Double Jeopardy & Process Hazard Analysis

Hey guys, hope you are doing well. Today we are discussing "Double Jeopardy" which creates regular dilemma and stirs up arguments during PHA sessions. If you have participated as a team member or facilitated or scribed in a PHA session, you would be aware of the term "Double Jeopardy". When someone declares, “That’s double jeopardy,” during a PHA, they are definitely not fighting a legal case in court where double jeopardy prevents a person from being tried in court twice for the same offense. Instead, they are arguing that because two things have to go wrong to cause a scenario, the likelihood is so low that it is not credible and there is no need to consider the scenario.

Strategy to define risk reduction measures in PHA

Hope you and your families are keeping safe from COVID. I have been away from writing for some time now as I took up a new professional role in July and had a lot going on. But one of my new year resolutions was to again start writing the blog and share valuable information with you all. Today I am writing about a strategy one can opt for while providing recommendations in a PHA in order to ensure the provision of effective safeguards.

Process Hazard Analysis (PHA) identifies and evaluates hazardous scenarios forming an initiating event - consequence of interest pair. Evaluating a hazardous scenario helps to determine the adequacy of safeguards for a scenario and to establish requirements for improvement of existing safeguards or installation of new safeguards. 

The need for risk reduction measures is defined based on risk assessment usually utilizing predefined risk matrices. Risk reduction measures fall in either of the two categories “Preventative” and “Mitigative”. Preventative is a category that focuses on preventing the hazard while Mitigative is a category that focuses on minimizing the consequences of an event. 

In order to define risk reduction measures, one of the useful strategies is to employ the hierarchy of controls:

Recent incidents in Indian Industry creating turmoil

Yesterday's fire and explosion incident in Yashashvi Rasayan has made me ponder upon the prevention and protection measures taken by the manufacturing plants.

The incident has been said to be in the tank farm area. As per the initial reports, the fire in the tank farm has lead to an explosion of solvent storage tank/ tanks. In multiple images, damaged tanks, hydrogen trolley and multiple other plant units could be seen in the near vicinity of the tank. The other images of the incident are quite disturbing with charred bodies lying on the ground. There is a disturbing video of a charred man asking for help outside the plant that is being circulated in social media. The root cause of the incident still needs to be confirmed by the authorities. 

This incident combined with Vizag Styrene release and Tarapur surfactant factory explosion has put multiple questions in my mind. 

• Do you think that the understanding of Indian industry to process safety has improved? Do you think enough measures are taken in a plant to prevent unsafe acts and unsafe conditions? 

• Do you think that management of your plant or the neighbouring plant is seriously implementing measures and filling gaps identified in audits and PHA studies? 

• Do you think that government authorities are seriously making proactive reviews of the sites? 

• Do you think our laws and regulations related to industries are stringent enough to make the industries realise that they have more to lose in an accident than to gain in the normal operation of the plant? 

In my opinion, some industries have a better understanding of the importance of process safety in their plant and they implement preventive and protective measures as well. But several of them lack resources and knowledge related to process safety and how to prevent unsafe conditions and acts in their plants. They are still limited to hard hat and steel toe shoes safety which is important, but there is so much more to safety.

Many do not understand the importance of a good PHA study and how it can help in preventing and safeguarding against incidents. For example, I have worked with companies representatives who have asked me "why are you taking a scenario of external fire in a tank farm as I have enough fire monitors and hydrant points available in plant to fight such a scenario?" or "Why are you recommending a dump tank for a PSV release as I have high-pressure alarm and interlocks for my vessel?"

Although we have many existing guidelines, laws and regulations. Also, frequent inspections keep on going on in our plants. But it is high time to bend our perspective towards Process Safety along with general safety. It is high time that we understand and focus on topics like chemical reaction and thermal runaway hazards, facility siting, the importance of Management of Change and quality PHAs, risk of Dust Explosion, risk of fire/ explosion due to electrostatic discharges, the importance of QRA (Quantitative Risk Assessment) and LOPA (Layer of Protection Analysis) studies for the major accident hazard scenarios, the importance of Process Safety Management (PSM), etc.

These incidents leave us and our families devastated and in turmoil. We need to learn from these incidents and improve our facilities. At the end of the day, we all should return to our families safe and sound.

Remote HAZOP & LOPA Workshops

Hope you and your families are keeping safe and following the safety guidelines. During these tough times of COVID-19, face-to-face meetings have become a major challenge. To avoid any project delays and missed deadlines, many of my clients have asked me to host HAZOP and LOPA workshops via video conferencing while working from home.

I thought it would be helpful to share some tips for remote facilitation based on my experiences:

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.

Process Safety Strategy - Chemical Reaction Hazard

It has been some time since I wrote my last post. I was on leave for my marriage. I have returned to the office now and I am back with another post on Chemical Reaction Hazards. Many times, I have come across people asking us what steps should be followed for identifying and mitigating the chemical reaction hazards. Today we will be talking on the same.

First, of all, I would like to thank Fauske & Associates LLC (FAI) for their continuous support and for publishing my last blog post on their website. If you have missed the same, you can access it by clicking on the link below

https://www.fauske.com/blog/should-set-point-for-pressure-relieving-device-be-equivalent-to-design-pressure

As per the research conducted by Dr Phil Nolan (South Bank University, UK) and Dr John Barton (UK Health and Safety Executive) and graduate students based on data analysis, the following four gaps have contributed equally i.e. 25% each to thermal runaway reactions leading to multiple incidents in past:

1. Lack of proper understanding of the thermochemistry (heat of reaction) and chemistry (balanced chemical equation)
2. Insufficient engineering design for reactor heat transfer system
3. Inadequate control and safety back-up systems including emergency relief systems, process vent, and other engineering controls
4. Poorly written batch procedures and insufficient operator training.

Concept Sciences Inc. Explosion

Hence, it is imperative to develop a process safety strategy to address these four gaps. A process safety strategy should include the following:

Should set point for Pressure Relieving Device be equivalent to Design Pressure?

Hope all of you are doing well. Today's topic is focusing on the general practice sometimes followed in industry related to the set point of Pressure Relief Devices of process equipment. Many times during PHA, I have come across a general philosophy of keeping the set point of the reactor's pressure relieving devices equivalent to its design pressure. This might be adequate for a non-reactive system. But the question is, is it adequate for a reactive system?

Here, the reactive system is one where there are hazards due to a chemical reaction, including the possibility of decomposition or polymerization or some side reaction, etc. We know based on normal kinetics that the rate of reaction is directly proportional to the temperature which in turn is proportional to pressure. In simple terms, it is said that the rate of a chemical reaction doubles with every 10 deg C rise in the reaction temperature. Hence it can be said that:

Higher set pressure leads to a correspondingly higher "set" temperature (i.e. the relieving temperature).  This, in turn, leads to a higher rate of reaction which results in higher self-heating or higher temperature rise rate (dT/dt i.e. deg C/min) and a higher pressure generation rate (dP/dt i.e. bar/min). This is very important because for a chemically reactive system the required pressure relief area depends directly on the self-heating and pressure rise rates at the relief conditions.

When is risk low enough : Risk Acceptance and ALARP

I would like to thank you all for continued interest in the blog posts. Keep reading and do like, share and comment. In this blog, we will be discussing what is the risk acceptance criteria and what is ALARP to define When is the risk low enough.

No activity is entirely free of risk in an industrial plant and hence it is imperative that safety risks are reduced to acceptable levels. The key question that remains is what level of risk is considered to be acceptable? 

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). 

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.

Shortcomings of Explosion Venting Design

Hey guys, let me thank you all for making this blog a success and for sharing your thoughts. I hope you are gaining some useful insights for the queries which arise in your mind related to process safety. I can really add more value if, you drop in other queries and I probably can select some of them for the upcoming blog posts.

Now let’s discuss Dust Explosion Venting, which I guess many of you out there struggle with. 

For each dust, maximum overpressure and rate of pressure rise can be measured in an explosion severity test carried out using a 20-Litre Sphere, where a controlled explosion is carried out and the resultant pressure is measured in order to determine the (dP/dt)max and Pmax. This (dP/dt)max is then used to find Kst value utilising cubic law. 

Any vendor who is designing explosion vents will ask for at least Kst value of the powder handled, size of equipment and equipment drawing.

Next question which people ask is "What to do if we handle multiple powders in a single equipment?"

The answer is simple, understand the worst Kst dust being handled in your equipment and design your system according to that. 
Since Minimum Explosible Concentration (MEC or what is called as LEL of dust) is usually as low as 10-30 g/m3 as well for powders. So even if you are only expecting a small amount of a dust inside the equipment, its wise to consider the worst case Kst of the powder. 

Then the question comes “Is my system safe now I have provided explosion venting?”

The answer still depends on whether you have isolated the other systems connected to the equipment or not. I know this sounds alien to many of you, but its very simple to understand. Any pressure will be diverted to the easiest path with least resistance possible. 
On one side we provide explosion vent to the equipment which will burst open at a certain pressure (or a small resistance), however, the connected system is the easiest path for the pressure wave to travel (due to negligible resistance). So the answer is your system is safe only if you prevent the propagation of blast wave to the connected system by utilisation of EXPLOSION ISOLATION (can be active or passive, will be discussing on these in future) designed adequately to hold. 

The next question which arises here is that “Is my plant safe now since I have provided explosion vent and isolated other systems as well?”

The answer is dependent on where the explosion is being relieved. The relieved blast wave with flames or flameless (depends on the type of explosion vent used) has to go to a safe location such that it doesn’t hurt people and plant. I have seen plants, where explosion vent is facing a wall or two explosion vents are facing each other or an explosion vent is reliving on plant’s internal busy pathway. This can escalate the event and might lead to damage to people, equipment and property.

So there is the recipe for explosion protection using explosion venting. The ingredients involve Powder Kst, adequately sized explosion vent (designed as per Kst) relieving to a safe location, Explosion Isolation device to prevent propagation.

Hope this helps you guys in understanding the concept of explosion venting.

Do like, share, comment and follow the blog because this is just the beginning. You can always follow using email to receive updates on any new post.

And remember, all of you can drop me an email on himanshuchichra@gmail.com if you would like me to write up on any specific aspect. 

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.