How to Optimize Dust Testing
Most pharmaceutical owners/operators know that potentially combustible dust must be tested. Combustible dust testing is required by the NFPA to determine whether it’s combustible (can burn) or explosible (rapid increase in volume creating a subsonic shock wave). This can be done by researching published data for common materials or having a dust sample from the facility tested.
However, once a dust is known to be explosible, owners/operators must test further to assess the hazard and specify explosion protection equipment.
Clients
Clients often ask me which tests they should request from a lab, and the short answer would be: Run them all. However, engineering is about optimization and performing tasks as efficiently as situational constraints allow. You might not need to run them at all. While several published sources provide properties of well-known excipients such as sugar, gelatin and corn starch, active pharmaceutical ingredients (API) present a different challenge. Since there often is no published data for these powdered compounds, they need to be tested for explosivity. And what about materials that are in-process?
For example, could dust from a natural organic material mixed with dust from a synthetic organic or metallic material be considered “similar enough” to already-tabulated combustibility property values? Is that data accurate enough to determine the size of that explosion vent panel? When it comes to personal safety and asset protection, I would say no. It’s crucial to be as accurate about hazardous materials as possible. This also means using “fresh” dust from a process, not dust collected off the floor, since it might be contaminated with other particles.
Know the Types of Combustible Dust
When it comes to testing, there is no one-size-fits-all solution. There will be circumstances in which owners/operators need to know multiple explosibility properties, and others that are not necessary to ensure safety. . Dust testing encompasses many acronyms and abbreviations for combustibility properties, and nearly all are associated with a separate lab test. Below, I break down the types of dust testing and which ones, in my experience, leverage resources best:
- Kst (Explosion Severity): Always. It’s the standard index to compare dust explosibility.
- Pmax (Maximum Explosion Pressure): Always. It’s crucial to know how much pressure an explosion can generate, then engineers can specify an explosion vent.
- LIT or Tc (Layer Ignition Temperature): Always. The temperature at which a dust layer begins to smolder is important because it creates an ignition source for fire or explosion. Hot surfaces that could accumulate dust need to be kept below the LIT, which includes: light fixtures and bearings on rotating equipment. Lights can be specified with acceptable temperature ratings, while bearings can be monitored to ensure they stay below the LIT.
- MIE (Minimum Ignition Energy): Usually. If personnel handle dust in flexible intermediate bulk containers (FIBCs, commonly called bulk bags or super sacks), MIE helps specify the type of FIBC material that can be safely used. Distinct types of FIBC material are required for materials with low MIE. A low MIE coupled with a material that is a good insulator may result in NFPA code requirements that limits the container transfer rate, which can them limit choices for conveying equipment and operating procedures for that equipment.
- MEC (Minimum Explosion Concentration): Usually. This data helps define whether a dust deflagration hazard may be present. For example, dust within collection ducting often has a concentration of less than 25 percent of the MEC. Those ducts would not be likely locations for a deflagration to start. Those ducts would still allow a deflagration flame front to travel from one piece of dust handling equipment to another. Meaning, there would still be a need to place protection on the ducts.
- LOC (Limiting Oxygen Concentration): Sometimes. Dust deflagration hazards are rarely controlled by limiting oxygen concentration. An inert gas blanket requires sensitive pressure and vacuum relief devices that can be affected by a dusty environment.
- CIT or Tc (Cloud Ignition Temperature): Sometimes. The LIT is typically lower than the CIT, and since the LIT is more restrictive, the CIT is not necessary. Also, CIT is frequently greater than 300º C (572º F). A surface that hot may not be present in many facilities, unless they have fuel-fired equipment. CIT can be important when it is possible to have hot surfaces that will not collect a dust layer (i.e., vertical surfaces), but can become ignition sources for suddenly released dust clouds.
Mitigate Risk
Remember, no matter which tests pharmaceutical owners/operators decide to perform, it’s imperative that unidentified dust is tested and proper procedures are put in place to mitigate risk to personnel and assets.
Allow Us to Help
Whether you need a dust hazard analysis consultant or a trusted partner in dust explosivity testing and risk mitigation, EAD can help. We offer comprehensive pharmaceutical dust explosivity testing services to labs, organizations and anyone that needs a helping hand when it comes to combustibility testing and safety.
Our pharmaceutical dust explosivity testing services provide a reliable and straightforward way to ensure that the ingredients you use are safe and free from any inherent danger or risk. Beyond the common materials and their well-known, published figures, most pharmaceutical ingredients must be rigorously tested prior to every use to prevent issues with powder handling or reactive chemical processing.
Based on ASTM and ISO standards, our pharmaceutical dust explosivity testing services adhere to OSHA standards, NFPA guidelines and other consensus engineering standards. The work we do tests combustibility and explosivity, as well as burning, minimum ignition energy and minimum auto-ignition temperatures, in addition to other tests. Our goal is to give you the information you need to make the proper safety adjustments throughout the entire manufacturing process.
We also provide reaction data, thermal stability data and lower and upper limits of flammability information of the compounds you’re working with, which can help improve process safety. Even in the case of a discovered dust that is known to be explosible, we provide additional information as to the exact hazard and how it can be addressed with explosion protection equipment or other safety measures.
For other types of assistance, our dust hazard analysis consultants are available to support any need, from on-site dust safety assessments to implementation of comprehensive safety management systems and protocols.
If combustible dust and process engineering services are needed at your pharmaceutical plant, don’t hesitate to reach out to EAD at our Contact Us page or at 402.884.8650. You can also follow us on LinkedIn to learn more about our in-plant expertise.
References
- NFPA 652: Standard on the Fundamentals of Combustible Dust
- NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
- Intertek.com: Safety Services Dust Explosion