In today’s episode of the Dust Safety Science podcast, Tim Heneks, Director of Engineering Services at Dustcon Solutions, talks about the steps involved in completing a hazard area classification assessment for combustible dust.
Tim leads a team of expert consultants who assist clients with combustible dust and process safety. This work has also led them to specialize in hazardous area classification. As an active member of the NFPA technical committees, Tim gains detailed insights into industry standards, which he and his team use to offer specialized services.
Initially, Tim referred clients needing such services to electrical engineers, but found that many engineers were either uninterested or lacked the necessary expertise. Recognizing a gap, his team decided to provide this service themselves, leveraging their expertise in combustible dust and Class @ environments, along with significant experience in class one environments involving gases and vapors.
Located in North America, Tim’s team primarily relies on standards like NFPA 70 and NFPA 499 for guidance. However, they are also attuned to global standards such as ATEX or the ICEX zoning systems. Beyond defining hazardous locations and their boundaries, they coach clients on strategies to minimize these hazards, which is crucial as upgrading electrical equipment for hazardous areas can be very costly. Over the past three to four years, Tim’s team has expanded their knowledge and services in hazardous area classification.
What Are The Different Classes and Why Are They Important?
Tim explains that there are three classes of hazardous areas. Class 1 includes flammable or combustible liquids, vapors, and gases such as propane or ethanol. Class 2 covers all types of combustible dust, ranging from agricultural materials and wood to specialty chemicals and metals. Class 3 involves ignitable fibers and flyings, which, although slightly outside of their usual discussions, still form an important part of understanding hazardous environments. Most facilities handling combustible dust do not deal with Class 3 materials, but it remains a relevant category within the scope of combustible dust hazards.
Tim emphasized the need for a hazardous area classification assessment. This assessment typically produces two key outputs: a set of detailed drawings or plots that clearly mark hazardous locations and their boundaries, and a report providing the rationale for these designations. These documents ensure clear communication to clients, their personnel, contractors, and regulatory authorities about the identified hazardous locations and the reasons behind them.
Tim’s team provides an HVAC drawing packet and an HVAC report as deliverables from the assessment. These tools are crucial for ensuring that everyone involved, from engineering teams to vendors, understands where hazardous locations are situated and whether new installations, like a packaging line, can safely be implemented in these areas. The assessments can also prompt necessary improvements, such as relocating or upgrading electrical equipment to meet safety standards or replacing it entirely to manage risks effectively.
What Is NFPA 499 And How Does It Relate To Hazardous Area Classification?
Tim explained that NFPA 499 provides guidelines for classifying combustible dust in hazardous locations for electrical installations, particularly in chemical process areas. It’s important to note that NFPA 499 is a recommended practice, not a mandatory code or standard, meaning it offers guidance rather than enforceable rules. This document builds upon the requirements found in NFPA 70, specifically articles 500 through 506 of the National Electrical Code, which is the primary driver for hazardous area classification in North America.
NFPA 499 specifically helps identify indoor locations with combustible dust, setting criteria like requiring a ten-foot radius around certain points. It serves three main purposes: it outlines the hazards related to combustible dust, reiterates the criteria for hazardous locations as described in NFPA 70, and provides detailed guidance on defining and classifying these dust locations. This includes visual aids like bubble diagrams found in chapter six.
Tim also highlighted a key difference between standards in the United States and those in Europe, such as ATEX or ICEX. In the U.S., the focus is less on the classification of the interior of closed process equipment and more on the exterior. This distinction arises because electrical components are typically external to the process equipment in the U.S., reducing concerns about interior classifications. Additionally, most of the process equipment in the U.S. usually meets the more stringent Class 2 Div 1 classification due to handling combustible particulate solids.
What Are The Divisions?
Tim explained that in the context of combustible dust, Class 2 is the relevant classification, which is further divided into divisions and groups based on specific criteria. Divisions relate to how often potentially explosive or flammable dust clouds occur in a location. Division 1 indicates that combustible dust clouds appear under normal operating conditions with some regularity, even if not continuously. For example, if a piece of equipment is typically well-sealed but requires regular maintenance that involves opening an access door, releasing a significant dust cloud, that scenario could classify the area as Class 2 Div 1.
On the other hand, Division 2 is used when explosive or flammable dust clouds could form under abnormal conditions, such as an unexpected disturbance of accumulated dust or a catastrophic failure of equipment that releases a large quantity of dust into the environment.
Tim also discussed the groups within Class 2, which specify the types of materials involved. Group E includes combustible metals; importantly, there is no Class 2 Div 2 for Group E—combustible metals always fall under Class 2 Div 1. Group F consists of carbon-based materials like coal, and Group G includes all other types of combustible dust, such as wood, agricultural products, and plastic resins. These classifications help determine the safety measures needed to manage and mitigate the risks associated with different types of combustible dust.
NFPA 70 Is Compulsory
Tim wanted to make it clear that while NFPA 499 is optional guidance, NFPA 70 is mandatory in the U.S. and heavily influences building code standards. Article 500 of NFPA 70 must be adhered to in any case, and NFPA 499 helps by providing specific guidance on how to apply these requirements effectively in the field of process safety.
He pointed out that although NFPA 499 includes example diagrams, there is still room for professional engineering judgment. For instance, engineers might decide to extend or reduce the safety boundaries defined in these diagrams based on specific factors or their professional experience. While the standard might suggest a ten-foot safety radius, an engineer might determine from experience that a three- or four-foot radius is sufficient.
Ultimately, NFPA 499 is a crucial resource for hazardous area classification related to combustible dust. Tim’s team at Dust Con uses it as a starting point to create their HVAC diagrams, but they also review these guidelines critically to adapt them to the specific conditions of each application.
What Does a Hazardous Area Classification Assessment Look Like?
When Tim takes on a hazardous area classification project, he starts by gathering detailed information about the client’s processes, materials, and equipment. He needs to understand the characteristics of the materials, such as the type of combustible dust, how easily it can be suspended in the air, its bulk densities, and ignition temperatures. This foundational knowledge helps him grasp the specifics of the materials involved.
From there, Tim focuses on the design aspects of new equipment or systems, identifying potential points where the closed process system might be opened to the atmosphere. These points could include open conveyors, filters, process openings, or access hatches where materials are added or removed, all of which are potential sources of fugitive dust.
Tim also considers other significant dust sources, such as truck dumps where large quantities of particulate matter are unloaded, likely causing substantial dust. He evaluates the existing dust controls, such as dust collection systems, to determine if they are effectively capturing dust from all relevant sources. He assesses the facility’s housekeeping standards, the space’s indoor or outdoor nature, and the expected levels of ventilation or wind.
Next, Tim and his team overlay these potential dust source points onto facility drawings, which could be plot drawings, elevation views, or even 3D models provided by the client. They begin constructing bubble diagrams to visually represent areas of concern. These diagrams help them determine whether large portions of a room or even entire rooms should be classified as hazardous due to the presence of combustible dust.
Finally, Tim makes engineering judgments about the extent of hazardous zones and finalizes the classification drawings. He compiles a detailed report that explains how each hazardous location was determined and documents the rationale behind the boundary decisions. This thorough process ensures that all potential risks are identified and appropriately managed.
What About With Retrofits?
Tim explained that it’s not practical to label every poorly maintained facility as Class 2 Div 1 for hazardous locations because upgrading their electrical systems to meet such stringent requirements could be prohibitively expensive. Instead, his team has developed a methodical approach to help facilities improve. They assess the current state of a facility, identify where it should ideally be, and then provide a list of recommendations. By implementing these changes, a facility can downgrade from a Class 2 Div 1 to a Class 2 Div 2 environment, or even to an unclassified environment, if they adequately control dust.
Tim noted that this approach has proven successful with clients, especially when they understand the potential cost savings in capital expenditures required to upgrade electrical systems. He shared a case study where a client improved their housekeeping after an OSHA citation but later faced another citation for electrical hazards in a different plant area due to accumulated combustible dust on non-rated electrical equipment. This incident highlighted that effective dust control could have prevented the electrical classification issues.
Tim concluded that good dust control practices can significantly lessen the need for stringent electrical classifications. Conversely, if a facility opts to upgrade to a Class 2 Div 1 environment, they might not need strict dust control measures. This balance between dust control and electrical safety standards is crucial, offering clients flexibility and potentially significant cost savings.
Conclusion
Tim mentioned that an important aspect of the discussion that wasn’t fully explored involves the types of equipment suitable for Class 2 environments, distinguishing between Class 2 Div 2 and Class 2 Div 1. He highlighted the need for clear labeling and documentation of equipment to ensure compliance. For example, while totally enclosed fan-cooled (TEFC) motors are acceptable in Class 2 Div 2 locations, it’s crucial that these motors do not reach temperatures that could ignite dust accumulations, a specification that can be difficult to confirm from manufacturers.
Tim believes there is more guidance needed for clients on this topic, especially as they seek to equip their facilities correctly following hazardous area classifications. He suggested that clients can find additional resources and support through searches on platforms like Google or Bing, or directly through their website, dustconsolutions.com. The website aims to provide useful resources on combustible dust safety and hazardous area classification. For those with more specific inquiries, Tim encourages reaching out via the contact forms or email addresses provided on their site, assuring that any queries will likely reach him eventually, and he is always ready to assist further.
If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Tim Heneks directly:
Website: https://dustconsolutions.com/
LinkedIn: https://www.linkedin.com/in/timothyheneks/
Email: [email protected]
If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.
Resources mentioned
The resources mentioned in this episode are listed below.
Dust Safety Science
Combustible Dust Incident Database
Dust Safety Science Podcast
Questions from the Community
Companies
Dustcon Solutions
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Completing an Hazardous Area Classification Assessment for Combustible Dust | Dust Safety Science
