manufacturer's design necessitates use of bottom guide bearing.
(5) Chain and Belt Drives: Chain or belt drives incorporated in
the drive assembly shall be designed with a minimum factor of
safety of 5 as applied to the ultimate breaking or transmission
strength of the chain or belt with respect to loads transmitted at
twice the continuous output torque rating of the unit. Roller
chain and sprockets or V-belt and pulleys shall be enclosed in a
weatherproof fabricated steel or fiberglass guard provided with
service openings. Chains shall be of the steel roller type.
Sprockets shall be high test cast-iron conforming to ASTM A 48M
ASTM A 48, Class 40, cast in a chill and shall have a Brinell
hardness of not less than 360 with a chill depth of not less than
5 mm 3/16 inch. Sprocket teeth shall be accurately ground to fit
the chain. V-belts shall be rayon corded with heat and oil
resisting rubber covering. Motor position of V-belt drives shall
be adjustable to increase or decrease belt tension. The drive
sprocket keyed on the output shaft of the speed reducer shall be
bronze with a grease-lubricated bronze busing and provided with
shear pin overload protection. A chain tightener shall be
provided to adjust and tighten the chain.
c.
Sludge Collector Assembly: Assembly shall include scraper arms,
scraper blades, and center shaft. Collector assembly shall have
scraper blades arranged to move settled sludge to a centrally
located sludge hopper.
(1) Scraper Arms: Scraper arms shall be of structural steel
shapes supported by steel guy wires and/or steel tie rods. Scraper
blades shall be steel plate, minimum thickness 6 mm 1/4 inch.
(2) Scraper Blades: Scraper blades shall be steel plate, minimum
thickness 6 mm 1/4 inch. Brass scrapers, minimum thickness 3 mm
1/8 inch, shall be secured to the scraper blades by brass bolts
with brass nuts. Scrapers shall be adjustable for 50 mm 2 inches
in the vertical plane. A scraper blade shall also be provided to
scrape the sludge hopper.
(3) Center Shaft: Center shaft shall be a solid steel shaft or
steel pipe conforming to ASTM A 53, Schedule 40. Steel pipe shall
have solid shaft stub ends or machined flange at the top and steel
cap or plug at the bottom. Scraper arms shall be connected to the
center shaft by welded and/or bolted connections.
d.
Supporting Bridge: Supporting bridge shall be the bridge spanning
the settling tank and supporting the entire rotating type sludge
collector. Supporting bridge shall include two structural steel
beams and braces of sufficient depth and thickness to support the
entire rotating sludge collector within the specified maximum
allowable deflection.
e.
Overload Alarm System: Overload alarm system shall be a
overload unit designed to indicate the load on the mechanism at
all times and to sound an alarm in case of impending excessive
load, and to stop the mechanism when such load is reached. The
overload alarm shall include an industrial type horn, relay, and
reset button in a weatherproof metal housing with a removable
gasketed cover. The horn shall be constructed of
SECTION 11375N
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