Combustible dust particulates from manufacturing processes need to be collected and filtered for the safety of the facility and in accordance to relevant standards and regulations. NFPA standards permit the use of enclosureless dust collectors based upon specific criteria that differ upon the application type.
Manufacturing processes that create combustible dust particulates require them to be collected and filtered for the safety of the facility and in accordance with relevant combustible dust standards and fire prevention regulations. However, serious precautions need to be taken during the process of collecting and storing these particulates, since the process to do so may lead to explosions and fires too.
Applications generating large amounts of dust, high airflow requirements and / or contaminant with highly explosive characteristics require a robust filtration solution with appropriate safety equipment including isolation valves, explosion vent devices, monitoring devices and many others. These systems can be quite complex and in some cases very expensive.
However, some less demanding indoor applications, especially within the woodworking industry, have another option referred to as ‘Enclosureless Dust Collectors’ that can deliver adequate filtration performance, comply with combustible dust regulations, and reduce the financial burden associated with larger systems. While these systems may be simpler and less expensive, when considering using enclosureless dust collectors, it is critical to consider the application and operation requirements outlined within the National Fire Protection Association (NFPA) combustible dust standards.
There is a serious risk of dust explosions with industrial processes that handle combustible dusts. For safe operation, NFPA standards permit the use of enclosureless dust collectors, based upon specific criteria differing upon the application type.
There are two prominent NFPA standards that that govern the type of applications where enclosure dust collectors may be used and additional limitations to how they are operated.
NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids
NFPA 664: Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
These two standards focus on different application areas. NFPA 664 standard pertains only to wood processing and woodworking facilities where NFPA 654 covers a wide range of general dust applications not covered specifically in other NFPA standards. Both standards allow the use of enclosureless collectors but NFPA 654 include much more stringent requirements. Accordingly, it’s essential to review your process, determine which standard is applicable and understand the requirements to achieve compliance before making a decision on whether an enclosureless dust collector is feasible.
Both of the standards has the following requirements;
- Sizing of the filter can be up to 5,000 CFM (8,495 m3/h),
- The filter cannot be connected to sanders, abrasive planes, or molders,
- Collected dust shall be removed daily or more frequently if necessary,
- The collector must be to be located at least 20’ (6.1 m) from any safety exit, emergency evacuation points and any place routinely occupied by personnel,
- If there are multiple enclosureless dust collectors in the same room, they should be separated from each other by 20’ (6.1 m).
- The filter cannot be connected to sanders for both standards, but each standard has additional separate limitations applicable to the type of machinery:
- In accordance to NFPA 664, the filter cannot be connected to molders/and or abrasive planes having mechanical feeds
- In accordance to NFPA 654, the filter cannot be connected to abrasive planers or similar sanding equipment
In addition to the requirements above, in the NFPA 654 contains more specific limitations and requirements:
- The Minimum Ignition Energy (MIE) of the dusts must be greater than 500 mJ
- No metal dusts or processes that generate sparks such as metal grinding, hot work processes are allowed
- Requires the collector to be more than 35’ (10.7 m) from open flame or hot surfaces capable of igniting a dust cloud
- Requires additional fan specifications if the air stream dust concentration is greater than 10% of Minimum Explosive Concentration (MEC)
- Filter cleaning should be done when the fan is offline
- Accumulation of the collected dust must not exceed 22 pounds [10 kg]. For example, for dusts with a bulk density ranging from 20-40 (lbs/ft3), the 22 pound [10 kg] corresponds to 4-8 gallons [15-30 liters] of waste collection volume/ capacity
Between these requirements, especially the requirement limiting the weight of the collected material, may be particularly important for consideration. For example, for dusts with a bulk density ranging from 20-40 (lbs/ft3), the 22 pound [10 kg] corresponds to 4-8 gallons [15-30 liters] of waste collection volume/ capacity. Accordingly, enclosureless collectors used for applications other than wood, may only be viable for light-duty, low-density material applications but not for applications expecting high amounts of waste.
A well completed Dust Hazard Analysis (DHA) as required and outlined in NFPA 652, is the right place to start in order to collect the necessary information to properly assess the application of enclosureless collectors.
S-Series collectors provide safety and reliability for your workplace and are manufactured in compliance with the latest NFPA standards. For full NFPA compliance, the owner or operator must install and operate the collector in accordance with the requirement for enclosureless dust collectors.
The S-Series collectors are designed and manufactured as an efficient solution for a wide range of applications, but the owner / operator carries the complete responsibility to understand and perform the necessary requirements for NFPA compliance. The limitations need to be evaluated comprehensively and alternative solutions should be considered as well.
Nederman is a global leader in dust collection solutions with a proven track record of over 10,000 S-Series installations globally. Consult our combustible dust experts to ensure a properly designed solution for your wood dust collection needs.Learn more about Nederman S-Series collectors and see the values we bring to our customers.