Safe Practices for Sulphur Handling

Thanks for overwhelming responses on the recent blog post on Housekeeping and Secondary Dust Explosion & Relief Device Sizing.

I have recently published one of my articles in an Indian Magazine called "Chemical Weekly" in 10th July Edition. Attached below is a copy of the article.

Safe Practices for Sulphur Handling

The purpose of this document is to enable companies to establish reasonable prevention and protection measures, to eliminate or reduce the risks of fire and explosion inherent to handling of sulphur. This document is primarily concerned with the hazards arising from processing of solid sulphur, but also considers the major risks associated with handling sulphur in liquid form.

Hope you will find it useful. Do share the same with your friends and colleagues. Do follow the blog and keep writing to me for any questions and issues on himanshuchichra@gmail.com.

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.

Partial Inerting - A Cost Efficient weapon against Dust Explosion

Hey everybody, hope you are enjoying my blog and finding the information useful in your field of work. Today we are talking about a topic which is rather less explored and understood in many industries as of now i.e. "Partial Inerting".

Let's start first with understanding Inerting. Inerting is defined as the replacement of "oxidant" in a system by a non-reactive, non-flammable gas, to make the atmosphere within the system unable to propagate flame. Inerting may be achieved by using a non-flammable gas, which will neither react with the fuel nor with the oxidant. There are many gases used for inerting such as Nitrogen, Carbon Dioxide, Flue Gases, Noble Gases (Argon, Helium), etc.

P.S: Some material may react with these inert gases under some conditions. Hence, correct selection of gases is critical.

Now let's discuss the concept of PARTIAL INERTING to prevent dust fire and explosion. Partial Inerting means dilution of oxidising atmosphere with an inert gas but not up to the extent of LOC i.e. oxidant concentration lies between LOC and atmospheric concentrations. In other words, for partial inerting, the oxidising atmosphere (most often air) in which the explosible dust is dispersed is mixed with a fraction of inert gas (e.g. nitrogen) considerably smaller than that required for complete inerting (i.e. below LOC). 

Selection of Flexible Intermediate Bulk Containers (FIBC) and their relevance

Hey everybody! A big shout out to all the people who have helped me reach more than 1k viewers on the blog. Keep sharing with your friends, colleagues and to all others for whom you feel that this content will be relevant to.

The next concept which I have seen people struggling with is the selection of FIBC.

FIBCs are flexible, rectilinear containers constructed of woven plastic with a suitable liner. The typical FIBC is made of woven polypropylene with a polyolefin liner. Various designs exist for the basic container and grounding arrangements (if any), and larger capacities are also available.

There are four types of FIBCs which are available, i.e. Type A, Type B, Type C and Type D. Each of these have different specifications and different utilization & relevance.

Explosion Severity Test and St Class : Modified Hartmann vs 20 Litre (St 0H/1H/2H vs St 1/2/3)

Hope you have enjoyed the posts till now. The response has been overwhelming with the number of emails regarding the queries and some regarding the requests for upcoming posts. I would again like to request to all of you that, I am always in search of some good topics related to Process Safety, Dust Explosion, Electrostatic Hazards, Hazardous Area Classification or any other process safety-related concern. Do send in your queries and requests here in comments or on himanshuchichra@gmail.com. Let's continue with the present discussion topic now.

It has recently been told to me by one of the clients’ that their explosion severity test states the results as St 1H in place of St 1/2/3. His question was simply that should I go ahead and provide an explosion vent corresponding to St 1? Now, this is a tricky one.

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.

Can Electrostatic Discharge (ESD) from Non-Conductive Bags act as an Ignition Source?

Hope you are enjoying the posts and able to gain some insights from the blog.

Now for this week blog, I am touching on a more sensitive question, which people have asked me in almost all Electrostatic Hazard Seminars. "Can Non-Conductive Bag act as an ignition source?"

A non-conductive bag, being an insulator can act as a source of Brush Discharge which has approximate energy of up to 3-4 mJ associated with it. Depending on the type of flammable atmosphere, brush discharge from the non-conductive bag may/ may not act as an ignition source.

Based on the equivalent energy of brush discharges, it must be assumed that most potentially explosive gas/air mixtures, solvent vapor/air mixtures and hybrid mixtures (vapor/gas and dust with air) can be ignited by brush discharges.

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?