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SPECIFICATIONS -
NON-METALLIC HELICAL SKIMMERS
1.0 - GENERAL
Helical scum skimmers shall be suitable for installation in
rectangular sedimentation tanks as shown on the drawings.
Each skimmer shall be designed for operation in a ____ foot
wide basin in which the normal water surface may vary 2
inches from the normal elevation of ____. The equipment
shall be supplied by a manufacturer with 10 years experience
in similar equipment, "Non-Metallic Helical Skimmer" by
Polytech Systems, Inc. or engineer approved equal.
1.1- OPERATION
Each skimmer shall effectively remove sewage scum and
floating materials from the sedimentation tanks and
discharge it into a scum trough as shown on the drawings.
____ skimmer assemblies shall be provided per tank.
1.2 - DESIGN
Each skimmer shall consist of two helical reels formed as
one integral component on a center tube without mechanical
attachment, and include divider wall-mounted sprockets,
drive chain and guard, and drive unit. Assemblies shall
include beach plate and end cap bearings. Neoprene wipers
shall be bolted onto the integral helical reel sections for
efficient wiping action.
1.3 - MATERIALS
Skimmer Body shall be 150-PSI filament wound FRP tubing
formed with premium grade vinylester resin and have a beige
color gel coat. UV inhibitors shall be added to the
vinylester during the forming process for maximum UV
protection. Two (2) 6 inch x 1/4" thick 180 degree helical
shape reels shall be formed integrally, equidistant around
the periphery of the center tube and shall be fabricated
from a single mold running the length of the center tube,
plus extended each end per manufacturers
recommendations.
2.0 - HELICAL REEL
Each helical reel shall be bonded to the center tube at time
of forming with 6" wide, 1-1/2 oz mat from the center of the
helical shape to a minimum length of 3" onto the pipe center
body for a minimum 3/8" thickness each side. A neoprene or
synthetic rubber strip shall be bolted through the
non-metallic spiral blades by use of a steel clamp bar and
back-up hardware. Mounting hardware shall be 316 stainless
steel. The spiral blades shall be formed perpendicularly to
the centerline of the pipe. For each reel unit, two (2)
helical blades molded diametrically opposite on the center
pipe. Each blade shall be pitched to complete one spiral in
the length of pipe and shall have a 1-foot 6-inch diameter.
The helical blade of the adjacent unit on the same side of
the scum trough shall have its pitch in the opposite
direction. Maximum deflection per reel unit shall be
1/4-inch.
2.1 - REEL SHAFT
All center tube or reel shafting shall be formed of 150 PSI
filament wound FRP pipe of sufficient and ample size to
transmit the power required. Inner pipe ends shall be
flanged with 150 PSI FRP flanges fabricated from premium
grade vinyl ester resin with UV inhibitors to form a flange
to the flange spool.
2.2 -BEARING ASSEMBLIES
Each reel unit shall have two 316 series stainless steel
shaft ends mounted in a wall ring type with a U.H.M.W.
insert bearing located generally as shown on the drawings.
Bearings shall be provided with industrial type lubrication
fittings with stainless steel grease tubing extended up to
the operating walkways. Bearing assemblies shall be
aligning.
2.3 - DRIVE CHAIN
Drive chain shall be non-metallic NH-78 manufactured of a
reinforced nylon resin with stainless steel pins. Chain
shall consist of 2.609 inch pitch links, and shall have a
minimum working load of 1740 pounds.
2.4 - SPROCKETS
The collector chain drive sprockets shall have chain-saver
rims and shall be split construction to facilitate
installation. Sprockets shall be 100% cast nylon-6. All
sprockets to be compatible with non-metallic chain.
The DRIVING SPROCKET shall be provided with key way and set
screw for attachment to the reducer shaft. Sprockets and hub
assembly shall be 100% cast nylon-6 with shear pin hubs.
Drive sprockets requiring jaw clutches shall be 100% cast
nylon-6.
The DRIVEN BULL SPROCKETS shall be split construction to
facilitate installation. Sprockets shall be provided with
key way and set screws for attachment to head shaft.
Sprockets shall be 100% cast nylon-6.
3.0 - DRIVE UNIT
The drive unit shall consist of an electric motor and
helical gear reducer, complete with properly sized shear
pin, driving two ____ foot long helical reel units by means
of two output shafts with a driver sprocket on each shaft
connected to a driven sprocket. Two drive units shall be
provided for each primary tank. Gear reducer shall have an
AGMA service factor rating of 2.0 and shall be equipped with
anti-friction bearing with a bearing life of 25,000 hours,
minimum. Gears shall be steel, cut to accurate form and
encased in a heavy moisture and oil proof case. The helical
reel speed shall be 1 rpm with the drive unit operated at
1.75 rpm with an output ration of 1000 to 1. The coating
shall be for corrosive overload protection and independent
operation shall be provided. Approved drive unit enclosures
shall be provided.
3.1 - DRIVE MOTORS
The drive motor shall be rated 460 Volts, 3-phase, 60 Hz,
3/4 hp minimum, 1.800 rpm, horizontal, TEFC, with a 1.00
service factor. Motor shall comply with this specification
in all other respects and all other reference
specifications.
Nameplate Information ( for reference only)
4.0 - SPARE PARTS AND SPECIAL TOOLS
The following spare parts and special tools shall be
furnished. All parts and tools shall be suitably marked and
boxed for shipment and storage.
ITEM
Drive chains, complete for one tank
Shear pins
Complete flexible wiper set an mounting hardware
Plate ring babbitted bearings
Wall ring babbitted bearings
4.1 - ACCESSORIES
Lifting lugs: Equipment or components over 100 pounds in
weight shall be provided with lifting lugs.
Anchor bolts: Provide anchor bolts, submit size, material
and design in accordance with section______________.
4.2 - EQUIPMENT IDENTIFICATION PLATE
A 16 gauge type 316 stainless steel identification plate
shall be securely mounted on all equipment in a readily
visible location. The plate shall bear the 1/4 inch
die-stamped equipment number indicated in this specification
and shown on the drawings. Stamped equipment shall include
the mechanism drives and the torque switch devices.
5.0 - WORKMANSHIP
General - All parts of all equipment shall be amply
proportioned for all stresses that may occur during
fabrication, shipment erection and intermittent or
continuous operation. Workmanship shall be of high grade in
all respects.
5.1 - PAINTING
Shop and finish painting shall be in accordance with, and as
specified in section PAINTING _______.
5.2 - FIELD TESTS
Functional Test - Prior to tank start-up, all equipment
shall be inspected for proper alignment, quiet operation,
proper connection and satisfactory performance by means of a
functional test. Any deficiencies in alignment, operation,
connection and satisfactory performance shall be corrected
prior to manufacturer's certification.
5.3 - MANUFACTURER'S CERTIFICATION
The supplier or his representative shall certify the
correctness of the installation.
5.4 - PREPARATION FOR SHIPMENT
Equipment shall be prepared and protected for shipment and
shipped a follows. Insofar as is practical, the equipment
specified herein shall be factory assembled into components
as large as may be practically shipped, in order to minimize
field assembly requirements. The parts and assemblies that
are of necessity shipped unassembled, shall be packaged and
tagged in a manner that will protect the equipment from
damage and facilitate the final assembly in the field.
Generally, unpainted machined parts shall be protected from
damage by the elements with the application of a strippable
protective coating. Provide all lubricants required for
initial lubrication. There will be no storage allowed in the
plant warehouse.
5.5 - GENERAL
Payment for the work in this section will be included as
part of the lump sum bid amount stated in the Proposal.
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