Dust explosions: little known hazards

Hazards of dust and consequences arising out of dust explosions are still little understood by manufacturing facilities that handle dust of variety of materials, let it be, sugar, plastic, floor (wheat/maize/corn/...), metals (iron, zirconium, thorium,uranium, titanium,...), etc. Otherwise, there would have not been so many incidents every year leading to injuries and deaths of so many.
Proper measures like closed ventilation, maintaining humidity, earthing and bonding, flameproof electrical fittings, static discharge stations, cotton uniforms, periodical cleaning,etc will prevent dust explosions and its consequences.
Proper collection and disposal of dust needs to be given due attention.
An article in the following link is good reading material. There are few reports and video in www.csb.gov on the same subject.
http://www.iwatchnews.org/2012/05/29/8957/unchecked-dust-explosions-kill-injure-hundreds-workers?utm_source=iwatchnews&utm_medium=web&utm_campaign=rss

Hydrogen balloon fireball injures 140 in Armenia

Balloon fireball injures 140 in Armenia: More than 140 people have been injured after gas-filled balloons exploded at a concert in the Armenian capital ahead of parliamentary polls, officials say.
"The balloons exploded and caught fire after people holding the bunches released them from their hands into the air," a witness told AFP.
From the witness statement, it can be said that the friction between balloons in the bunch while going up could have caused this. As hydrogen can easily diffuse through rubber, it could have caught fire from the friction as the ignition energy for hydrogen is as low as 0.0017 mJ and this could have resulted in bursting of balloons and fireball. One may recall the famous Hindenburg disaster in 1937. Only the quantity of flammable substance differs but reason can be same, that of static charge generated due to friction.
Such incidents were also reported at several places. In an incident, the hydrogen balloons burst in the hands of children who suffered burn injuries.

LINK

Static electricity experience

Yesterday, I was talking to my colleague sitting in a plastic chair. When he got up to go out, his fingers touched my shoulder and I felt needle like pricking. He also felt sudden shock and could hear some sound. We thought this may be due to static charge on the body as he was sitting on a plastic chair and during movement, and may be because of synthetic dress, some charge accumulated on the body discharged in the form of sparkling sound.
Few times, I feel pain at the edges of the fingers when I touch clothes in the spinner of the washing machine. Reason may be same, due to charge accumulated during the spinning action.

Static charge ?

Yesterday, I was using washing machine. It is a semi automatic type, i.e it contains two separate drums one for washing and another for spinning (drying). After washing, when I started taking out the clothes, I felt slight pain at the edges of my hand fingers. Earlier also I experienced the same, but I assumed it as pain from nails. I think this tingling pain is because of static charge generated during rotation of the washing drum. This charge may be dissipated if I do not touch the machine for few minutes after stopping it.


LINK

Static Electricity - my experiences

I am into the field of industrial safety for the last 10 1/2 years. Before that, I was involved in process equipment design. When, I joined safety department, I started reading about various topics in safety and one such topic is static electricity. For first few years, I had only book knowledge and no experience of what it is.

What already read in books is that static charge will be generated, when we

- comb our hair
- wear synthetic dress
- walk on wool carpets, etc

Following are my practical experiences

- when I approached TV, the hair on the forearm attracted to the picture tube
- After travelling, to get down, I tried to open the vehicle door by lifting the knob on door outside and I received shock
- my friend took out pen drive from his shirt pocket and when he inserted in the USB port, cracking sound came
- when I touched the monitor of desktop computer, I heard noise


- one night, I got up and went to bathroom for pressure relief. I saw some flash from my dhoti ( a cloth worn around instead of knickers / shorts ). I thought it is light reflection because of someone outside my apartment switched ON the light in his house or some vehicle light from ground floor. I had some fear also thinking it as some ghost, as a person died in the house above my house in the apartment block (though I don't believe, but a serious discussion on the issue before sleep with my family members and my denial of existence of ghosts made me to think that something of such sort is there). Then, next day while thinking about the flash in my dhothi, suddenly it occurred to me that my dhothi is synthetic and as it is in two layers, friction between layers might have caused charge accumulation and discharge in the form of flash. After reaching home from office, I waited for night and then closed window and door of my room, covered the window with thick curtain and blanket. Then, I took the same dhothi and rubbed fast and saw flashes generated. Then, I repeated the same and showed to my wife and children. The flashes were light green in colour. I don't know the reason for the colour of the flash, which I has to explore or search.

The last one narrated above is the one which I want to share with all and the lesson is that we should not wear synthetic dress when we work on or near flammable solvents / pyrophoric materials. The practical application of this information is that we should not wear synthetic dress when we go for petrol / gas filling. As we travel for sometime before we reach the pump, charge would have accumulated on the synthetic dress and it is likely that the discharge in the form of spark can initiate fire in the petrol pump station.