Page 79 - 2018_IMC

EXHAUST SYSTEMS

510.9 Duct construction. Ducts used to convey hazardous 510.10 Supports. Ducts shall be supported at intervals not
exhaust shall be constructed of materials approved for instal- exceeding 10 feet (3048 mm). Supports shall be constructed
lation in such an exhaust system and shall comply with one of of noncombustible material.
the following:
1. Ducts shall be constructed of approved G90 galvanized
sheet steel, with a minimum nominal thickness as spec- SECTION 511
ified in Table 510.9. DUST, STOCK AND
REFUSE CONVEYING SYSTEMS
2. Ducts used in systems exhausting nonflammable corro-
sive fumes or vapors shall be constructed of nonmetal- 511.1 Dust, stock and refuse conveying systems. Dust,
lic materials that exhibit a flame spread index of 25 or stock and refuse conveying systems shall comply with the
less and a smoke-developed index of 50 or less when provisions of Section 510 and Sections 511.1.1 through
tested in accordance with ASTM E84 or UL 723 and 511.2.
that are listed and labeled for the application. 511.1.1 Collectors and separators. Collectors and sepa-
Where the products being exhausted are detrimental to the rators involving such systems as centrifugal separators,
duct material, the ducts shall be constructed of alternative bag filter systems and similar devices, and associated sup-
materials that are compatible with the exhaust. ports shall be constructed of noncombustible materials and
TABLE 510.9 shall be located on the exterior of the building or structure.
MINIMUM DUCT THICKNESS A collector or separator shall not be located nearer than 10
DIAMETER OF MINIMUM NOMINAL THICKNESS feet (3048 mm) to combustible construction or to an
DUCT OR unprotected wall or floor opening, unless the collector is
MAXIMUM SIDE Nonabrasive Nonabrasive/ Abrasive
DIMENSION materials abrasive materials materials provided with a metal vent pipe that extends above the
highest part of any roof with a distance of 30 feet (9144
0.028 inch 0.034 inch 0.040 inch
0–8 inches mm).
(No. 24 gage) (No. 22 gage) (No. 20 gage)
Exceptions:
0.034 inch 0.040 inch 0.052 inch
9–18 inches
(No. 22 gage) (No. 20 gage) (No. 18 gage) 1. Collectors such as “Point of Use” collectors,
0.040 inch 0.052 inch 0.064 inch close extraction weld fume collectors, spray fin-
19–30 inches
(No. 20 gage) (No. 18 gage) (No. 16 gage) ishing booths, stationary grinding tables, sanding
0.052 inch 0.064 inch 0.079 inch booths, and integrated or machine-mounted col-
Over 30 inches
(No. 18 gage) (No. 16 gage) (No. 14 gage) lectors shall be permitted to be installed indoors
provided that the installation is in accordance
For SI: 1 inch = 25.4 mm.
with the International Fire Code and NFPA 70.
510.9.1 Duct joints. Ducts shall be made tight with lap
joints having a minimum lap of 1 inch (25 mm). Joints 2. Collectors in independent exhaust systems han-
used in ANSI/SMACNA Round Industrial Duct Construc- dling combustible dusts shall be permitted to be
tion Standards and ANSI/SMACNA Rectangular Indus- installed indoors provided that such collectors are
trial Duct Construction Standards are also acceptable. installed in compliance with the International
Fire Code and NFPA 70.
510.9.2 Clearance to combustibles. Ducts shall have a
clearance to combustibles in accordance with Table 511.1.2 Discharge pipe. Discharge piping shall conform
510.9.2. Exhaust gases having temperatures in excess of to the requirements for ducts, including clearances
600ºF (316ºC) shall be exhausted to a chimney in accor- required for high-heat appliances, as contained in this
dance with Section 511.2. code. A delivery pipe from a cyclone collector shall not
TABLE 510.9.2 convey refuse directly into the firebox of a boiler, furnace,
CLEARANCE TO COMBUSTIBLES dutch oven, refuse burner, incinerator or other appliance.
TYPE OF EXHAUST OR CLEARANCE TO COMBUSTIBLES
TEMPERATURE OF EXHAUST (ºF) (inches) 511.1.3 Conveying systems exhaust discharge. An
exhaust system shall discharge to the outside of the build-
Less than 100 1
ing either directly by flue or indirectly through the bin or
100–600 12 vault into which the system discharges except where the
Flammable vapors 6 contaminants have been removed. Exhaust system dis-
charge shall be permitted to be recirculated provided that
For SI: 1 inch = 25.4 mm, ºC = [(ºF) - 32]/1.8.
the solid particulate has been removed at a minimum effi-
510.9.3 Explosion relief. Systems exhausting potentially
explosive mixtures shall be protected with an approved ciency of 99.9 percent at 10 microns (10.01 mm), vapor
explosion relief system or by an approved explosion pre- concentrations are less than 25 percent of the LFL, and
approved equipment is used to monitor the vapor concen-
vention system designed and installed in accordance with tration.
NFPA 69. An explosion relief system shall be designed to
minimize the structural and mechanical damage resulting 511.1.4 Spark protection. The outlet of an open-air
from an explosion or deflagration within the exhaust sys- exhaust terminal shall be protected with an approved
tem. An explosion prevention system shall be designed to metal or other noncombustible screen to prevent the entry
prevent an explosion or deflagration from occurring. of sparks.

62 2018 INTERNATIONAL MECHANICAL CODE 
Copyrighted © 2017 by, or licensed to, ICC (ALL RIGHTS RESERVED); licensed to UL, LLC pursuant to License Agreement with ICC. No further reproductions authorized or distribution authorized.
ANY UNAUTHROIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT; AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.