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I <br />II. «r <br />%\» . * <br />1. Duct sleeves and closure collars: Fabricate from 20 <br />gauge galvanized steel. Where sleeves are installed <br />in bearing walls or partitions use blaclc steel pipe, <br />standard weight, instead. <br />2. Prepared Openings: Provide one-inch clearance between <br />the duct and the sleeve. <br />B. Deflectors: Factory-fabricated and factory-or-field assembled <br />units consisting of curved turning vanes for uniform air <br />distribution and change .of direction with minimum turbulence <br />and pressure loss. Provide curved vanes for square elbows. <br />C. Access Doors: Door frame shall be welded in place. Door <br />shall be rigid and airtight with neoprene gaskets and two <br />or more galvanized steel hinges and tension fasteners. <br />Provide doors as large as practical. Mount doors, if pos­ <br />sible, so that air pressure holds then closed. <br />D. Panels: Where motorized dampers, fire dampers, control <br />equipment, etc., are installed in ducts, provide access panels. <br />Makre airtight with gasketed edges. Use Ventlok sponge rub­ <br />ber or felt gasketing material. The panels shall be attached <br />to the duct with cam latches. The access panels shall be <br />of adequate size to permit maintenance of the equipment. <br />This Contractor has the option of furnishing prefabricated <br />access doors of identical construction characteristics as <br />specified above. <br />E. Dampers and louvers shall be two gauge heavier than ducts <br />in which installed. Dampers shall be opposed blade type. <br />The construction shall be of aluminum or galvanized steel <br />with interlocking edges and maximum 10 inch blade width, <br />conform with SMACWA. Quadrants shall be marked to indicate <br />damper position. <br />1. Backdraft Dampers (Gravity Dampers or Shutters): Factory- <br />fabricated with delicately balanced blades that open <br />automatically when the ventilator fan starts and close <br />by gravity when the fan stops. Provide the edges of <br />blades with felt or rubber strips to prevent rattling. <br />2. Splitter and Manual Volume Dampers; Balancing, factory- <br />fabricated type. Equip dampers with accessible mechanism <br />suich as quadrant operators chains or 3/16 inch rods <br />brought through the side of ducts with locking set screw <br />and bushing. Where operators occur in finished portions <br />of the building, operators shall be chrome-plated with <br />all exposed edges rounded. <br />3. Automatic Dampers: Section 15900 "Controls and Instrumen­ <br />tation" . <br />a. Control dampers to be supplied and installed by <br />Mechanical Contractor. Damper operators by Control <br />Contractor. <br />4. Bird Screens: Bird screens shall be 1/2" by 1/2" mesh, <br />0.63" diameter aluminum wire or 0.013" diameter stain­ <br />less steel wire. Insect screen frames shall be grooved <br />15840-4