Exploring Dust Hazards in Pharmaceutical Tablet Production

Facilities that handle or generate dusts are at risk for explosions and flash fires. This newsletter by Kathy Anderson, CCPSC, provides an introduction to the regulatory standards that apply to combustible dust hazards, followed by a case study on a Dust Hazard Analysis (DHA) for a pharmaceutical tablet production process to understand a dust hazard evaluation.

Regulatory Standards Overview

Standards established by the NFPA are relied upon by the Occupational Safety and Health Administration (OSHA) as evidence in support of general duty clause violations in the event that an employer fails to prevent or fix a recognized serious hazard in the workplace (OSHA, 2023).

• NFPA 652 Standard on Fundamentals of Combustible Dust
• NFPA 61 Standard for the Protection of Fires and Dust Explosions in Agricultural and Food Processing Facilities
• NFPA 484 Standard for Combustible Metals
• NFPA 654 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
• NFPA 655 Standard for Prevention of Sulfur Fires and Explosions
• NFPA 664 Standards for Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
• Center for Chemical Process Safety (CCPS) Guidelines for Combustible Dust Hazard Analysis, 2017

NFPA 652 Standard 2019 Requirements

• Determine combustibility and explosibility hazards of materials
• Identify and assess any fire, flash fire, and explosion hazards
• Manage identified hazards
• Communicate hazards to affected personnel

NFPA 652 Compliance Defined

Chapter 5 Hazard Identification

• The operator of a facility with potentially combustible dusts shall be responsible for determining whether the materials are combustible or explosible.
• Where dusts are determined to be combustible or explosible, controls to address the hazards associated with the dusts shall be identified and implemented.

Chapter 6 Performance-Based Design

• The performance-based design shall be documented, including the use of passive controls for dust collection systems such as deflagration venting and flameless venting.
• A description of combustible dust fire and explosion design scenarios shall be documented.
• A DHA can be used to document that an acceptable level of protection was achieved.

Chapter 7 Dust Hazard Analysis (DHA)

• A DHA is a systematic review to identify and evaluate the potential fire, flash fire, or explosion hazards associated with the presence of one or more combustible particulate solids in a process facility.
• A DHA shall be completed for all new processes and facility components. For existing processes and components, a DHA shall be completed by September 7, 2020. For agricultural and food processing facilities (NFPA 61) a DHA shall be completed by January 1, 2022.

Chapter 8 Management Systems

• The operator shall establish written procedures for operating its facility and equipment to prevent or mitigate fires, deflagrations, and explosions from combustible dust.
• These requirements include housekeeping, hot work, PPE, contractors, emergency planning and response, incident investigation, training, management of change (MOC), and more to ensure ongoing safety.

Chapter 9 Hazard Management: Mitigation and Prevention

• The operator shall evaluate facility processes in relation to the presence of combustible dust in the facility.
• The dust collection standards and how-tos for eliminating and minimizing the possibility of combustible dust accumulations are detailed in the Standard.

CCPS DHA Steps

Both approaches can be used for efficiency based on the complexity of the process:

• Risk-based DHA ― Includes HAZard & OPerability (HAZOP) and Layer of Protection Analysis (LOPA) methodologies.
• Traditional Dust Hazard Analysis (DHA) ― Includes identifying unit operations, determining which standards apply, determining the fire or explosion hazard location, and reviewing equipment vs. standard requirements.

Dust Combustibility and Explosibility Testing

NFPA 652 regulations require facilities to determine if dusts are combustible or explosible using screening tests.

• Explosibility Screening Test ― Determines if dust is combustible.
• KSt Testing ― Rates the pressure rises in an enclosed vessel.
• Pmax Testing ― Determines the maximum explosion pressure for a dust cloud.
• Minimum Explosible Concentration (MEC) ― Measures the minimum concentration that will propagate an explosion.
• Minimum Ignition Energy (MIE) ― Identifies the lowest spark energy that will ignite a dust cloud.
• Minimum Auto Ignition Temperature (MAIT) ― Measures the lowest surface temperature that will ignite powder or cloud.
• Layer Ignition Temperature (LIT) Minimum ― Determines the temperature that will ignite a dust layer.
• Limiting Oxygen Concentration (LOC) ― Minimum Identifies the concentration of oxygen in an inert dust mixture that will support combustion.
• Volume Resistivity ― Measure of electrical resistance.

Improper Housekeeping Dangers

A secondary explosion brought on by dust accumulation in the area causes the majority of the damage in a dust explosion. Ensure that a housekeeping evaluation is included in the DHA. You can utilize the general dust hazard checklist.

Compliance Update to Housekeeping

The 2020 Edition of NFPA 654 introduced a new approach to Housekeeping.

The NFPA lists 4 methods for completing the evaluation. All are deemed to provide equivalent levels of safety, however, NFPA goes on to say that using 'Mass Method B' is more accurate when evaluating potential hazards.

• Layer depth criterion method
• Mass Method A
• Mass Method B
• Risk evaluation method

Housekeeping Inspection

Check for the following when doing a plant walkthrough:

• Can you write your name in the dust?
• Can you tell the color of the surface below the dust?

If either of these occur most likely there is a combustible dust hazard present.

DHA for a Pharmaceutical Tablet Production Process Case Study

A pharmaceutical company needed a Dust Hazard Analysis (DHA) to meet NFPA inspector requirements. To determine which areas posed true risks, the ioMosaic team conducted laboratory testing of products and onsite assessments of compliance with NFPA standards, CCPS Publications, the OSHA National Emphasis Program (NEP) for combustible dusts, and recognized and generally accepted good engineering practices (RAGAGEPs).

Dryer HAZOP Study Results

• Deviation – High Flow
• Cause – Air blower VFD Failure
• Consequence – particle damage with the creation of excess dust in the dryer with possible dust explosion
• Safeguards: Dryer rated for 10 bar vs. Pmax 8.4 bar, high air flow alarms, and material filtered through 200 microns to the dust collector
• Risk – Acceptable

Dryer Checklist Results

• Item – Where an explosion hazard exists, are isolation devices provided to prevent deflagration propagation between connected (upstream and downstream) equipment?
• Answer – Yes
• Safeguards: Isolation valves in place on inlet and discharge of the dryer and dryer rated for 10 bar vs. Pmax 8.4 bar
• Risk – Acceptable

Extruder HAZOP Scenario Results

• Deviation – No flow
• Cause – Extruder feeder plugs
• Consequence – Release of product with possible fire and injury
• Safeguards: Proximity switch on feeder cover shuts down feed system and electrical classification
• Risk – Acceptable

Conveyor Checklist Results

• Item – Are bearings exposed to a combustible dust atmosphere or subject to dust accumulation monitored for overheating?
• Answer – No
• Safeguards: Conveyor is inert with low N2 shutdown
• Risk – Medium
• Recommendations: Install bearing temperature monitoring with alarm on conveyor bearings and ensure that conveyor bearings are included in the site PM program

Sieves What If Results

• What If? – Sieves not properly grounded
• Consequence – Potential dust explosion with injury
• Safeguards – None
• Risk – Unacceptable
• Recommendations: Install grounding indication with alarm on the sieve system and ensure grounding/bonding check on sieves is part of site MI program

Dust Collector Checklist Results

• Item – Where an explosion hazard exists, are isolation devices provided to prevent deflagration propagation between connected equipment in accordance with NFPA 69?
• Answer – No
• Consequence – Possible spread of dust explosion to mezzanine with injury
• Safeguards – Dust collector has explosion vent venting to the outside
• Risk – Unacceptable
• Recommendations – Install rotary valve meeting NFPA requirements for isolation at the bottom of dust collector

The Benefits

The task of addressing combustible dust issues has become so large it seems impossible to manage. Excessive testing, costly investment in equipment modifications, and uncertainty of the hazard all contribute to anxiety. We can help. These analysis reports were beneficial to the managers and operators of their facility to address and manage hazards, hazards that may not have been noticed.

We used our software Process Safety Office? PHAGlobal? which simplifies the recording of findings and tracking follow-up from DHAs. It also eliminates the need for any special application software when working with the results. The client was especially pleased with the detailed analysis, as it helped them select the appropriate corrective and preventive measures and plan for their future needs.

Dust Hazards Fundamentals Course

This course is designed to prepare you with an awareness and understanding of dust hazards to prevent dust incidents. Combining methodology and real-world incidents with regulation, industry standards, and best practices, this course aims to equip learners with the knowledge and information needed to develop a safer work environment and a framework for implementing effective safeguards against combustible dust.

To learn more and register, visit our website > https://bit.ly/44Q0NcS

Safety Moment – Details Matter

Learn how overlooking seemingly minor details about a process or a procedure in your everyday work practice can lead to devastating results. Watch this PStv? Safety Moment for important lessons on details and why they matter in process safety. The incidents shown in this video emphasize the need to account for all information, as well as practical recommendations on tracking processes and their modifications.

To watch the video, visit our website > https://bit.ly/2SrtVDo

Tools You Need to Conduct a Quality Hazard Analysis

Remember, Occupational Safety and Health Administration (OSHA) regulations mandate that a PHA or DHA needs to occur every 5 years or sooner if a MOC occurs. Get your team the tools they need to conduct a quality risk analysis now. Watch a demonstration of its newest features and find out why this is the most useful and cost-effective PHA/DHA tool on the market.

To watch the video, visit our website > https://bit.ly/3rI7jPT

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