Blog | Fauske and Associates, LLC

Good Housekeeping Program Controls Combustible Dust Hazards

Written by AnnMarie Fauske | Sep 30, 2014 4:37:00 PM

By Sara Peters, Fauske & Associates, LLC

You may have heard the saying that ‘a clean house is a happy home’. Well, in industrial processingfacilities, that saying takes on a different connotation in that a clean facility is not only happier, it is safer.

If you read our blog with any frequency, you know that we have repeatedly addressed the importance of characterizing the type of fugitive dust in industrial workspace –combustible or explosible – as the first step of any combustible dust mitigation program.  But, that is just one piece of the equation.

Although it is important to understand how your dust could behave if lofted into a cloud, a proper Combustible Dust Management System needs to be put in place to minimize this type of occurrence. One critical element to such a program to control the accumulation of fugitive dust is establishing an effective housekeeping plan for your facility.

Housekeeping is often one of the first things that OSHA will consider during an inspection. Additionally, establishment of a proper housekeeping plan for a facility that produces fugitive dust is a requirement of NFPA 654, Chapter 8 – Fugitive Dust Control and Housekeeping.

Housekeeping Plan Components: 
  1. Threshold: Establish an allowable threshold value for dust accumulation

  2. Frequency: Determine frequency of cleaning

  3. Equipment & Techniques: Ensure proper equipment is available for cleaning and that personnel are trained on appropriate cleaning techniques

  4. Fugitive Dust Control: Minimize the release of dust during normal operations

  5. Inspections: Routinely inspect the identified areas where combustible dust could accumulate

A proactive and comprehensive cleaning program should consider all horizontal areas where dust can accumulate including floors, tops of  hoods, equipment, conveyers, overhead structural supports such as beams and joists, tops of  ducts, walls, light fixtures and even hidden areas such as spaces above ceiling tiles.  

It is critical to establish a visual baseline in the process area where dust can be clearly seen, and accumulation measured over specific periods of time – shift, day, etc can be measured. This will help identify the proper cleaning frequency required to ensure dust accumulation stays below 1/32”, which is the benchmark thickness noted in NFPA 654. Refer to the chart below for suggested cleaning frequencies based on depth of dust layer. 

Depth of Dust Accumulation (in.)

Frequency

Housekeeping Requirements

Area Electrical Classification

< 1/32

Continuous / frequent

Clean up as necessary to maintain an average accumulation below 1/64 in.

Unclassified; however, electrical enclosures should be dust tight

1/32 to 1/8

Infrequent

Clean up during

 same shift

Unclassified; however, electrical enclosures should be dust tight

1/32 to 1/8

Continuous / frequent

Clean as necessary to maintain an average accumulation below           1/16 in.

Class II, Division 2

> 1/8

Infrequent

Immediately shut down  and clean

Class II, Division 2

Once the proper cleaning frequency is determined, then appropriate procedures for safe cleaning should be applied including:

  • Written procedures for operations, maintenance and training

  • Utilizing the preferred method of vacuuming with appropriately rated Class II vacuum cleaners that are bonded and grounded to minimize accumulation of static charge

  • Gentle sweeping with soft brooms or brushes with natural fiber bristles and water wash downs is generally permitted as well

  • Avoiding vigorous sweeping or blow downs with steam or compressed air when dealing with combustible dust unless the following requirements are met:

    • Vacuuming, sweeping or water wash-down methods are first used to clean surfaces that can be safely accessed prior to using compressed air

    • Dust accumulations in the area after the above cleaning method do not exceed the threshold dust accumulation.

    • Compressed air hoses are equipped with pressure relief nozzles limiting the discharge gauge pressure to 30 psi (207 kPa)

    • Electrical equipment potentially exposed to airborne dust in the area meets, as a minimum, the requirements of NFPA 70 (National Electric Code), NEMA 12 or the equivalent.

    • All ignition sources and hot surfaces capable of igniting a dust cloud or layer are shut down or removed from the area

Of course, the simplest solution would be to minimize the release of fugitive dust in the first place. This can be accomplished through various means such as:

  • Continuous suction to minimize the escape of dust shall be provided for processes where combustible dust is liberated during normal operation, NFPA 654, 7.1.1

  • Making system components dust-tight, except for openings designed for intake and discharge of air and material, NFPA 654, 7.3.2.3

    • Pneumatic conveying systems

    • Dust collection systems

    • Centralized vacuum systems

  • Assuring fixed spouts are dust-tight NFPA 61, 7.3.5

  • Making certain that bin vents are properly sized

Once you have your plan, your schedule, the proper equipment and techniques for cleaning and you have implemented proper steps to control the build-up of fugitive dust, it does not end there. The final critical element is implementing planned inspections to ensure ongoing effectiveness of the program.

As you can see from this list of actions, the role of good housekeeping in process safety is one that shouldn’t be overlooked. Fauske & Associates, LLC has a dedicated risk management team that can counsel on the topic of housekeeping for industrial processes as well as provide a full process hazard analysis, if required. For more information, please contact Jeff Griffin at griffin@fauske.com or 630-887-5278. www. Fauske.com