PART 1 - GENERAL

1.1 SCOPE: The work covered in this section includes the furnishing of all labor, materials, equipment and incidentals to install complete and ready for operation a sludge thickening device as shown on drawings and as specified herein.

1.2 APPLICABLE PUBLICATIONS: The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by the basic designation only.

American National Standards Institute (ANSI) Publication:
B16.5-81 Pipe Flanges and Flanged Fittings

American Society for Testing and Materials (ASTM) Publications:
A36 Structural Steel
A53 Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded Seamless
A283 Low and Intermediate Steel Plates of Structural Quality

American Welding Society (AWS) Publication:
D1.1-84 Structural Welding Code, Steel
A5.1 Mild Steel Arc-Welding Electrodes
Standard Welding Terms and Definitions
Standard Welding Symbols
Steel Structures Painting Council (SSPC) Publication:
SSPC-SPC-10 Near White Blast Cleaning

1.3 SUBMITTALS:
1.3.1 Contracting officer will review and approve all submittals.
1.3.2 Submit the following before fabrication
1.3.2.1 Shop drawing: Shop drawings for clarification and accessory equipment including principle dimensions and location of fittings. Data shall include weight and distribution of weight with the unit empty and filled with water.
1.3.2.2 Certified Test Results: Submit test results, signed by the manufacturer, which;
a. Indicate sludge thickener tank is capable of specified requirements. Test on this model shall have been done within the last 3 years.
1.3.3 Submit the following after fabrication:
1.3.3.1 Verification:

1. Written verification on the fabricator’s letterhead that surface preparation and coating application were performed in accordance with the specification and coating specification and system manufacturer’s printed recommendations;
2. That the unit was hydraulically leak tested for a period of at least 12 hours before further surface preparation and coating;
3. That the surface preparation and coating process was performed at a facility owned and operated by the manufacturer;
4. That welding procedure, surface preparation and coating process was observed and approved by the manufacturing quality central personnel;
5. That the manufacturer has been manufacturing this type of thickener for 5 years and has this model thickener in service for 5 years.

1.4 MANUFACTURER’S SERVICE REPRESENTATIVE’S REPORT AND CERTIFICATE: Submit service representative’s complete signed report of results of the inspection, operation, adjustment, and tests. Report shall include detailed descriptions of points inspected, tests and adjustments made, quantitative results obtained if such are specified, and suggestions for precautions to be taken to ensure proper maintenance. Include the manufacturer’s certificate that equipment conforms to specified requirements and is ready for permanent operation and that nothing in installation will render manufacturer’s warranty null and void.

1.5 DELIVERY, STORAGE, AND HANDLING MATERIALS:
1.5.1 Delivery and Storage: Inspect materials delivered to site for damage; unload and store with minimum handling. Store materials on site in enclosures or under protective coverings. Protect materials not suitable for outdoor storage to prevent damage during periods of inclement weather, including subfreezing temperatures, precipitation, and high winds. Store materials susceptible to deterioration by direct sunlight under cover and avoid damage due to high temperatures. Do not store materials on ground. Store and protect materials according to manufacturer recommendations.

1.5.2 Handling: Handle sludge thickener in such a manner as to ensure delivery to final location in sound, undamaged condition. Take special care not to damage interior and exterior surfaces of the sludge thickener and associated equipment. Make satisfactory repairs to damaged material(s) at no cost. Carry and do not drag materials. Handle sludge thickener according to manufacturers information.

1.6 QUALITY ASSURANCE:
1.6.1 Inspection: Examine each component of sludge thickener for compliance with requirements specified. Redesign or modification of equipment to comply with specified requirements, or necessary redesign or modification following failure to meet specified requirements, shall receive particular attention for adequacy and suitability. This element of inspection shall encompass visual examinations and dimensional measurements. Noncompliance with specified requirements, or presence of one or more defects preventing or lessening maximum efficiency of clarifier operation, shall constitute cause for rejection.

1.7 WELDER QUALIFICATIONS:
1.7.1 Welders shall be previously qualified by passing the tests prescribed in the AWS Standard Qualification Procedure, or by passing such other tests as the Engineer may accept.

1.7.2 Welders shall have been tested within the past twenty four months and their qualifications shall be considered as remaining in effect unless the welder is not engaged in a given process of welding for a period exceeding six months.

PART 2 - SLUDGE THICKENER AND DESIGN CRITERIA AND DESCRIPTION

2.1 SLUDGE THICKENER CRITERIA
2.1.1 Applications: The sludge thickener shall be used to store and gravity thicken sludges from the waste treatment processes. Settled sludges shall be mechanically raked to the center of the tank and discharged on an as needed basis to the sludge compaction system via air diaphragm sludge pumps. Excess supernatant will gravity flow from the tank with provisions for manual decanting of waters via valves located on the side of the tank.

2.1.2 Performance: The sludge thickener tank shall have a minimum volume of   *   gallons plus 6 inches of freeboard and be designed with a flat bottom center outlet to thicken the sludge to 3-5 percent.

2.2 SLUDGE THICKENER - MANUFACTURING SPECIFICATIONS
*2.2.1 Tank shall be of welded carbon steel construction, minimum thickness ¼ inch. The tank shall be approximately   *   feet in diameter with   *   feet sidewalls and have a capacity of   *   .

2.2.2 Tanks shall be supplied with a flat bottom with flanged outlet connection as indicated. A center recessed well shall collect the concentrated solids. A 2" minimum pipe with flanged outlet shall extend from the center well. The pipe shall have at least one welded support bracket. A 20" manway shall be installed in all tanks taller than 8’.

*2.2.3 Thickener shall have a top mounted fully suspended rake, to move the settled sludge to a center discharge port located in the tank bottom. The rake mechanism shall produce   *   inch pounds of torque and be driven by a 440 VAC, 3 phase TEFC motor of a maximum   *   HP. The rake drive shall be a cantilevered design with the motorized drive supported above the liquid surface eliminating all submerged rotating seals and bearings. The gear reducer drive assembly shall be of the high efficiency cyclical type. Worm gear reducers are not acceptable. The rake tip speed shall not exceed 13 feet per minute.

2.2.4 Tank shall be provided with four (4) @ 2 inch diameter flanged decant withdrawal outlets located at approximately two (2) foot intervals down the straight wall of the thickener. A flanged overflow outlet shall be located approximately one (1) foot from the tank top.

2.2.5 The following materials shall be used in the construction of the sludge thickener:

2.2.5.1 Structural Steel: Shall conform to ASTM A36 or ASTM A283, Grade C.
2.2.5.2 Fittings: Two inches IPS or less shall be flanged or threaded; larger sizes shall be flanged. Flanged fittings shall conform to ANSI B16.5.
2.2.5.3 Piping: Piping shall be standard weight carbon steel pipe conforming to ASTM A53 Grade A.

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*COMPLETE BLANKS FROM ATTACHED CHART

2.2.6 Provide ladder access to top of thickeners for observation purposes. Ladder shall be of design and materials to provide service intended and meet OSHA standards. A work platform shall be installed to service the rake drive.

2.2.7 At least two (2) zinc anodes mounted to 3/4" pipe plugs shall be installed to galvanically protect the steel.

2.3 SURFACE PREPARATION AND COATING
2.3.1 Surface Preparation: The steel surfaces must be dry and clean in accordance with the following requirements. Remove all grease, oils and contaminants as outlined in SSPC SP1. Remove all weld splatter and grind burrs on cut edges and rough welds smooth. Blast clean all surfaces after fabrication in accordance with SSPC SP10 with profile depth of 1.5-2.0 mils. Apply first primer before any rust bloom forms.

2.3.2 Caulking: All exterior non-seal welding joints shall be filled with rubber caulking before painting. Allow sufficient time for caulking to dry before applying the finish coat.

2.3.3 Exterior Surfaces:
Shop First Coat: Apply one coat average dry film thickness of two mils minimum, of a high-build catalyzed epoxy. Apply to all steel surfaces except the areas within 2 inches adjacent to field welds and surfaces specified to be hot-dip galvanized. The paint shall be Hempel 4563U.

Shop Finish Coat: Apply one coat average dry film thickness of 1.0 mils minimum, of a polyurethane paint. Recoat at time interval recommended by the manufacturer, the final coat shall be Hempel 5595U.

Third Coat: Field touch-up of damaged and unpainted areas shall be the same as specified first and second coats at the same film thickness.

The total dry film thickness shall be an average of 4 mils.

2.3.4 Interior Surfaces:
Shop First Coat: Apply one coat average, dry film thickness of four mils, of an immersion grade high-build catalyzed epoxy. Apply to all steel surfaces except the areas within 2 inches adjacent to field welds and surfaces specified to be hot-dip galvanized. The paint shall be Hempel 15409.

Shop Finish Coat: Apply one coat average, dry film thickness of 4 mils, of an immersion grade high-build catalyzed epoxy. Recoat at time interval recommended by the manufacturer, the final coat shall be Hempel 15409.

Third Coat: Field touch-up of damaged and unpainted areas shall be the same as specified first and second coats at the same film thickness. (Liquid Contact).

The dry film thickness shall be an average of 6 mils.

PART 3 - DELIVERY, STORAGE AND HANDLING MATERIALS

3.1 Delivery and Storage: Inspect materials delivered to site for damage; unload and store with minimum handling. Store materials on-site in enclosures or under protective coverings. Protect materials not suitable for outdoor storage to prevent damage during periods of inclement weather, including subfreezing temperatures, precipitation and high winds. Store material susceptible to deterioration by direct sunlight under cover and avoid damage due to high temperatures. Do not store materials directly on ground. If special precautions are required, prominently and legibly stencil instruction for such precautions on outside of equipment or its crating. Store and protect materials according to manufacturers recommendations.

3.2 Handling: Handle sludge thickener tank in such a manner as to ensure delivery to final location in sound, undamaged condition. Take special care not to damage interior and exterior surfaces of sludge thickener tank and associated supports and pipe coatings or linings. Make satisfactory repairs to damaged material(s) at no cost. Carry and do not drag materials. Handle sludge thickener tank according to manufacturers information.

PART 4 - EXECUTION:

4.1 Installation: Sludge thickening tanks to be installed as indicated and as recommended by the manufacturer. Equipment delivered to the site in advance of installation to be stored per the manufacturer’s requirements. Make all connections as required to make sludge thickener fully operation. Do not weld tank surfaces, interior or exterior, it will permanently damage the interior lining. If welding has inadvertently occurred, the interior surface affected shall be abrasively ground to white metal and two coats of Hempel 15409 applied, with air dry between coatings.

4.2 Field Inspection Services: Examine each component of sludge thickener tank for compliance with requirements specified. Redesign or modification of equipment to comply with specified requirements, or necessary redesign or modification following failure to meet specified requirements, shall receive particular attention for adequacy and suitability. This element of inspection shall encompass visual examinations and dimensional measurements.

Noncompliance with specified requirements, or presence of one or more defects preventing or lessening maximum efficiency of sludge thickener tank operation, shall constitute cause for rejection.

4.3 Start-up Testing: Manufacturer’s field representative shall inspect and test unit and certify that the installation has been performed in accordance with manufacturer’s recommendations and that the system is ready for operation by others. Inspection shall consider, but not be limited to, the following:

1. Soundness (without cracked or otherwise damaged parts).
2. Completeness in all details, as specified.
3. Correctness of settling alignment, set points and relative arrangement of each component.
4. Confirm that the unit is level within ¼" side to side and end to end.
5. Inspect unit for leakage and that all mixers are operating as specified.
6. Inspect coating integrity to insure installation contractor has applied touch-up paint to all scratches, blemishes and/or coating discontinuity that occurred during shipping and installation.