NATIONAL ALUMINIUM COMPANY LIMITED - Rites

15.2.3 Transfer chutes shall be adequately sized and sloped to ensure smooth flow of coal without
any accumulation anywhere.
15.2.4 Complete chute work above the drive floor for conveyors provided with ‘In ‘In-line belt
magnetic separators’ shall be of 10 mm thick SS - 304 in the zone of magnetic field.
15.2.5 Direct impact of material on conveyor belt shall be avoided by providing an inclined surface
at 60 degrees valley angle at the feeding point to guide the material in the direction of belt
travel. Further, chute ute construction below flap gate shaft shall be such that there will not be
any accumulation of coal dust between chute and flap gate in that zone.
15.2.6 Hoppers and Chutes shall be made of minimum 20 mm thick TISCRAL or equivalent material.
However, Contractor ntractor to submit test certificates stating composition of material and
mechanical properties of these wear resistant steel to the Owner during detail engineering.
Long chutes guiding flow from considerable height shall be provided with impact plates
wherever ever change in direction of flow takes place. Hinged inspection doors (generously sized)
of leak proof construction shall be provided for access/ maintenance purpose, at
approachable heights for chutes and flap gates. All chutes should have one inspection door
at every floor and for the ones in between the floors (more then 1.5 meter above the
operating floor level) suitable access for trouble free maintenance shall be provided.
Maximum distance between two inspection doors in a chute shall be 2 mtrs. For s ssealing
of
inspection doors labyrinth type arrangement (with rubber inserted in grooves) to be
provided. In addition to positive locking arrangement, mounting bolts, to tighten the door
further against rubber shall also be provided.
15.2.7 Bottom side of the chutes on which the coal slides shall be welded to the side plates to form
a trough. Bottom sides along with its adjacent sides shall be flanged and made from TISCRAL
or equivalent material of 20 mm thickness. The non non-striking striking surface i.e. the covers oof
the
trough shall be of 10 mm thick mild steel and bolted to the flange provided on the trough.
Inside welding shall be provided in the corners for permanent sealing. Further, the chute
boxes not more than 1.5 m in length shall be joined through bolted fl flange connection to
form the chute legs. Adequate care shall be taken to locate the flange joint away from floor
level for easy maintenance. Bolted flange joints shall be of dust tight construction and
necessary sealing material shall be provided in all the flange connections for adequate
sealing. Complete chute work in the region of flap gates shall be fabricated from 20 thk
TISCRAL or equivalent. In case of vertical chute (valley angle more than 80 degree) complete
chute, work shall be of 20 mm thick TISCR TISCRAL AL or equivalent material. While finalising the
chute work inside the building, arrangement for shifting and replacing chute legs, proper
handling arrangement/wall openings, trolleys, hoists shall also be provided. While
fabricating the chute, the constitu constituent ent plates used shall be in one piece. No welds in between
shall be allowed. In the zones of direct impact due to Coal trajectory, wear resistant backing
plate with stiffners shall be provided in coal flow chutes. Similar backing plates & stiffening
arrangement ement shall also be provided on the chute surfaces having direct coal fall.
Technical Specification:Sec-4,System System Parameters, Operation & Control Philosophy
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