CIRCULAR GRAVITY FILTER REHABILITATION

Transcription

1 PART 1 GENERAL 1.1 SUMMARY CIRCULAR GRAVITY FILTER REHABILITATION A. Section Includes: 1.2 REFERENCES 1. Furnish and install the filter equipment as specified herein and shown on the drawings. The manufacturer shall design and supply a new stainless steel pipe under-drain consisting of a manifold with perforated pipe laterals and brass nozzles. Additionally, the manufacturer shall provide new steel wash troughs with wall brackets and fasteners, surface sweeps, and filter media for four (4) circular filters. The existing tank shells shall be reused. 2. The Contractor shall blast clean each tank shell (inside and out) once each unit is drained and the internals are removed. Once blasted clean the Contractor shall replace and/or repair any tank damage, welded in trough supports, welded in tank spools and associated flanges, and replace any air/water piping as shown on the drawings or otherwise found to be corroded or otherwise defective. The ENGINEER shall be responsible for working with the CONTRACTOR to determine which parts shall be reused once each filter is cleaned and disassembled. The ENGINEER shall also be responsible for providing the CONTRACTOR with any tank shell repair plans, including the bottom plate and interface between the steel tank, the tank bottom plate and concrete foundation. The Contractor is responsible for all associated work with regard to demo, disposal, cleaning existing tank steel, disassembly, repair, replacement, coatings, etc. for and areas required by the specs or plans, which are not part of the equipment supplier s proposed scope of supply. A. American Water Works Association (AWWA): 1. AWWA B Granular Filter Material. 1.3 SUBMITTALS A. Drawings: 1. Submit necessary drawings to site contractor and/or plant for filter part replacement prior to commencing any work on the system in accordance with the requirements of Section 01330, Submittal Procedures. Page 1 of 8

2 Submittal data shall include: a. General Arrangement drawings with Materials of construction. b. Installation details and leveling requirements. B. Field Reports: 1. Submit to the ENGINEER within 2 weeks of site visit. 1.4 PRODUCT HANDLING, STORAGE, AND DELIVERY A. Place or store underdrains, troughs, and specialties only in designated staging areas as approved by the ENGINEER. B. Store underdrains and specialties off the ground, under ultravioletresistant tarps from time of delivery on-site until final installation in the filters. C. Replace underdrains and specialties damaged during storage and delivery. D. Underdrains and specialties are subject to inspection at the ENGINEER s request if visual evidence of damage is observed. 1.5 SYSTEM DESIGN A. Existing Filter Size and Construction: The filter underdrain system shall be as shown and specified. Each existing filter cell shall be of nominal dimensions as listed below: No. of Filters: 4 No. of Cells per Filter: 1 Filter Cell Radius (ft): 9.25 Filter Tank Depth (ft) 9.05 Area per Filter (ft 2 ): 269 ft 2 Total Filter Area for All Four Filters (ft 2 ): 1076 ft 2 Existing Tank material Painted carbon steel Page 2 of 8

3 B. Filter Design Conditions: The filter under-drain and backwash trough parts shall be furnished and installed to perform satisfactorily and as specified when operated under the following flow conditions: Flow Capacity per Filter (clean) 1,050 gpm max. Backwash Rate per Filter 20 gpm/ ft 2 C. General Design Requirements: 1. A single responsible MANUFACTURER shall furnish all equipment components as specified herein, and shall be experienced in the design and manufacture of gravity filters. The MANUFACTRER shall have a minimum 40 years of successful filter operation using circular gravity type filters with pipe under-drain laterals while treating lime softened clarifier water at this facility. 2. Design the filter under-drain parts to ensure long-term stability in its operating characteristics. 3. Due to the assembled size of the under-drain, the pipe laterals shall ship loose from the manifold header pipe for field assembly by the Contractor. D. Performance Requirements: 1. Design the filter under-drain parts to produce uniform water flows throughout the filter cell over the full range of normal backwash flow rates. Flow uniformity per square foot of filter area shall be as required to permit efficient and effective filtration and backwashing. E. Other Requirements: 1. Furnish such installation details and recommendations as are necessary to acceptably interface the filter parts with all surrounding structures, including requirements for leveling, grouting keys and pockets, dowels, piers, and anchorage. Prior modifications by the plant to the original tank structure, piping or associated part interfaces, which may affect the installation and/or operation of the new filter parts, shall be the responsibility of the Engineer and Contractor. 1.6 QUALITY ASSURANCE A. Certification: Provide a manufacturer s certificate of proper installation that states the filter parts have been installed in accordance with the manufacturer s requirements and has been supervised by an authorized representative of the manufacturer and that all of the specified testing has been conducted to insure proper performance. Page 3 of 8

4 B. Under-drain piping, supports, wash troughs, media, surface wash agitators, and any specialties required for installation such as special anchorage, leveling shims, etc. shall be the products of a single MANUFACTURER. PART 2 PRODUCTS 2.1 MANUFACTURERS A. Filter Parts: as originally provided by: 1. Infilco Degremont, Inc. 2.2 UNDERDRAIN MATERIALS & FABRICATION A. Underdrain 1. Each existing filter tank shall be supplied with a new under-drain consisting of a 16 manifold pipe and 2 ½ pipe laterals. The manifold pipe and pipe laterals shall be Type 304 stainless steel. Brass nozzles shall be provided for mounting to the top of the manifold pipe and shipped loose for field installation by the Contractor. Each pipe lateral shall include shop drilled, downward facing orifices, which are 1/4" in diameter. Manifold nozzles and pipe lateral orifices shall be spaced to match the existing design. The new manifold pipe shall be designed to fit inside the existing tank and the existing nozzle pipe, which is welded to the tank shell. The Contractor shall fit the pipe, provide packing to prevent leakage between the new manifold and existing tank nozzle. The Contractor shall also provide and install new grout as noted on the drawings below the under-drain piping. The ENGINEER shall direct the CONTRACTOR as to whether the old under-drain grout must be removed in order to clean and paint the tank bottom plate. Grout removal, repair and new grout shall be provided and installed by the CONTRACTOR. 2.3 WASH TROUGHS A. General: One (1) Wash trough Assembly consisting of seven individual troughs shall be provided per filter 1. All necessary wash water troughs shall be supplied and installed as shown on the plans. 2. Troughs shall have round bottoms and vertical sides. Top edges of the troughs shall be straight with no more than 1/8-inch deviation from a true plane. Longitudinal stiffening ribs shall be welded on the outside of the troughs to assure rigidity. 3. Spacer bars shall be spaced to prevent buckling, and to provide Page 4 of 8

5 2.4 FILTER MEDIA maximum resistance to water loading on the sidewalls of the trough. 4. Troughs shall be A36 carbon steel and shop coated with NSF-61 certified epoxy coatings. 5. Trough layout, outlet, and support system shall be as shown on the approved submittal drawings. All anchors and fasteners shall be Type 304 stainless steel. Shims shall be provided to place under trough ends for leveling at each existing tank wall bracket. Stabilizers shall be provided where necessary to restrict lateral movement (oscillation). The contractor shall perform final weir plate adjustment after installation of troughs. A. General: The following media shall be supplied, shipped in Supersacks. Media provided as follows: Layer Media Type Depth Amount Per Filter 1 Anthracite cu. Ft 2 Silica Sand cu. Ft 3 Torpedo Sand 3 67 cu. Ft. 4 Gravel (1/8-1/4 ) 3 67 cu Ft. 5 Gravel (1/4-1 ½ ) cu. Ft 6 Gravel (1/2-3/4 ) cu. Ft 7 Gravel (3/4 1 ½ ) cu Ft. 1. A layer of torpedo sand, at least 3 finished depth, after backwashing, scraping, and removal of fines, shall be placed on top of gravel support layer and filter underdrain. The sand shall have an effective size of 0.8 mm to 1.2 mm, well rounded, not flat or angular, with a uniformity coefficient of A layer of torpedo sand at least 9 finished depth, after backwashing, scraping, and removal of fines, shall be placed on top of gravel support layer and filter under-drain. The sand shall have an effective size of 0.45 mm to 0.55 mm, well rounded, not flat or angular, with a uniformity coefficient of A layer of anthracite, at least 18 finished depth, after backwashing, scraping, and removal of fines, shall be placed on top of the filter media and gravel support layers. The anthracite shall have an effective size of 0.9 to 1.0 mm with a uniformity coefficient of The filter media supplier shall include sufficient media to allow for scraping of fines during media placement and cleaning. Media levels specified are considered finished depths. Page 5 of 8

6 2.5 SURFACE WASH AGITATORS A. General: Each filter cell shall be provided with one (1) 15-0 surface wash agitator assemblies. 1. The surface wash system shall provide effective cleaning of the filter. The plant shall provide water flow to each surface wash assembly as follows: a. Pressure: 85 psi minimum b. Flow: 179 gpm minimum 2. Each agitator shall include two arms supported by center bearing assembly. The arm piping and end caps shall be constructed of Brass. 3. The center bearing shall be constructed of bronze (ASTM-B ) and shall have a 2 FNPT to connect to the existing 2 ½ supply header assembly piping (by the Contractor). The Manufacturer shall provide a 2-2 ½ transition fitting with dielectric fitting where required. 4. The spray nozzles shall be connected to the agitator arms and shall be spaced and sized according to the filter underdrain manufacturer. There shall be an adequate number of nozzles to produce the flowrate at the specified pressures. The nozzles shall be threaded to the agitator arms for easy removal. The nozzles shall be constructed of Delrin. 5. Pipe, fittings and valves up to the center bearing assembly shall be by others. 2.6 FILTER CONTROL PANEL A. No filter controls are provided for this project. All filter controls are existing. 2.7 COATINGS A. All carbon steel parts shall be shop blasted to SSPC-SP 10 and painted. The troughs shall be coated with Tnemec Pota-Pox Series 20, 2 coats at MDFT each coat for a total DFT of mils or MANUFACTURER approved equal, color 39BL Delft Blue. The stainless steel under-drain piping shall be not be painted. All coatings shall be NSF- 61 certified. Brass parts shall not be painted. The tank shell and all other field applied coatings shall be by the Contractor and as directed by the Engineer. B. The Contractor shall be responsible for touch-up paint after field installation as needed. Page 6 of 8

7 PART 3 EXECUTION 3.1 INSTALLATION A. General: Install the filter under-drain parts in strict accordance with the manufacturer s installation drawings and printed recommendations and as specified. Obtain from the underdrain MANUFACTURER such written installation details, recommendations, and training required to acceptably interface the filter underdrain system with all existing structures. B. Placement and Cleaning: 1. Take all necessary precautions recommended by the underdrain manufacturer s published instructions and as specified to insure that the filter parts and piping are completely clean and free of any debris, dirt, or other foreign materials which could clog the underdrain system or interfere with flow. Before pouring of the underdrain concrete and installation of the filter media, vacuum clean the underdrain area, all cell effluent and backwash supply piping, and all surfaces that come into contact with backwash supply water. C. Installation: 1. The underdrain supplier shall retain on its permanent staff, field service staff who is experienced in the placement of the filter underdrain. Such persons shall be available on a fee-paid basis to guide the Contractor in the proper placement and testing of the underdrain. 2. Follow the filter manufacturer s specific installation instruction. 3. Following the installation, the system shall be completely cleaned and washed free of all loose materials and debris. The underdrain shall be allowed to set for three days before applying internal water pressure. The system shall be installed and tested completely in accordance with the specifications of the filter manufacturer, and under the direction of an experienced superintendent provided by the filter manufacturer. 4. Place filer media in strict accordance with the filter media supplier s recommendations, and under the direct supervision of his authorized field supervisor. Wash each layer of media by backwashing. Each media layer shall have fines scraped after backwashing. The Contractor shall be responsible for insuring the availability and connection of water for backwashing each filter to remove fines and to perform scraping of fines from each media layer. Page 7 of 8

8 3.2 MANUFACTURER S FIELD SERVICES A. The filter parts manufacturer shall provide the services of a technical representative for one (1) trip and two (2) working days per filter train (2 filters) to inspect the completed installation and witness preliminary leak tests. One (1) trip and two (2) working days shall be provided during media installation, backwashing and scraping of fines by the Contractor per filter train (2 filters). One (1) trip and two (2) working days shall be provided during start-up and for training per filter train (2 filters) A total of six (6) trips and twelve (12) days maximum shall be provided by the filter parts Manufacturer to complete onsite service of both filter trains. END OF SECTION Page 8 of 8