Importance of Facility Siting

Is the control room in your facility located close to the tank farm? Is any occupied or functionally significant buildings close to a Maximum Credible Loss Scenario? Is your cylinder storage shed close to the drum filling area?

If you have wondered about this ever, then you should read this article to understand Facility Siting. Some incidents from the past have cleared the importance of facility siting in a plant.

The Flixborough explosion in 1974, where cyclohexane explosion shattered control room windows, collapsed its roof and demolished the brick-constructed main office block. Twenty­ eight people died, and thirty-six were injured in this accident out of which Eighteen of the fatalities were in the control room. Fortunately, over 200 fatalities were averted as the incident took place on Saturday when the main office block was unoccupied.

The Phillips disaster of 1989, where 40000 kg (85000 lbs) of a mixture of ethylene, isobutane, hexene and hydrogen was released and exploded. The second explosion involved BLEVEs of two isobutene storage tanks and the third explosion was the catastrophic failure of the ethylene plant reactor. The explosions killed 23 employees and injured 314.

Operator Earthing - Are you doing it correctly?

Thank you guys for such an awesome response to my last blog post on Partial Inerting. It was made clear from the responses, that it is rather an unexplored topic in many parts of the world. Keep sharing your thoughts and keep sharing the blog with your colleagues, friends and students.

For today's blog post, I am picking up a basic concept of OPERATOR GROUNDING and what is the correct way to actually do it. There are many industries who provide Safety Shoes (maybe antistatic/ static dissipative) to their employees working on the shop floor, however, a substantial misconception regarding grounding practices exist in the industries that "If I have provided my operator dissipative shoes he has been grounded adequately." Also, there are many who purchase shoes with higher resistance to the ground then what is recommended by the standards.

Dust Explosion - Which Powder should be tested? Can I use the properties from internet for my powder?

"Nothing has happened in my facility and it has been running for 20 years"; "My powder cannot explode, we use this at home commonly"; "Are you still wondering if you have combustible dust?" Just because nothing has happened yet doesn't mean it's not about to.

This week I received an interesting query about which powder should be tested. Interestingly, there was an additional statement attached to the question, "I have searched over the Internet and have found my powder explosive properties. Can I use these properties for my site assessment?"

Some of the powders which can explode include food materials (including sugar, spice, starch, flour, etc.), plastics, wood, paper, rubber, pesticides, pharmaceuticals, chemicals, coal, metals, etc.

According to OSHA, "any combustible material can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosible. Even materials that do not burn in larger pieces, given the proper conditions, can be explosible in dust form."

For liquids and gases, flammability data are well understood & usually established and available at least under atmospheric pressure and normal temperature conditions. However, for powders/ dusts is not available and is dependent on multiple parameters such as particle size, moisture content and also on particle shape/ morphology.

Usually, the properties which shall be tested for each of the unit operations differ depending on their requirement for that unit operation. We will pick this topic in our next blog.

Now let us look at each of these parameters:

• Particle Size: It has to be noted that explosion properties of a powder usually worsen with decrease in particle size. This means that finer the particle size easier it will be to burn and consequences can be worse as well. Powder used in industries is a distribution of smaller and larger particles. Whenever it disperses, the larger particles will fall to the ground because of more weight, however, the fines will remain suspended in the air forming a dust cloud. As per IEC standards, a particle size of less than 63 microns is used for conducting various tests. As per standard thumb rule, a particle size of more than 500 microns is not considered to be capable of propagating dust explosion.

• Moisture Content: First and foremost impact of using water is that it suppresses the dust cloud formation. Also, increased moisture content act as an inert and makes the ignition of powder more difficult and also impacts explosive properties of a powder. As per IEC standards, the powder is dried to moisture content of less than 10% before testing.

• Particle Shape and Morphology: Even with a change in particle shape and morphology from crystalline to amorphous, the material properties change significantly.

Hence the answer to the question is, one should test the finest and driest sample being handled on their site. Don’t depend on the Internet properties as one doesn't know what condition it has been tested for, what was the particle shape, size, etc.

Also, it is imperative to test the powder if a vendor is changed or if the manufacturing process is modified or if physical characteristics of the final material change or if any material has a combination of various particle sizes.

This will give you worst possible characteristics of the powder based on which assessment should be carried out and measures should be provided.

Do not forget to like and share with your team & friends. You can always drop an email on himanshuchichra@gmail.com regarding your query or a future blog post.

Are there two types of Minimum Ignition Energy (MIE) for powders?

Here we go. The first blog; let’s begin the blogging and sharing together.

Yes, there are two types of MIE, where one type is carried out without inductance and the other is carried out with inductance.

Minimum Ignition Energy is the minimum energy that is required for ignition of fuel. In other words, the minimum energy an ignition source must provide to the fire triangle for the fuel to burn in presence of an oxidant.
The test to establish MIE is carried out in an apparatus called MIKE3 (refer image below). It is performed using ASTM E2019, “Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air” or EN13821 “Potentially explosive atmospheres — Explosion prevention and protection — Determination of minimum ignition energy of dust/air mixtures”

MIE (Without inductance) corresponds to the energy required by electrostatic discharge to ignite a dispersed cloud. The circuit of MIKE3 for this test is purely capacitative and the spark energy can be related straight to 1/2*C*V^2 based on the capacitance selected.

MIE (With inductance) simulates the longer duration discharges from electronic circuitry that can occur from machines or control equipment (essentially a spark from short in a wire or electronic equipment) or mechanical sparks, by adding an inductance in the existing circuit.

Now one thing to remember is that MIE (With Inductance) is more conservative as compared to MIE (Without inductance). 

Next question that comes is which one to choose?

And we are Live!!!!

Do you feel trouble understanding Process Safety Concepts? Do you feel that there is no place where someone in Process Safety business is not giving you any information for free? Have you ever felt sitting in a process safety seminar that why the author is not explaining the basic, before going into the detailed concept? Well if that's the case, this is the perfect portal for us to discuss. No one is judging you here for your lack of knowledge or for asking what you considered as a "DUMB" question or a basic concept.

I am a Chemical Engineer by qualification and Process Safety & Risk Consultant by profession catering to various sectors primarily Pharmaceuticals, FMCG, Metal, Chemicals, Plastic & Polymer, Wood & Paper and Oil & Gas. I do perform training, seminars, and webinars with the help of my present employer on different process safety aspects such as Electrostatic Hazards and controls, Dust Explosion protection and prevention, Hazardous Area Classification, Quantitative Risk Assessment, SIL & LOPA, HAZOP, Process Safety Testing for Powders, etc.

I have started this blog to share some of the insights of Process Safety and also to provide solutions to various general queries that we receive on day to day basis. Will also like to share my personal experiences while working on site and some views related to incidents happening around the globe.

Would love, if all the avid readers can share their thoughts and their queries related to process safety here or on my email; so I can continue to upkeep the content on this blog.