Sludge Collection: Screw Conveyors

SLUDGE COLLECTION:  SCREW CONVEYORS

PART 1 - GENERAL

1.1      SUMMARY

A.   Section Includes:

1.   Screw conveyors and appurtenances.

a.   Classifying (shafted) screw conveyors.
b.   Cross and collection (shaftless) screw conveyors.
c.   Conveyor chutes and slide gates.
d.   Structural supports.

B.   Related Work Specified Elsewhere

1.   The requirements of the following sections and divisions apply to the Work of this section.   Other sections and divisions of the Specifications, not referenced below, shall also apply to the extent required for proper performance of this Work.

2.   Division 01, Additional General Requirements

3.   Section 05505, Metal Fabrications

4.   Section 09800, Protective Coating

5.   Section 11005, Equipment: Basic Requirements

6.   Section 11250, Sludge Cake Pumping System

7.   Section 15101, Valve Operators

8.   Section 16220, Electric Motor

9.   Section 17300, Control Strategies

10. Section 17405, Process Instrumentation and Control

1.2      QUALITY ASSURANCE

A.   Reference Specifications, Codes, and Standards:

1.   All Work specified herein shall conform to or exceed the applicable requirements of  the  referenced  portions  of  the  following  publications  to  the  extent  that  the provisions thereof are not in conflict with other provisions of these Specifications.



2.   Comply with  the  applicable editions  of  the  following codes,  regulations and standards.

a.   American Bearing Manufacturers Association (ABMA):
b.   American Gear Manufacturers Association (AGMA):
c.   American Iron and Steel Institute (AISI)
d.   ASTM International (ASTM)
e.   American Welding Society Publication (AWS)
f.    Institute of Electrical and Electronics Engineers (IEEE)
g.   National Electrical Manufacturers Association Standards
h.   Occupational Safety and Health Act

B.   Miscellaneous:

1.   All equipment specified in this section to be supplied by one manufacturer.

1.3      CONTRACTOR QUALIFICATIONS

A.   Provide evidence of at least fifteen (15) years demonstrable experience in the design and manufacture of shafted and shaftless conveyor systems. The Supplier shall have at least ten (10) full-scale shafted and shaftless conveyor systems operating successfully for at least five (5) years that were designed and furnished under the supplier’s own name. References shall be similar in size and length as indicated in this section. Equipment bought and re-sold; or supplied under a license or marketing agreement shall not be considered for meeting the experience clause.

1.4   WARRANTY

A.   The screw conveyors and all components specified in this section shall be warranted by the manufacturer for a minimum three (3) year period after Beneficial Occupancy of the Work pursuant to “Use Prior to Final Completion” of the General Conditions, against defects in workmanship and materials.

1.   Liner:

a.   For a wear indicator (two color) liner, excessive wear shall be indicated by appearance of the bottom indicator layer (second color) along more than 30 percent of the conveyor length during the first three year period after beneficial occupancy of the Work.  If these wear indications occur, the conveyor supplier shall provide new formed and banded liner to replace all the liner in the conveyor that has excessive wear.
b.   If a one color liner is used the excessive wear shall be indicated if the thickness of the liner, at three points over a 30 percent long section of the conveyor, is 1/4 inch thick or less at the thinnest point of the liner, during the first three year period after Beneficial Occupancy of the Work.  Since one color liners prohibit a simple visual inspection confirmation for the liner thickness status at the spiral-liner contact point, the conveyor manufacturer shall supply a  field technician to the jobsite on the annual acceptance date for three consecutive years to remove a minimum 30 percent of all liners and demonstrate to OCSD that at a minimum 1/4 inch of liner is remaining.  If excessive liner wear is found, the conveyor supplier shall provide new formed and banded liner to replace all the liner in the conveyor that has excessive wear.

2.   Screw:  Excessive wear on the screw shall be indicated by loss of more than 20 percent of the height of the main outer screw section over 30 percent of the total length of the screw. If excessive screw wear is found during the first three year period after Beneficial Occupancy of the Work, the conveyor supplier shall provide new screw to replace the screw in the conveyor that has excessive wear.

1.5      SUBMITTALS

A.   Shop Drawings:

1.   See Section 11005, Equipment: Basic Requirements.

2.   Fabrication and/or layout drawings.
a.   Detailed drawings showing supports, drives, connection details, materials of construction, etc.
b.   Structural calculations signed by a professional Civil or Structural Engineer registered in the State of Virginia for all structural support members.

3.   Product technical data:
a.   Cut sheets for electric motors and ancillary items manufactured by others.
b.   Conveyor torque requirement calculations.
c.   Torque calculations for the gear reducer and reducer motor.
d.   Horsepower calculations for the drive motor(s).
e.  Utilize spiral strength calculations for spring (spiral) compression and elongation showing the supplied spiral meets or exceeds spring effect intent of 9.1.2 herein (for conveyors 40 feet or longer).
f.    The CONTRACTOR is responsible for coordination of all mechanical and electrical equipment, and structural interconnecting or otherwise interfacing with the  conveyor  and  any  site  measurements required  for  a  detailed  conveyor submittal.
g.   Acknowledgement that products submitted meet requirements of standards referenced.
h.   Manufacturer's installation instructions.

PART 2 - PRODUCTS

2.1      ACCEPTABLE MANUFACTURERS

A.   Subject to compliance with the Contract Documents, the following manufacturers are acceptable:

1.   Screw conveyors:
a.   Custom Conveyor Corporation.
b.   Jim Myers & Sons (JMS).
c.   Spirac.
d.   Or Equal.

2.2      MATERIALS

A.   Material Standards:

1.   Flighting:
a.   Shafted Conveyors: AISI 304 stainless steel.
b.   Shaftless conveyors:

1)   Cold-formed high-strength alloy steel, minimum hardness 225 Brinell. Steel composition shall be: .31 percent C, 1.44 percent Cr, .64 percent Mo, 64 percent V, 4 percent Mn.

2)   Tensile Strength, Minimum: 110,000 pounds per inch.

3)   Yield Strength, Minimum: 80,000 pounds per inch.

2.   Pipe Shaft: AISI 304 stainless steel.

3.   Troughs: AISI 304 stainless steel.

4.   Covers: AISI 304 stainless steel.

5.   Chutes and Inlets: AISI 304 stainless steel.

6.   Wear liner:
a.   UHMW polyethylene.
b.   Shore Hardness D: 65.
c.   Dynamic Coefficient of Friction: 0.11.

7.   Slide gates:
a.   Frame: AISI 304 stainless steel. b.   Liner: UHMW PE.

8.   Structural Supports: AISI 304 stainless steel.
a.   Grease extension tubes and grease rack: AISI 304 stainless steel.

9.   Hardware & Fasteners: AISI 316 stainless steel.

10. Fabrication:   All welds to be continuous unless otherwise specified.   Facing surfaces of field-welded components shall be beveled and match marked.

11. Edge Grinding:   Sharp corners of all cut and sheared edges shall be made smooth.

12. Surface Preparation

a.   All iron and mild steel surfaces to be painted shall be dry abrasive blasted in accordance with SSPC-SP6, and in accordance with Section 09800, Protective Coating.   Surfaces shall be painted or hot dip galvanized within 24 hours to prevent rusting and surface discoloration.

b.   Stainless steel shall be cleaned with mild abrasive wheels and/or nonferrous blast media to remove heavy scale and welding carbon and/or passivated with stainless steel cleaner then rinsed.

c.   Painting:  After surface preparation, ferrous metal surfaces, if any, except for the spiral flighting shall receive a minimum of one (1) coat of epoxy primer. Provide a total minimum dry film thickness of 3 mils prior to shipment to jobsite. Primer  shall  be  compatible  with  the  paint  system  specified  in  Specification section 09800, Protective Coating.  Finish coats shall be applied at the jobsite by the CONTRACTOR.

d.   The spiral shall be furnished with one coat of shop primer only.

e.   Electric motors, gear reducers, and other purchased sub-components shall be furnished with the manufacturer’s standard finish.

f.    Stainless steel surfaces do not require painting.

2.3      DESIGN REQUIREMENTS

A.   Application:
1.   Provide the Following Conveyors:  Refer to construction drawings for equipment location.

B.   Physical Properties of Material to Convey:
1.   Centrifuge Dewatered Cake, 25 – 35 percent total solids.

C.  Design Criteria:
Type:  Shafted or Shaftless  
Performance  
Material Density (lb/cf): 65  
Capacity (cfh): 1827  
Trough Fill Rate: 30 percent  
System Design  
Approx. Length, feet: Refer to Construction Drawings  
Degrees Incline: 15 
Feed Inlet From: Cross Conveyor  
Discharge Outlet: Cake Pumps  
No. of Discharges: 2  
Shaft Min OD, inches: 4  
Spiral OD, Min, inches: 24  
Spiral Min Thickness, inches: 3/8 (2) 3 inch x1 inch outer  
Min. Spiral Pitch, inches: 24  
Max Liner Length, feet: 4  
Min Liner Thickness,inches: 1/2  
Trough Width: Refer to Construction Drawings  
Min chute thickness, inch: 3/16  
Min lid length, inch: 60  
Min Lid Thickness, inches:   1/8  
Location of Drive: Pull
Type of Drive: Constant Speed reversible  
Maximum HP: 50  
Motor Enclosure: TEFC  
Max Speed (RPM):  20

2.4      COMPONENTS
A.   Troughs:

1.   Trough:
a.   Provide U-type troughs, 3/16 inch minimum thickness.
b.   Use only channel type trough with built-in parallel steel channels.
c.   End seals, shrouds, inlet, discharge, etc., to be constructed from 3/16 inch
(minimum) thick steel.
d.   All openings shall be reinforced with steel angle.
e.   Coordinate opening sizes and connection details with all affected equipment.
f.    Drains: Drain connection with 150-pound flange per conveyor of sizes and at
locations shown on construction drawings.
g.   Provide  spray  wash  system  for  classifying  conveyors  as  indicated  on construction drawings including but not limited to valves, actuators and nozzles.
h.   Provide  flanged  flush  water  connections  as  indicated  on  construction drawings.

B.   Liners (Shaftless Conveyors):

1.   Wear Liner (UHMW):
a.   The wear liner for each conveyor shall be fabricated of Durawear’s Xythelon
3/8 inch thick ultra high molecular weight polyethylene.  The wear liner shall be
furnished in maximum four foot sections to provide ease of replacement.  The liner shall be held in place with clips; no fasteners will be allowed.

C.  Flighting:

1.   Shafted conveyors:
a.   Welding: Continuous, all sides, to pipe shaft.
b.   Pitch between flights to vary no more than 2 percent of the flight outside diameter.
c.   Classifying type screw with paddles at drain zone, ribbon flights at inlet zone, solid face flights to solids discharge point

2.   Shaftless Conveyors:

a.   Formed from one continuous flat bar.   The spiral flights shall be designed with the stability to prevent distortion and jumping in the trough. The torsional rating of the auger flighting shall be reached at 30 percent of the Fy value in the extreme fiber of the flight material. The spiral shall be rolled in such a way as to limit "neckdown" of the outside edge of the cold rolled spiral to 10 percent of the thickness of the inside edge of the spiral. The spiral edges shall be smooth in the as-rolled condition and not show cracks or grinding marks when tested with a dye-penetrant.
b.   Full penetration welds at all splice connections.  Spiral connections shall be welded according to AISC B-U3-GF and be six full-pass full-penetration welds. Flights shall be welded in a jig or the trough to assure true alignment. The OD of the joined spirals shall be completely concentric with no misalignment.   Weld jointed spirals shall be straight and not show any misalignment or thump when rotated.
c.   Concentric to within plus or minus 2 millimeter.
d.   Torsional rating to exceed 150 percent of drive torque rating.  The torsional rating of the auger flighting shall be reached at 30 percent of the Fy value in the extreme fiber of the flight material.   Supplier shall demonstrate that, at 250 percent of the motor nameplate horsepower, the drive unit cannot product more torque than the torsional rating of the flighting, and that the “spring effect” of the spiral shall not exceed +1/32 inch per foot of length at maximum load conditions.
e.   Design with adequate stability to prevent distortion and jumping in the trough
f.    Connect to drive through flanged connection plate welded to spiral.   The spiral flighting shall be connected to the drive shaft by welding the spirals to the 3/4 inch (20 millimeter) minimum circular Drive/Coupling torque transmission plates welded to the spiral as follows:

1)   The drive-coupling plate and drive shaft shall first be machined with 45 degree 1/4 inch matching bevels for welding. The drive-coupling plate shall be bevel machined on both sides for welding. The Drive Coupling plate attached to  the  drive shaft will  use a  six  (6)  pass full penetration weld cleaning after each pass.

2)   The shaft and coupling plate must be maintained at a 90 degree angle. Place the coupling plate and shaft into a sturdy jig made for this purpose and tack weld. Proceed with the first pass.  The drive coupling plate shaft shall then be put into a  lathe and the plate side opposite the shaft shall be machined to ensure a 90 degree connection.
a)   Weld both sides of the shaft with six (6) passes to the coupling plate.
b)   Weld the second spiral coupling torque transmission plate to the spiral. The spiral end shall have a 45 degree clean ground edge at the coupling plate.    Place  the  spiral  and  coupling into  a  sturdy jig  that maintains the spiral level, and the coupling plate at the correct height for welding to the spiral.
c)   Grind smooth on both matching sides and properly reinforced and welded with a curved gusset plate at 180 degrees.  The centerline of the spiral shall be perpendicular to the torque plate within plus or minus
0.015 inch.   A separate 3/4-inch (20 millimeter) minimum torque transmission plate shall be bored with a countersunk and chamfered hole equal to the 1/4 inch less than the shaft diameter and the drive shaft
shall be lathe-turned, keyed and undercut concentrically to a tight fit then
welded to the plate with a six pass full penetration weld technique.  The shaft shall be perpendicular to the torque plate within plus or minus 0.015 inch.  The torque plates shall be connected with three (3) 3/4-inch No. 8 bolts and no space shall show between the connected plates. Spirals welded directly to a shaft or connected in any other way will not be accepted.

D.  Slide Gates:
1.   Maximum vertical dimension of 4 inches excluding the electric motor operator.
2.   In the full, open position 1.5 x spiral pitch is exposed to the opening in the direction of transport.
3.   Opening at least the full width of the conveyor trough.
4.   Steel and UHMW PE 3/16 inch minimum thickness.
5.   The UHMW PE shall have a machined groove to accept the gate blade and give a positive seal.

6.   Actuators:
a.   Electric  actuators  meeting  the  requirements  of  Section  15101,  Valve
Operators.
b.   The  conveyor  manufacturer  shall  provide  electric  motor  operated  gate operator by Rotork model IQ 10, Limitorque model MX 05, Or Equal.
c.   The actuator shall be NEMA 4 rated, have internal adjustable limit switches, and a manual override hand wheel.
d.    The actuator shall be supported underneath the conveyor trough by supports designed and supplied by the conveyor manufacturer.

E.   Trough Cover:
1.   Classifying  Conveyors:  Provide  hinged  access/inspection  cover  over  drain section with toggle clamps and wire mesh safety guard.
2.   Provide  fresh  air  supply  and  foul  air  withdrawal  connections  as  shown  on construction drawings.

F.   Chutes:
1.   Provide chutes constructed from 3/16 inch (minimum) thick steel plate reinforced with steel angles.
2.   Attach chutes to conveyors with bolted and gasketed flanges.

G.  Drive:    Complete  with  motor  mount,  trough  plate,  speed  reducer,  drive  shaft assembly.

H.  Electric Motors:
1.   Motors shall be in accordance with Section 16220, Electric Motors.
2.   1750 rpm.
3.   480 V, 3 PH, 60 Hz.
4.   TEFC.
5.   Torque overload cutout.

I.    Speed Reducer:
1.   Output: As scheduled.
2.   Hollow shaft mounted type gear motor rated a minimum AGMA Class II, single, double reduction or triple reduction
3.   NORD Gear Corporation Unicase, Atlas Gear Company, Or Equal.
4.   Shaft mounted drive with shrink disc hollow shaft design.
5.   Shaft of sufficient diameter to transmit the required torque and welded with a six pass welding process to a coupling plate to effectively transmit torque from the drive shaft to the flight.
6.   A gland packing ring consisting of two Teflon coated packing rings shall seal the drive shaft at its penetration through the end plate.
7.   Connection  of  the  spiral  to  the  drive  system  shall  be  through  a  flanged connection plate that  is  welded to  the  spiral  forming a  smooth and  continuous transformation from the flange plate to the spiral.
8.   The drive shaft shall have a mating flange and shall be bolted to the spiral connection plate.
9.   A  grease  lubricated  labyrinth  seal  shall  be  shaft  mounted  internally  in  the conveyor between the back plate and spiral coupling connection.

J.   Lubrication:
1.   Furnish stainless steel grease extension tube to each bearing.
2.   Centralize the  location of  grease fittings  and  mount  on  rack  constructed of stainless steel.
3.   Locate racks in easily accessible locations.

K.   Structural Supports:
1.  Provide structural supports as required to install conveyors as shown on construction drawings.
2.   Include  beams,  angles,  etc.,  as  required  and  anchoring  devices  to  attach conveyors to structure.

L.   Accessories:

1.   Emergency Stop Switch: Provide each conveyor with and emergency safety stop switch NEMA 4X, with orange vinyl coated galvanized aircraft cable along both sides and mounting hardware. The quantity of emergency stop switches shall be as shown on the P&IDs and Electrical control schematics.
2.   Motion Sensor:
a.   Provide each conveyor with  zero  speed (motion) switch  installed at  the opposite end of the motor.
b.   NEMA 4X, 120V.
c.   Shaftless: Control Concepts or equal.
d.   Shafted: Milltronics MFA-4 with MSP-12 probe, Or Equal from Turck Inc.
3.   Conveyor Door Switch:  Provide a NEMA 4 direct acting limit switch with normally open contacts rated at 10 Amps, 120 Vac for each access door on the shaftless conveyors. The limit switch shall be a series 802T type by Allen Bradley, Series 9000 by Square D, Or Equal.

M.  Comply with Section 11005, Equipment: Basic Requirements.

PART 3 - EXECUTION

3.1      INSTALLATION

A.   General: Install screw conveyors to locations and lengths shown on Drawings.

B.   Install per manufacturer's written instructions and Section 11005, Equipment:  Basic
Requirements.

3.2      MAINTENANCE OF INSTALLED EQUIPMENT, GATES AND VALVES

A.   Maintain the operability and functionality of all installed equipment, gates and valves between the time of installation and the commissioning period.  See Specification section
01660, Shipping, Storage and Handling Requirements, for requirements.

3.3      MANUFACTURER’S FIELD SERVICES

A.   Furnish the services of authorized technical representatives of the Manufacturer to assist/inspect the installed equipment and to certify that the equipment has been properly installed and is ready to operate, train OCSD personnel, conduct pre-operational mechanical checkout of the equipment, place equipment into operation, optimize the performances of the equipment and perform the field performance testing.

B.   At a minimum, conduct four separate site visits as follows:

1.   Inspection of equipment installation – two trips (8 hours minimum, each)

2.   Training of OCSD personnel.  See Specification section 01820, Training of OCSD Personnel, for requirements.

3.   Commissioning:       See   Specification   section   01810,   Commissioning,   for requirements.   Number of  hours shall be  as  required to  meet all testing and commissioning requirements, but shall not be less than 16 hours.