OO-B-2925
pieces shall be as specified (see 6.2). Boiler plant layout dimensions and relative locations of the boiler and stack transition pieces shall be as specified (see 6.2). Ductwork shall be field welded with no gasketed joints. Low points in the ductwork shall be fitted with a threaded plug drain of not less than 1.0-inch (25.4 mm) in size.
3.9.5 Access. Adequate access shall be provided that allows ease of bag replacement and performance of other routine maintenance. A lockout system shall be provided that prevents entry into the baghouse while the unit is operating. The lockout system will be such that the baghouse cannot be operated unless all access doors are locked in the closed position.
3.9.6 Hopper. The hopper walls shall have a slope of not less than 60 degrees to prevent bridging of the collected material during dumping operations. Unless otherwise specified
(see 6.2), the bottom of the hopper shall be not less than 5.0 feet (1.52 m) above grade. A hopper material level indicator shall be furnished with each hopper. The hopper flue gas inlet shall have a damper valve to isolate the module during dumping operations. Hopper heating, dumping, and vibrating systems shall be as specified in 3.9.6.1 through 3.9.6.3.
3.9.6.1 Hopper heating system. Hoppers shall be heat traced to prevent condensation of flue gas moisture. Heaters, except hopper throat heaters, shall be of low-watt density, multiple resistance path, modular design. Watt densities for the modules shall be not greater than 3 watts per square inch (4 650 watt per square metre (w/m2)). The heaters and insulation shall be adequate to maintain a hopper wall temperature of not less than 280 °F (138 C) at all times. Hopper throat heaters shall be flexible, electric blankets or tapes rated at not less than 800 °F (427 C). Temperature indicators shall be provided to confirm the operation of the heating system. A manually adjustable setpoint control shall be furnished with the heating system.
3.9.6.2 Hopper dumping system. Material shall be removed from the hopper with the dumping system. The system shall include either a manual slide valve, trickle or double tipping valve, rotary valve, or screw conveyor as specified (see 6.2). When a manual slide valve is provided, it shall be furnished with high temperature gaskets and easy opening and securing devices. When a trickle or double tipping valve is provided, it shall be furnished with gas tight seals and an adjustable speed motorized operator. When a screw conveyor is provided, it shall be furnished with the means to convey material from the bottom of each hopper to a common material collection area.
3.9.6.3 Hopper vibrating system. When specified (see 6.2), a variable speed vibrating device shall be furnished and installed on each hopper. This device shall be able to mechanically agitate the hopper side walls during dumping operations to prevent material bridging within the hopper. The device shall either be pneumatically or electrically operated as specified (see 6.2). The device shall be either manual or automatic controlled as specified (see 6.2).
3.9.7 Bags. Bags shall be of fiberglass material able to withstand extended service at temperatures of not less than 500 °F (260 C). The bags shall be treated with a silicone based or similar lubricant to minimize abrasive wear between the individual yarns of the bag. Bag diameter
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