sensitivity adjustment can be made from outside the bin. Type and number
of contacts and voltages shall be as indicated on the control diagrams.
2.9.18.2
Type B - Paddle Type Presence Indicator
Paddle mounted on a counterweighted horizontal shaft so that deflection of
the paddle rotates a cam which actuates a limit switch in a control box
mounted on the shaft. Unit shall consist of paddle, shaft, enclosure,
limit switches, wiring, and mounting brackets. Shaft shall be cold rolled
steel and paddle shall be stainless steel with control enclosure of cast
iron, stainless steel, or suitably protected cast aluminum. Type and
number of contacts and voltages shall be as indicated on the control
diagram. Mount shaft in ball bearings equipped with suitable dust seals
and fittings for pressure grease lubrication.
2.9.18.3
Type C - Tilt Type Presence Indicator
Conical steel float that shall be tilted by presence of coal. Unit shall
consist of housing, conical float, universal pivot-collar, pendant
mechanism, dust seal, limit switches, wiring, and mounting brackets. Unit
shall operate so that the tilting of the float actuates a limit switch in
the enclosed housing above. Provide a hood constructed according to
manufacturer's recommendations for the indicator's location of not less than
5 mm 3/16 inch thick steel plate. Provide access panel for servicing the
unit. Tilt type indicator may be a totally enclosed type in which tilting
causes a ball to roll off the center actuating a limit switch. Design unit
to be cable hung and to tilt on the presence of coal.
Type and number of
contacts and voltages shall be as indicated on the control diagram.
2.9.18.4
Type D - Rotating Type Presence Indicator
Rotating paddle where presence of coal stalls motor and actuates a limit
switch. Unit shall have either cast iron or cast aluminum housing,
stainless steel paddle, couplings, and flexible shaft. Shaft seal shall be
spring loaded and shall prevent the buildup of fines between shaft and hub.
Operation shall be such that when paddle stalls, motor continues to
operate until the limit switch is actuated, which in turn shuts off the
current to the motor. Vane and baffle arrangements shall be according to
manufacturer's recommendations for each indicator location. Type and
number of contacts and voltages shall be as indicated on the control
diagrams.
2.9.18.5
Type E - Vibrating Type Presence Indicator
Vibrating sensing rod so that the presence of coal dampens the vibrations
actuating a control signal. Sensing rod shall be stainless steel not less
than 10 mm 3/8 inch in diameter. Control unit shall be solid state, with
type and number of contacts and voltages as indicated on the control
diagrams.
2.9.18.6
Equipment Speed Response Switch
Actuates a control signal when preset abnormal equipment operating
conditions are encountered. Switch shall be adjustable so that it may be
used as an underspeed switch, overspeed switch, or zero speed switch.
Switch shall consist of input shaft from which the equipment speed is
measured and compared to a preset point. Enclosure shall be cast iron or
suitably protected cast aluminum. Mount speed response switches as
indicated on drawings. Type of switch adjustment, type and number of
SECTION 15502N
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