Health and Safety
Fire safety in wood processing facilities
By John Bachynski
By John Bachynski
For the last five years most woodworking facilities have seen an increase in efforts to ensure wood processing facilities which create combustible dust meet the safety standards as defined by the NFPA (National Fire Protection Association). In several instances this is their first exposure to the NFPA and how it affects safety and cost.
NFPA codes are the basis of the fire code of Canada and have specific sections for industry fire and explosion safety can be found online at including for example, building sprinkler systems, electrical equipment, wood combustible dust, agricultural combustible dust and explosion prevention. In total there are over 100 NFPA code sections, which can be found at www.nfpa.org.
In many cases in the wood manufacturing section it was common that the facility owner was not aware that compliance to NFPA fire codes were applicable to their facility or the original equipment due to age and wear does not meet the original intended or current NFPA codes. In either case it still remains the responsibility of the owner to ensure that all equipment which produces, transports or stores combustible dust must meet either the NFPA codes at the time the facility was built or must meet the current NFPA safety and fire codes. This is not only required to meet the building code of Canada, it simple makes good sense. No owner would knowingly put his or her employees and facility at risk of an explosion. In some cases the upgrades are relatively easy and inexpensive and other upgrades can require significant cost and years to bring up to code.
The first step is to define if the dust being handled is explosive. NFPA 664 Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities section 22.214.171.124 defines dry nondeflagrable wood dust as “Wood Particulate with a mass medium particle size greater than 500 microns having a moisture content of less than 25% (wet basis)”. For example this may apply to some planer operations which through material testing could result in an acceptance that the collected material is either too large or too wet to be explosive, hence would not require explosion protection only fire protection. An example where the dust would definitely be explosive would be a sander operation. For sanders the medium particle size is significantly lower than 500 micron and has a low moisture content (dry). An owner could demonstrate that the planer dust does not meet the deflagration standard and the sander dust does. The caution is if both dusts are collected into the same dust collector or silo, the mixture could meet the deflagration standard and all relevant NFPA codes would apply.
If the dust is determined to meet the deflagration standard (is explosive), the next step is to identify what the risks are and create an action plan to install the proper explosion safety features as specified
in the respective NFPA standards. In industry there is some confusion on how this is done. In most cases the first step will include an NFPA compliance audit, Combustible dust risk assessment or Hazardous area classification. Regardless of the report type, the objective is to identify what the risks are and prioritize the risks to ensure the potentially most damaging deficiencies can be addressed first.
It is a common misconception that purchased fire and explosion equipment is certified by NFPA. The purpose of the NFPA is to establish what explosion and fire prevention methodology is acceptable, it is then up to the owner to decide which methodology they want to install. The finished explosion and fire prevention safety system must meet the “intent” of the respective NFPA code section(s) usually with the assistance of a certified safety professional such as a professional engineer licensed in the province who has established sufficient experience in applying the NFPA codes correctly. A typical example is the NFPA acceptable methods to install explosion protection on dust collectors and storage silos. The owner can decide between NFPA accepted methods, which include explosion burst panels, chemical suppression or flameless vents. Each method meets the NFPA code and each method has it’s own pros and cons. The suitability of which explosion protection system to use can only be established by a site-by-site assessment of the benefits and challenges of each protection method and it’s effect on equipment and personnel working in the area. This is why NFPA cannot dictate which method to use, the method chosen by the owner must meet the intent of the recognized methods outlined by NFPA and demonstrate that the risk to personnel is minimized and/or eliminated.
The development of the NFPA codes is culmination of decades of industry fire and explosion safety professionals who offer their experience and knowledge to include, in most cases, real life experiences on how to make facilities safer. As a safety engineer with over 35 years experience, I have investigated and/or experienced over 99 per cent of the failures identified by the NPFA which could have been prevented if the original installation was installed to meet the required NFPA fire and explosion codes. Explosion and Safety design engineers rely on the guidance of the NFPA codes to ensure that all anticipated risks are addressed and have the required explosion and safety equipment installed. For any installation regardless of size the owner should expect and request a NFPA compliance document for any new or modifications to the dust collection, transport and storage equipment. The compliance document should be signed for acceptance by a licensed professional for the province the equipment was installed.
Facility owners are not expected to be experts in NFPA explosion and fire safety compliance, they are expected to ensure the suppliers and contractors they hire have the required experience and knowledge. This is clearly defined in NFPA 664 Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities Section 4.5 Designer and Installer Qualifications “Systems that handle combustible wood particulates shall be designed by and installed under the supervision of qualified engineers who are knowledgeable of these systems and their associated hazards.”
To ensure that new or modifications to existing combustible wood dust handling systems will be installed to meet NFPA compliance, the following are examples of the type of instructions which should be added to the suppliers or contractors purchase orders or contracts:
- Equipment and installation must meet NFPA 664 and all relevant NFPA and provincial codes.
- Contractor/supplier to provide a compliance certification document signed by a provincial licensed professional.
John E. Bachynski, B.Sc. P.Eng., is president of EPM Consulting located in Halifax. He has over 30 years experience in the field of mechanical engineering, specializing in plant air quality, dust collection, transport, storage and dust explosion prevention.