S03938 - Testing and Repair of Leaks in Digester by csgirla

VIEWS: 17 PAGES: 4

									                                                    SECTION 03938

                         EPOXY COATING, TESTING, AND REPAIR OF LEAKS
                      IN DIGESTERS AND DIGESTED SLUDGE STORAGE TANK


PART 1          GENERAL

1.01     SUMMARY

         A.     Section Includes:
                1. Applying epoxy coating to digesters and digested sludge storage tank domes.
                     a. Application of the epoxy coating to the top surface of the digesters and
                          digested sludge storage tank domes shall be provided regardless of
                          whether leaks in the dome have been identified or not.
                2. Testing and repairing leaks in digesters and digested sludge storage tank.

         B.     Related Sections:
                1. Section E03300 - Cast-in-Place Concrete: Requirements for Repair of
                     Defective Concrete.
                2. Section 03931 - Epoxy Injection System.
                3. Section 09960 - Coatings.

1.02     DEFINITIONS

         A.     Gas Leak: Is defined as recurrent formation of bubbles in soap solution.

         B.     Water Leak: Is defined as presence of visible moisture on outside of digester walls.

1.03     SUBMITTALS

         A.     Product Data: Submit data completely describing products.


PART 2          PRODUCTS

2.01     EPOXY FOR SEALING DIGESTER AND DIGESTED SLUDGE STORAGE TANK
         DOMES

         A.     Manufacturers: One of the following or equal:
                1. BASF Construction Chemicals, LLC, Epoxeal GS Structural.
                2. Sika Corporation, Sikadur 55 SLV.


PART 3          EXECUTION

3.01     EPOXY COATING

         A.     Repair imperfections in digesters and digested sludge storage tank encountered
                during construction, which in opinion of the ENGINEER are structural, as specified
                in Section E03300.



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         B.     Application of Epoxy Coating to Exterior Surface of Digester Domes and Digested
                Sludge Storage Tank Dome:
                1.   After minimum of 28 days after digester concrete and digested sludge storage
                     tank concrete has been placed and after exterior piping is connected, apply
                     epoxy coating as follows:
                     a. Lightly sandblast concrete surfaces before applying epoxy.
                     b. Fill digesters with water to elevation of 1,518.17 feet. Fill digested sludge
                          storage tank with water to elevation of 1,508.50 feet.
                     c. Lower water level in sealed digesters and digested sludge storage tank to
                          place not more than 3 inches of water column of vacuum on interior of
                          dome.
                     d. Manually unseal vacuum release valve on digester domes and digested
                          sludge storage tank dome should vacuum release valve fail to operate at
                          3 inches of water column vacuum.
                     e. Coat entire concrete exterior surfaces of digester domes and digested
                          sludge storage tank dome with primer and epoxy while 2 to 3 inches of
                          water column of vacuum are maintained on interior of digester domes and
                          digested sludge storage tank dome.
                     f. Maintain 2 to 3 inches of water column of vacuum on interior of digester
                          domes and digested sludge storage tank dome for published cure time
                          and for not less than 1 hour after placing of epoxy.
                     g. Application of Epoxy:
                          1) Apply epoxy in accordance with manufacturer's instructions.
                          2) Apply minimum of 2 coats of epoxy.
                          3) Multiple applications may be required to comply with manufacturer's
                               instructions and to attain satisfactory results.
                     h. Sprinkle white cement on final epoxy application in order to approximate
                          concrete color.

         C.     Preparation for Testing:
                1.  Prepare digesters and digested sludge storage tank for testing by sealing and
                    plugging visible cracks and imperfections in walls and floor with epoxy.

         D.     Testing Digester Domes and Digested Sludge Storage Tank Dome for Leaks: After
                epoxy coating has been applied and cured for the digester domes and digested
                sludge storage tank dome, conduct leak test as follows:
                1.   Pipe Pieces, Hatches, Holes Through Roof, and Pressure-Relief and Vacuum
                     Breaker Valve: Ensure following:
                     a. Pipe pieces and hatches that are installed through walls have been
                           installed and plugged.
                     b. Holes through dome shall have their final fittings in place.
                     c. Pressure-relief and vacuum breaker valve assemblies are in place and
                           operable.
                     d. Block and anchor piping. No temporary blocking or anchoring will be
                           allowed.
                2.   Fill digesters with water to elevation of 1,518.17 feet and fill the digested
                     sludge storage tank with water to elevation of 1,508.50 feet and allow to stand
                     full for 48 hours.
                     a. Maintain gas pressure of 10 inches of water column for this period by
                           trapping air in the dome and adding such air as is necessary by means of
                           a compressor.



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                       b.   Periodically examine outside of digesters and digested sludge storage
                            tank walls for water leaks and mop entire exterior surface of domes with
                            soap solution to detect gas leaks.
                       c. Mark any leaks discovered by foregoing methods for repair.
                       d. At conclusion of 48-hour period, lower water level in sealed digesters and
                            digested sludge storage tank until vacuum release operates, but not to
                            more than 3 inches of water column of vacuum without manually
                            unsealing.
                3.     Test gasketed connections around safety equipment, hatch covers, and similar
                       type items.
                4.     Repair leaks as specified in this Section.
                5.     After leaks have been repaired, retest digesters and digested sludge storage
                       tank by repeating entire test procedure for digesters and digested sludge
                       storage tank.
                6.     Sewage Effluent:
                       a. DISTRICT will supply effluent for testing digesters and digested sludge
                            storage tank for leaks.
                       b. Transport said effluent to and from digesters and digested sludge storage
                            tank. Furnish pumps, mechanical and electrical materials, power,
                            equipment, and labor used in testing digester and digested sludge storage
                            tank for leaks.

         E.     Required Results: Successful test is defined as no leaks using definitions as
                specified in this Section.

3.02     ADJUSTING

         A.     Repair of Leaks in Digesters and Digested Sludge Storage Tank:
                1.  Preparation for Epoxy Repair: Lightly sandblast concrete surfaces before
                    applying epoxy.
                2.  Repairs of Leaks in Digester Domes and Digested Sludge Storage Tank
                    Dome:
                    a. Repair leaks by placing domes under vacuum, as specified in this Section,
                          and applying epoxy to areas marked for repair.
                    b. Fill digesters with water to elevation of 1,518.17 feet and fill the digested
                          sludge storage tank with water to elevation of 1,508.50 feet.
                    c. Lower water level in sealed digesters and digested sludge storage tank to
                          place not more than 3 inches of water column of vacuum on interior of
                          dome.
                    d. Manually unseal vacuum release valve on digester domes and digested
                          sludge storage tank dome, should vacuum release valve fail to operate at
                          3 inches of water column vacuum.
                    e. Coat concrete exterior surface of domes which are marked for repair with
                          primer and epoxy while 2 to 3 inches of water column of vacuum are
                          maintained on interior of domes.
                    f. Maintain 2 to 3 inches of water column of vacuum on interior of domes for
                          published cure time and for not less than 1 hour after placing of epoxy.
                    g. Application of Epoxy:
                          1) Apply epoxy in accordance with manufacturer’s instructions.
                          2) Apply minimum of 2 coats of epoxy.
                          3) Multiple applications may be required to comply with manufacturer’s
                               instructions and to attain satisfactory results.


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                       h.  Apply 2 pounds-per-square-foot of 30-grit sand after first layer of epoxy
                           coating.
                       i.  Sprinkle white cement on final epoxy application in order to approximate
                           concrete color.
                3.     Repair Leaks in Walls:
                       a. Drain digesters and digested sludge storage tank and repair leaks with
                           epoxy.
                       b. Repair leaks at both interior and exterior of digesters and digested sludge
                           storage tank as specified in Section 03931.
                4.     Repair Leaks in Floor:
                       a. Drain digesters and digested sludge storage tank and repair leaks with
                       epoxy as specified in Section 03931.

                                                    END OF SECTION




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