Duct Specifications
Recommended Specifications for Exhaust Duct Equipment
Exhaust Duct
- All ventilation duct to be fabricated of Type 1, Grade 1 or Type 2, Grade 1, high impact P.V.C. Extruded Type 1 P.V.C. duct 6" diameter to 18" diameter will be acceptable where applicable.
- All KCH systems are designed in accordance with the recommended practice of the American Conference of Governmental Industrial Hyglenigts and fabricated in accordance with (SMACNA) Sheet Metal and Air Conditioning Contractors National Association, manual on Thermo Plastic Construction.
- All P.V.C. used in fabrication of KCH products is unplastisized and conforms U.S. Commercial Standard CS 201-55 and also ASTMD 1784-69, Type II, Grade 1 LP-535b, Type II, Grade GU. All P.V.C. conforms to ASTM standard D 635 and has a flame spread rating of 20.
Fittings - Round & Rectangular Duct
- Flanges - To be made of P.V.C. Type 1 or Type 2 angle material formed and continuously welded to duct. 1.5 X 1.5 x .1875" (3/16) angle and 2" x 2" x .250" angle are used in relationship to duct sizes. Bolt holes to be .3125" (5/16) diameter for .25" stainless steel bolts and no more than six (6) inches apart on centers. Gasket material to be of soft mastic type or form P.V.C.
- Sleeves - To be formed from three (3) inch wide flat P.V.C. material of a thickness equal to or greater than the wall thickness of duct to be joined. Weld to one end of duct section leaving one half the sleeve length for adjoining section to slip into.
- Elbows - To have a minimum center line radius of 1 1/2 times diameter unless field conditions make it impossible. Ninety degree elbows to have five (5) gores and forty-five degree elbows to have three (3) gores.
- Branches - To enter main at no more than forty-five degrees (thirty degrees preferred) to direction of flow and wherever practical to enter on an enlarging taper section. Branches should not enter opposite each other. Branches to be continuously welded to main.
- Taper Section - 1" change in diameter to 5" in length, where practical.
Construction - Rectangular Duct
All straight lengths to have formed corner construction for maximum strength. This includes taper sections where practical. Elbows to have welded corner construction.
Installation
- All joints to be flanged or sleeved and made air-tight. Sleeves may be welded or cemented.
- Flanges joints should be provided at all connections where dismantling may be required.
- Ductwork should be fitted with saddle bands at 8' to 12' centers suspended with all thread rod.
- Ductwork should also be suspended at each change in direction.
Welding
- Welding shall be done by the hot air fusion welding method for P.V.C. and hot gas fusion welding method for polypropylene.
- Ductwork, hoods and similar air passage enclosures must be finished completely air and water tight.
- Ductwork shall be completely free from cracks distortion or other imperfections.
Exhaust Blowers
- Exhaust blowers shall be centrifugal, arrangement 9 with backwardly inclined wheels Type NH and Type CI Paddle Wheel as manufactured by KCH Services, Inc.
- Wheels shall be steel with FRP coating, fiberglass or stainless steel.
- Coating will be spark tested to insure integrity.
- Housing shall be constructed of Type 2, Grade 1, high impact P.V.C.
- Frames shall be steel with coating.
- All Blowers shall be equipped with a vacuum formed inlet cone, drain, access door, O.S.H.A. approved belt and shaft guards and flexible inlet and flanged outlet.
- All exhaust blowers shall carry a one year replacement guarantee against failure due to corrosion.
- Fans are to be balanced prior to shipment.