to the gas still are suffering from the effects of the gas. Bhopal is an ongoing tragedy and should never be forgotten. The Bhopal gas disaster comprises actually of three disasters - the first was the actual incident, the second was the inadequate compensation received and the third is the ongoing legacy of genetic defects and effects of the hazardous waste that has seeped into the ground water. Every plant operating, maintenance and safety personnel must never forget the lessons of Bhopal. They are still relevant today:
1. Do not cut costs without looking at the effects on process safety
2. Maintain all your layers of defense including asset integrity
3. Continually ensure that competency of personnel operating and maintaining plants are updated and current
4. Be prepared for the worst case scenario.
5. Understand the risks and measures to eliminate / reduce or control them
6. Learn from your past incidents. Those who do not learn are condemned to repeat the incidents.
7. Pay heed to your process safety management system audit reports

As you are aware, this blog is also dedicated to the surviving victims of Bhopal and for my regular subscribers, I appeal to you to buy my book "Practical Process Safety Management", the proceeds from which are donated to the surviving victims of Bhopal.Contact me at bkprism@gmail.com for buying the book.

See a presentation on the Bhopal Gas Tragedy by Vijita S Aggarwal, Associate Professor, University School of Management Studies,GGS Indraprastha University,Delhi, India in this link.
Read my older post comparing the Bhopal and the BP incident of 2005 in this link
Read the then Police Chief’s account of the tragedy in this link.

Witness to a catastrophic near miss!

On 29.11.1984, I was working  in an ammonia plant when a cylcone hit the place. Management had taken advance action and instructed us to shut off the back end of ammonia plant (the back end of the ammonia plant involves high pressures). We had shut down the back end and were waiting for the cyclone to hit us. The wind speeds were very high and all of us were taking shelter in the control room. A complaint then came in from the  another plant that was located within the same complex, that they were experiencing severe ammonia odour.  Thinking that the pilot burners of the ammonia derrick supported flare that was provided for emergency venting of the ammonia storage tank was put off by the high winds, I requested operators to go out and check them. Three operators had to go, holding each other tightly,as the wind speed was so high and could blow a man off his feet. After a short while they came back and reported that the flare was missing. I went out to check with another team and we found to our horror that the flare structure had collapsed on the main ammonia vapor line coming from the tank. The derrick structure was weak and could not bear the brunt of the wind speeds, but the main flare gas pipe was in good condition and when the derrick toppled, the main gas pipe prevented it from falling all of a sudden. Instead it fell slowly and came to rest on the ammonia vapor line! The 8" main ammonia vapour line from the tank was dented, but did not leak.
When you conduct your asset integrity program, pay attention to structures. Nowadays, in many plants, painting schedules are taking a back seat, with the net result that corrosion creeps in. Corrosion is a silent killer. It will hit you one day if you don't maintain your assets.
Interestingly, recently I read an article where a complete flare structure repair was done with minimum downtime in a plant.Read the article in this link.

Escaping from steam

Many of you will be working with steam. During startups the possibility of water hammer in a steam pipeline has the potential to rupture the line or flange joints. Your SOPs must warn operators about the dangers of water hammer. An article mentions that the best way to escape from a closed space in which a steam leak has been triggered due to water hammer is to escape in the direction in which the steam is leaking through an exit. Read this article in this link

Heat transfer fluids

Paratherm have brought out a good booklet on heat transfer fluids - do's. dont's and best practices. Some of the points brought out are:
"If any hydrocarbon liquid (oil, grease, heat transfer fluid, hydraulic fluid) is allowed to enter porous insulation, it will begin to oxidize, raising the insulation’s internal temperature. If this temperature exceeds the fluid’s autoignition temperature, the fluid is likely to spontaneously combust into a smoldering fire. Thoroughly inspect all insulation for signs of wetness and other damage.Although “hydro” testing is a commonly accepted practice with heat transfer systems,alternatives such as pressure-testing with inert gas or with the heat transfer fluid itself should be considered. Water in a system can cause pump cavitation and corrosion and, if trapped in a “dead leg” and hit by high-temperature oil, can flash to steam and literally blow the pipe or tubing apart. And if the pipe doesn’t burst, the expansion can push a slug of hot oil out the expansion tank’s vent—a serious safety hazard".
Read the complete article in this link.

Blast in melamine plant kills 14

A BBC news report indicates that 14 people were killed in a blast in a melamine plant in China when work was going on an heat exchanger. Read the news report in this link. The cause of the explosion is not known.
The European agency for safety and health and work reports an incident in 2003, in Netherlands, where three maintenance workers were killed when a gas oven in a melamine plant exploded and the three workers who were standing on the cover of the oven fell into it.The gas oven was fired by natural gas and off gases from neighbouring plants. The off gases were contaminated and were filtered before use. The filters had to be cleaned regularly. A short cut taken during maintenance of these filters created a combustible mixture of gas and air in the oven which was ignited by a stray spark. Although this was the immediate cause of the explosion, investigations concluded that the underlying cause was a company culture which had allowed the untested short cut procedure to be used.
The lesson is to follow safe procedures and not to take short cuts even under time pressure. The accident also highlights the importance of the safety culture. Read the report in this link.

Chlorine leak in paper mill

Thanks to Abhay Gujjar for sending information about a chlorine leak from a chlorine dioxide storage tank in a paper mill. Four people are reported taken to hospital.
TAPPI, the leading association for the worldwide pulp, paper, packaging and converting industries has published a booklet on safe handling and storage of Chlorine dioxide. The following points are mentioned:
Chlorine dioxide gas is unstable and readily decomposes to chlorine and oxygen under upset conditions
Chlorine dioxide decomposition is a propagating reaction similar to a combustion front or flame. Providing a sweep of fresh air across the vapor space of a storage tank has shown to reduce the probability and violence of decomposition.
Read the complete guidelines in this link. 
Read about the incident in this link.

Bio Fuels and Process Safety - Ethanol Tanks

The bio fuel industry is growing at a rapid pace. However, from a process safety point of view, it is hazardous as it deals with flammable chemicals like ethanol.  An article mentions the following:
"Steel tanks containing fuel-grade ethanol develop leaks due to stress corrosion cracking, says Oliver Moghissi, president of the National Association of Corrosion Engineers. Corrosion can be an issue near vents and any external appurtenances exposed to air, allowing ethanol to pick up moisture. Storing hydrous ethanol can produce even more corrosion due to higher water content.
There are a number of corrosion mitigation strategies, he adds, drawing on technical input from Narasi Sridhar, vice president of DNV USA, a classification society, and a fellow member of NACE. Galvanic sacrificial coatings, such as zinc or aluminum, will protect steel tanks containing ethanol. The main limitation to this system of corrosion mitigation is that it could have a negative effect on product quality. “Any dissolved metal species in the ethanol can render the ethanol unacceptable to the automotive industry, its main customer,” he tells EPM. “Any galvanic coating therefore must be tested rigorously by the end-user, the automotive community, which can be time consuming and expensive.”
Cathodic protection, however, doesn’t work for the insides of metal structures containing ethanol, the corrosion engineers add. The fuel has low electrical conductivity when compared to water and, as a result, much of the applied voltage is insulated from the metal needing to be protected. “Therefore, impressed or sacrificial cathodic protection systems will not work in ethanol,” Moghissi says. “In ethanol-gasoline mixtures, the situation is even worse since gasoline has a lower electrical conductivity than ethanol.”Read the full article in this link. 

Vacuum - a deadly killer

A news article mentions that a man was sucked into a huge duct conducting gaseous silicic acid that led to his death. The duct was about three feet in diameter. Besides inhaling the gas, he had also suffered injuries on the head while being sucked in. Another employee was also partially sucked into the duct but managed to escape with minor injuries.Read the article in this link.

Dust explosions - status of regulations in USA

An AP news article mentions the lack of regulations in the USA regarding dust explosions.
"Figures compiled by the U.S. Chemical Safety Board illustrate the scope of the problem. A 2006 study reported there were at least 281 dust explosions in the U.S. between 1980 and 2005 that killed 119 workers and injured 718. In 2007, it recommended that the Occupational Health and Safety Administration create workplace rules to control dust and cut down on explosions. The Chemical Safety Board is charged with investigating industrial accidents, but it must rely on regulatory agencies like OSHA to effect change from its findings.
"Despite the seriousness of the combustible dust problem in industry, OSHA lacks a comprehensive standard to require employers in general industry to implement the dust explosion prevention and mitigation measures," the Chemical Safety Board wrote in its 2007 report".
Read the full news article in this link.

Ammonia tank safety valve release

An ammonia tank in a plant in Australia apparently released close to 1 MT of ammonia through its safety valves due to overpressure of the tank. The plant has been ordered to close down.The Government spokesperson  correctly mentions that a safety valve is the last line of defence and this is a serious incident. Many atmospheric ammonia tanks and LPG bullets have their safety valves open to atmosphere. With rampant unauthorized residential settlements still happening around chemical industries and refineries in India, is a disaster waiting to happen?
See the video and report of the incident in this link.
Read a press release of the incident by the company in this link.

More chlorine incidents

Thanks to Mr Harbhajan Singh Seghal for sharing these incidents.

INCIDENT #1
Chlorine leakage was noticed from the valve of a chlorine tonner. They tried to control the leakage but when it became uncontrollable, they dumped the leaky tonner into the alkaline sump to neutralize the remaining chlorine. According to media, about thirty persons complained of eye irritation.
ROOT CAUSE

• 4 Nos filled chlorine tonners were stored since Dec 2008 in the open area. Out of which one toner has leaked
• Valve caps & protection domes were also not provided on these tonners.
• Minor chlorine leakage from the valve of chlorine tonner remained unattended which resulted into a major leak
• Chlorine is a dry gas .On leakage it attracts moisture from the atmosphere and increase the corrosion rate at a very high rate
• Storage in the open makes the accessories weak and further adds up to corrosion

LESSONS LEARNT

• Tonners should be stored under proper shed to protect them from direct sun light & heat.
• Valve caps & protection domes must be provided on the valves of tonners, if they are not being used.
• Regularly chlorine tonners area to be inspected for any chlorine leakage with the help of ammonia torch.
• Even if minor chlorine leakage is noticed, the same must be attended immediately and should not be left unattended.
• Filled Tonners should not be stored for more than 90 days.
• Sufficient nos of necessary PPE’s & tonner emergency handling kit should be readily available at user end.
• Periodic refresher training should be organized for employees handling chlorine tonner.
• Emergency handling procedure should be available at consumer end.

MOST IMPORTANT
Under no circumstance, leaky chlorine tonners should be dumped in alkaline water sump which may cause major mishap.
Tonner keeps floating on the surface of water and chlorine does not neutralize in the solution but spreads in the atmosphere
Chlorine attracts moisture from water and further adds to corrosion
Filler should be informed on first sight of leakage
Even the leaked tonner though empty should be made safe by washing and drying and destroy as per rules

INCIDENT #2
The Incident of bulging of filled chlorine toner occurred but there was no chlorine leakage.
INCIDENT CONTROL
The bulged tonner was immediately depressurized partly by releasing the chlorine to a 200 litre barrel having 5% dilute Caustic lye solution to reduce the pressure & temperature of the tonner and avoid its bursting. Thereafter the tonner was emptied by using the balance chlorine in their process. The emergency could be handled safely & successfully by the chlorine user.
ROOT CAUSE ANALYSIS

• Quantity of liquid chlorine was higher than the desired quantity and moreover the filled tonner was kept in the sun
• The temperature and pressure of the tonner increased due to this.
• The tonner got bulged due to high thermal expansion of liquid chlorine with temperature.

LESSONS LEARNT

• Filling of chlorine toner should be done as per filling ratio-1.19. Water capacityx1.19
• Weight of tonner should be rechechecked after filling
• Filled tonners must be stored in cool and well ventilated place
• Tonner can bulge at 45 degree centigrade with 5%excess filling.it can bulge at any time at room temperature with 10% excess filling

Electrical Safety - part of process safety

Mr Vijayraghavan shared news about an incident in Germany on 4th November when a worker died in an accident during repair work at a petrochemicals hub. The worker died as a result of an electrical shock suffered during repair work on a crane. Investigation is on to determine the cause
Schneider Electric has brought out a very good free safety video on electrical hazards . They mention that “Arc flash accidents that cause serious and sometimes fatal injuries occur five to 10 times every day in the United States. Schneider Electric has produced this electrical safety video as an awareness tool for anyone who faces a risk from electrical accidents that might occur when work is performed on energized electrical equipment. Safety standards are now in place to address the safety of workers who may be exposed to these hazards, as well as to inform employers of their responsibilities to provide employment and a place of employment which are free from recog­nized hazards that are causing or are likely to cause death or serious physical harm to his employees. This video provides information about arc flash, arc blast, shock, and electrocution hazards”.
See the low resolution video in this link
Download the high resolution video from this link and share it with all your colleagues,technicians and operators. It may prevent a fatality.

Domino effects in a disaster

A good example of domino effects of a blast occurred in July 2011 in Cyprus when munitions in a military dump located near to a power generation station blew up. The blast damaged the power station leading to severe power shortages in Cyprus. An article mentions the following:
'Twelve people have been killed and about 30 injured in a blast at a munitions dump in Cyprus. The island's largest power station has been damaged, resulting in widespread power cuts.
The force of the dawn explosions blew out virtually every window in the neighboring village of Zygi and extensively damaged the islands main power station, which remains offline.
Large-scale damage could be seen to a huge section of the barriers of the main Larnaca-Limassol highway and a huge crater about 500 meters from the power station was shown on state TV."
Read the article in this link
See pictures of the blast damage in this link.

Chlorine leak incident

Thanks to Mr Harbhajan Singh Seghal for sending this incident report:

INCIDENT OF CHLORINE LEAKAGE
Two persons were gassed in one of the chlorine consuming industry near Baroda. When the operator disconnected the tonner on the pretext of the hard valve operation of the tonner.
DETAILS OF INCIDENT 

The consumer withdraws liquid chlorine 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 date the operator tried to isolate the tonner at 1.0kg/cm2 pressure when about 40-50 kgs liquid chlorine was there in the tonner and ice formation was there 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 and affected two persons in the surrounding 

ROOT CAUSE OF THE PROBLEM

• 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 as gas by keeping the tonner in line for more time This 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 exhaust of liquid chlorine. 1.0 kg/cm2 pressure can lead to about -20 degree C and takes 8-10 hrs to become completely empty.
• Normally chlorine in the tonner is dry. But under such conditions (-20 degree) the same chlorine become wet. Water in the chlorine separates out and freezes in the sprindle of the chlorine valve. It makes the valve hard to operate at that time.
• After achievement of normal temperature chlorine evaporates first and water later. This chlorinated water reacts with the spindle 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.

ACTION TAKEN

• The tonner brought to the works.
• It was depressurized and valve dismantled.
• Iron chloride rust and greenish color sludge observed in the threading of the valve.
• Damaged valve replaced with new valve.

SUGGESTED ACTION

• The tonners containing some quantity of liquid chlorine are not to be cut off at 1.0kg/cm2 till Chlorine pressure is released to neutralization system through header or evaporator.
• No Cl2 gas from the upper valve of the tonner
• No ice formation appears on tonner or pipe lines after depressurization.
• 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 evaporation 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.

CONCLUSION

• No chance should be taken with liquid chlorine system. Help of the filler 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 not take this type of emergency job.
• Always there should be two persons with safety equipment.

Taking mock drills seriously

Mock drills, if well planned, do deliver inputs where areas for improvements are needed. It is very important to follow up on the results of mock drills and act on them. An off site mock drill conducted in the US demonstrates the seriousness of the effort. In an article about the drill, it mentions that
"The drill, which began just before 9 a.m. Wednesday with the sounding of emergency sirens throughout the county, serves to ensure all emergency agencies in the county are ready in the event of a chemical emergency at the Blue Grass Army Depot, said Justine Barati, congressional liaison with the Joint Munitions Command who also works with CSEPP.A group of 28 evaluators from across the country watched the drill in Madison County, and will report on the strengths and weaknesses of the various agencies’ response, Barati said.Wednesday’s “accident” happened when two people working in the chemical area at the depot fell into some of the chemical. A third person then suffered a heart attack, Barati said. The spill involved an M55 rocket that contained GB nerve agent."
Read the report on the drill in this link.
View a video on another Homeland Security Drill where 300 zombies participated, in this link.

The importance of sight glasses in process safety

IIChE special issue on Process Safety

The Indian Institute of Chemical Engineers is bringing out a special issue on Process Safety and risk management to coincide with the anniversary of Bhopal disaster in December. You can view the call for papers in this link.

Safe distances during a BLEVE

Firefighters have to maintain a safe distance when responding to a possible Boiling Liquid Expanding Vapour Explosion. A video in you tube demonstrates that for a 400 L bullet, the minimum observations distance is at least 90 M. But at this distance, they may still be hit by projectiles. See the video in this link. Worth watching for all emergency response teams. Another information in the video is that for a 400 L bullet, you will need 200 lpm of water to keep it cool, for a 4000 L bullet you will need 700 lpm and for a tanker you will need 2000 lpm of water...

When things go wrong – Parkinsons law in emergencies

A hydrocarbon spill occurred in a plant and caught fire. Sulphuric acid pipelines nearby leaked and were dumping suplhuric acid into the hydrocarbon spill. The sulphuric acid was breaking down the fire fighting foam used by firefighters and delayed the extinguishing of the fire.
In my experience of handling many emergencies, things will go wrong during an emergency. The better prepared you are, the better you are equipped to handle surprises.

Chlorine incidents

An article in the Scientific American highlights the following:
"Over the past 10 years, chlorine has been involved in hundreds of accidents nationwide, injuring thousands of workers and townspeople, and killing some, according to federal databases. It is second only to carbon monoxide when it comes to the percentage of accidents that cause injuries, according to the newest federal data.
 Chlorine is one of the most widely used industrial chemicals in the world today, with 13 million tons produced annually in the United States alone.
In 2009 alone, chlorine was involved in 181 reported accidents with 56 resulting in injuries, based on the latest report from a federal database called Hazardous Substances Emergency Events Surveillance (HSEES). That amounts to 3.8 percent of all the reported chemical emergencies that year. Chlorine had a high percentage with victims, 30.9 percent, second only to carbon monoxide, which had 41.7 percent with victims. Roughly one-third of the states reported, and only for a part of the year, so the real number of accidents and injuries is much higher, experts say
Incidents are rare" in the production of chlorine among Chlorine Institute members, said Frank Reiner, president of the national trade group of 220 manufacturers and distributors. In an e-mail, Reiner said, "the safety performance of the industry has been very good" and his group shares information among members to avoid future problems".Read the article in this link

H2S leak in lubricant plant

A H2S leak has been reported at a lubricant plant in USA. It is reported that a small amount of the gas was released when an additive for oil-based vehicle engine lubricants overheated. Other news reports indicate that a tanker truck overheated and released H2S. I just randomly looked up a MSDS of an automotive lubricant and it does warn about heat as one of the conditions to avoid and also identifies H2S under exposure controls/personal protection.
Read the article in this link. Read another report in this link
Read the MSDS of a automotive lubricant in this link
Read a technical bulletin of an overview of H2S including its hazards in this link.

Explosion protection and instrinsic safety

Pepperl + Fuchs have brought out a simple and effective presentation of explosion protection and intrinsic safety. Their presentation summarizes the following:

• "A hazardous location is an area in which the atmosphere is explosive or anticipated to be explosive
• Intrinsic safety dates back to 1913 following a disastrous mine explosion in England
• The Ignition Triangle consists of three components (fuel, ignition energy and oxidizer) that must be present simultaneously, and in suitable proportions, to cause an explosion.
• Minimum Ignition Energy (MIE) is the ideal ratio of fuel to air where the mixture is most easily ignited
  Any area above or below the Minimum Ignition Energy contains a smaller fraction of air or combustible gas/fuel and cannot be ignited
• Hazardous areas in North America are broken down into three classifications: Class I (flammable gases or liquids), Class II (dust), and Class III (fibers and flyings)
• The classifications are further broken down in Division 1 or Division 2 based on the probability of the materials being present in a potentially hazardous quantity
• The Division Method of North America is comparable to the Three-Zone Model practiced in Europe
• There are three basic methods of explosion protection: containment, segregation, and prevention
• Intrinsic safety is the principle of keeping the electrical energy below the MIE and is the preferred method of explosion protection for low power devices"

Download the complete presentation from this link

Adding chemicals -fast or slow??

An incident occurred in UK in 2007 when an operator was adding a solid chemical to a reactor containing a liquid chemical. When they initially failed to react, he added more of the solid chemical Suddenly an uncontrolled runaway reaction occurred. A report by UK Health and Safety executive mentions the following:
 "None of the workers were in the production hall when the alarms - set off by the incident - began to ring, but one of them returned to investigate. He was driven back by the fumes and fled from the building.
The HSE investigation concluded the company had failed to adequately assess the risks of the chemical reaction and ensure that suitable control measures were in place. It also found the employee had not received adequate training, instruction and supervision on the operating procedures, and did not appreciate the danger of increasing the quantity of the chemical".
Read the full report in this link.

Process Safety - Ensure you use correct materials of construction

An Australian company has been fined for a sulphuric acid valve failure that led to the amputation of a worker's leg.It appears that when employees went to check the cause of of an acid line choke, a valve failed and sprayed them with concentrated sulphuric acid.Investigation determined that the valve that failed was not of correct material of construction and was designed to carry 40% sulphuric acid. This resulted in the failure of the valve. Often material changes go unnoticed till a catastrophe happens. Ensure your management of change process and your inspection procedures are stringent.

Blackberry and Process Safety

The recent disruption is services for people using the Blackberry phone was attributed to the failure of a core switch and failure of its back up. There are lessons in process safety from the blackberry incident! Are your back up systems working properly? Do you check the reliability of your back up devices? Remember, many incidents have occurred because the back up failed when it was needed....
Read the article about the Blackberry failure in this link.

Process Safety - Have you considered Tank Tsunami's?

On April 7th this year, a 30,000 gallon water tank in the US state of Florida failed creating a Tsunami like wave that caused a building to collapse, killing two workers. Read about it in this link.
With storage tanks for petroleum and other chemicals becoming larger and larger, you must have a strong integrity management program to ensure these tanks do not collapse and create a man made Tsunami, with accompanying catastrophic consequences.

Safety features at Kudankulam Nuclear Plant

The Kudankulam nuclear plant has been in the news recently due to the protests by the locals. An article in the Business Standard by the former Chairman and current member of the Atomic energy commission mentions the following additional safety features provided:
"The nuclear power units in Kudankulam belong to the third generation of design evolution; the Fukushima reactors belong to the first generation design. A special feature of the Kudankulam design is the passive cooling system for the nuclear reactor core. The water cooling the reactor transfers its heat to the water in the steam generators. After driving the turbine, steam condenses into water in the condenser and is pumped back to the steam generator. In an abnormal situation, when no power is available to drive these pumps, the hot water in the steam generator flows to an air-cooled heat exchanger located at a height outside the reactor building. Owing to the difference in height, the hot water rises up on its own due to its lower density and cold water flows down to the steam generator. This is called the “thermo siphon effect” and it does not need any pump to move the water. This feature was incorporated in the Kudankulam design at India’s insistence. The Kudankulam reactors are the first to have the passive cooling feature. The Kudankulam design has another important feature” a “core catcher”. In the event of an extreme accident and were the molten nuclear fuel to breach the reactor pressure vessel, it falls on to a matrix containing a large amount of neutron-absorbing substances (such as boron). Once mixed with this material, the nuclear fuel is rendered incapable of starting a nuclear chain reaction. Only the latest design of nuclear power units have this safety back-up system".
Read the complete article in this link.

R & D and Pilot Plant Vs Process Safety

I visit a number of pilot plants that are run by the R & D department of companies. I see a common trend that affects process safety. In many plants, the R &D and pilot plant is being run by competent doctorates in Chemistry. However, designing and operating a pilot plant requires knowledge of chemical engineering principles. The common gap I observe is the lack of application of chemical engineering principles when pilot plants are attached to R & D setups. Ideally the pilot plant must be designed by technical personnel and operated by experienced plant operators, in the presence of R & D personnel. What is occurring in your unit?

Nuclear Safety in India - lessons to learn

The Nuclear Power Corporation of India Limited had conducted an extensive study on the safety of the existing nuclear power generation facilities after the Fukushima disaster. Their recommendations are given as follows:
"The four task forces after evaluating the four different designs of reactors in NPCIL fleet have come out with certain recommendations which are common to all the types of NPCIL reactors. These are:

• Provision of automatic reactor trip on seismic event at all plants except where it is already available (NAPS & KAPS)
• Additional Diesel operated fire tenders and diesel operated pumps to enable water addition at high and low pressures to the different systems based on the need.
• Diesel driven electric generators (air cooled and not requiring external cooling) to cater to power needs.
• Use of nitrogen gas from liquid nitrogen tanks to passively pressurize water tanks and transfer the water to systems at required pressure.
• Provisions to use water from suppression pool except in RAPS-2 
• Qualifying existing water storages/tanks in the plants like deaerator storage tanks, for earthquake resistance
• Conditioning signal override facility for ECCS in PHWRs where it is not available.
• Additional Battery operated devices to monitor important plant parameters
• Providing shore protection structures to withstand tsunami at coastal plants where they are not available
• Review of Emergency Operating Procedures for external events and retraining of operator
• Alternate make up provisions for spent fuel pool during extended station black out
• Feasibility of providing solar powered lighting
• Provision of boreholes at suitable locations to augment water supply.
• Provision of suitably designed flood proof enclosure and doors for important safety related electrical power sources
• Review of containment venting provisions at suitable points to vent the containment structure to stack" 

Read the complete report in this link.
While appreciating the work done by the NPCIL, there are lessons also to learn from them in the field of process safety also.

Four Process Incidents

A spate of process incidents have been reported in the past week.
In Kuwait, in a major refinery 4 Indian contract workers were killed due to exposure to a "gas" during maintenance work in a gas liquefaction unit. Read about it in this link.
A major fire has been reported in Dallas in a chemical mixing plant. The fire apparently overwhelmed the sprinkler system and destroyed a fire truck. Massive explosions are heard in the video. Read about it in this link. See the video in this link.
In India an explosion has taken place in a fireworks manufacturing facility killing two people. A news article in the Times Of India mentions that "This takes the number of deaths in the fireworks industries to 26 this year, making it the highest death toll recorded in recent years. The latest mishap is the fifth major accident in 2011". Read about it in this link.
In a fertilizer plant in USA, while workers were performing hot work on tank containing aqua ammonia an explosion occurred. Be very careful when doing hot work on tanks. They may appear harmless but are very dangerous! See the video in this link.

PSM and Money

I am slightly changing a statement made by the great Mahatma Gandhi (Earth has enough for every man’s  need but not enough for every man’s greed), to suit process safety management – PSM has enough for every man’s need but not for every man’s greed! In PSM’s context, by “greed”, I mean pressure to cut costs and increase profits without looking at the process safety consequences. Time and again, when you look at various incidents that have occurred and continue to occur even today around the World, the finger points towards cost cutting or insufficient budgets implicitly affecting process safety performance. Whatever model of PSM you adopt, “greed” cannot be managed by a system– is has to be managed by a human being and that too the ones at the top.  .They can manage this only by understanding the consequences of their actions. Not understanding the consequence of a decision that involves cost cutting or even by not properly allocating and approving budgets can have serious consequences on any process safety management system. Even though you might have implemented a system that addresses cost cutting etc, such systems have a tendency to get bypassed in times of pressure.This happens even in the "best" of companies. Any solutions???

Cathodic protection and process safety

Any corrosion protection system is an integral part of  maintaining process safety. One of them is cathodic protection. For a plant operator, these systems are seldom seen and operators are often not trained on the importance of these systems. A good interview by the Australian Pipeliner with Mr Mark Drager stresses the following points:
"Typically there are two types of CP systems:
Impressed – This CP system works by applying a small current (typically milliamps per kilometre) to the pipeline via units known as transformer-rectifiers. These units convert AC electricity into DC and use this electricity to lower the ‘energy’ of the pipeline. This system enables an asset owner to protect several kilometres of pipeline, provided the AC power remains connected.
Sacrificial – This CP system essentially performs a similar function via the electrical connection made between the pipeline and the buried anodes, namely zinc or magnesium. This system differs in that the DC electricity generated is due to the galvanic difference between the pipeline and the anodes. This system is also limited in protection range but is relatively maintenance free, however the anodes have a finite life and will need to be replaced.
There are few limitations to the usage of CP, but all can be overcome through careful design, construction and operation:

• Excessive negative potentials;
• May cause pipeline coating disbondment due to the excess hydrogen evolution;
• In some instances hydrogen cracks have also developed within pipelines due to the excess hydrogen evolution;
• Combined with the incorrect coating selected for the operating conditions, it may contribute to the development of stress corrosion cracks;
• Interference (stray currents) from the anode bed can affect neighbouring foreign utilities if the location of the anode bed is too close them; and,
• Disbonded coating or other foreign objects located next to the pipeline can cause a shielding effect. This would mean that the pipeline could not be protected locally at that point of shielding."

Read the full interview with more details in this link.

Fire in refinery

A massive blaze at a Shell refinery in Singapore has been reported.
Read and see videos about it in these links:
Refinery fire 1
Refinery fire video1
Refinery fire video 2
Refinery fire video 3

Diesel tankers accident

The Telegraph reports that "Fifteen tankers loaded with fuel were gutted and more than 10 lakh litres of diesel burnt when a goods train carrying them jumped tracks in Chanabana on the Bihar-Bengal border this morning.The inferno caused the tracks to melt, leading to disruption in train services on the Aluabari-NJP route.The heat from the burning fuel also scorched to death a villager, whose body was found after the flames were doused. Paddy on 500 acres along the tracks have been burnt.

The Northeast Frontier Railway (NFR) said the goods train, with 51 tankers and each of them filled with 70,000 litres of diesel from the Numaligarh Refineries Limited, was on its way to Jamshedpur from Maligaon in Assam. 

Read the report (with photos) in this link.

Molten Aluminium + water = explosion

An interesting theory by a scientist postulates that the twin tower collapse on 9/11 was cause by an aluminium water explosion. The article mentions the following:
"If my theory is correct, tonnes of aluminium ran down through the towers, where the smelt came into contact with a few hundred litres of water," Christian Simensen, a scientist at SINTEF, an independent technology research institute based in Norway, said in a statement released Wednesday.
"From other disasters and experiments carried out by the aluminium industry, we know that reactions of this sort lead to violent explosions." Given the quantities of the molten metal involved, the blasts would have been powerful enough to blow out an entire section of each building, he said.
This, in turn, would lead to the top section of each tower to fall down on the sections below.
The sheer weight of the top floors would be enough to crush the lower part of the building like a house of card, he said."The aluminium industry had reported more than 250 aluminium-water explosions since 1980," he said. Aluminium alloy, which in jet hulls also contains magnesium, melts at 660 degrees Celsius (1,220 degrees Fahrenheit). If heated to 750 C (1382 F), the alloy "becomes as liquid as water," Simensen said. This molten aluminium could then have flowed downward through staircases and gaps in the floor, causing a chemical reaction with water from sprinklers on the levels below.
The mix would immediately boost temperatures by several hundred degrees, releasing combustible hydrogen in the process. Such reactions are even more powerful in the presence of rust or other catalysts, which can boost temperatures to more than 1,500 C (2,700 F)."
Read the complete article in this link.

Chlorine leak incident

Thanks to Mr Harbhajan Singh Seghal for sending this incident: 

Incident:
A company in Gujarat was manufacturing Chlorinated Paraffin Wax by feeding Cl2 from the 900 kgs toner in Heavy Normal Paraffins (HNP). On the day of the incident a contract labourer disconnected the empty tonner and took the fresh 900 kgs tonner in line. Immediately after taking it in line, gas started coming out from the fitting of the copper tube at high pressure. The valve of the header and tonner was attempted to be closed by wearing SCBA. But by the time the gas had already spread. Total of 34 person were affected including 15 person from one village Out of the 15 village persons,5 were minor including a 9 month old child. All the affected persons of area were admitted in hospital. The people were complaining about breathing problem, vomiting, & loose motion but their condition was stable.
Root Cause of the Incident:
· Weak copper tube and its fittings
· Not following the correct procedure of taking the filled tonner in line
· Non availability of Safety equipment near the site and extraordinarily long time for its use.
· Non competent person handling Cl2
· Inadequate facilities for Cl2 handling
· Lack of proper training to the operating persons
Action Required:
· Copper tube and its fitting are not to be kept in the open in the atmosphere. It is to be connected with the tonner immediately
· Copper tube should be 8mm I.D., 12mm O.D. and annealed for stress relief and tested at 19.9 kg/cm2 pressure
· Ammonia torch and safety equipments should be near the installation
· While connecting the tonner, the valve should be crack opened to check for leakage. In case of minor leakage the valve is to be closed immediately
· Provision of high capacity vacuum blower to be available at site. The blower to be started in case of heavy leakage in order to avoids spreading of gas
· The operating persons should be trained to wear the safety equipment particularly SCBA in shortest possible time
· In case of leakage beyond control on site/ off site emergency should be initiated
Conclusion:
· Copper tube and its fittings have limited life. Life varies from plant to plant. The tube needs to be replaced before the established Avg. life.
· Leakage must be checked from the Cl2 tonners at the time of connection/ disconnection with ammonia torch by slightly cracking the valve in case of connection and slightly loosening the connection at the time of disconnection
· Regular drills should be conducted for usage of safety equipment and critical equipment need to be provided and tested at regular intervals.

Process Safety - union's perspective

The steelworkers union of USA has published an article mentioning that Oil refiners fail to learn from past safety incidents and near misses. This was published in 2009. The article mentions the following:
"OSHA is seeing the same problems repeatedly at refineries as it inspects them as part of its national emphasis inspection program. In the first year of the inspection program OSHA issued nearly 350 process safety management (PSM) citations to 14 refiners. The OSHA statement said the agency sent letters to the management of more than 100 oil refineries, providing them with data on compliance issues found under the emphasis program and urging them to comply with the (PSM) standard.
The API and industry are fighting us on the level of transparency and public reporting for process safety performance indicators.The goal of such transparency and public reporting is to allow refiners and petrochemical companies to learn from each other so accidents and catastrophic events are prevented.
This process also makes the companies more accountable to their workers and the communities where their refineries and petrochemical plants are located. It forces them to not just say they are being safety conscious, but to show they’re actually doing something about it".
Read the article in this link
UPDATE: An article published on Sept. 23rd, 2011 mentions the following:
"The lead negotiator for the United Steelworkers said the union representing employees at 69 U.S. oil refineries is prepared to strike if companies don’t agree to stricter safety procedures at plants and pipelines.
The USW, which failed during contract negotiations in 2009 to get companies to agree to have a USW-trained safety specialist at each refinery, will make a similar demand during talks that begin in January for a new three-year pact, Gary Beevers, a USW vice president, said today."
Read the article in this link.

Hydrogen Sulphide leak kills 4

In a leak at a chemical manufacturing facility in Thane, a leak of hydrogen sulphide gas has reportedly killed 4 people. Read about the incident in this link.
In a publication made in 1996, the Oil, Chemical and Atomic Workers International Union has made a simple yet effective safety bulletin on the dangers of H2S. They also list some incidents. Read it in this link.
I have investigated fatalities involving H2S, some of them involving release of H2S when an open vessel containing sludge was moved. The trapped H2S gas under the sludge was released and killed two people. Do not take it for granted.

Explosion in Chemical Factory

A news report mentions that fire and explosions in a chemical factory in Canberra made residents think that the place was being bombed! It appears that the fire and explosion was caused by transformer oil. See the news report and video in this link.

Process safety and Maintenance spends

Penny wise pound foolish. If you do not maintain your assets well, you will end up paying more in the long run. Maintaining your assets not only improves process safety, it improves reliability and morale of the plant and maintenance personnel.In these days of cost cutting and lack of competency in companies, many plant managers turn a blind eye to the deteriorating assets. This also brings me to another question - how much can you flog your equipment? By debottlenecking efforts, you may increase your capacity by 30% but have you studied the effect of running on high load on the remaining plant equipment?
Read an article by  Jim McCarty on "spend now, save later" in this link. It applies to chemical plants also.

Process safety and technology

I have always strongly felt that technology alone cannot solve your process safety problems, its your approach towards your people and your plant that will keep you safe.
An article in the Moscow Times mentions "The United States suffered only 20 aviation fatalities in 2010, according to the Aviation Safety Database. Russia suffered 110 fatalities in the same year, the bulk of which were accounted for by the Polish Tupolev-154 that crashed in foggy conditions near Smolensk in April.
While declining to comment on the situation in Russia, one U.S. aviation professional concurred that "technology does not equal safety."
"The U.S. is lagging in air traffic control — we're using 1950s equipment and ground-based radar that means we have to fly these circuitous, occasionally inefficient routes — but it is safe," said Charles Duncan, United Airlines vice president for transatlantic, Middle East and India sales, in an interview with The Moscow Times.

 "If fewer airlines meant safer skies, the world would be a much simpler place than it is," Oleg Smirnov, chairman of the Federal Transport Agency's commission on civil aviation, said in reference to government plans to slash some of Russia's hundred-plus airlines.The real problem is a misguided, laissez-faire policy of registration and approval that allows "almost anyone" to set up an airline extremely easily, Smirnov said. He also blamed a culture that promotes profits over professionalism and a blurred hierarchy of responsibility that allows companies to pressure pilots not to abort flights."

Doesn't the above sound familiar in our Chemical Industry, too? Putting profits over people and plant will not help you even if you have the latest technology. Read the full news article in this link. 

Refinery cited for PSM violations

A news item mentions that a refinery has been cited in the US for PSM violations. Included in the serious violations are "failing to investigate incidents as being related to process safety management, equipment repair, address inconsistent thickness measurements collected during pressure vessel inspections, maintain accurate and updated engineering drawings, and ensure that written operating procedures were certified as being current and accurate".
Read the article in this link

Dust explosions - Ignorance is Deadly!

A dust explosion can be deadly. The sugar dust explosion at Imperial Sugar Industries, Port Wentworth, Georgia, USA in 2008 killed 11 people and injured 42 workers, some of them critically. Dust explosions have known to occur as far back as the 18^th century when a baker reported an explosion in a flour warehouse. Most organic materials and many metals will burn or explode if they are finely divided and dispersed in air and contact an ignition source. Dust explosions have occurred in a many industries including flour, coal, aluminum, plastic, vitamins, pharmaceutical compounds, sugar, tea, corn starch etc.A normal fire triangle consists of fuel, oxygen and ignition source. However for a dust explosion to occur, two additional elements are required – dispersion of the combustible dust in air in a concentration sufficient to ignite and confinement.Hence for a dust explosion to occur, the following are needed:

1. Fuel

2. Air (oxygen)

3. Ignition source

4. Dispersion of combustible dust

5. Confinement (The confinement causes and explosion to occur)

The above 5 elements needed for a dust explosion to occur are called a dust explosion pentagon.

The damage from a dust explosion is catastrophic because the primary dust explosion causes the loose dust present in beams and on top of other equipment to shake loose and fall down. This causes a secondary explosion which is far more deadly than the first one. Thus the domino effect of the primary dust explosion can be carried forward through elevators, conveyors and silos. The result is a catastrophic explosion. NFPA 654 states that dust layers 1/32 inch thick can create hazardous conditions.

The Material Safety Data Sheets for many substances do not indicate the potential for dust explosions. Many organisations implement changes that inadvertently create an atmosphere for a dust explosion. Enclosing an open conveyor is one such change. The Chemical Safety Board of the USA has recorded 197 incidents involving dust explosions since 1980, with 109 fatalities and 592 injuries.

Preventing dust explosions:

To prevent a dust explosion, it is necessary to eliminate the fuel (combustible dust), oxygen or ignition source.

While complete elimination of the fuel (combustible dust) may not be possible, it is possible to eliminate the chance of a secondary explosion by proper training and housekeeping. Dust collectors must be maintained properly to avoid a drop in their collection efficiency. Another method is to add an inert material like rock dust into the combustible dust.

Complete removal of oxygen is also not possible in a system comprising of conveyors, elevators, bins and silos. Inerting (use of an inert gas) also brings along safety issues of asphyxiation of personnel.

Eliminating all sources of ignition may also not be possible. Normal sources of ignition include the following:

•   Hot bearings and surfaces
•   Static electricity
•   Hot work (welding, cutting, brazing or spark producing activity)
•   Electrical system including faulty equipment

Mitigating dust explosions:

Effective mitigation requires properly designed engineering solutions. These solutions include explosion venting, explosion suppression and explosion isolation.

Explosion Venting

Explosion vents are designed to direct the gases from a dust explosion to a safe location and prevent over pressurization and damaging the equipment. The location of the vent should be placed in such a way as not to harm personnel.

Explosion Suppression

An explosion suppression system consists of a pressure or temperature sensor that detects the start of a dust explosion and a chemical suppression or inerting system that is automatically activated when the start of an explosion is detected. The chemical suppression or inerting system cools or extinguishes the flame front before it can cause damage.

Explosion Isolation

The explosion isolation systems work on the principle of detecting a dust explosion early and isolating long sections of pipelines leading to the protected equipment. A fast acting valve is used to isolate the protected equipment. The explosion venting systems are not suitable for dusts that burn quickly as the flame front speed will be high in such cases.