Proposed changes after oil rig accident

The Coast Guard issued a Federal Register Notice of recommended interim voluntary guidelines concerning mobile offshore drilling units, or MODUs, and manned fixed and floating offshore facilities engaged in activities on the U.S. Outer Continental Shelf. This is part of the Coast Guard’s continuing response to the explosion, fire and sinking of the MODU DEEPWATER HORIZON in the Gulf of Mexico on April 20, 2010.

- See more at: http://mariners.coastguard.dodlive.mil/2014/05/02/522014-federal-register-notice-of-outer-continental-shelf-units-fire-and-explosion-analyses/#sthash.zFvYwSqf.dpuf

The Report highlighted the following considerations as areas not specifically addressed by current regulations:
Minimum values are needed for explosion design loads for use in calculating the required blast resistance of structures;
Explosion risk analysis of the design and layout of each facility should be performed to identify high risk situations;
H-60 rated fire boundaries between the drilling area and adjacent accommodation spaces and spaces housing vital safety equipment may be necessary dependent on the arrangement of the facility;
Uniform guidelines for performing engineering evaluations to ensure adequate protection of bulkheads and decks separating hazardous areas from adjacent structures and escape routes for likely drill floor fire scenarios are necessary;
Performance-based fire risk analysis should be used to supplement the prescriptive requirements in the MODU Code; such analysis should use defined heat flux loads to calculate necessary levels of protection for structures, equipment, and vital systems that could be affected by fires on the drill floor;
Maximum allowable radiant heat exposure limits for personnel at the muster stations and lifesaving appliance launching stations in anticipated evacuation scenarios should be implemented.

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Dangers of oxidising chemicals

Oxidizing chemicals give off oxygen or other oxidizing substances and also include materials that react chemically to oxidize combustible materials. Oxidizing chemicals can be severe fire and explosion hazards. Read a good description in this link. 

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Hazards of Gas build up in drums

Many times, drums or barrels are used for storage of chemicals. Be careful about drums. They are potential time bombs if not handled and stored properly. In many places I audit, I see that drums are taken for granted. A safety bulletin mentions the hazards of storing chemicals in drums. The hazards include chemical reactions, decomposition, change in altitude or temperature, exposure of drums to heat. Read the safety bulletin in this link.

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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.

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.

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.

Boiler explosion in Gujarat

"The Hindu" newspaper has reported a boiler explosion in a diary in Gujarat that has killed 7 and injured 21 others. Apparently a leaking gas pipeline was being repaired when the explosion occurred. In many companies, I have observed hot work allowed in many gas fired utility boilers and incinerators after the operators have just isolated the natural gas supply but not blinding it. In one case, the operators had isolated the natural gas to the burner of a utility boiler and removed the burner. Their argument was that they have disconnected the burner and hence no gas could get into the boiler. However, the open gas pipe (after the burner was removed) was pointing towards the boiler and when we tested the area around the pipe with a flammable gas detector, it was in flammable range. Do not depend on isolation valves alone to stop the gas from leaking through.
Read about the boiler explosion in this link.

Hydrogen peroxide accident kills two

Thanks to Abhay Gujar for sending information about an accident in a chemical unit in Hyderabad tht has killed two women. As per the Times of India article, "The incident took place at 11.30am when the two workers were mixing hydrogen peroxide, methyl ethyl ketone and sodium sulphate to produce a chemical substance used in the manufacturing of asbestos sheet moulds and coolants. The high intensity of the explosion damaged a portion of the chemical unit's roof and severely injured both Venkata Lakshmi and Kalpana". Read the article in this link.

The MSDS of hydrogen peroxide warns of the following:
"Soluble fuels (acetone, ethanol, glycerol) will detonate on a mixture with peroxide over 30% concentration, the violence increasing with concentration. Explosive with acetic acid, acetic anhydride, acetone, alcohols, carboxylic acids, nitrogen containing bases, As2S3, Cl2 + KOH, FeS, FeSO4 + 2 methylpryidine + H2SO4, nitric acid, potassium permanganate, P2O5, H2Se, Alcohols + H2SO4, Alcohols + tin chloride, Antimoy trisulfide, chlorosulfonic acid, Aromatic hydrocarbons + trifluoroacetic acid, Azeliac acid + sulfuric acid (above 45 C), Benzenesulfonic anhydride, tert-butanol + sulfuric acid, Hydrazine, Sulfuric acid, Sodium iodate, Tetrahydrothiophene, Thiodiglycol, Mercurous oxide, mercuric oxide, Lead dioxide,
Lead oxide, Manganese dioxide, Lead sulfide, Gallium + HCl, Ketenes + nitric acid, Iron (II) sulfate + 2-methylpyridine + sulfuric acid, Iron (II) sulfate + nitric acid, + sodium carboxymethylcellulose (when evaporated), Vinyl acetate, trioxane, water + oxygenated compounds (eg: acetaldehyde, acetic acid, acetone, ethanol, formaldehyde, formic acid, methanol, 2-propanol, propionaldehyde), organic compounds. Beware: Many mixtures of hydrogen peroxide and organic materials may not explode upon contact. However, the resulting combination is detonatable either upon catching fire or by impact.
EXPLOSION HAZARD: SEVERE, WHEN HIGHLY CONCENTRATED OR PURE H2O2 IS EXPOSED TO HEAT, MECHANICAL IMPACT, OR CAUSED TO DECOMPOSE CATALYTICALLY BY METALS & THEIR SALTS, DUSTS & ALKALIES. ANOTHER SOURCE OF HYDROGEN PEROXIDE EXPLOSIONS IS FROM SEALING THE MATERIAL IN STRONG CONTAINERS.UNDER SUCH CONDITIONS EVEN GRADUAL DECOMPOSITION OF HYDROGEN PEROXIDE TO WATER + 1/2 OXYGEN CAN CAUSE LARGE PRESSURES TO BUILD UP IN THE CONTAINERS WHICH MAY BURST EXPLOSIVELY."

Static electricity and CO2 extinguishers

Thanks to Mr Harbhajan Singh Seghal for sending this incident:
"During the plant round of Shift Incharge at Compressor House, it was observed that there is smoke and spark on Non-Drive side bearing of Cooling Tower No.1 – Pump No.D. Immediately this pump was stopped. After stopping the pump fire took place at that place which was extinguished by CO2 Fire Extinguisher. While carbon dioxide cylinder was opened for extinguishing the fire, it was observed that there was continuous spark from the surface of the horn (Outlet Black Nozzle) of the Carbon Dioxide Cylinder. This was informed to Fire Section. As per Fire Section, this is due to static current".

A safety bulletin prepared by the safety advisory group mentions the following:
"The Safety Advisory Group, SAG, has been informed of several fatal accidents caused by explosions which occurred while using CO2 during inerting equipment and storage tanks that had previously contained flammable materials. In most cases the flammable
materials were liquids or gases but dust explosions may also be triggered by the same cause.
Examples of fatalities:
• Two navy firemen were killed in an explosion while attempting to inert an 18,9 m3 Jet Fuel tank by use of portable CO2 fire extinguisher.
• Four persons were killed in an explosion on board the tanker Alva Cape while inerting naphtha tanks using CO2 cylinders.
• Twenty nine persons were killed in an explosion while witnessing the demonstration of a newly installed CO2 fire-extinguishing system for a partially filled 5000 m3 jet fuel tank, in Bitburg, Germany.
Subsequent investigations have shown that, during the inerting process, static charges of several tens of kV were generated and accumulated at the end of the piping connected to the tank. Voltage of this nature is sufficient to produce sparks which act as points of ignition for the flammable mixtures. When liquid CO2 expands up to absolute pressures of less than approximately 5 bars, the result is the formation of small particles of solid CO2 (dry ice). As the two-phase solid/gas flows through the piping, static charges are produced by the particles rubbing against other particles, between themselves, piping and equipment. Subsequently, these charges accumulate in the zones that are not earthed/grounded at the end of the pipelines, most often in valves and nozzles. The sizes of these fields, as determined by experiments, can reach values of between 50 and 180 kV/m. Similarly, static electricity can be generated by the dry ice particles after they leave the discharge nozzle.
The pressure and impurities in the CO2, equipment materials in transfer line hoses, etc. all influence the generation of static electricity".
Read the safety bulletin in this link.

Magnesium dust explosion?

An I pad manufacturing facility in China has experienced a possible magnesium dust explosion injuring 16 workers. The incident is being investigated. The news article mentions the following:
"Currently, little is known about the cause of the explosion. However, reports by the local Chinese media have stated that the explosion was caused by the ignition of magnesium dust. Magnesium is a highly flammable metal that is commonly used in industrial polishing processes. As reported by CNET, magnesium is also used in the manufacture of fireworks and flares. Faulty or deficient ventilation systems at the Chengdu plant may have allowed magnesium dust to accumulate in the atmosphere. If that was the case, even a small spark would have been enough to trigger an explosion". Read the news article in this link

Combustible dust hazards - the explosions continue

The CSB has concluded that combustible iron dust has caused and explosion that killed one worker. The CSB mention the following:
"The first incident occurred on January 31 as two maintenance mechanics on the overnight shift inspected a bucket elevator that had been reported to be malfunctioning due to a misaligned belt. The bucket elevator, located downstream of an annealing furnace, conveyed fine iron powder to storage bins. The two mechanics were standing alone on an elevated platform near the top of the bucket elevator, which had been shut down and was out of service until maintenance personnel could inspect it. When the bucket elevator was restarted the movement immediately lofted combustible iron dust into the air. The dust ignited and the flames engulfed the workers causing their injuries. A dust collector associated with the elevator was reported to have been out of service for the two days leading to the incident.
The second incident occurred less than two months later on March 29 when a plant engineer, who was replacing igniters on a furnace, was engulfed in combustible dust which ignited. In the course of the furnace work, he inadvertently dislodged iron dust which had accumulated on elevated surfaces near the furnace. He experienced serious burns and bruises as a result of this second event; a contractor witnessed the fireball but escaped without injury."
Read the news release in this link.

Read these process incidents

The department of occupational safety and health, Malaysia has these process incidents put up on their website. Follow the links to learn useful lessons:
1. Combustible dust explosion in motorcycle rim manufacturing facility
2. Fire and explosion in LPG facility
3. Fire and explosion in LPG storage
4. Fire and explosion in biotechnology factory (static electricity)
5. Fire in bulk petroleum storage tanks
6. Fire and storage in LPG storage facility
7. Combustible dust explosion

Recipe for a dust explosion

I chanced upon a newsletter by Fike Corporation written in 1997. This was way before the Imperial sugar dust explosion incident in 2008. Its a pity that though the potential for dust explosions are known for a very long time (more than 50 years), still these explosion continue to occur. Salient points form the article are quoted below:
"Combine complacency with lack of housekeeping and you have the perfect recipe for a dust explosion.
At too many facilities, the ingredients are already there. All you need is a building with layers of combustible dust, like corn starch. Add unvented equipment that draws in suspended dust. Let a few airborne particles stray and find a spark. The first explosion will rupture the equipment, tossing the building dust into the air. The second will probably collapse the walls. And, if by chance you attached a sprinkler riser to one of the load bearing walls, forget your sprinkler protection. It’s gone. A suspended, combustible dust cloud burns much more violently than a pile of sawdust. When suspended dust particles are completely surrounded by oxygen, they rapidly release a tremendous amount of energy. The pressure wave produced by the initial exploding dust cloud shakes and suspends more dust from other surfaces to fuel a chain reaction of violent explosions. Usually, the second or third explosion is worse than the first.Industries producing dust as a product, such as some pharmaceutical industries, tend to be more aware of the hazards than industries that produce dust as a by-product. Unfortunately, it’s very easy for personnel to overlook the fallout from operations, such as grain handling or furniture making. Then an explosion hits, endangering the facility and equipment as well as the employees".

Read the newsletter in this link.

Static charge + Flammable dust = EXPLOSION

A news article mentions that OSHA is investigating an explosion that occurred on Thursday morning,caused by static charge and flammable dust at a facility in the US.

"Six employees were working, but none were near the eruption, said Trumbauersville Fire Chief Josh Mallery.“They were very lucky,” said Mallery, whose company led the blaze battling effort. The explosion blew an interior wall eight inches back off the foundation and sparked spot fires in the walls, said Rafferty. A corrugated roll up door was blown out, its bottom half ripped off and flung about 30 feet. A portion of the plant’s exterior wall bellied out, and a heap of cinderblocks from the structure tumbled on the ground outside the plant.“It was amazing. I’ve been a firefighter for 15 years and I’ve never seen anything like it,” said Mallery.

Fearing more explosions, firefighters first directed their hoses at about 1,200 pounds of Polyclar10, the powdered substance that was at the root of the explosion. In a wetted, condensed form, the powder does not pose the explosive threat it does when airborne as fine, particulate dust, said Mallery.

Firefighters then concentrated on extinguishing the flames. “It was about 2 ½ hours before we had the situation stabilized,” said Mallery.The explosion happened while the Polycar10 was being packaged. The packaging equipment was grounded to prevent static charges that could combust the compound, but a bag the powder was being deposited into was not grounded, said Rafferty. As the powder moved across the plastic interior of the bag, a static charge was generated, providing the heat source that ignited the powder, which is used to clarify beer before bottling, the fire marshal said".

Read the full article in this link

Dust explosions

After the Imperial sugar dust explosion incident, a lot of awareness has been created regarding dust explosions, even though it was well known even prior to the incident that dust explosions are very dangerous. An article mentions the following to reduce the chances of dust explosion:
"1.Properly assess your dust's fire and explosion characteristics so adequate measures can be taken for the prevention and mitigation of hazards in your own facilities and, if you are shipping the dust to some other facilities, at those locations.
2. Understand your own powder handling and processing operations. You should be able to identify likely ignition sources during both normal and abnormal operating conditions. Also pinpoint location(s) where combustible dust clouds could exist during normal and abnormal operating conditions.
3. Take effective measures to avoid or control ignition sources and formation of combustible dust clouds. Also consider explosion protection (such as venting and suppression) and isolation to lower the risk to a tolerable level.
4. Maintain dust explosion prevention and mitigation measures".
Read the full article in this link.
Another article about the ongoing investigation on the explosion in the AL solutions plant in by the CSB mentions that the CSB is also looking at the possibility of explosion of zirconium dust......read the article in this link.

Detecting the spark that causes fires and explosions

An article mentions that German scientists developed a new method to prevent explosions due to electrical sparks.
"In most cases, a spectacular accident must first occur in order to make the public aware of a problem that lurks continually in many areas of industry: the danger of explosions due to electrical sparks. The simplest method to prevent such explosions is called "Intrinsic Safety". The intention thereby is to prevent ignitable sparks from even being created. Up to now, this has only been possible with small devices having a power of up to approx. 2 Watts - thus, above all, in process measuring and control technique.
A new concept that has been developed at the Physikalisch-Technische Bundesanstalt (PTB) in cooperation with industrial partners, increases this limit now up to 50 Watts and thus makes application possible in many more technical fields. The technology which is already being marketed under the name "Power-i"/DART and which is to be launched as an international IEC standard, promises the industry great cost savings".
"For a long time now, end users and manufacturers have wanted a considerably higher active power while at the same time keeping all the positive characteristics of Intrinsic Safety. And this is exactly what the new "Power-i"/DART technology offers. DART here stands for "Dynamic Arc Recognition and Termination".
"Power-i is different from previous concepts", states Udo Gerlach, the project leader at PTB. "The principle of an emergency shutdown is just as simple as it is effective." The safety-related validated, intelligent monitoring system recognizes a spark already while it is forming and then shuts down the system in a controlled and quick manner, before the spark can even become ignitable. "Thus, complex, expensive constructural safety measures can now be replaced with the new technology".
Read the full article in this link.

Dust explosions and vacuum cleaners

The CSB has been doing a great service by increasing awareness about dust explosions. Dust explosions can occur in sugar, sawdust, coal, and in fact anything that is combustible including combustible metals. Housekeeping plays a very important part in eliminating dust in the work area. Industrial vacuum cleaners are available to do the job safely. One such cleaner is given in this youtube link. I am not endorsing their product but I thought that the video was a good one!

Domino effect and Process Safety

An interesting article on Domino Effects in the developed countries mentions the following "A study of 261 accidents involving domino effect has been carried out. The main features have been analyzed: origin, causes, consequences and most frequent sequences. The analysis has shown that the most frequent causes are external events (31%) and mechanical failure (30%). The storage areas (37%) and process plants (27%) are by far the most common places where domino accidents have occurred. The most common sequence in the event trees resulted to be explosion–fire (21%), followed by release– fire–explosion (15%) and fire–explosion (14%)".
While the study concludes that "The historical analysis has shown that the frequency of domino effect accidents has decreased over the last two decades. Most of these accidents have occurred –as could be expected– in the most industrialized countries (from which, furthermore, more information is available). The most frequent sequences are explosion–fire, release–fire– explosion and fire–explosion. From the analysis of the causes, although the most frequent ones are external events and mechanical failure, a relatively high frequency is found for human error. This would indicate the need to further promote the training of employees, as well as an additional improvement of safety measures, specially in storage areas".

As more and more chemical industries are coming up in India, it becomes very important to study facility siting issues.Incidents like the Jaipur fire clearly indicate the need for a stronger implementation of facility siting rules.
Read the whole article in this link.