USACE / NAVFAC / AFCESA / NASA UFGS-44 46 19 (October 2007) ---------------------------- Preparing Activity: USACE Superseding UFGS-44 46 19 (April 2006) UNIFIED FACILITIES GUIDE SPECIFICATIONS References are in agreement with UMRL dated January 2009 SECTION 44 46 19 SLUDGE-DIGESTER GAS, HEATING, AND MIXING SYSTEM 10/07 NOTE: This guide specification covers the requirements for sludge-digester gas, heating, and mixing system for sewage treatment plants. Edit this guide specification for project specific requirements by adding, deleting, or revising text. For bracketed items, choose applicable items(s) or insert appropriate information. Remove information and requirements not required in respective project, whether or not brackets are present. Comments and suggestions on this guide specification are welcome and should be directed to the technical proponent of the specification. A listing of technical proponents, including their organization designation and telephone number, is on the Internet. Recommended changes to a UFGS should be submitted as a Criteria Change Request (CCR). PART 1 GENERAL 1.1 REFERENCES NOTE: This paragraph is used to list the publications cited in the text of the guide specification. The publications are referred to in the text by basic designation only and listed in this paragraph by organization, designation, date, and title. Use the Reference Wizard's Check Reference feature when you add a RID outside of the Section's Reference Article to automatically place the reference in the Reference Article. Also use the Reference Wizard's Check Reference feature to update the issue dates. References not used in the text will automatically be deleted from this section of the project specification when you choose to reconcile references in the publish print process. The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only. AMERICAN PETROLEUM INSTITUTE (API)API Spec 6D(2008; Errata 2008; Errata 2008) Specification for Pipeline ValvesAMERICAN WATER WORKS ASSOCIATION (AWWA)AWWA C110/A21.10(2008) Ductile-Iron and Gray-Iron Fittings for WaterAWWA C115/A21.15(2005) Flanged Ductile-Iron Pipe With Ductile-Iron or Gray-Iron Threaded FlangesASME INTERNATIONAL (ASME)ASME B16.1(2005) Standard for Gray Iron Threaded Fittings; Classes 125 and 250ASME B16.3(2006) Malleable Iron Threaded Fittings, Classes 150 and 300ASME B16.5(2003) Standard for Pipe Flanges and Flanged Fittings: NPS 1/2 Through NPS 24ASME B31.1(2007; Addenda 2008) Power PipingASME BPVC SEC IV(2007; Addenda 2008) Boiler and Pressure Vessel Code; Section IV, Recommended Rules for the Care and Operation of Heating BoilersASME BPVC SEC IX(2007; Addenda 2008) Boiler and Pressure Vessel Code; Section IX, Welding and Brazing QualificationsASME BPVC SEC VIII D1(2007; Addenda 2008) Boiler and Pressure Vessel Code; Section VIII, Pressure Vessels Division 1 - Basic CoverageASTM INTERNATIONAL (ASTM)ASTM A 307(2007b) Standard Specification for Carbon Steel Bolts and Studs, 60 000 PSI Tensile StrengthASTM A 36/A 36M(2008) Standard Specification for Carbon Structural SteelASTM A 53/A 53M(2007) Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and SeamlessCSA AMERICA, INC. (CSA/AM)CSA/AM Z21.15(1997; R 2003; A 2006) Manually Operated Gas Valves for Appliances, Appliance Connector Valves and Hose End ValvesEXPANSION JOINT MANUFACTURERS ASSOCIATION (EJMA)EJMA Stds(2003) EJMA StandardsMANUFACTURERS STANDARDIZATION SOCIETY OF THE VALVE AND FITTINGS INDUSTRY (MSS)MSS SP-58(2002) Standard for Pipe Hangers and Supports - Materials, Design and ManufactureMSS SP-69(2003; R 2004) Standard for Pipe Hangers and Supports - Selection and ApplicationMSS SP-70(2006) Standard for Cast Iron Gate Valves, Flanged and Threaded EndsMSS SP-78(2005a) Cast Iron Plug Valves, Flanged and Threaded EndsMSS SP-80(2008) Bronze Gate, Globe, Angle and Check ValvesNATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION (NEMA)NEMA 250(2003) Enclosures for Electrical Equipment (1000 Volts Maximum)NEMA ICS 1(2000; R 2005; R 2008) Standard for Industrial Control and Systems General RequirementsNEMA ICS 2(2000; Errata 2002; R 2005; Errata 2006) Standard for Industrial Control and Systems: Controllers, Contractors, and Overload Relays Rated Not More than 2000 Volts AC or 750 Volts DC: Part 8 - Disconnect Devices for Use in Industrial Control EquipmentNEMA ICS 3(2005) Standard for Industrial Control and Systems: Medium Voltage Controllers Rated 2001 to 7200 Volts ACNEMA ICS 4(2005) Industrial Control and Systems: Terminal BlocksNEMA ICS 6(1993; R 2006) Standard for Industrial Controls and Systems EnclosuresNEMA MG 1(2007; Errata 2008) Standard for Motors and GeneratorsNEMA SG 6(2000) Standard for Power Switching EquipmentNATIONAL FIRE PROTECTION ASSOCIATION (NFPA)NFPA 58(2007; Amendment 1 2007; Amendment 2 2007; Amendment 3 2007; Amendment 4 2008) Liquefied Petroleum Gas CodeNFPA 70(2007; AMD 1 2008) National Electrical Code - 2008 EditionUNDERWRITERS LABORATORIES (UL)UL 508(1999; Rev thru Sep 2008) Standard for Industrial Control EquipmentUL 845(2005; Rev thru Aug 2006) Standard for Motor Control Centers1.2 SYSTEM DESCRIPTION Provide a complete gas, heating, and mixing system for sludge digesters shown. The system shall consist of a digester gas handling system, digester heating system, auxiliary fuel system, sludge mixing system and appurtenances as required for a complete and operating system. Coordinate the system with the digester cover specified in Section 44 46 20 FLOATING COVER FOR SLUDGE-DIGESTION TANKS. 1.3 SUBMITTALS NOTE: Review submittal description (SD) definitions in Section 01 33 00 SUBMITTAL PROCEDURES and edit the following list to reflect only the submittals required for the project. Submittals should be kept to the minimum required for adequate quality control. A “G” following a submittal item indicates that the submittal requires Government approval. Some submittals are already marked with a “G”. Only delete an existing “G” if the submittal item is not complex and can be reviewed through the Contractor’s Quality Control system. Only add a “G” if the submittal is sufficiently important or complex in context of the project. For submittals requiring Government approval on Army projects, a code of up to three characters within the submittal tags may be used following the "G" designation to indicate the approving authority. Codes for Army projects using the Resident Management System (RMS) are: "AE" for Architect-Engineer; "DO" for District Office (Engineering Division or other organization in the District Office); "AO" for Area Office; "RO" for Resident Office; and "PO" for Project Office. Codes following the "G" typically are not used for Navy, Air Force, and NASA projects. Choose the first bracketed item for Navy, Air Force and NASA projects, or choose the second bracketed item for Army projects. Government approval is required for submittals with a "G" designation; submittals not having a "G" designation are for [Contractor Quality Control approval.][information only. When used, a designation following the "G" designation identifies the office that will review the submittal for the Government.] The following shall be submitted in accordance with Section 01 33 00 SUBMITTAL PROCEDURES: _{SD-02 Shop Drawings Equipment Installation}[; _G][; _{G, [_____]}] Drawings containing complete wiring and schematic diagrams and any other details required to demonstrate that the system has been coordinated and will properly function as a unit. Show on the Drawings proposed layout and anchorage of equipment and appurtenances, and equipment relationship to other parts of the work including clearances for maintenance and operation. _{SD-03 Product Data Materials and Equipment} A complete list of equipment and material, including manufacturer's descriptive data and technical literature, performance charts and curves, catalog cuts, and installation instructions. _{Spare Parts} Spare parts data for each different item of material and equipment specified. _{Framed Instructions} A copy of the instructions proposed to be framed and posted. _{SD-06 Test Reports Testing} Performance test reports in booklet form showing all field tests performed to adjust each component and all field tests performed to prove compliance with the specified performance criteria, upon completion and testing of the installed system. Indicate in each test report the final position of controls. Include in the boiler and heat exchanger test reports manometer readings at the main gas regulator, pilot gas regulator, burner inlet, burner and the furnace; amperes drawn by all motors; voltage of main flame and pilot controller signal; and flue gas readings including percent oxygen, percent carbon dioxide, temperature, efficiency, and smoke test results. _{SD-10 Operation and Maintenance Data Operating and Maintenance Manuals}[; _G][; _{G, [_____]}] [Six] [_____] copies of operation and [six] [_____] copies of maintenance manuals for the equipment furnished. One complete set, prior to performance testing and the remainder upon acceptance. Operation manuals shall detail the step-by-step procedures required for system startup, operation, and shutdown. Operation manuals shall include the manufacturer's name, model number, parts list, and brief description of all equipment and their basic operating features. Maintenance manuals shall list routine maintenance procedures, possible breakdowns and repairs, and troubleshooting guides. Maintenance manuals shall include piping and equipment layout and simplified wiring and control diagrams of the system as installed. Manuals shall be approved prior to the field training course. 1.4 QUALIFICATIONS Qualify procedures and welders in accordance with the code under which the welding is specified to be accomplished. 1.5 DELIVERY, STORAGE, AND HANDLING Protect all equipment, delivered and placed in storage, from the weather, excessive humidity and excessive temperature variation; and dirt, dust, or other contaminants. 1.6 _{SPARE PARTS} Submit spare parts data for each different item of material and equipment specified, after approval of the related submittals and not later than [_____] months prior to the date of beneficial occupancy. Include with the data a complete list of parts and supplies, with current unit prices and source of supply. PART 2 PRODUCTS 2.1 MATERIALS AND EQUIPMENT _{Materials and equipment} shall conform to the following respective publications and other specified requirements. 2.1.1 Standard Products Provide materials and equipment which are the standard products of a manufacturer regularly engaged in the manufacture of such products and that essentially duplicate items that have been in satisfactory use for at least 2 years prior to bid opening. Equipment shall be supported by a service organization that is, in the opinion of the Contracting Officer, reasonably convenient to the site. 2.1.2 Nameplates Provide each major item of equipment with the manufacturer's name, address, type or style, model or serial number, and catalog number on a plate secured to the item of equipment. 2.1.3 Special Tools Provide one set of special tools, calibration devices, and instruments required for operation, calibration, and maintenance of the equipment. 2.1.4 Steel Shapes, Plates and Bars Steel shapes, plates, and bars shall conform to ASTM A 36/A 36M. 2.1.5 Digester Gas Pipe and Fittings 2.1.5.1 Digester Gas Pipe Smaller Than 100 mm 4 Inch Diameter Pipe shall be screwed joints galvanized steel in accordance with ASTM A 53/A 53M. Fittings shall be galvanized malleable iron in accordance with ASME B16.3. Couplings shall be in accordance with ASTM A 53/A 53M. 2.1.5.2 Digester Gas Pipe 100 mm 4 Inch Diameter and Larger Pipe shall be ductile iron in accordance with AWWA C115/A21.15. Joints shall be ASME B16.1, Class 125 flanged joints. Fittings shall be ductile iron in accordance with AWWA C110/A21.10. Bolts and nuts shall be in accordance with ASTM A 307, Grade B. 2.1.6 Sludge Piping Pipe shall be flanged ductile iron pipe in accordance with AWWA C115/A21.15. Pipe 100 mm 4 inch diameter and smaller shall be thickness Class 51. Pipe 150 mm 6 inch through 600 mm 24 inch diameter shall be thickness Class 50. [Pipe 750 mm 30 inch diameter and larger shall be thickness Class 51]. Fittings shall be ductile iron in accordance with AWWA C110/A21.10. Joints shall be ASME B16.1 Class 125 flanged joints. Bolts and nuts shall be in accordance with ASTM A 307, Grade B. 2.1.7 All Other Piping Pipe shall be standard weight black steel pipe in accordance with ASTM A 53/A 53M. Pipe smaller than 100 mm 4 inch diameter shall have screwed joints and malleable iron fittings in accordance with ASME B16.3. Pipe 100 mm 4 inch diameter and larger shall have class 150 flanged joints and fittings in accordance with ASME B16.5. 2.1.8 Valves 2.1.8.1 Angle, Check and Globe Valves Valves shall conform to MSS SP-80, Type 3, globe and angle. 2.1.8.2 Gate Valves Valves shall conform to MSS SP-80, Type 1, Class 150 or MSS SP-70, Type I, Class 150 bronze trim. 2.1.8.3 Plug Valves Bronze plug valves shall comply with MSS SP-78. Iron plug valves shall comply with API Spec 6D. 2.1.8.4 Gas Valves Shut-off valves on gas lines shall be of the cast brass plug-cock type for sizes up to and including 50 mm 2 inch diameter and of the cast iron brass mounted or wholly brass plug-cock type for sizes 65 mm 2-1/2 inch diameter and larger. All gas line valves shall be in accordance with the applicable requirements of CSA/AM Z21.15. Gas valves shall be tested with air at 861.8 kPa 125 psiwithout developing leakage. 2.1.9 Expansion Joints Expansion joints shall conform to EJMA Stds. 2.1.10 Pipe Hangers and Supports Pipe hangers and supports shall conform to MSS SP-58 and MSS SP-69. 2.1.11 Electric Motors Motors shall conform to NEMA MG 1. 2.1.12 Motor Controls and Motor Control Centers Controls and motor control centers shall conform to NEMA ICS 1, NEMA ICS 2, NEMA ICS 3, NEMA ICS 4, NEMA ICS 6 , UL 508, and UL 845. 2.2 DIGESTER GAS HANDLING SYSTEM NOTE: Coordinate with Section 44 46 20 FLOATING COVER FOR SLUDGE-DIGESTION TANKS. Coordinate with paragraph COMPRESSED GAS SLUDGE MIXING SYSTEM. A complete system shall be provided for distribution and disposal of gas produced in the digesters. The system shall include all necessary gas safety equipment to insure maximum protection against fire, explosion, and fume hazard at all times. Gas equipment shall be designed for digester gas having a calorific value of 22.3 MJ per cubic meter (600 Btu per cubic foot) 600 Btu per cubic foot, a specific gravity of 0.8, and a maximum pressure of [_____] Pa inch water column. The system shall provide distribution to the [compressed gas sludge mixing system,] and [gas storage tank,] sludge heating system and waste gas burner. 2.2.1 Waste Gas Burner Waste gas burners, having a capacity for burning [_____] cubic meters cubic feet of gas per hour at a pressure loss not to exceed 127 Pa 1/2 inch of water column, shall be provided to dispose of excess digester gas. The burner shall be provided with a [_____] mm inch screwed inlet and a pilot-line connection not less than 19 mm 3/4 inch in diameter. The burner shall be provided with a readily adjustable pilot light, properly designed air inlet and mixing chamber, a burner bowl supported by a cast iron or steel pipe pedestal filled with insulating material, and a flanged base with anchor bolts for installation on a concrete foundation or concrete curb. The pilot light and burner shall be arranged to prevent the pilot light from being blown out by gas ignition, wind, or other accidental means. A shut-off valve shall be provided in the pilot gas line. The waste gas burner shall be located a minimum of 15 m 50 feet from the [gas storage tank] [and] [digester]. 2.2.2 Flame Checks Flame checks shall be provided in the pilot line to the waste gas burner. Flame checks shall block flame return and shall have threaded end connections of the same size as the pilot line. 2.2.3 Flame Traps Flame traps shall be provided in the gas piping system between each source of ignition and the digesters. Flame traps shall be located as close as possible to the source of ignition, the distance not to exceed 7.5 m 25 feet . Each flame trap shall have a capacity to pass at least [_____] cubic meters cubic feet of gas per hour at a pressure loss not to exceed [_____] 127 Pa 1/2 inch of water column. The flame trap element shall prevent the passage of flame and shall permit convenient replacement of the entire element. The unit shall also include a spring actuated thermal shut-off valve, held open by a fusible element, to automatically close in the presence of burning mixtures. 2.2.4 Sediment Traps Sediment traps shall be provided in the gas piping system prior to all other equipment. Traps shall be baffled and provided with a sealed, safe means of determining the liquid level without closing the gas supply line. Sediment traps shall be of cast iron, ductile iron, or galvanized steel construction with a minimum capacity of 38 L 10 gallons of accumulated sediment and condensate. Supply line connections shall be equal to the supply line size. A manual drip trap shall be provided to drain accumulated condensate from the sediment trap. 2.2.5 Drip Traps Drip traps shall be provided in the gas piping network at the low points and on the upstream side of each gas meter. Drip traps shall be manually operated, shall be constructed of cast iron, ductile iron, or galvanized steel, and shall have a minimum capacity of 2 L two quarts. Trap construction shall effectively prevent leakage of gas from the system when the trap is being drained. 2.2.6 Gas Meters Gas meters shall be provided to measure the gas production of each digester and the volume of gas delivered to the waste gas burner and the sludge heating system. Gas meters shall be rated at [_____] cubic meters/second cfm at [_____] Pa inch water column pressure drop with a capacity of 200 percent rated flow. Meters shall be constructed of materials resistant to the corrosive effects of digester gas. A valved bypass shall be provided around each gas meter. 2.2.7 Pressure Indicating Gauges Pressure indicating gauges shall be provided in the gas piping system to enable monitoring of digester pressure and to enable the pressure balancing at the waste gas burner and the digester heating system. Gauges shall be direct reading in Painch of water and shall be [assembled as one unit, wall mounted,] [individually mounted on the pipe,] with shut-off cocks. Shut-off cocks shall be pinned and sealed to prevent gas leakage. 2.2.8 Pressure Relief Valves A pressure relief valve shall be provided in the gas line to the waste gas burner and connected to the upstream side of the flame trap. Pressure relief valves shall maintain a predetermined back pressure throughout the system at settings from 1.25 to 2.49 kPa 5 to 10 inch of water column and shall release surplus gas to the waste gas burner. The relief valve shall be actuated by a protected diaphragm. The diaphragm shall be a readily adjustable weighted type or compression spring type of ample area to allow sensitive control of the gas pressure. The valve shall be capable of passing [_____] cubic meters cubic feet of gas at a pressure loss not to exceed [_____] Pa inch water column. 2.2.9 Pressure Controls Pressure controls shall be provided to maintain proper distribution of gas flow on a priority basis to the [compressed gas sludge mixing system,] [gas storage tank,] digester heater, and the waste gas burners, respectively. 2.2.10 Digester Gas Piping NOTE: If removal of hydrogen sulfide gas, present in some anaerobic sludges, is desired, then iron oxide impregnated wood chip filters should be added to the gas piping system. Pipe shall be installed with a minimum slope of 20 mm/meter 1/4 inch/foot toward drip traps and sediment traps. 2.2.11 Digester Gas Storage A digester gas storage tank, gas compressor, controls, and appurtenances shall be provided as required for the storage of digester gas. 2.2.11.1 Storage Tank NOTE: Design of supports should be according to UFC 3-310-01 for windload and snowload design. Specific site information on wind and snow loadings must be included in the design. Provide seismic details, if a Government designer (either Corps office or A/E) is the Engineer of Record, and show on the drawings. Delete the bracketed phrase, in the penultimate sentence, if seismic details are not provided. Pertinent portions of UFC 3-310-04 and Sections 13 48 00 SEISMIC PROTECTION FOR MISCELLANEOUS EQUIPMENT and 13 48 00.00 10 SEISMIC PROTECTION FOR MECHANICAL EQUIPMENT or 22 05 48.00 20 MECHANICAL SOUND, VIBRATION, AND SEISMIC CONTROL, properly edited, must be included in the contract documents. Other types of storage, other than the expensive relatively high pressure spherical gas storage tank and supports, should be considered. Digesters with gas holder covers or cylindrical steel tanks with adjusting covers, which supply gas at constant pressure at variable volume, generally supply digester gas at low pressures but at pressure sufficient to operate many boiler burners. A small auxiliary compressor may be added, if required, to boost gas pressure. The gas storage tank shall be capable of storing [_____] cubic meters cubic feet of gas operating between [_____] kPa maximum and [_____] kPa minimum [_____] psig maximum and [_____] psig minimum pressure. The tank shall be cylindrical above ground tank with supports designed to withstand dead shell load plus a [_____] km/hour mph wind load and a [_____] kPa psisnowload. Seismic details shall be in accordance with UFC 3-310-04 SEISMIC DESIGN FOR BUILDINGS and Sections 13 48 00 SEISMIC PROTECTION FOR MISCELLANEOUS EQUIPMENT and [13 48 00.00 10 SEISMIC PROTECTION FOR MECHANICAL EQUIPMENT] [22 05 48.00 20 MECHANICAL SOUND VIBRATION, AND SEISMIC CONTROL] [as shown on the drawings]. The tank shall be air tested in accordance with ASME BPVC SEC VIII D1 to 125 percent of the design maximum pressure. 2.2.11.2 Compressor A reciprocating type electric motor driven gas compressor, capable of compressing [_____] cubic meters cubic feet of digester gas per minute at [_____] kPa psig to a maximum operating pressure of [_____] kPa psig, shall be provided. Compressor components shall be stainless steel or equally noncorrosive materials. Motor shall conform to NEMA MG 1. Controls shall conform to NEMA ICS 1, NEMA ICS 2, NEMA ICS 3, NEMA ICS 4, NEMA ICS 6, UL 845, and UL 508. Electric controls shall be provided as required for automatic operation of the compressor. Control panel shall include circuit breaker, magnetic starter, and manual-off-automatic selector switch. Power supply to the control panel shall be [_____] volts ac, [_____] phase, 60 Hz and shall be equipped with thermal overload protector with manual reset. All electrical wiring and motors shall be explosion-proof and be installed according to NFPA 70. Panel shall be NEMA 250, Type 7. 2.2.11.3 Pressure Relief Valve A pressure relief valve shall be provided on the gas storage tank. A stop valve, locked open except for maintenance shall be provided between the gas storage tank and the pressure relief valve. Sediment traps and drip traps shall be provided in gas lines at the base of the tank. Pressure controls for gas distribution shall be provided. A remote pressure indicator shall be provided in the compressor building to indicate tank pressure [in kPa psi gauge]. 2.3 DIGESTER HEATING SYSTEM NOTE: Boilers providing building radiation and digester heating operate at 71 to 82 degrees C (160 to 180 degrees F). Hot water to heat exchanger is mixed to maximum 66 degrees C (150 degrees F) to prevent caking on sludge tubes. 2.3.1 System Performance Requirements A complete system shall be provided for automatic control of the digester operating temperature at 35 degrees C 95 degrees F, within plus or minus 0.3 degrees C 0.5 degrees F, by means of an external sludge heating system. The digester heating system shall have a minimum sludge heating capacity of [_____] kW Btu/hr based on heating [_____] L/second gpm of sludge from digesters operating at 35 degrees C 95 degrees F. Boiler shall be fire tube hot water boiler with maximum operating pressure of 207 kPa 30 psig, with boiler, burners, draft fans, combustion safety controls and equipment, breeching and stacks, fuel system, and fittings and accessories in accordance with Section 23 70 02.00 10 CENTRAL STEAM GENERATING SYSTEM-COMBINATION GAS AND OIL FIRED. Draft fan shall be designed for corrosive application. 2.3.2 Heat Exchanger The heat exchanger shall be of the water bath or concentric tube type and shall be provided with an integral factory-fabricated insulation jacket. Heat exchanger insulated jacket shall be insulated with a minimum of 40 mm 1-1/2 inch of fiberglass having a density of 12.0 kg/cubic meter 0.75 pcf and a K-factor of 2.15 at 38 degrees C 0.38 at 100 degrees F. The jacket shall have minimum 16 gauge sides and 5 mm 3/16 inch plate top and bottom. 2.3.2.1 Sludge Tubes Sludge tubes shall be standard weight ductile iron pipe with cast iron return bends with flanged, gasketed connections. Return bends shall be readily removable for inspection, cleaning, or replacement. Sludge tubes and return bends shall be large enough to pass a [_____] mm inch diameter sphere. Sludge tube connections shall be arranged to prevent sludge contamination of the heating water due to a gasket or connection failure. 2.3.2.2 Pressure Relief Valve A pressure relief valve, constructed and installed in accordance with ASME BPVC SEC IV shall be provided. The valve discharge shall be piped to within 150 mm 6 inch of the floor in full line size. 2.3.3 Burning Equipment NOTE: Delete type of burner and fuel train for inapplicable fuels. The burning equipment shall be of the capacity to develop the specified boiler capacity and shall have dual fuel, combination or separate, burners. The burning equipment shall include equipment for burning either digester gas, with heat content of approximately 22.3 MJ per cubic meter 600 Btu per cubic foot and a specific gravity of 0.8, or [No. 2 fuel oil, with heat content of 39,000 MJ per cubic meter 140,000 Btu per gallon] [natural gas, with heat content of 37.3 MJ per cubic meter 1,000 Btu per cubic foot or a mixture of the two gases] [LP gas with heat content of [_____] MJ per cubic meter Btu per cubic foot]. Gas piping and equipment for LP gas shall conform to NFPA 58. 2.3.4 Electric Control Panel A single electric control panel, containing the digester temperature controller, the burner controller, and the branch circuit breakers and magnetic starters for the sludge circulating pump, induced or forced draft fan motor, and heat exchanger water circulating pump shall be provided. Induced or forced draft fans, motor, and associated boiler and burner controls shall be in accordance with Section 23 70 02.00 10 CENTRAL STEAM GENERATING SYSTEM COMBINATION GAS AND OIL FIRED. Controllers shall be in accordance with NEMA ICS 1, circuit breakers shall be in accordance with NEMA SG 6, and motor controls and motor control centers shall be in accordance with NEMA ICS 1 , NEMA ICS 2, NEMA ICS 3, NEMA ICS 4, NEMA ICS 6, UL 508, and UL 845. [The control panel shall include provision for integrating the control function of the building radiation hot water circulating pump into the control package.] The control panel shall be NEMA 250, Type 12 construction and shall have [dual swing-out doors.] [a single swing out door.] All equipment shall be mounted and wired with rigid steel conduit and flexible water-tight connectors, all in accordance with NFPA 70. Main power to the control panel shall be [480] [_____] volts ac, [3] [_____] phase, 60 Hz, and control power at 120 volts ac, single phase, 60 Hz. Interlocks shall be provided as required for sludge heater operation with raw sludge pumps. The following selector switches and indicating lamps, clearly labeled, shall be provided on the control panel doors: a. Digester heater switch (manual/automatic/off). b. Fuel selection switch (digester gas/[oil] [natural gas] [LP gas]/automatic). c. Constant water bath switch (on/off). d. Induced draft fan (automatic/continuous). e. Sludge recirculation pump (continuous/intermittent). f. Low boiler water lamp with alarm horn and silencer. g. Induced draft [or forced draft] fan failure lamp with alarm horn and silencer. h. Flame failure lamp with alarm horn and silencer. i. Boiler high temperature lamp with alarm horn and silencer. 2.3.5 Digester Temperature Control Digester temperature control shall be permitted by the manual/automatic off switch mounted on the control panel. Automatic control of the digester temperature shall be by means of a thermostat located at the inlet to the sludge tubes of the heat exchanger. The water circulation pump for sludge heating and the burner equipment shall be automatically controlled by the temperature of the sludge passing the thermostat. A repeating cycle time switch shall be provided for periodic starting of the digester recirculation pump, with controls arranged such that the recirculation pump will continue to operate until the digester heating requirements are satisfied or shall stop after a short cycle if heat is not required by the digester. Indicating thermometers, with a range from minus 18 to 66 degrees C 0 to 150 degrees F, shall be provided in the sludge inlet and outlet of the heat exchanger. Each thermometer shall be provided with a mounting socket that will enable the removal of the thermometers without draining the sludge tubes. 2.3.6 Sludge Circulating Pump Pump shall be as specified in Section 44 46 00 PUMPS; SEWAGE AND SLUDGE. 2.3.7 Sludge Piping Sludge piping shall be arranged to permit heating of the digester contents by pumping the digester sludge through the heat exchanger and back to the digester. The piping arrangement shall also include provision for heating of raw sludge before it enters the digester or for heating a mixture of raw sludge and recirculating sludge. 2.3.8 Water Circulation Pumps Water circulation pumps shall be single stage, centrifugal, enclosed impeller, electrically driven, non-overloading type with integrally mounted motor. The pump shall be connected to the motor with a flexible coupling. Motor shall conform to NEMA MG 1 for operation on [_____] volts ac, [_____] phase, 60 Hz and shall be equipped with thermal overload protector with manual reset. Motor frame shall be [open] [dripproof] [totally enclosed] [explosion-proof] type. 2.3.8.1 Heat Exchanger Water Circulation Pump The heat exchanger water circulation pump shall be mounted in line with the heat exchanger package. Pump rating shall be determined by the heat exchanger manufacturer as required to provide turbulent flow across the sludge tubes. 2.3.8.2 Building Heat Water Circulation NOTE: Delete paragraph Building Heat Water Circulation if system is not used for building heat. Coordinate criteria with building heating system specification. The building heat water circulation pump shall be rated at [_____] L/second gpm and [_____] mm feet TDH. 2.4 MECHANICAL SLUDGE MIXING SYSTEM NOTE: For projects with single-stage sludge-digestion, delete "primary" and include reference to bottom 1/10 of contents. For projects with two-stage sludge digestion, include "primary" and delete reference to bottom 1/10 of contents. Electric motor driven mechanical mixers shall be provided in each [primary] [_____] digester, each capable of producing a flow of [____] L/second gpm of sludge. The combined action of all the mixers shall effectively circulate all [except the bottom 1/10] of the digester contents. Mixers shall be suitable for mixing sludge on a continuous basis. 2.4.1 Motor The electric drive motor shall be mounted on the outside of the digester on the [gear reduction unit] [or] [mixer bearing support.] Motors shall be in accordance with NEMA MG 1 and shall be of explosion-proof design for operation near digester gas. Motor shall be sized for and shall not overload under the intended conditions. Motor shall operate on [_____] volts ac, [3] [_____] phase, 60 Hz and shall be provided with thermal overload protection. 2.4.2 Speed Reducer A unit shall be provided for the mechanical reduction of speed while transmitting power from the motor to the mixer shaft. The reducer shall be either V-belt drive or gear drive type. Reduction ratio shall be as required for proper mixer operation. 2.4.2.1 V-Belt Speed Reducer The unit shall consist of sheaves and V-belts, properly sized for the required horsepower transmission. Belts shall be of the static-conducting type for operation near digester gas. A means of adjusting belt tension shall be provided. An enclosure shall be provided to protect the unit from weather and to protect personnel from injury. 2.4.2.2 Gear Reducer The unit shall consist of gears, shafts, and bearings, mounted in a cast metal housing. Unit shall be sized to transmit the intended horsepower. Lubrication shall be by oil bath and the unit shall have provision for filling, draining, and checking the oil level. Seals shall be provided on all shaft penetrations to prevent the escape of oil and the entry of contaminants. A vent shall be provided to allow the entry and escape of air. The vent shall be designed to minimize contaminant entry. 2.4.3 Shaft A cold-rolled steel shaft, [_____] mm feet long, shall be provided for support and rotation of the [impeller] [or] [propeller]. The shaft shall be designed to prevent excessive deflection under normal load conditions. The shaft shall extend from the speed reducer unit through the bearing and support assembly to the [impeller] [or] [propeller]. 2.4.4 Bearing and Support Assembly A cast metal unit, complete with bearings, shall be provided for the support of all other mixer components. The assembly shall mount directly on the digester [cover] [wall] and shall provide a gas tight seal. The unit shall contain two bearings, mounted sufficiently apart from each other to give stable support to the shaft. Bearings shall be self-aligning roller or ball bearings designed for axial loading and sized to support the shaft and [impeller] [or] [propeller] under all load conditions. The assembly shall have grease fittings, passages, and relief ports as required for proper bearing lubrication. 2.4.5 Seals NOTE: Coordinate with Section 44 46 20 FLOATING COVER FOR SLUDGE-DIGESTION TANKS. Coordinate with paragraph COMPRESSED GAS SLUDGE MIXING SYSTEM. Shaft seals shall be provided at the top and bottom of the bearing and support assembly. The upper seal shall both retain grease and prevent the entrance of contaminants. The lower seal shall be designed to retain grease and to prevent the passage of digester gas under [_____] kPa psi pressure. 2.4.6 Impeller or Propeller An [impeller] [or] [propeller] shall be provided on the end of the shaft to impart motion to the sludge. The unit shall effectively transmit the mixer's mechanical energy to the sludge without producing unbalanced forces on the shaft. The unit shall be constructed of a material capable of withstanding rapid motion through sludge without undue wear or corrosion. [The unit may operate unenclosed or enclosed in a draft tube. The draft tube shall be flared at the bottom and shall be constructed of at least 6 mm 1/4 inch thick steel plate.] [The propeller shall be designed to avoid fouling and also to pump sludge in either direction.] 2.4.7 Controls Each mixer shall be provided with a magnetic starter; forward, stop, and reverse pushbuttons; and a circuit breaker with manual reset. Controls shall be [120] [_____] volts ac, single phase, 60 Hz, and shall be housed in explosion-proof NEMA 250, Type 7 enclosure Reverse operation shall be provided for periodic dislodging of sludge from the [impeller] [or] [propeller]. 2.5 COMPRESSED GAS SLUDGE MIXING SYSTEM NOTE: Include only the applicable system. Consult with various manufacturers to determine correct system for the project and to obtain criteria to be specified. For projects with single-stage sludge-digestion, delete "primary" and include reference to bottom 1/10 of contents. For projects with two-stage sludge digestion, include "primary" and delete reference to bottom 1/10 of contents. A system shall be provided for mixing [all except the bottom 1/10] of the [primary] [_____] digester contents by the circulation of digester gas. The system shall be designed for safe handling of digester gas. [The system for each digester shall consist of a compressor, piping system, and [_____] diffusers located within each digester as indicated. The system shall provide [_____] cubic meters/second cfm of digester gas at [_____] kPa psi sequentially to each of the diffusers to provide thorough mixing of the digester contents.] [The system for each digester shall consist of a compressor, piping system, and [_____] diffusers within a centrally mounted draft tube, forming a confined gas lift for circulation and mixing of the digester contents. The system shall provide a total of [_____] cubic meters/second cfm of digester gas at [_____] kPa psi to the diffusers.] [The system for each digester shall consist of a compressor, piping system, and [_____] diffusers located [on] [near] the bottom at the center of each digester as indicated, forming an unconfined gas lift for circulation and mixing of the digester contents. The system shall provide a total of [_____] cubic meters/second cfm of digester gas at [_____] kPa psi to the diffusers.] 2.5.1 Compressor NOTE: For gas recirculation and low pressure gas handling, rotary displacement, sliding vane, or liquid ring compressors may be used. A positive displacement, electric motor driven, air cooled compressor shall be provided for circulating the digester gas. The compressor shall be capable of providing [_____] cubic meters/second cfm of gas at [_____] kPa psi and shall be driven by a [_____] kW horsepower explosion-proof electric motor. The motor shall operate on [_____] volts ac, [3] [_____] phase, 60 Hz. Motor shall conform to NEMA MG 1. Controls shall conform to NEMA ICS 1, NEMA ICS 2, NEMA ICS 3, NEMA ICS 4, NEMA ICS 6, UL 845, and UL 508. Panel shall be NEMA 250, Type 7. Motor power shall be transmitted to the compressor through a static-conducting V-belt drive. 2.5.2 Diffusers Diffusers capable of diffusing the specified quantity of gas into the sludge shall be provided. The diffusers shall be constructed of a material resistant to corrosion caused by digester sludge and shall be of a nonclogging design which prevents the backflow of sludge into the gas piping upon loss of gas pressure. [Draft tubes shall be constructed of at least 6 mm 1/4 inch thick steel plate and shall have flared bottoms.] 2.5.3 Piping System NOTE: Certain gas recirculation piping systems provide discharge wells which allow removal of the discharge tubes within the wells for inspection or change of depth of discharge without interrupting digester operation and provide sealing in of gas during removal and replacement of discharge tubes. 2.5.3.1 Piping Piping shall comply with paragraph DIGESTER GAS HANDLING SYSTEM. 2.5.3.2 Motor Operated Multiport Rotary Valve NOTE: Include this paragraph only if paragraph COMPRESSED GAS SLUDGE MIXING SYSTEM is specified. A single motor operated multiport rotary valve or multiple motor operated valves shall be provided for control of gas supply to the individual diffusers. 2.5.4 Supernatant Removal NOTE: Include this paragraph if supernatant removal is included in project. [Overflow box with weir or supernatant piping] [Rotatable draw-off supernatant pipe to pull supernatant at varying levels] shall be provided. Digester sight glass or depth indicator shall be provided. 2.5.5 Controls 2.5.5.1 Compressor Controls A magnetic starter, start-stop pushbuttons, and a circuit breaker with manual reset shall be provided for the compressor. Circuit breaker shall be in accordance with NEMA SG 6 and motor controls shall be in accordance with NEMA ICS 1, NEMA ICS 2, NEMA ICS 3, NEMA ICS 4, NEMA ICS 6, UL 508, and UL 845. A relief regulator system consistent with the system operational pressures shall be provided. A flame arrestor, moisture separator, and sediment trap shall be provided on the suction piping to the compressor. All controls shall be 120 volts ac, single phase, 60 Hz, and shall be housed in an explosion-proof NEMA 250, Type 7 enclosure. 2.5.5.2 Automatic Programming NOTE: Include this paragraph only if paragraph COMPRESSED GAS SLUDGE MIXING SYSTEM is specified. Equipment shall be provided to automatically program a predetermined discharge period through the diffusers in sequence. The time period shall be adjustable. A selector switch shall be provided to allow discharge to any desired diffuser. 2.5.6 Compressor Housing A weatherproof enclosure shall be provided for the compressor and motor assembly. The enclosure shall have lockable access doors and shall be louvered for ventilation. [The enclosure shall be insulated and equipped with a thermostatically controlled electric heater.] The enclosure shall be mounted on the digester cover. PART 3 EXECUTION 3.1 EXAMINATION After becoming familiar with all details of the work, verify all dimensions in the field, and advise the Contracting Officer of any discrepancy before performing the work. 3.2 WELDING NOTE: If the need exists for more stringent pipe welding requirements, delete the sentences in the first set of brackets. [Piping shall be welded in accordance with qualified procedures using performance qualified welders and welding operators. Procedures and welders shall be qualified in accordance with ASME BPVC SEC IX. Welding procedures qualified by others, and welders and welding operators qualified by another employer may be accepted as permitted by ASME B31.1. The Contracting Officer shall be notified 24 hours in advance of tests and the tests shall be performed at the work site if practical. The welder or welding operator shall apply his assigned symbol near each weld he makes as a permanent record. Structural members shall be welded in accordance with Section 05 05 23 WELDING STRUCTURAL.] [Welding and nondestructive testing procedures for piping shall be as specified in Section 43 02 00 or 40 17 26.00 20 WELDING PRESSURE PIPING.] 3.3 PAINTING All ferrous metal equipment shall be cleaned, primed, and given two coats of machinery enamel at the factory. Fiberglass, stainless steel, and galvanized components need not be painted. Field painting shall be in accordance with Section 09 90 00 PAINTS AND COATINGS. 3.4 _{EQUIPMENT INSTALLATION} NOTE: Coordinate with Section 44 46 20 FLOATING COVER FOR SLUDGE-DIGESTION TANKS. Install equipment where indicated and in accordance with the manufacturer's written instructions and under the supervision of the manufacturer's representative. Provide sufficient clearances around all equipment to allow for proper operation and maintenance. Connections with or protrusions through the digester cover or walls shall be gastight. Special attention shall be given to the proper installation of gas and fuel systems to insure safe operation. [Equipment installed on floating digester covers shall be counterbalanced to insure proper operation of the cover.] 3.5 _{FRAMED INSTRUCTIONS} Post framed instructions, containing wiring and control diagrams under glass or in laminated plastic, where directed. The framed instructions shall be posted before acceptance testing of the system. Show with the instructions wiring and control diagrams and complete layout of the entire system. The instructions shall also include, in typed form, condensed operating instructions explaining preventive maintenance procedures, methods of checking the system for normal safe operation and procedures for safely starting and stopping the system. 3.6 _TESTING 3.6.1 Gas Piping Test Test gas piping by subjecting it to pneumatic pressure of not less than 105 kPa 15 psi for 6 hours. During the test the system shall be disconnected from the source of pressure and, with corrections made for barometric and temperature changes, the pressure shall remain constant for the test period, as indicated by a test gauge. 3.6.2 Piping System and Heat Exchanger Test The piping system and heat exchanger shall be isolated and shall be tested for a period of at least 6 hours at a hydrostatic pressure of 310 kPa 45 psi. 3.6.3 Operational Test Subject the entire gas, heating, and mixing system to an operational test to demonstrate satisfactory functional efficiency. 3.6.4 Boiler and Heat Exchanger Test Test boiler and heat exchanger as specified in Section 23 05 93TESTING, ADJUSTING, AND BALANCING. 3.7 MANUFACTURER'S SERVICES Provide thr services of a manufacturer's representative who is experienced in the installation, adjustment, and operation of the equipment specified. The representative shall supervise the installation, adjustment, and testing of the equipment. 3.8 FIELD TRAINING Provide a field training course for designated operating and maintenance staff members. Training shall be provided for a total period of [_____] hours of normal working time and shall start after the system is functionally complete but prior to final acceptance tests. Field training shall cover all of the items contained in the _{operating and maintenance manuals}.