SECTION 340-EXPLOSION VENTS
Many common dusts used or generated by industrial processes are combustible. Solid particles smaller
than 420
µ
m (capable of passing through a U.S. No 40 standard sieve) are classified as dusts
2
.
Special
precautions should be taken to protect against injury, loss of life, and property damage when conveying,
collecting and processing explosive dusts. The National Fire Protection Agency (NFPA) provides
comprehensive guidelines for dealing with explosive dusts. Following is a list of publications that are
highly recommended by Farr for use in determining if the installation of your dust collection system meets
all of the NFPA recommendations with regards to conveying, collecting and processing explosive dusts.
•
NFPA 654 –Standard for the Prevention of Fire and Dust Explosions from the Manufacturing,
Processing, and handling of Combustible Particulate Solids
•
NFPA 69 – Standard on Explosion Prevention Systems
•
NFPA 68 –Guide for Venting of Deflagrations
•
NFPA 664 – Standard for the Prevention of Fires and Explosion in Wood Processing and
Woodworking Facilities
•
NFPA 651 – Standard for the Machining and Finishing of Aluminum and the Production and
Handling of Aluminum Powders
•
NFPA 77 – Recommended Practice on Static Electricity
This is not a complete comprehensive list of NFPA publications that may apply to your application and
NFPA publications sited in these publications should also be referenced when applicable.
340.1 Important Note Concerning Explosion Vents:
Farr provides dust collectors that constitute only one component of a complete dust collection system. In
many cases the installation of an explosion vent on the dust collector is insufficient in meeting the current
NFPA recommendations. NFPA 654 states “Systems that handle combustible particulate solids shall be
designed by and installed under the supervision of qualified engineers who are knowledgeable of these
systems and their associated hazards”
3
. The complete dust collection system should be designed in a
manner that conforms to the NFPA standards and recommendations in order to minimize the risks
associated with a deflagration. Farr does not participate in the design of the dust collection system and
makes no guarantee that the inclusion of an explosion vent on the dust collector will satisfy the
requirements of the NFPA recommendations.
The following is a list of safety precautions that have been paraphrased from the referenced NFPA
publications. These are provided to you solely for the purpose of demonstrating some of the conditions
that NFPA recommends when dealing with explosive dusts. The inclusion of this list in this manual does
not relieve the owner/operator of the responsibility to assure that the complete system is designed and
installed in accordance with the NFPA standards and recommendations.
340.2 General Explosion Vent Guidelines
•
It is important to note that venting does not prevent a deflagration; venting can, however, minimize the
destructive effects of a deflagration.
•
Refer to NFPA 654 Standard for design requirements for the complete dust collection system.
•
Systems that handle combustible particulate solids shall be designed by and installed under the supervision
of qualified engineers who are knowledgeable of these systems and their associated hazards.
•
Several methods are available for the design of explosion protection for equipment. Explosion venting is
one acceptable method and can be combined with others. See NFPA 68, Section 3.1.1
•
Where an explosion hazard exists, isolation devices shall be provided to prevent deflagration propagation
from air–material separators upstream to the work areas. Isolation devices include, but are not limited to,
those listed in NFPA 654 section 3.1.3.1(1) through (5).
•
The choice of the most effective and reliable means for explosion control should be based on an evaluation
that includes the specific conditions of the hazard and the objectives of protection. Venting of deflagrations
only minimizes the damage that results from combustion.
2
NFPA 68, 2-3.4.1
25
3
NFPA 654 , 2.1.1
