This article is about Grease Duct Installation as per international codes and standards.
Grease Duct Installation
Grease ducts and plenums serving a Type I hood shall be constructed of at least 0.055-inch-thick (1.40 mm) (No. 16 manufacturers standard gauge) steel or stainless at least 0.044 inch (1.10 mm) in thickness. (UMC Para 507.3)
Joints and seams of grease ducts shall be made with a continuous liquid-tight weld or braze made on the external surface of the duct system. (UMC Para 507.3.2)
Note: A vibration isolation connector may be used, provided it consists of noncombustible packing in a metal sleeve joint of approved design. (UMC Para 507.3.2)
Duct bracing and supports for grease ducts shall be of noncombustible material securely attached to the structure. (UMC 507.3.3)
A separate grease duct system shall be provided for each Type I hood (UMC Para 507.9)
Exception:Single duct system may serve more than one hood located in the same story of the building, provided that all hoods served by the system shall be located in the same room or adjoining rooms;
Portions of the interconnecting ducts shall not pass through any con-struction which would require the opening to be fire protected as per Saudi Aramco (UMC Para 507.9)
Exposed grease duct systems serving a type I hood shall have a clearance from unprotected combustible construction of at least 18 inches (457mm). (UMC Para 507.10)
Note: This clearance may be reduced to not less than 3 inches (76 mm), provided the combustible construction is protected with material required for one-hour fire-resistive construction.
Exhaust outlets for grease ducts serving Type I hoods shall extend through the roof unless otherwise approved by Saudi Aramco. See item No. 9, 10 and 11of this SAIC for extension requirements
(UMC Para 507.11)
Exhaust outlets for grease ducts serving Type I hoods shall extend at least 2 feet (610mm) above the roof surface(UMC Para 507.11)
Exhaust outlets for grease ducts serving Type I hoods shall be at least 10 feet (3048mm) from parts of the same or neighboring buildings, adjacent property line or air intake opening into any building.
(UMC Para 507.11)
Exhaust outlets for grease ducts serving Type I hoods shall be located at least 10 feet (3048 mm) above the adjoining grade level. (UMC Para 507.11)
Exhaust outlets for ducts serving Type II hoods over heat-processing equipment shall terminate at least 10 feet (3048 mm) from adjacent property lines or air intake openings into any building, and shall be located at least 10 feet (3048 mm) above adjoining grade level.(UMC Para 507.11)
EXCEPTIONS: 1. Exhaust outlets for grease ducts serving commercial food heat-processing equipment may terminate not less than 5 feet (1524 mm) from an adjacent building, adjacent property line or air intake opening into a building if the air from the exhaust outlet is discharged away from such locations.
2.Upon approval of the building official, the exhaust from any hood serving commercial food heat-processing equipment may terminate in a properly engineered air-recovery system for recirculation to the room in which the hood is located
A grease duct serving a Type I hood which penetrates a ceiling, wall or floor shall be enclosed in a duct enclosure from the point of penetration. (UMC Para 507.6)
Grease duct enclosures shall be of at least one-hour fire-resistive construction in all buildings and shall be of two-hour fire-resistive construction in Types I and II fire-resistive buildings. (UMC Para 507.6)
The grease duct enclosure shall be sealed around the duct at the point of penetration and vented to the exterior through weather-protected openings. (UMC Para 507.6)
The grease duct enclosure shall be separated from the duct by at least 3 inches and not more than 12 inches (at least 76mm and not more than 305mm) and shall serve a single grease exhaust duct system.
(UMC Para 507.6)
Ducts exposed to the outside atmosphere or subject to a corrosive environment shall be protected against corrosion. (UMC 507.3.5)
Note: Galvanization of metal parts, protection with noncorrosive paints and waterproof insulation are considered acceptable methods of protection.
Duct systems serving a Type I hood system shall be sloped not less than 1/4 unit vertical in 12 units horizontal (2% slope) toward the hood or toward an approved grease reservoir. (UMC Para 507.4)
Note: Where horizontal ducts exceed 75 feet (22 860 mm) in length the slope shall not be less than 1 unit vertical in 12 units horizontal (8.3% slope).
Grease duct systems shall not have openings therein other than those required for proper operation and maintenance of the system. (UMC Para 507.5)
Grease duct system having sections inaccessible from the duct entry or discharge shall be provided with adequate cleanout openings. (UMC Para 507.5)
Clean-out openings shall be equipped with tight fitting doors constructed of steel having a thickness not less than that required for the duct. (UMC Para 507.5). See Item No. 22 of this SAIC.
Doors shall be equipped with a substantial method of latching, sufficient to hold the door tightly closed. Doors shall open without the use of a tool.(UMC Para 507.5)
Joints and seams of grease ducts shall be made with a continuous liquid-tight weld or braze made on the external surface of the duct system. A vibration isolation connector may be used, provided it consists of noncombustible packing in a metal sleeve joint of approved design. (UMC Para 507.3.2)
Ducts exposed to the outside atmosphere or subject to a corrosive environment shall be protected against corrosion. (UMC 507.3.5)
Note: Galvanization of metal parts, protection with noncorrosive paints and waterproof insulation are considered acceptable methods of protection.
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