sprocket or V-belt and pulleys connecting motor and speed reducer
shall be enclosed in a weatherproofed fabricated steel or
fiberglass guard. Chain connecting motor and speed reducer shall
be steel roller type. Sprockets shall be hardened ground alloy
steel or high-test cast-iron, having a minimum tensile strength of
276 MPa 40,000 psi cast in a chill, and shall have 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 shall be keyed on the output shaft of the speed reducer
and shall be bronze bushed with a grease-lubricated bronze bushing
and provided with shear pin overload protection. The drive chain
shall be of the steel roller type, shall weigh not less than 1.36
kg per 300 mm 3.0 pounds per foot, and shall have an average
ultimate tensile strength of 110 MPa 16,000 pounds. The drive
chain shall have a minimum pitch of 65 mm 2.6 inches. A drive
chain tightener shall be provided to adjust and tighten the chain.
c.
Sludge Collector Assembly: Assembly includes collector chain,
driven sprocket, idler sprockets, shafts, bearings, collector
flight and collector return rail.
(1) Collector chain shall have an average ultimate strength of
96.5 MPa 14,000 pounds. Chain links shall be of corrosion
resisting malleable iron having average tensile strength of 517 MPa
75,000 psi and an average Brinell hardness between 170 and 190.
Attachments for scrapers shall be full depth of scraper and
attached with four bolts. Coupling pins shall be not less than 19
mm 3/4 inchdiameter heat treated high carbon steel. All cotter
pins shall be stainless steel. Pivoted attachments shall be
provided for at least two scrapers on each collector, so designed
as to assure positive cleaning of tank corners. All special links
shall be of the same material as the main chain links.
(2) Sprockets shall be high-test cast-iron, having a minimum
tensile strength of 138 MPa 20,000 psi cast in a chill and shall
have a Brinell hardness of not less than 360 with a chill depth of
at least 5 mm 3/16 inch. Sprockets shall be stress relieved
before machining. Sprocket teeth shall be accurately ground to
fit chain. Sprockets shall be split construction assembled with
cadmium plated nuts and bolts. Driven sprocket on the headshaft
shall be of the offset type. The three sprockets on the head
shaft shall be key seated. The idler and chain take-up shaft
sprockets shall not be key seated but, except for number of teeth,
shall be identical in other respects to the head shaft sprockets.
On each idler and take-up shaft, one sprocket shall be set-screwed
and one sprocket shall turn free between two set-screwed collars.
(3) Shafting shall be solid, cold-finished steel, ASTM A 108,
straight and continuous for full width of tank. Shafting shall be
of sufficient size to transmit the maximum force developed by the
drive assembly. Keyways shall be provided where necessary to
attach or locate sprockets on shafting. Keys and key seats shall
conform to ASME B17.1 or ASME B17.2. Shafting shall be polished
in areas of contact with bearings.
(4)
Bearings shall be babbit-lined, sleeve type, self-aligning
SECTION 11375N
Page 47
Previous Page
