Translate

Friday, April 21, 2017

Functional Safety Audit vs. Functional Safety Assessment

From Chemical Processing



Don’t Confuse a Functional Safety Audit with a Functional Safety Assessment

Understand the critical differences between the two essential evaluations

By John Walkington, ABB Safety Lead Competency Centre



Many people working in safety instrumented system (SIS) project development, execution, operation and maintenance treat a functional safety audit (FS Audit) and a functional safety assessment (FSA) as one and the same. So, based on this assumption, they simply ensure that such an activity is undertaken and perhaps signify the need to perform this evaluation at some point when it appears as a milestone on the project schedule. Moreover, often they call upon someone working on the project,
who may or may not have had some previous experience in quality auditing, to deliver this audit/assessment. However, this is not a reasonable approach because the concepts for the audit and assessment markedly differ.


An FS Audit provides a systematic and independent examination of the particular safety lifecycle phase activities under review. It determines whether the “procedures” specific to the functional safety requirements comply with the planned arrangements, are implemented effectively, and are suitable to achieve the specified objectives.


Industry good practice is encapsulated in the IEC 61511 standard [1]. Its clause 5.2.6.2.1 notes: “The purpose of the audit is to review information documents and records to determine whether the functional safety management system (FSMS) is in place, up to date, and being followed. Where gaps are identified, recommendations for improvements are made.”


Download Chemical Processing's eHandbook: Tips For Safer Processing



This review of the FSMS process essentially focuses on the procedures that shall be defined and executed at the time of the project schedule/associated execution activities and, as a result, the following management activities should be in place:


• FS Audit strategy;
• FS Audit program; and
• FS Audit plan, reporting process and follow-up mechanism.


So, in essence, the process and expectations of an FS Audit resemble those of a normal project quality management system (QMS) ISO 9001 audit regarding a “systematic review” of the execution strategy being applied. [For details on the latest edition of ISO 9001, see “Embrace ISO 9001:2015.”]


This usually means the QMS department (with support from the project safety team) performs the FS Audit. People in that department have the relevant audit skills to verify that procedures, forms and templates that constitute the contents and requirements of the FSMS are being correctly implemented. Functional safety competency is not a primary skill-set requirement for them.


An FS Audit is undertaken to ensure compliance with procedures. Auditors do not assess the adequacy of the work they are auditing and do not make specific judgments about functional safety and integrity.


In contrast, an FSA is an independent in-depth investigation into the previous and current lifecycle phase activities based on evidence, aimed at evaluating whether functional safety has been achieved. FSAs rely heavily on assessor judgements and competency. One of the inputs to the FSA process is the FS Audit processes and findings.


As with the FS Audit, there are requirements to formalize a procedure for how this activity shall be defined, executed and planned into the project schedule. However, that’s where the similarity in approach and delivery ends. For an FSA, the focus is on “judgement” about the functional safety and safety integrity achieved by the safety-related project activities under assessment. Its goal is to ensure that functional safety has been achieved within the specific scope of supply for the organization(s) under assessment and in the context of the safety lifecycle.


The safety-related-systems project team implementing one or more phases of the functional safety lifecycle should plan FSA activities, but independent resources with the necessary competencies and SIS application skill set should execute the activities. Note that the FSA team undertaking the assessment must include at least one “senior competent person.” Often, two assessors form the assessment team to ensure the necessary depth and rigor for subject matter coverage.


The two key international safety standards — IEC 61508 [2] and IEC 61511 — cite requirements on how and when to execute one or more FSAs. For IEC 61508, this is Part 1 clause 8, and for IEC 61511 Part 1 clause 5.2.6.


Performing FSAs requires staff with a high level of competency and more often than not relies heavily on subjectivity, particularly when applied to earlier phases of the safety lifecycle.


The FSA activity is a mandatory (“shall”) requirement for claiming compliance to either of the safety standards; justifying such a claim requires documented evidence of an adequate FSA.


Besides helping to satisfy the standards, an FSA usually provides tangible benefits in terms of functional safety assurance and avoidance of costs and resource issues regarding potential rework at later lifecycle phases.


Planning Your FSA Requirements

Two points in the standards bear stressing: FSA requirements apply to all phases throughout the overall safety lifecycle; and the organization performing the FSA (and by implication its assessors) must meet a defined level of independence.


Keeping those points in mind, before embarking on developing an FSA methodology, you must consider:


• which IEC safety standard is being used for the development of the FSA process;
• the organizational and management models operating within the company and how these impact the levels of independence;
• the availability of “competent” resources and the necessary documented
evidence to support the standard’s requirement regarding competency
assurance;
• the role of the FSA requirements within the supply chain
and who is managing the overall activity across the various
organizations;
• the level of planning required, which depends upon
the size of the project, e.g., whether it involves a large capital
expenditure (capex) or a small modification to an existing operational
SIS; and
• optimizing the number of FSA stages and individual FSA phases within each stage regarding the overall cost of safety.


A typical capex safety project likely will require more than one FSA. This will depend upon:


• the specific safety lifecycle phase(s) under assessment;
• the duration of the project and operation-and-maintenance lifetime;
• the number and type of safety systems implemented within the project;
• the degree of commonality across the technology solution; and
• the requirements for SIS management of change/modification covering the initial project and the entire SIS mission time.


Therefore, the person with lead responsibility for FSA planning and
execution within the organization that will manage the FSA requirements
must prepare a “functional safety assessment plan” for the safety
project and ensure this appears as a featured “milestone” on the overall
SIS project schedule/plan.


The FSA plan must be written to enable performing a systematic and comprehensive FSA (or a number of FSAs). It must specify:


• the stage(s) within the safety lifecycle when the FSA(s) will occur;
• the schedule and estimated duration of the assessment(s);
• the scope of the FSA(s) to be planned;
• the membership of the assessment team at each FSA stage;
• the degree of independence in accordance with IEC 61508/IEC 61511;
• the skills, responsibilities and authorities of the assessment team;
• the information that will be generated as a result of the FSA;
• the identity of any other safety bodies and departments involved in the assessment;
• the documents referenced at each FSA stage;
• the findings and recommendations from each FSA stage;
• follow-up and corrective action resolution; and
• FSA closure and management of continuous improvement/learning.


At some point in the planning process, the FSA plan will need to be approved by the responsible manager and issued to all parties prior to the assessment. Typically, only one plan is developed for the specific project FSA stages and phases. The individual phase reports effectively become a “living document.” After completion of each phase, evidence is reviewed, and findings, conclusions and recommendations are added to the FSA report to provide the necessary forward/backwards traceability for the assessment process.


Ongoing operational modifications of a smaller nature associated with an installed SIS may not need such regimented formal planning. However, IEC 61511 clause 17.2 requires implementation of some level of planning and verification for any such modifications. More importantly, the proposed changes shall not take place until completion of an appropriate FSA and receipt of proper authorization.

The Essentials Of Performing An FSA

The FSA must address the appropriate part(s) of the safety lifecycle in accordance with the recommended stages in IEC 61511 (see Part 1, Figure 7 — SIS safety life-cycle phases and FSA stages). Essentially, the FSA will review within the lifecycle activities under assessment if
appropriate methods, techniques, competencies, results and processes have been used to achieve functional safety.


The FSA, dependent on the applicable scope and the necessary backwards traceability at the time of the assessment, should check among other things that:


• The SIS has a defined and well-documented concept, hazard and risk identification, and risk reduction allocation to allow it to be designed, constructed, modified, verified and tested in accordance with the hazard and risk assessment, safety requirements specification, functional design specification, installation and commissioning safety acceptance test and eventual operation and maintenance of the SIS (not forgetting that the FSA also applies to part or full decommissioning of
any installed SIS).
• Regulations, mandatory standards and any stated codes of practice have been met and evidence of the requirements is available as part of the safety manual for the project/modification.
• The safety lifecycle activities under assessment have appropriate validation planning in place and the validation activities have beencompleted.
• Adequate and complete documentation is provided throughout and, in particular, the necessary independence is evident between authors, reviewers and approvers.
• Project change-management procedures are in place and have been applied throughout the lifecycle
phases. (There should be evidence of impact assessments, technical project queries, approved solutions and verification specifications, test planning and test records inclusive of document/records analysis and final approvals.)
• The safety integrity level (SIL) for each defined safety instrumented function (SIF) “achieves” and continues to “maintain” the SIL target requirements from design into operation and
maintenance.
• Any support, calculation, development and production tools used have been included in the FSA and have been assessed as being fit for purpose, e.g., “T classification” for support tools in
accordance with IEC 61508.
• Disparities within any of the lifecycle activities have been identified and resolved to ensure functional safety has not been compromised.


Use of specific checklists usually can assist the assessment team in focusing on the key areas to be covered during the required FSA(s). Such checklists are geared towards achieving the necessary functional safety requirements linked to the specific clauses and requirements of the IEC standards. This provides the basis for a robust assessment structure and enables the assessment to build upon a common format, e.g. structured observation recording, and by association, to develop the necessary traceability.

Such checklists:

• provide assessment enquiry consistency regarding project documentation to be presented that is necessary for the safety system being produced;
• support the focus on any shortcomings in requirements, design, implementation or procedure identified by the assessment process; and
• act as an aide memoire to ensure critical appraisal of all aspects of the project. This would be based on the assessment team judgment regarding the questions being raised and their relationship to the particular safety lifecycle activities under assessment.


An important underlying question is who in the organization manages the overall requirements for FSA deliverables and assigning the lead FSA role to a “competent” person? Is there evidence available to support any specific FSMS FSA training and mentoring processes applied for those
“approved” to conduct such FSAs?

What Is The Benefit?

Experience teaches that FSAs can reveal real errors and deficiencies in processes, technical capabilities and alignment with the safety requirements for either the new build or installed operational SIS. These are lapses and omissions that almost certainly would go undetected
in an FS Audit.


Here are only a few examples as found on a number of end-user delivered FSA assignments:


• Insufficient independence between protection layers that is not revealed and not acknowledged during the process of safety function allocation to protection layers, thus leading to inappropriate SIF
requirements and the wrong target SIL.
• Management-of-change issues caused by a loss of system “freeze’ for SIS modifications, resulting in different teams working on differing versions of SIS documentation and associated common SIF modification requirements.
• Lack of substance in change management “impact assessments,” leading to changes being
approved that potentially compromise both safety functionality and safety integrity.
• SIS corrective maintenance that has evolved to a “modification” without supporting impact assessment and document revision controls.
• Real discrepancies and misunderstanding between SIF device response times (DRTs) and overall process safety time (PST), resulting in non-compliant PST claims.
• Deviations in device safety manuals and, by detailed review of supporting device certification
reports, identification that purchased devices do not meet the application and operating environment requirements for use.
•Inadequate hardware reliability calculation where the use of too low failure rates results in too low average probability of failure on demand achieved and omission of compliance with systematic capability requirements, both leading to higher claimed SILs than in reality
• Conflicting specification requirements for both application program
“destruct” and “construct” using the same field devices and input/out for different SIF requirements.


And just for good measure, let’s not forget the FS Audit and FSA time-honored systematic capability chestnut:
• Identification of document and test “authors,” “reviewers” and “approvers” being one and the same person.

Perform A Proper FSA

Shortcomings in planning and executing the FSA process during different stages of the safety lifecycle can contribute significantly to potential SIS failures during the operational lifecycle phase. So, organizations involved in and responsible for the management of any stage of the safety lifecycle of the SIS must ensure the execution of such FSAs rests with assured competent resources. This will form part of the company FSMS and will support the systematic capability for the specification, design, engineering, operation and maintenance of a SIS.


In some cases, FSAs can span several organizations and the FSA activities will require overall management control because they can drill down to specifics, technicalities and results of any verification and validation. Therefore, they should have the relevant senior management support across the supply chain involved for reserving the right to re-do activities where functional safety may be compromised.


In considering industry good-practice expectations, performance of such FSAs should comply with the IEC 61508/IEC 61511 safety standards, which demand prescriptive independence and a high level of competency assurance. For more on FSAs, see Reference 3.



JOHN WALKINGTON is manager of the ABB Safety Lead Competency Centre, St. Neots, U.K. E-mail him at john.walkington@gb.abb.com.


REFERENCES
1. “Functional Safety — Safety Instrumented Systems for the Process Industries Sector,” IEC 61511, 2nd ed., Intl. Electrotechnical Commission, Geneva, Switz. (2016).
2. “Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems,” IEC 61508, 2nd ed., Intl. Electrotechnical Commission, Geneva, Switz. (2010).
3. Nunns, Stuart R., “Functional Safety Assessment: Setting the Boundaries of the FSA, Defining the Scope and Planning the FSA,” ABB, St. Neots, U.K. (2009), downloadable at http://goo.gl/mvmVRX.


ACKNOWLEDGEMENTS
The author gratefully acknowledges the support provided by Rafal Selega and Suresh Sugavanam,
as part of the ABB Safety Lead Competency Centre, based in both the UK and Poland, in developing this article.

Friday, March 31, 2017

Should Leaders Be Fired For Poor Safety Records?

Should Leaders Be Fired For Poor Safety Records?

Should Leaders Be Fired For Poor Safety Records?

My apologies for procrastinating. I’m just now circling back to a webinar that I moderated in February. Don’t judge me – I know I need to work on getting to these things sooner.

It was the first webinar in our process-safety series and it covered leadership skills and  responsibilities as they apply to creating safety as a core value at all levels of leadership. Our speaker, Dr. Sam Mannan, Regents Professor in the Artie McFerrin Department of Chemical Engineering at Texas A&M University and Director of the Mary Kay O'Connor Process Safety Center, helped us develop the series concept.

According to Mannan, “Impact of leadership cannot be overemphasized. In my opinion, unless these leaders are engaged and fully committed, it's very difficult to accomplish best in class performance and safety culture.”

Among the many lessons and tough-love insights he provided, he noted it is best to be wary of consensus. Whenever you have too many “yes” people in the room, you should look out for problems.

At the conclusion of the webinar, Mannan fielded questions in his straight-shooting manner. The first question out of the gate: Should leaders get credit for good safety performance of a company?

Dr. Mannan: I mean, that's really an interesting question, and my answer is absolutely, one-word answer, absolutely. Now, let me kind of go beyond that. They should definitely get credit if safety performance is good, just as they should be blamed or held accountable when safety performance is bad. That is the bottom line. I'll give you an analogy of NFL of football coaches. They have a good winning record, they get the credit, doesn't matter who else did what. But when they are not producing a good winning record, they get fired. And that's the way I view it. Leaders are the ones who have their fingers on what happens in the plant. They have lots of authority. And so if safety record is good, they should get credit for it, and if the safety record is bad, they should be blamed for it or held accountable. And that's why I say in every organization annual reviews of leaders should include a review of their safety record. Also, what I would say is that when a leader comes in, for example, a plant manager comes in and says, "This year we are saving 30% of our cost," instead of giving him or her a bonus, I would ask them, "Sit down and show me how you're saving this 30%." And if he's cutting maintenance, if she is cutting safety, then I'll ask them, "Have you done a risk analysis of what this means?"

You can watch the on-demand version of this webinar by registering here. You can also download a complete transcript of the presentation, including the Q&A at the end.

I promise to be more timely in my blogging about webinar events. Although, next week I plan to blog about another webinar that happened in February. But after that I swear I will jump right on them!


Traci-bio-photo.jpgTraci Purdum is Chemical Processing’s senior digital editor and webinar moderator. She has a long history of procrastinating. She hopes that by publicly admitting her problem, she will do better in the future. You can send her words of encouragement via email to tpurdum@putman.net

Wednesday, March 29, 2017

What is Fire?

From the Harrington Group

Back to the Basics: What is Fire?

As fire protection engineers we spend a lot of time talking about how to prevent fires and mitigate their damage. Technology has come a long way over the years and the profession is constantly evolving, but let’s take a moment to go back to the basics.


Let’s start at the very beginning: what is fire? It’s a rapid chemical reaction that requires fuel, heat, oxygen and an uninhibited chemical reaction—four components that make up what is known as the fire tetrahedron. A fire can be considered friendly (think cozy fireplaces, campfires, candles, cigarette lighters, gas stoves, etc.) or hostile (any unwanted fire that’s out of control and has limitless fuel and oxygen to feed on). And beyond that, a fire can be classified into one of five categories, according to the type of fuel that’s consumed and certain hazard characteristics. The three most common types of fire are as follows:

Class A: Fires that burn ordinary combustibles like wood, paper and cloth

Class B: Fires that burn combustible liquids like hydrocarbons, alcohols, and gases that support combustion

Class C: Fires involving energized electrical equipment (but if the energy source is disconnected, the fire typically becomes a Class A)

The other two classifications are a little less common:

Class D: Fires that involve combustible metals like potassium, sodium, aluminum and magnesium

Class K: Fires that involve cooking oils like animal and vegetable fats

As professionals in the field of fire protection, it’s our job to identify the potential hazards that exist in any given facility so we can effectively design a protection and mitigation scheme in case of fire. But even if you don’t have a degree in fire protection engineering, with the right knowledge and tools you can arm yourself as the first line of defense during the incipient fire stage. We’re talking, of course, about portable fire extinguishers. And just like fires, fire extinguishers can fall into one of five categories. There are several types of fire extinguishers, each serving a specific purpose.

Stay tuned for our next post about how to choose the right fire extinguisher.

Monday, March 27, 2017

What is Risk Based Inspection?

How Does it Relate to Process Safety Management (PSM)?

Posted by AnnMarie Fauske on Thu, Mar 23, 2017 @ 12 37 PM


A Risk Based Inspection (RBI) is basically a risk analysis of operational procedures.  It assesses the safety risks and plant integrity that exist and further prepares it for possible inspections.  The end result is a document that outlines, measures and defines organizational procedures based on standards, codes and best practices. risk-based-inspection-rbi-400-5848655.jpg

Per Wikipedia, "RBI is most often used in engineering industries and is predominant in the oil and gas industry. Assessed risk levels are used to develop a prioritised inspection plan. It is related to (or sometimes a part of) Risk Based Asset Management (RBAM), Risk Based Integrity Management (RBIM) and Risk Based Management (RBM). Generally, RBI is part of Risk and Reliability Management (RRM)."

Generally, RBI's are used when a company wants to change the required fregency of inspection for pressure-rate vesels.  This is applicable to the mechanical integrity element of a Process Safety Management (PSM) plan and one of the top most cited elements of OSHA.

Also per Wikipedia: "Process Safety Management is an analytical tool focused on preventing releases of any substance defined as a 'highly hazardous chemical' by the Environmental Protection Agency or OSHA. PSM refers to a set of interrelated approaches to managing hazards associated with the process industries and is intended to reduce the frequency and severity of incidents resulting from releases of chemicals and other energy sources (US OSHA 1993). These standards are composed of organizational and operational procedures, design guidance, audit programs, and a host of other methods."

The U.S. Occupational Safety and Health Administration (OSHA) 1910.119 defines all 14 elements of a Process Safety Management plan. Within the 14 elements is "Mechanical Integrity of Equipment":


29_CFR_1910.119_14_Elements_of_Process_Safety_Management.png"Employers must review their maintenance programs and schedules to see if there are areas where 'breakdown' is used rather than the more preferable on-going mechanical  integrity program. Equipment used to process, store, or handle highly hazardous chemicals has to be designed, constructed, installed, and maintained to minimize the risk of releases of such chemicals. This requires that a mechanical integrity program be in place to ensure the continued integrity of process equipment.


Elements of a mechanical integrity program include identifying and categorizing equipment and instrumentation, inspections and tests and their frequency; maintenance procedures; training of maintenance personnel; criteria for acceptable test results; documentation of test and inspection results; and documentation of manufacturer recommendations for equipment and instrumentation."

Where there might be a bit of overlap/similarity in RBI and PSM is in the area of mechanical integrity with regard to structural engineering.  Structural engineering is an important field of engineering that deals with the integrity of objects such as plant components or structures and serves the industry by performing analytical assessments, experiments, walkdowns or numerical modeling.  Some companies specialize in supporting industrial process facilities and power plants.

In plants, the structural challenges are often related to pressure, temperature and dynamic forces.  An example is the seismic adequacy of piping or components under power operation.  Engineers perform seismic walkdowns on a regular basis to screen for the seismic adequacy of systems.  Some companies are able to follow industry guidelines such as EPRI 1019199  “Experience-Based Seismic Verification Guidelines for Piping and Tubing”.  Alternatively, some have developed their own seismic screening methodology which provides an even more cost effective and conservative assessment approach.  Several specialty engineers and contractors have undergone professional seismic training which also allows them to assess safety-related electrical components such as instrumentation and control components, etc.

To support plant modernization and power uprate projects, for example, there is a need to utilize all facets of structural engineering.  For example, we have seen an increasing demand for vibration analyses.

Increasingly, it is imperative to effectively study the cause of the vibration and to propose solutions for elimination or mitigation. Engineers are available for on-site support which includes measurement, troubleshooting and root cause analysis in a team setting together with the client.

Proper application of structural engineering expertise can help mitigate issues by ensuring that the plant and components are properly engineered.  This will avoid machinery breakdown and costly plant outages. The goal is to support customers to achieve a safer and more efficient work environment along with enhanced plant durability.

Thus, for several aspects of RBI and PSM, an engineering firm with testing labs are ideal in providing a one-stop-resource for structural engineering issues including analyzing a problem, engineering a solution, verification, as well as oversight of fabrication and installation, as required.


What else?

Also within the PSM Elements defined by OSHA is Process Hazards Analysis (PHA) - a systematic evaluation of the hazards involved in the process.  PHAs are required for initiation of a process and at least once every five years after that.  It is important to address normal operating conditions as well as start-up, normal shut down and emergency shutdown procedures during the PHA.  The PHA team should be multi-disciplinary, including operations, engineering and maintenance.  To properly conduct a PHA, the process safety information (PSI) must be as complete as possible.

Due Diligence on Black-Golden Watch Face with Closeup View of Watch Mechanism..jpegIn response to continued rapid growth in safety needs for the chemical, nuclear and other industries, a few process safety engineering labs offer a complete range of Risk Management Services (RMS) such as Combustible Dust Hazard Assessment (DHA) Explosion and Fire Hazard Evaluation, Process Hazard Analysis (PHA), Hazard Identification Risk Analysis, Consequence Analysis, Safer Process Scale-up, Process Safety Management (PSM) Program Development, and Relief System Design Review to name a few.

 

Benefits to having RMS to help an RBI are:


  • Understand and address hazards that pose the highest level of risk to your process facility
  • Ensure compliance with relevant national, local and industry standards
  • Implement best engineering practices
  • Reduce overall level of risk
  • Increase productivity and employee morale
  • Make organization more competitive
  • Decrease insurance premiums
 
Combustible Dust Hazard Analysis (DHA) Explosion and Fire Hazard Evaluation

Experts provide onsite Combustible Dust Hazard Assessments (DHAs), Process Hazard Analyses (PHAs), OSHA Combustible Dust NEP compliance support, training and other services related to characterizing, preventing and mitigating combustible dust explosion and fire hazards.  An onsite assessment provides an experienced engineer to visit a facility, evaluate its compliance with relevant national, local and industry standards and provide recommendations for risk reduction.  Additional services can include deflagration vent sizing calculations, desktop reviews, equipment selection guidance, training of personnel on combustible dust hazards as well as development of process safety programs to address these issues.

 

Process Hazard Analysis (PHA)

Process safety professionals can provide PHA services including PHA auditing / review, revalidating PHAs and facilition. Process Hazard Analysis-1.jpgSome perform PHAs for compliance to OSHA PSM requirements as well as combustible dust related PHAs for compliance per National Fire Protection Association (NFPA) guidelines: NFPA 654, NFPA 664 and NFPA 484.

Look for an organization that can provide a full range of PHA services, using a variety of techniques including, hazard and operability (HAZOP) analysis, what-if, checklists, failure modes and effects analysis (FMEA) as well as quantitative risk assessments such as layer of protection analysis (LOPA).

 

Hazard Identification & Risk Analysis

Consulting services to identify hazards related to the handling or storage of flammable and combustible liquids and gases, combustible dust and reactive chemicals may be needed for your organization.  Extensive testing experience provides the ability to identify potentially hazardous conditions that may not be readily discernable.

 

Consequence Analysis

Experts can evaluate the effect of various process upset scenarios including fire and explosions, vessel overpressure scenarios, chemical reactivity concerns, vapor cloud dispersions and chemical releases.  Computer models may be used in conjunction with appropriate data to determine the effects.  The benefit or risk reduction of safeguards or mitigation strategies can also be evaluated.

 

Fire Protection Engineering

Provides life safety and fire protection consulting, engineering, and design services to architects, owners and developers, construction teams and facility operators. Helps clients to understand and achieve essential life safety goals like complying with codes, meeting egress requirements, choosing sustainable fire protection systems, analyzing hazards, and preparing for and responding to emergencies. Why? Risk mitigation; help to lower design, construction, and operating budgets; and ensure enhanced safety for end users. May include:

  • Building and fire code consulting
  • Means of egress evaluation
  • Plan review
  • Commissioning and construction management services
  • Fire modeling
  • Explosion modeling
  • Dispersion modeling
  • Quantitative risk analysis
 
Safer Process Scale-Up

Also seek services for safer scale-up of batch, semi-batch and continuous processes.  Consultation is available for process development groups involved in the scale-up of chemical processes throughout the development cycle.  Areas of expertise may include the following topics:

  • Onsite or desktop review
  • Determine critical process parameters to avoid or mitigate unwanted reactivity
  • Development of customized scale-up program designed for safer operation at various stages
  • Perform calorimetry testing to characterize desired and undesired reactions
  • Identify safe operating limits for temperature, pressure and other safety-critical parameters
  • Emergency relief design calculations for pilot plant, kilo lab and commercial scale equipment
  • Independent safety assessment
 
Process Safety Management (PSM) Program Development and Support


Seek a review or develop a process safety program to support chemical manufacturing facilities or development programs.  This can be performed for facilities including a kilo lab, pilot plant, medium scale and commercial scale plants.  Services/needs might include:
  • Auditing, reporting and presenting
  • Gap assessment to identify and prioritize needs
  • Process validation
  • Safe scale-up guidance
  • Development report documentation
  • Consulting on process safety issues for change control (management of change)
 

Relief System Design Review

Look for experts in the Design Institute of Emergency Relief Systems (DIERS) research project team.  Those who participate in the DIERS users group and contribute to developments in relief system design technology provide testing experience and the unique capability to consult on this topic with proficiency. Your organization may need:


  • Third party review of existing relief system design
  • Provide cost-effective solutions if existing relief system design is not adequate
  • Ensure current design basis is appropriate and credible
  • Develop / review pressure relief guidelines
  • Specialists in effluent control for two-phase flow systems
 
Training!

Professionals are happy to train your staff in the understanding of technical issues, process safety programs or audits, regulations and more.  Look for organizations that perform process safety audits as part of a comprehensive hazards analysis and can work with you to make sure your staff is supplied with training needs in many ways including:

Level I - Gap Analysis
Level II - Training & Consulting
Level III - Program Development and Implementation

Partial List of Services To Seek in an Engineering and Testing Lab:

  • Reviews and upgrades of all your safety process systems and regulatory requirements
  • VPP Consulting
  • Audits, reviews, and upgrades of all your Operating, Safety, and Maintenance Procedures
  • Training program evaluations for both completeness and effectiveness (from technical skills to professional development) and upgrades where needed
  • Reviews and upgrades of your program elements such as Employee Participation and Process Safety Information for effectiveness and completeness
  • Work process effectiveness evaluations and upgrades
  • Overall organizational development (e.g., motivation, work processes)
  • Stress reduction
  • Evaluations of the effectiveness of communication
Your organization may benefit from design, custom development and delivery of site specific training materials needed.  Engineers and technical specialists are available to deliver the classroom, lab or on-the-job training your staff needs. In addition, they  can assist with the identification and procurement of commercially available training materials where available.

Because of the unique work we do in the fields of safety for chemical process, nuclear and industrial areas, we are constantly able to cross examine and engineer, test and consult with new applications and capability.  For more discussion or information, please contact AnnMarie Fauske, afauske@fauske.com, 630-887-5313. www.fauske.com


By AnnMarie Fauske, Customer Outreach & Digital Media Manager

Wednesday, March 22, 2017

Technology Is The Key In Mitigating The Inherent Threat Of Fire In Waste & Recycling Operations

From Ryan Fogelman | Pulse | LinkedIn

Technology Is The Key In Mitigating The Inherent Threat Of Fire In Waste & Recycling Operations

A fire occurred at your operation. If it is a fire incident that is caught and contained, we all breath a collective sigh of relief. "Pats on the back" are passed out for having the safety and procedural processes in place to successfully prevent a fire event from becoming a major incident. In simple terms, the safety and operations teams did their job, and our processes and training worked.


Alternatively, a fire occurred at your operation. The fire got out of control and caused significant damage. The "Active" protection layer, which in Waste & Recycling operations typically consists of water sprinklers that are automatically set off when radiant heat passes 180 degrees -- more often than not -- contain the fire, protecting the lives of your employees and most of the building structure. However, in reality, your operations are offline. The cleanup process is sprung into action to re-start the revenue generating operations of your business with the goal of having the shortest amount of downtime. The subsequent investigation begins as the team starts to search for answers for what went wrong. The backroom discussions and finger-pointing begin, typically pointing to a combination the Operations and EH&S Departments of the Organization to develop processes or training to avoid another incident in the future like the one that occurred.


My belief is that there is an inherent risk of fire in our Waste & Recycling Industry operations is not secret (See: Is The Waste & Recycling Industry Facing A Fire Epidemic?). As an Industry, for us to begin to solve the problem we are facing, we only need to borrow an approach used by the Chemical Industry that looks to the “layers of protection” to ensure the highest level of safety.


“To prevent disaster, we design safety in layers, each one of these layers is designed to perform independently, providing its own safety function, so when we talk safety and disaster prevention, we talk about ‘layers of protection,’” notes Pete Skipp, engineering manager of applied technology with Rockwell Automation (See: Milwaukee, Wisc.; www.rockwellautomation.com).



A general industry illustration shows the layers of protection. The lowest two layers show the areas of prevention provided by the control system and operator intervention. The next two layers demonstrate where technology kicks in to prevent significant disaster from occurring. (See: Don't Let Your Disaster Recovery Plan Collect Dust)


The fact is that Fire Incidents that continue to plague the Waste & Recycling Industry do not discriminate against poorly run operations. Some of the best operators in the Industry are still victims of fire incidents. Why?


In my opinion, the answer lies in the fact that most organizations focus the bulk of their operational and safety resources around the "Prevent" & "Mitigate" stages. They create processes and training programs that teach their employees how to use equipment and run their operations safely. Also, they train how to effectively deal with an emergency by finely balancing containment and response with the employee and environmental protection.


The issue is our lack of investment and, frankly, our lack of reliable options to invest in as an Industry available to protect our operations from the "Incident" stage. When it comes to using technology, most organizations utilize the options that come as options on the equipment, such as automatic sensors and shut offs. However, when it comes to the tools we use during the "Incident" stage, including standards such as fire alarms, strobe lights and even water sprinklers, the current technology available simply does not cut it.



The issue lies in the fact that developing operation and safety processes and procedures, while important, can only take you so far in lessening the risk of fires in the Waste & Recycling Industry. That is where the Fire Rover solution comes in. The Fire Rover works diligently to provide a safety system that has the primary function of preventing incidents that may cause damage, pollution or injury. Our solution was designed to detect an out-of-control process and take automatic action to ensure that the process and the plant are returned to a safe state. Unlike the options available in the past, our solution combines (1) Proactive Automated Detection Of Heat; (2) Manual Verification Of The Source Of the Abnormality, and; (3) On-site Remotely Operated Coolant Options To Eliminate/Contain The Threat.



Our solution is a living, breathing layer of protection meant to compliment and work within all of the diligence and hard work that our safety and operations teams have developed, maintained and continuously improve upon. Imagine if a surgeon only had humans (without the help of technology) available to keep us alive during a surgical procedure. Surely the percentage of incidents during surgery would increase. There is finally a proven solution that works to compound the level of safety within our organizations and can give our EH&S and Operations folks the right tools to meet their goal of "No Fire Incidents." The Fire Rover fills the void between our operations manual processes and proactive fire protection, with the right combination of human knowledge and technology working together for the greater goal of fewer fire incidents in our Waste & Recycling Operations.


If you are interested in learning more or discussing your specific operation and its applicability, please feel free to reach out through LinkedIn or rfogelman(at)firerover.com.

Monday, March 20, 2017

12 Journal Articles Investigating Explosion of Hybrid Mixtures


From MyDustExplosionResearch.com


12 Journal Articles Investigating Explosion of Hybrid Mixtures

Hybrid Mixture Explosion

Hybrid mixtures contain both a combustible dust and flammable gas. Explosion of hybrid mixtures represent an enhanced industry hazard as both the severity and likelihood can increase from the presence of the second fuel.

12 Journal Articles Investigating Explosion of Hybrid Mixtures


This post briefly summarizes 12 journal articles in this research area. Relevant industries, main findings, and points of disagreement are discussed. The final two sections give links to three minute summaries of each article and the full reference information.
The main focus of this post is hybrid explosion parameters determined in closed chambers at laboratory scale. For the current purposes, explosion severity is indicated by maximum rate of pressure rise and likelihood is indicated by explosibility limits. It is important to note that other parameters such as maximum overpressure, minimum ignition energy, and minimum ignition temperature may also be important to consider.
Other posts relevant to hybrid explosion can be found under the Hybrid Explosion and Hybrid Flame Structure keywords. A full listing of posts in other areas relevant to dust and gas explosion can be found from the Blog Keywords or Blog Categories pages.

Industry Coverage

The industries covered in this summary include mining, nuclear, pharmaceutical, and general processing. Explosion of hybrid mixtures in the mining industry is explored by Li et al., 2012 [1] and Ajrash et al., 2016 [2]. Both authors focus on adding small amounts of methane gas to explosible coal dust concentrations.
Hybrid mixtures in the nuclear industry are explored by Denkevits, 2007 [3], Denkevits, 2010 [4], Khalil, 2013 [5], and Denkevits and Hoess, 2015 [6]. These authors investigate explosion of hydrogen gas with the addition of graphite/carbon, tungsten, and aluminum dusts.

ATEX Marking for Explosion of Hybrid Mixtures


A variety of hybrid mixtures relevant to the pharmaceutical industry are explore by Dufaud et al., 2008 [7], Dufaud et al., 2009 [8], Garcia-Agreda et al., 2011 [9], Sanchirico et al., 2011 [10], and Hossain, 2014 [11]. These studies cover the largest breadth of explosion characteristics including severity, explosibility limits, and characterizing the explosion process for hybrid mixtures.
The last paper included in this review is from Pilao et al., 2006 [12]. This paper investigates the explosibility of cork dust and methane gas mixtures, and is relevant to the manufacturing of cork stoppers. This work demonstrates the importance of hybrid mixtures in general processing industries.

Summary of Main Findings

The largest finding across all papers is that even small amounts of the second fuel can greatly change the explosion severity and likelihood of the first. In most cases explosion severity is enhanced significantly, especially at fuel lean concentrations (e.g., see [1, 4, 11]). Adding a combustible dust to a fuel rich flammable gas, may cause a reduction in explosion severity [3]; However, it is important to keep in mind that dust may also increase the local turbulence leading to increased explosion severity instead (e.g., see Amyotte et al., 1988 [13]).
Almost all papers that investigate explosibility limits report explosions for mixtures below the gas lower flammability limit (LFL) and dust minimum explosible concentration (MEC) [2, 5, 8, 9, 10, 12]. This is important for explosion prevention as the presence of hybrid conditions mean that explosions can occur more easily than if only a single fuel is anticipated. The work of Dastidar et al., 2005 [14] presents considerations for hazard analysis of these mixtures in processing plants.
Two competing theories have been proposed for predicting explosion limits of hybrid mixtures: Le Chatelier’s Law and Bartknecht’s relation. See the derivation by Mashuga and Crowl [15] and the textbook by Bartknecht [16] for more information on these two theories, respectively. Further discussion on the experimental findings from the 12 papers summarized here is given in the “Points of Disagreement” Section below.
The work of Garcia-Agreda et al., 2011 [9] attempts to characterize the explosion process for hybrid mixtures. These authors proposed five explosion regimes depending on the amounts of fuel relative to their flammability criteria:

Risk of Explosion of Hybrid Mixtures


  • Dust Driven Explosion – Dust > MEC, Gas < LFL
  • Gas Driven Explosion – Dust < MEC, Gas > LFL
  • Dual Fuel Explosion – Dust > MEC, Gas > LFL
  • Synergistic Explosion – Dust < MEC, Gas < LFL
  • No Explosion
This approach is useful for envisioning the combustion phenomena occurring for hybrid mixtures. This work was extended by Sanchirico et al., 2011 [10] to different ignition energy and turbulence levels. The work of Denkevits, 2007 [3], Denkevits, 2010 [4], and Denkevits and Hoess, 2015 [6] also demonstrate the combustion stages for hybrid mixtures and these authors developed the following groupings: gas-only explosion, two-step explosion, single-step explosion, and dust-only explosion.

Points of Disagreement

The first major point of disagreement focuses on the worst-case-scenario for explosion of hybrid mixtures. The results of Garcia-Agreda et al., 2011 [9] and Sanchirico et al., 2011 [10] suggest that the worst-case condition is pure gas near its stoichiometric concentration. These findings are in contrast to several studies [7, 8, 5, 4, 6] which demonstrate “more than additive effects” (term used by Dufaud et al., 2008 [7]). In these studies the worst case explosion occurred at different mixtures of dust and gas. The effect of chemical kinetics and dust-turbulence interaction on hybrid explosion severity is not well understood and the worst-case explosion severity question poses real problems for researchers and industry alike.
The second unresolved point of disagreement involves explosion limits of hybrid mixtures. Two competing theories have been presented in the literature. Le Chatelier’s Law treats the solid/gas mixture as a gas/gas mixture and assumes linear mixing between the explosion limits:
c = MEC\left(1 - \frac{y}{LFL}\right)


where the dust concentration at the flammability limit (c) can be estimated from the gas concentration (y). The individual flammability limits MEC and LFL are from the pure fuels alone. As explained by Mashuga and Crowl [15], this theory assumes that the fuels have similar flame temperature and combustion properties.
The second competing theory is Bartknecht’s quadratic relation which states that explosion limits are wider than predicted using Le Chatelier’s Law. It is generally applied for fuels with low burning velocities (e.g., methane):
c = MEC\left(1 - \frac{y}{LFL}\right)^{2}


. This relation suggests that less dust is required to generate an explosible mixture than predicted using linear mixing at a given gas concentration.
From the 12 articles reviewed significant deviations were found in the conclusions on explosibility limits. Garcia-Agreda et al., 2011 [9] saw agreement between Le Chatelier’s Law and the flammability limits of methane gas and niacin dust mixtures. Dufaud et al., 2009 [8] and Ajrash et al., 2016 [2] found wider explosion limits as predicted using Bartknecht’s relation. However, in contrast to both these theories, several studies (Sanchirico et al., 2011 [10], Pilao et al., 2006 [12], and Khalil et al., 2013 [5]) found explosion limits narrower than predicted using either approach. These conflicting results demonstrate a need to better understand and characterize hybrid explosion limits.

Conclusion

This literature summary demonstrated several important points regarding explosion of hybrid mixtures. Again, it is important to highlight that parameters other than maximum rate of pressure rise and lower explosibility limits may be important to consider depending on the processing application.
The papers summarized in this post give a broad overview of the available literature. This summary is not all-inclusive and several important papers may be absent. For other paper summaries included on this website see the “Three Minute Papers” category or the Blog Keywords page.
Other papers that are of particular interest to explosion limits of hybrid mixtures include Amyotte et al., 1993 [17], Chatrathi, 1994 [18], Landman, 1995 [19], Nifuku et al., 2006 [20], Prugh, 2008 [21], Jiang et al., 2014 [22], Jiang et al., 2015 [23], and Addai et al., 2015 [24]. These papers should be reviewed by anyone looking to understand this research area.
Lastly, if you have any comments or questions please post them below. No thought is too small and I would love to hear from you! If you would like to connect further or discuss off-line you can reach me from the Contact Me page or at chris@mydustexplosionresearch.com.

12 Journal Articles for Explosion of Hybrid Mixtures

Summary of Explosibility of Cork Dust in Methane Air Mixtures Explosibility of Hydrogen–Graphite Dust Hybrid Mixtures - Summary.png Dust/Vapour Explosions: Hybrid Behaviors? - Summary
Citation:
  • R. Pilão, E. Ramalho, and C. Pinho, “Explosibility of cork dust in methane/air mixtures,” Journal of loss prevention in the process industries, vol. 19, pp. 17-23, 2006.
    [Bibtex] [Summary] [Link]

Citation:
  • A. Denkevits, “Explosibility of hydrogen–graphite dust hybrid mixtures,” Journal of loss prevention in the process industries, vol. 20, pp. 698-707, 2007.
    [Bibtex] [Summary] [Link]

Citation:
  • O. Dufaud, L. Perrin, and M. Traoré, “Dust/vapour explosions: Hybrid behaviours?,” Journal of loss prevention in the process industries, vol. 21, pp. 481-484, 2008.
    [Bibtex] [Summary] [Link]

Major Finding: Hybrid flammability limits for cork dust/methane mixtures are narrower than the predictions of Le Chatelier’s Law Major Finding: At medium gas concentration a two-stage explosion process occurs while at higher gas concentrations a single-stage explosion occurs Major Finding: Hybrid mixtures can have “more than additive” effects on explosion consequence
Explosions of Vapour/Dust Hybrid Mixtures: A Particular Class - Summary Hydrogen/Dust Explosion Hazard in ITER: Effect of Nitrogen Dilution on Explosion Behavior of Hydrogen/Tungsten Dust/Air - Summary Dust/Gas Mixtures Explosion Regimes - Summary
Citation:
  • O. Dufaud, L. Perrin, S. Traoré, S. Chazelet, and D. Thomas, “Explosion of vapour/dust hybrid mixtures: A particular class,” Powder technology, vol. 190, pp. 269-273, 2009.
    [Bibtex] [Summary] [Link]

Citation:
  • A. Denkevits, “Hydrogen/dust explosion hazard in ITER: Effect of nitrogen dilution on explosion behavior of hydrogen/tungsten dust/air mixtures,” Fusion engineering and design, vol. 85, pp. 1059-1063, 2010.
    [Bibtex] [Summary] [Link]

Citation:
  • A. Garcia-Agreda, A. Di Benedetto, P. Russo, E. Salzano, and R. Sanchirico, “Dust/gas mixtures explosion regimes,” Powder technology, vol. 205, pp. 81-86, 2011.
    [Bibtex] [Summary] [Link]

Major Finding: Hybrid explosibility limits are wider than predicted by Le Chatelier’s Law Major Finding: Explosion of hybrid mixtures involving tungsten and hydrogen are more violent then hydrogen alone under fuel lean conditions Major Finding: Hybrid explosions can be divided into five categories based on the fuel concentration
Study of the Severity of Hybrid Mixture Explosions and Comparison to Pure Dust-Air and Vapour-Air Explosions - Summary Explosion Characteristics of H2/CH4/Air and CH4/Coal Dust/Air Mixtures - Summary Experimental Investigation of the Complex Deflagration Phenomena of Hybrid Mixtures of Activated Carbon Dust/Hydrogen/Air - Summary
Citation:
  • R. Sanchirico, A. Di Benedetto, A. Garcia-Agreda, and P. Russo, “Study of the severity of hybrid mixture explosions and comparison to pure dust-air and vapour-air explosions,” Journal of loss prevention in the process industries, vol. 24, pp. 648-655, 2011.
    [Bibtex] [Summary] [Link]

Citation:
  • Q. Li, B. Lin, H. Dai, and S. Zhao, “Explosion characteristics of H$_{2}$/CH$_{4}$/air and CH$_{4}$/coal dust/air mixtures,” Powder technology, vol. 229, pp. 222-228, 2012.
    [Bibtex] [Summary] [Link]

Citation:
  • Y. Khalil, “Experimental investigation of the complex deflagration phenomena of hybrid mixtures of activated carbon dust/hydrogen/air,” Journal of loss prevention in the process industries, vol. 26, pp. 1027-1038, 2013.
    [Bibtex] [Summary] [Link]

Major Finding: Explosion severity decreases with dust addition along lines of constant mixed stoichiometric ratio Major Finding: Explosion likelihood and severity increases with an increase in hydrogen gas content in the coal volatiles Major Finding: Explosion severity of stoichiometric hydrogen is significantly increased by the presence of activated carbon dust
Influence of Liquid and Vapourized Solvents on Explosibility of Pharmaceutical Excipient Dusts - Summary Hybrid H2/Al Dust Explosions in Siwek Sphere - Summary Effects of Ignition Energy on Fire and Explosion Characteristics of Dilute Hybrid Fuel in Ventilation Air Methane - Summary
Citation:
  • N. Hossain, P. Amyotte, M. Abuswer, A. Dastidar, F. Khan, R. Eckhoff, and Y. Chunmiao, “Influence of liquid and vapourized solvents on explosibility of pharmaceutical excipient dusts,” Process safety progress, vol. 33, pp. 374-379, 2014.
    [Bibtex] [Summary] [Link]

Citation:
  • A. Denkevits and B. Hoess, “Hybrid H$_{2}$/Al dust explosions in Siwek sphere,” Journal of loss prevention in the process industries, vol. 36, pp. 509-521, 2015.
    [Bibtex] [Summary] [Link]

Citation:
  • M. J. Ajrash, J. Zanganeh, and B. Moghtaderi, “Effects of ignition energy on fire and explosion characteristics of dilute hybrid fuel in ventilation air methane,” Journal of loss prevention in the process industries, vol. 40, pp. 207-216, 2016.
    [Bibtex] [Summary] [Link]

Major Finding: Explosion severity and likelihood increase with addition of solvent to the dust in liquid or vapour form Major Finding: At high dust concentrations hydrogen gas only acts to ignite the dust but is not involved in the subsequent combustion process Major Finding: The explosion limits of coal/methane mixtures lie between Le Chatalier’s Law and Bartknecht’s relation

Reference List for Explosion of Hybrid Mixtures

  • Q. Li, B. Lin, H. Dai, and S. Zhao, “Explosion characteristics of H$_{2}$/CH$_{4}$/air and CH$_{4}$/coal dust/air mixtures,” Powder technology, vol. 229, pp. 222-228, 2012.
    [Bibtex] [Summary] [Link]

  • M. J. Ajrash, J. Zanganeh, and B. Moghtaderi, “Effects of ignition energy on fire and explosion characteristics of dilute hybrid fuel in ventilation air methane,” Journal of loss prevention in the process industries, vol. 40, pp. 207-216, 2016.
    [Bibtex] [Summary] [Link]

  • A. Denkevits, “Explosibility of hydrogen–graphite dust hybrid mixtures,” Journal of loss prevention in the process industries, vol. 20, pp. 698-707, 2007.
    [Bibtex] [Summary] [Link]

  • A. Denkevits, “Hydrogen/dust explosion hazard in ITER: Effect of nitrogen dilution on explosion behavior of hydrogen/tungsten dust/air mixtures,” Fusion engineering and design, vol. 85, pp. 1059-1063, 2010.
    [Bibtex] [Summary] [Link]

  • Y. Khalil, “Experimental investigation of the complex deflagration phenomena of hybrid mixtures of activated carbon dust/hydrogen/air,” Journal of loss prevention in the process industries, vol. 26, pp. 1027-1038, 2013.
    [Bibtex] [Summary] [Link]

  • A. Denkevits and B. Hoess, “Hybrid H$_{2}$/Al dust explosions in Siwek sphere,” Journal of loss prevention in the process industries, vol. 36, pp. 509-521, 2015.
    [Bibtex] [Summary] [Link]

  • O. Dufaud, L. Perrin, and M. Traoré, “Dust/vapour explosions: Hybrid behaviours?,” Journal of loss prevention in the process industries, vol. 21, pp. 481-484, 2008.
    [Bibtex] [Summary] [Link]

  • O. Dufaud, L. Perrin, S. Traoré, S. Chazelet, and D. Thomas, “Explosion of vapour/dust hybrid mixtures: A particular class,” Powder technology, vol. 190, pp. 269-273, 2009.
    [Bibtex] [Summary] [Link]

  • A. Garcia-Agreda, A. Di Benedetto, P. Russo, E. Salzano, and R. Sanchirico, “Dust/gas mixtures explosion regimes,” Powder technology, vol. 205, pp. 81-86, 2011.
    [Bibtex] [Summary] [Link]

  • R. Sanchirico, A. Di Benedetto, A. Garcia-Agreda, and P. Russo, “Study of the severity of hybrid mixture explosions and comparison to pure dust-air and vapour-air explosions,” Journal of loss prevention in the process industries, vol. 24, pp. 648-655, 2011.
    [Bibtex] [Summary] [Link]

  • N. Hossain, P. Amyotte, M. Abuswer, A. Dastidar, F. Khan, R. Eckhoff, and Y. Chunmiao, “Influence of liquid and vapourized solvents on explosibility of pharmaceutical excipient dusts,” Process safety progress, vol. 33, pp. 374-379, 2014.
    [Bibtex] [Summary] [Link]

  • R. Pilão, E. Ramalho, and C. Pinho, “Explosibility of cork dust in methane/air mixtures,” Journal of loss prevention in the process industries, vol. 19, pp. 17-23, 2006.
    [Bibtex] [Summary] [Link]

  • P. R. Amyotte, S. Chippett, and M. J. Pegg, “Effects of turbulence on dust explosions,” Progress in energy and combustion science, vol. 14, p. 293–-310, 1988.
    [Bibtex] [Summary] [Link]

  • A. G. Dastidar, B. Nalda-Reyes, and J. C. Dahn, “Evalutation of dust and hybrid mixture explosion potential in process plants,” Process safety progress, vol. 24, pp. 294-298, 2005.
    [Bibtex] [Summary] [Link]

  • C. V. Mashuga and D. A. Crowl, “Derivation of Le Chatelier’s mixing rule for flammable limits,” Process saftey progress, vol. 19, pp. 112-117, 2000.
    [Bibtex]

  • W. Bartknecht, Dust explosions: course, prevention, protection, Springer-Verlag Berlin and Heidelberg GmbH & Co. K, 1989.
    [Bibtex] [Link]

  • P. R. Amyotte, K. J. Mintz, M. J. Pegg, and Y. H. Sun, “The ignitability of coal dust-air and methane-coal dust-air mixtures,” Fuel, vol. 72, pp. 671-679, 1993.
    [Bibtex]

  • K. Chatrathi, “Dust and hybrid explosibility in a 1 m$^{3}$ spherical chamber,” Process saftey progress, vol. 13, pp. 183-189, 1994.
    [Bibtex] [Summary] [Link]

  • G. V. R. Landman, “Ignition behavior of hybrid mixtures of coal dust, methane, and air,” The journal of south african institute of mining and metallurgy, vol. 95, pp. 45-50, 1995.
    [Bibtex]

  • M. Nifuku, T. H., K. Fujino, K. Takaichi, C. Barre, P. E., M. Hatori, S. Fujiwara, S. Horiguchi, and I. Sochet, “Ignitability assessment of shredder dusts of refrigerator and the prevention of the dust explosion,” Journal of loss prevention in the process industries, vol. 19, pp. 181-186, 2006.
    [Bibtex]

  • R. W. Prugh, “The relationship between flash point and LFL with application to hybrid mixtures,” Process saftey progress, vol. 27, pp. 156-163, 2008.
    [Bibtex]

  • J. Jiang, Y. Liu, and S. Mannan, “A correlation of the lower flammability limit for hybrid mixtures,” Journal of loss prevention in the process industries, vol. 32, pp. 120-126, 2014.
    [Bibtex]

  • J. Jiang, Y. Liu, C. Mashuga, and S. Mannan, “Validation of a new formula for predicting the lower flammability limit of hybrid mixtures,” Journal of loss prevention in the process industries, vol. 35, pp. 52-58, 2015.
    [Bibtex]

  • E. Addai, D. Gabel, and U. Krause, “Lower explosion limit of hybrid mixtures of burnable gas and dust,” Journal of loss prevention in the process industries, vol. 36, pp. 497-504, 2015.
    [Bibtex]