A-A-50548
3.3 Design. The fan assembly shall be designed to handle clean or dust-laden air at temperature up to 250 degrees Fahrenheit (OF) (121 degrees Celsius (OC)), and up to 600OF (316OC) when equipped with a bearing cooling device (see 3.6.3.1). The design of the equipment and accessories shall permit accessibility for maintenance and service in the field. The design shall be such as to prevent conditions hazardous to personnel or deleterious to equipment. The assembly shall be built in accordance with AMCA 99.
3.4 Safety. All parts which are energized electrically shall be insulated, fully enclosed, or guarded when such parts are exposed to contact by personnel or otherwise create a hazard. All moving parts hazardous to personnel shall be enclosed or guarded. Nonfunctional sharp edges, projecting points, and excessive length of fastening devices shall be avoided. Protective devices shall be mounted on or near components containing hidden hazards. Applicable portions of OSHA Title 29, CFR, Part 1910.219 shall apply.
3.5 Performance. The fan shall deliver its rated capacity in cubic feet per minute at the static pressure in inches of water specified (see 7.2) with tolerances set forth in AMCA 210. Fan sound power level shall not exceed 90 decibels, A-weighted scale, continuous or intermittent, at five feet from the equipment.
3.6 Details of components. The unit shall consist of the components specified below; and when the motor is connected to the matching power source, the unit shall function in accordance with the performance requirements.
3.6.1 Fan wheel. Unless otherwise specified (see 7.2), the fan wheel shall be constructed of cast aluminum alloy or carbon steel plate, as specified shall function in accordance with the performance requirements.
3.6.2 Fan shaft. Unless otherwise specified (see 7.2), the shaft shall be turned, ground, and polished carbons steel alloy. The maximum allowable turnout after all machining shall be 0.001 inch (0.0254 millimeters (mm)) on shafts with diameter less than or equal to 1.5 inches (38.1 mm) in diameter. The shaft shall be sized for maximum speed of the size of fan involved and shall operate at not more than 80 percent of the first critical speed.
3.6.3. Fan bearings. Unless otherwise specified (see 7.2), the fan shall be equipped with precision anti-friction bearings with an average life of B-10. The bearings shall be of the self-lining type and shall be mounted in suitable pillow blocks having problem for attachment to the fan housing or base assembly.
3.6.3.1 Bearing cooling device. When specified (see 7.2), a bearing cooling fan of suitable size, of split design, or a heat slinger shall be provided with anti-friction bearing when the air temperature in the fan is greater than 250OF (121OC) but less than 600OF (316OC).
3.6.4 Fan housing. The housing shall be constructed of carbon steel plate or sheet and of a nominal thickness not less than that listed in table I. The scroll and side plate joints shall be made airtight. The housing shall be reinforced to minimize vibration. When specified (see 7.2), the discharge direction for types I and III larger than 33 inches in fan diameter, and type II
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