SECTION GROUND STORAGE TANK

Transcription

1 SECTION GROUND STORAGE TANK PART 1 GENERAL 1.01 Summary A. Section Includes: Provision for welded steel storage tank design, fabrication, construction and erection, including tank accessories. B. Related Sections: 1.02 References 1. Disinfection and Testing of Steel Storage Tanks: Section A. American Water Works Association: 1. AWWA D100, Welded Steel Tanks for Water Storage. B. National Fire Protection Association (NFPA) 1. NFPA Lightning Protection Code 1.03 Design Requirements A. Design two steel tanks for: 1. Raw water storage tank with a nominal capacity of 169,000 gallons, 30 feet in diameter and 32 feet from top of foundation to overflow. 2. Finished water storage tank with a nominal capacity of 16,000 gallons, 20 feet in diameter and 12 feet from top of foundation to overflow. B. Tank manufacturer is responsible for tank foundation design to assure its integrity and compatibility with tank design requirements based on site conditions. A geotechnical report for the Detention Center Site is available upon request. Contractor shall conduct additional geotechnical investigation and design necessary to ensure that the foundation is appropriate for the site and intended use. C. Tank design to comply with AWWA Specifications and dimensions specified or indicated on Drawings. Ramah Navajo Chapter Detention Center Ground Storage Tank

2 1. Tank to be designed for earthquake loads by the pseudo dynamic approach seismic zone 2, in accordance with AWWA D100, Section 13, with the exception that earthquake and wind loadings will not be assumed to act simultaneously. 2. Design to be governed by the more critical of the load conditions, either earthquake loading or wind loading. D. Welding to be in accordance with latest editions of applicable specifications of the American Welding Society Submittals A. Shop Drawings: Submit shop drawings where indicated in accordance with the Specifications. B. Tank Drawings: Submit detail drawings for steel tanks and accessories to Engineer for approval before fabrication or erection is begun. 1. State on tank shop drawings that design of tank foundation was reviewed with respect to its integrity and congruence with tank design, and the two designs are compatible. C. Design Computations: Submit design computations for steel tanks, foundation and accessories to Engineer for approval before tank fabrication is begun. Design computations as submitted are to be certified by a Licensed Professional Engineer. Engineer's approval does not in any way relieve responsibility for accuracy and completeness of design. D. Cleaning and Painting: Paint systems as follows: Inside- Paint AWWA paint system No. I and Outside AWWA paint system No. 2. Submit cleaning and painting systems to Engineer for approval before fabrication or erection of steel tank is begun. Outside paint color as selected by the Owner Quality Assurance A. Qualifications: Fabricated and erected by a firm with a minimum 10 years successful experience in this type of work. PART 2 PRODUCTS 2.01 Type Of Construction A. Tank walls to be of butt-welded construction. Roof to be a center column supporting type. Minimum shell thickness shall be 1/4 inch or as recommended by the manufacture. Ramah Navajo Chapter Detention Center Ground Storage Tank

3 B. Tank constructed so as to receive a stroke of lightning without damage as outlined by NFPA 780, Chapter 3 and 4. Have tank manufacturer submit sufficient evidence, in form of calculations or other justification of how this requirement will be met. 1. If tank manufacturer cannot meet these requirements, as determined by Engineer, provide a lightning protection system for tank, which includes air terminals, and down leads. 2. If tank manufacturer can meet these requirements, provide a lightning protection system, excluding air terminals and down leads, as indicated on Drawings for the tank. 3. In either case, perform installation by a Master Labeler Shop or company. C. Indicate on Proposal the name of the firm that will fabricate and erect the steel tank Accessories A. Roof Hatch (One required): Provide one hatch of minimum 30 inches in diameter with a 4 inch flanged neck with gasketed, bolted and hinged cover. B. Shell Manholes (Two Required): Minimum 30-inch diameter, gasketed, bolted, and hinged on outside. C. Bolting and Hinge Material: Stainless steel, ASTM A193 and A194 (Type 304), for all manholes, hatches and overflow piping. Provide gaskets of red rubber material. D. Overflow: Overflow pipe and weir box to have a 3800 gpm minimum capacity with a water level not more than 6 inches above the overflow elevation. Provide overflow with mesh bronze screen at bottom. E. Vertical Outside Ladder with Safety Cage: Start Safety Cage 10 feet above level of tank bottom. F. Roof Platform: Construct with steps and handrails on both sides to a point on roof as defined by AWWA walking slope requirement. Construction of platform is to allow stepped portion to be removed such that the roof plate and platform underside is accessible for repainting. Construction is to meet AWWA, OSHA, Federal, State and Local Requirements. G. Roof Vent with fiberglass #4 mesh screen. Screen to be protected from direct contact with snow or freezing rain. Size roof vent for a maximum flow rate in or out of tank of 15,500 cfm. H. Climb Prevention Cover as indicated on Drawings. Ramah Navajo Chapter Detention Center Ground Storage Tank

4 I. Water Level Target as shown on the drawings and approved by the Engineer. J. Level Indicating sensor: The sensor shall be Keller PSI Series 700. The sensor and cable shall be installed per Keller procedures, practices and instructions. The coaxial cable shall be housed in %" galvanized metal conduit, UL listed E32464, ANSI C The conduit shall be buried at a minimum depth of 3'-0". A splice between an existing coaxial cable and a cable extension shall be housed in a junction box which shall be weather proof and mounted on the wall of the booster station building. The conduit mounted on the side of the new tank shall be anchored to the outside of the tank with galvanized straps welded to the tank shell at a minimum of 4 foot intervals. The conduit and straps shall be painted to match the tank coat. PART 3 - EXECUTION 3.01 Fabrication And Erection A. Fabricate and erect tank in accordance with latest edition of AWWA D100, with or without Appendix C. B. Tank construction dimensional tolerances to comply with API Standard 650, Paragraphs 5.5.2, 5.5.3, 5.5.4, and Inspection Of Welds A. At completion of welding, have at least one spot radiograph taken in the field on four sides of every plate below overflow elevation. Consider spot radiographs required by AWWA D100 as a part of above requirements. B. All bottom plates to be tested by air pressure or vacuum method in accordance with AWWA Standard D100. C. Submit a report on x-ray inspections to Engineer. Report to include a layout sketch indicating location of radiographs with respect to plate edges, and inspector's acceptance record for all radiographs Coatings Certification A. Interior and exterior coatings shall be certified by an independent, certified, coating inspector accredited by the National Association of Corrosion Engineers (NACE) and acceptable to the Owner. B. Coatings Inspector's Obligations: 1. The Coating Inspector shall make all required site inspections and tests at the tank fabrication shop and the project site in order that he may certify the coatings system was constructed in compliance with the coating manufacturer's Ramah Navajo Chapter Detention Center Ground Storage Tank

5 C. Costs: recommendations, this specification, and the applicable standards referenced herein. 2. Tests performed at the project site will be scheduled in order that the owners representative on the project is present during all testing. 1. Costs associated with coatings certification are the sole responsibility of the Contractor and/or tank fabricator. 2. All necessary recoating work, including surface preparation required as a result of independent inspection and testing, shall be performed at no additional cost to the Owner. D. Coating Test Report: 1. A test report shall be prepared and submitted to the Owner at the conclusion of the dry film thickness and indicating: a. The film thickness gauge used. b. The locations where tests were made. c. The dry film thickness at each location. d. The name of the person making the tests. e. The names of the persons who are representing the Contractor and the Owner and who are witnessing the test. 2. The test report shall be certified by the NACE specialist, indicating compliance with this specification. 3. The report will also include the dates and times of inspections made at the tank fabrication site for surface preparation Special Requirements for this Project A. Qualifications of Painting / Coating Crew: 1. Painting crew superintendent will have at least five years of supervisory experience in the surface preparation and application of industrial coatings such as tank coatings or similar systems. Ramah Navajo Chapter Detention Center Ground Storage Tank

6 2. The superintendent will also be knowledgeable in all coating testing procedures. 3. Applicators will have at least two years of experience in the surface preparation and application of coatings described above. B. Prior to surface preparation and coating, a meeting with the general superintendent and coating crew superintendent will be held at the Engineer's office to ensure understanding of the specification requirements Eleven Month Inspection of Coating System A. General: I. Approximately 11 months after acceptance of the new tank by the Owner, the Owner, Engineer and Contractor shall conduct an inspection of the interior and exterior tank coating systems 2. Costs associated with the 1 I-month inspections shall be incidental to the construction of the tank. B. Contractor's Obligations: 1. The Contractor shall provide all necessary labor and equipment to perform the inspections 2. The Contractor may provide inspection of the tank's interior coating by means of a remote or manually operated underwater video camera that will provide good quality picture of all interior surfaces. 3. The location of any observed coating failures shall be documented. C. Drainage of Tank: 1. The tank will not have to be drained if there is no evidence of coating failure during the video inspection. 2. The tank will have to be drained if: D. Repair of Coating Failures a. Acceptable pictures cannot be provided b. Complete coverage of the entire surface cannot be documented. c. Coating failures are observed. Ramah Navajo Chapter Detention Center Ground Storage Tank

7 1. The Contractor shall repair documented coating failures in accordance with the coating manufacturer's recommendations. 2. If the repairs require that the tank be drained, the Contractor shall coordinate the work with the water system operator and provide all equipment, labor and materials, including temporary storage if necessary, to complete the repairs. 3. Upon completion of the repair work, the tank will be disinfected in accordance with the AWWA requirement and placed back into service END OF SECTION Ramah Navajo Chapter Detention Center Ground Storage Tank