manufacturer's published recommendations, unless specified otherwise. Base
power rating of a V-belt drive on maximum pitch diameter of sheaves.
Provide classical belt section adjustable sheave type, with a minimum
service factor of 1.5 for drives with motors rated up to and including 22 kW
30 hp. [Provide classical section or narrow section, fixed sheave or
adjustable sheave type with a minimum 1.5 service factor for drives with
motors rated over 22 kW 30 hp.] [Provide at least two belts for drives with
motors rated one hp and above.]
2.1.5.2
Sheaves
Statically and dynamically balanced, machined cast ferrous metal or
machined carbon steel, bushing type, secured by key and keyway. Pitch
diameter or fixed sheaves and adjustable sheaves, when adjusted to
specified limits, shall not be less than that recommended by NEMA MG 1.
Select adjustable sheaves that provide the required operating speed with
the sheave set at midpoint of its adjustment range. The adjustment range
for various size and type belts shall be: 16 percent, minimum for
Classical section belts; 12 percent, minimum for Narrow section belts.
[Belt deflection in adjustable sheave drives shall not exceed 1 1/2
degrees.] Provide companion sheaves for adjustable sheave drives with wide
groove spacing to match driving sheaves, except that standard fixed pitch
spacing may be used for all two-through-four groove drives whose
center-to-center dimensions exceed the following: "A" and "B" Section 406
mm 16 inches; "C" Section 635 mm 25 inches; "D" Section 914 mm 36 inches.
Furnish endless, static dissipating, oil-resistant, synthetic cloth or
filament reinforced elastomer construction belts.
2.1.6
Special Construction for Hazardous Areas
2.1.6.1
Spark-Resistant
Construct [_____] [specified or indicated] units in accordance with AMCA
99-0401-66; Type [A] [B] [C]. Provide [Type B] [or] [Type C] construction
and electrical grounding of fan parts and grounding to building structure
where fume or vapor handling systems conforming to NFPA 91 are specified.
Do not place bearings in the air stream.
2.1.6.2
Explosion Proof
Construct fans to AMCA 99-0401-66, Type [A] [B] [C] spark-resistant
requirements where explosion-proof electrical components are specified or
indicated to conform to NFPA 70, Class [_____], Group [_____], Division
[_____] requirements.
2.1.7
Protective Coating for Fans
Prepare and coat fans as follows: Replace bolts required to provide access
or adjustment and normally threaded into the coated surface with studs or
bolts having heads continuously welded inside. Omit sharp edges,
self-tapping screws, and permanent threads protruding into the coated
surface. Eliminate hairline cracks and sharp inside corners by continuous
welding, brazing, or filling with high melting point solder. Seal impeller
hub to the shaft. Construct housing split to use external throughbolts.
Flange inlet and outlet and consider as fan interior. Peen or grind welds
smooth, and grind outside corners to approximately 1.60 mm 1/16 inch
radius. Sandblast metal surfaces to white metal in accordance with SSPC SP 5
Coat interior surfaces of housing in contact with airstream, including
inlet, impeller and shaft, flange faces, shaft seal, [exterior surfaces of
SECTION 15801N
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