spaced at least three times the largest lump size. Foot shaft shall have
protected screw takeup with adjustment of not less than 300 mm 12 inches.
Trough shall be made of 4.8 mm 3/16 inch steel plate, minimum. All sliding
surfaces in contact with the chain or flights shall be lined with 19 mm 3/4
inch thick, removable, ultra high molecular weight polyethylene liners.
Both sides of trough shall be provided with a warning sign "DANGER - DO NOT
WELD - FLAMMABLE PLASTIC LINER." Signs shall be visible on each floor
level and at frequent intervals. Conveyor shall be provided with discharge
openings as indicated, each of which shall be provided with
rack-and-pinion-operated gates with handwheels. Motor shall drive conveyor
through a speed reduction unit which is either direct-connected or
roller-chain-connected to the drive shaft. Motor shall be [totally
enclosed, nonventilated type] [totally enclosed, fan-cooled type] [totally
enclosed, fan-cooled type suitable for installation in a Class II, Division
1, Group F hazardous location in accordance with NFPA 70]. [Motor starter
shall be [manual] [[magnetic] [across-the-line] [reduced voltage start]]
type with [general-purpose] [weather-resistant] [water-tight] [dust-tight]
[explosion-proof] enclosure.] Conveyor frame shall be constructed
essentially as indicated, with additional bracing as required for rigidity.
Dust controlling covers and inlet and discharge enclosures shall be
provided for each conveyor.
2.23.4
Bucket Elevators
**************************************************************************
NOTE: Where motor starters for mechanical equipment
are provided in motor control centers, delete the
description of motor starters.
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Vertical bucket elevators shall be furnished dust tight, complete with
continuous chain and attached buckets, upper and lower sprockets, gears,
shafts, bearings, casing with flanged connections including top hood and
discharge spout, bottom boot, access doors, electric motor drive, and all
accessories. Bucket elevators shall be [vertical spaced centrifugal
discharge] [positive discharge] [continuous bucket type]. The capacity of
the elevator shall be not less than [_____] metric tons/hour tons/hour when
handling coal weighing approximately 800 kg/cubic meter 50 pcf. Linear
velocity shall be as indicated below:
Type of Bucket Elevator
Linear Velocity (meters per second)
Centrifugal discharge
1.1-1.6
Continuous bucket
0.51-0.69
Positive discharge
0.61 Max
Type of Bucket Elevator
Linear Velocity (fpm)
Centrifugal discharge
225-305
Continuous bucket
100-135
Positive discharge
120 Max
The head shaft and foot shaft shall be constructed of cold-rolled steel
with the shaft diameters in accordance with manufacturer's standards. Both
shafts shall be mounted in roller bearings with forced-type lubricating
fittings. Foot shaft shall have screw takeup with adjustment of not less
than 229 mm 9 inches. An automatic backstop shall be installed on the head
shaft to prevent any backward motion of the chain. Boot plates [, loading
legs of continuous bucket elevator,] and bottom plate of stub discharge
SECTION 15555A
Page 69
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