Combustible dust collection

[mjesse]

Fire District alerted me to a dust collection system they noticed on a recent walk-through.Unit is used to grind up disposable clear plastic lids (like a take-out container)Looking in 2009 IFC Chapter 13, it directs me to several NFPA Codes of which I'm not familiar. 69, 654, 664, etc.While waiting for the building owner to submit cut sheets, any advice I where I should start my research?Thanks.mj

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[cda]

Looks clean????

check the mechanical code? maybe 511

 

[mjesse]

They did a nice clean-up before we arrived

Lots of super-fine (sugar crystal size and smaller) plastic dust on the equipment

 

[cda]

...............

 

[FM William Burns]

Chapter 4 of NFPA 624, 2013

4.2 Process Hazard Analysis. 4.2.1 The design of the fire and explosion safety provisions shall be based on a process hazard analysis of the facility, the process, and the associated fire or explosion hazards.

A.4.2.1 One method by which this requirement can be satisfied is with a process hazard analysis conducted in accordance with the methods outlined by the AIChE Center for Chemical Process Safety in Guidelines for Hazard Evaluation Procedures. To determine if a dust deflagration hazard exists, consider the following:

• (1) Determine if the dust is explosible using either ASTM E 1226, Standard Test Method for Explosibility of Dust Clouds, or equivalent.
  
• (2) Determine where in the process a dust cloud sufficient to support a deflagration could occur. Use loss records and knowledge of process conditions to make this assessment.
  
• (3) Identify likely ignition sources. Recognize that ignition sources are complex and not always predictable. It is best to assume ignition is possible in all cases.
  
• (4) Consider what the predictable consequences might be, using conservative assumptions to yield a credible worst case. Start with predictable primary events and then consider secondary events.
  
• (5) Assess the likelihood of the event. For example, a material with a low MIE has a greater likelihood of ignition, all else being equal. Determine the MIE, if appropriate, using ASTM E 2019, Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air.
  
• (6) Assess the risk of the event considering both the consequence and the likelihood. If the risk is intolerable to either the owner/operator or the AHJ, identify mitigation techniques that would reduce the risk by reducing the likelihood and/or the consequences.
  
• (7) Assign responsibility and due dates for implementing the additional mitigation techniques and follow up to ensure their implementation.
  

 

[ICE]

It has to pass through a 120 micron sieve to be classified as dust.

Beyond the obvious things that don't look right with it, ask for a listing.

 

[mtlogcabin]

COMBUSTIBLE DUST. Finely divided solid material which is 420 microns or less in diameter and which, when dispersed in air in the proper proportions, could be ignited by a flame, spark or other source of ignition. Combustible dust will pass through a U.S. No. 40 standard sieve.

 

[ICE]

COMBUSTIBLE DUST. Finely divided solid material which is 420 microns or less in diameter and which, when dispersed in air in the proper proportions, could be ignited by a flame, spark or other source of ignition. Combustible dust will pass through a U.S. No. 40 standard sieve.

There you go, it's 420 microns, not 120.

 

[cda]

So if it is not combustible dust and the IMc does not require anything

All that is left is good housekeeping

 

[mtlogcabin]

You can buy one for under $65.00 to put in your inspection bag

http://www.ascscientific.com/sieves.html

 

[ICE]

So if it is not combustible dust and the IMc does not require anythingAll that is left is good housekeeping

It might still be a product conveying system.

mjesse said this: "Fire District alerted me to a dust collection system they noticed on a recent walk-through." So it may be a done deal and it's dust.

 

[mjesse]

IMC 511 and NFPA 654 both have good info, thanks for the assist. Additionallly, 2008 NEC w/commentary Article 500 has LOTS of info.

I also found some language regarding a 420 microns vs. 500 microns debate, interesting read regarding particulate clouds and dust concentrations. I will stick with the IMC and 420 µm (did pot-heads write this Code?)

A few of the items of concern so far are;

1-Enclosure made of combustible material, plywood - IMC 511.1.1

2-System is indoors - IMC 511.1.1, Although, exception #2 permit indoors if installed per IFC, which, points to NFPA

3-Does spark protection exist? - IMC 511.1.4

4-Duct, systems, dust collectors and machinery bonded and grounded? - OSHA "Combustible Dust" handout

Learning new things everyday!

 

[Insurance Engineer]

Based on the photo I have some concerns. The dust at the roof is the problem, it is small and can give you a good explosion. Make sure they collect dust samples from the highest portion of the building to be sent out for testing. The stuff on the floor will be bigger and will not give you a true indication of the problem. Go to this web site noted http://www.thebuildingcodeforum.com/forum/fire-links/8484-combustible-dust-kst-test-results.html and look for the type of plastic they are using. This will give you KST numbers for the plastic and the rating. The higher the KST look out.

Have them hirer an expert in dust to conduct a PHA of the operation. Make sure the company knows what they are doing. Have them review the operation and tell you what needs to be done. Dust is not a one size fits all thing, you need to take a lot into consideration.