SECTION 5.10  COMBUSTIBLE DUST PRODUCING PROCESSES

Subsection 5.10.1.  Dust Collection

Application

5.10.1.1.  This Section applies to buildings, parts of buildings or equipment where combustible dusts are produced in quantities or concentrations that create an explosion or fire hazard.

Accumulations of combustible dusts

5.10.1.2.  (1)  Building and machinery surfaces shall be kept clean of accumulations of combustible dusts using cleaning equipment that

(a)   is made of materials that will not create electrostatic charges or sparks,
(b)   is electrically conductive and bonded to ground, and
(c)   except as permitted in Sentence (3), removes the dust to a safe location by vacuum.

    (2)  When used in atmospheres containing combustible dusts, the cleaning equipment required in Sentence (1) shall be listed and labelled for use in atmospheres containing combustible dusts.

(3)  Where it is not possible to effectively remove dust by vacuum, it is permitted to use compressed air or other means which cause dust to be suspended in air during removal if, in the dust removal area,

(a)   all sources of ignition are eliminated, and
(b)   all machinery and equipment is de-energized, unless such equipment is listed and labelled for use in atmospheres containing combustible dusts.

Dust containment

5.10.1.3.  (1)  Machinery that produces, agitates or conveys combustible dusts shall

(a)   have dust-tight casings or enclosures, and
(b)   be connected to a dust-collecting system that exhausts to the outside, subject to Sentence 5.10.1.5.(3).

Construction of dust-collecting equipment

5.10.1.4.  (1)  Dust-collecting systems shall be made of noncombustible material.

(2)  Dust-collecting systems shall be of a design which will prevent sparks due to physical contact in the fan assembly.

Location

5.10.1.5.  (1)  Except as provided in Sentences (2) and (5), a dust collector shall be located outside of a building.

(2)  A dust collector is permitted to be located inside a building if it is

(a)   provided with explosion venting to the outdoors in conformance with NFPA 68, “Standard on Explosion Protection by Deflagration Venting”,
(b)   equipped with an automatic explosion prevention system, or
(c)   located in a room

(i)   with fire separations having a fire-resistance rating not less than 1 h,
(ii)   provided with explosion venting to the outdoors, and
(iii)   used solely for the housing of dust-collecting equipment.

    (3)  Except for dust collectors described in Sentence (5), when air exhausted by a dust collector is returned to a building, the dust-collecting system shall be designed so that

(a)   returned air will not create an explosion hazard inside the building, and
(b)   the exhaust fan and ancillary equipment are automatically shut down in the event of a fire or an explosion inside the dust collector.

    (4)  Explosion venting to the outdoors is deemed to comply with Clause (2)(a) if the venting

(a)   was installed on or before November 21, 2007, and
(b)   provides not less than 0.1 m² of vent area for each cubic metre of dust collector enclosure volume.

    (5)  Sentences (1) and (2) do not apply to dust collectors having a capacity of less than 0.47 m³/s and used on wood working operations, except for wood flour manufacturing.

Grounding

5.10.1.6.  Electrically-conducting parts of duct systems, dust collectors and the machines they serve shall be grounded.

Explosion venting

5.10.1.7.  (1)  Except as provided in Article 5.10.1.8., an activity that creates an explosive atmosphere of combustible dusts shall be located only in a building provided with explosion venting to the outdoors.

(2)  When explosion venting is required in this Section, it shall be designed to prevent critical structural and mechanical damage to the building in conformance with NFPA 68, “Standard on Explosion Protection by Deflagration Venting”.

Explosion prevention system

5.10.1.8.  (1)  In processes where an explosion hazard is present and conditions exist that prevent adequate explosion venting as required in this Section, an explosion prevention system shall be provided.

(2)  When an explosion prevention system is required in this Section, it shall be designed in conformance with NFPA 69, “Standard on Explosion Prevention Systems”.

Interlocks

5.10.1.9.  Equipment required to have a dust-collecting system shall be interlocked to prevent it from operating if the dust-collecting system is not in operation.

Air velocity

5.10.1.10.  Dust-collecting systems shall be designed for an air velocity in the ducts of at least 1068 m/min.

Vent stacks

5.10.1.11.  (1)  Permanently open vent stacks may be used to ventilate storage containers where mechanical dust-collecting systems are not practical, provided that the vent stacks

(a)   have a cross-sectional area not less than twice that of spouts discharging into the container,
(b)   are installed not more than 30 degrees from the vertical,
(c)   extend from the top of the container to a point not less than 1.2 m above the roof, and
(d)   are designed to prevent the entry of snow and rain.

Separators

5.10.1.12.  Magnetic or pneumatic separators shall be installed to prevent the entrance of foreign materials that may cause sparks in equipment such as shellers, crackers, crushers, grinding machines, pulverizers or similar machines that produce combustible dusts.

Grounding

5.10.1.13.  Machinery and metal parts of the equipment in Article 5.10.1.12. and related conveying systems shall be electrically grounded.

Ignition sources prohibited

5.10.1.14.  Smoking shall not take place and open flame and spark-producing equipment shall not be used in areas containing combustible dust producing operations.

Subsection 5.10.2.  Woodworking Operations

Exhaust systems

5.10.2.1.  Every machine that produces sawdust, particles or shavings shall be provided with a blower and exhaust system installed in accordance with NFPA 91, “Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Noncombustible Particulate Solids”.

Operations that produce sparks or combustible vapours

5.10.2.2.  (1)  A machine that produces sawdust, particles or shavings shall not be used in an operation that generates sparks or combustible vapours.

(2)  An exhaust system shall not serve an operation that generates sparks or combustible vapours.

Disposal

5.10.2.3.  Loose sawdust, particles or shavings shall be swept up at frequent intervals and deposited in receptacles described in Sentence 2.4.1.3.(3).

Portable extinguishers

5.10.2.4.  A portable extinguisher that complies with Subsection 6.2.6. or a garden-type hose shall be provided within 7.5 m of any machine that produces sawdust, particles or shavings.