General Construction Specifications
SECTION 11375
MIXING EQUIPMENT
PART 1 - GENERAL
1.01 SECTION INCLUDES
A. Mechanical Floating Mixers located in Compartment Nos. 1 and 2 of Detention Basin.
1.02 RELATED SECTIONS
A. Section 09900 - Painting.
B. Section 09915 - High Build Glazed Coatings.
C. Section 11951 - Electric Motors.
D. Section 16010 - Basic Electrical Requirements.
E. Section 16480 - Motor Starters.
1.03 REFERENCES
A. American Society for Testing and Materials (ASTM).
B. American Welding Society (AWS).
C. American National Standards Institute (ANSI).
D. Institute of Electrical and Electronic Engineers (IEEE).
E. American Society of Mechanical Engineers (ASME).
1.04 SYSTEM DESCRIPTION
A. Electric Motor driven four (4) mechanical floating mixers located in Compartments No. 1 and No. 2 of Detention Basin.
B. Mixers support with all necessary anchorage parts.
1.05 DESIGN REQUIREMENTS
A. Provide mechanical floating mixers capable of handling raw combined sewage.
1.06 SUBMITTALS
A. Submit under provisions of Section 01300.
B. Shop Drawings: Indicate layout, general assembly, components, dimensions, anchor bolt setting, and weights for submersible mixers, including associated motors and drives.
C. Product Data: Provide manufacturer literature including general assembly, controls, wiring diagrams, and service connections. Refer to Section 11951 for required motor data.
D. Test Report: Provide impeller balance reports.
E. Submit manufacturer's field reports.
1.07 OPERATION AND MAINTENANCE DATA
A. Submit under provisions of Section 01730.
B. Operation Data: Include manufacturer's instructions, start-up data, and trouble-shooting checklists.
C. Maintenance Data: Include manufacturer's literature, recommended lubricants, replacement part lists, and repair data.
D. Additional instructions in manual: Include complete detailed instructions on the balancing procedure to be used for rebalancing to the propeller after it has been in service for an extended period of time. These instructions shall include, but not be limited to, a general procedural description, a detailed explanation of preparing the unit for balancing, for setting up the dynamic balancer, portable balancing technique, a detailed description of the vector chart method of single plane balancing and sample balancing record forms.
1.08 QUALITY ASSURANCE
A. System Responsibility: Submersible mixer manufacturer shall supply mixers, motors and their respective drives, and be responsible for their compatibility. The shall be the design and fabrication of a single manufacturer.
1.09 DELIVERY, STORAGE AND HANDLING
A. Deliver to site, store, protect, and handle mixers under provisions of Section 01600.
B. Protect mixers and components from physical damage including effects of weather, water, and construction debris.
1.10 EXTRA MATERIALS
A. Furnish under provisions of Section 01700.
B. Provide spare parts for each mixer:
1. One set of bearings.
PART 2 - PRODUCTS
2.01 - MANUFACTURERS
A. Agna - Aerobic Systems, Inc. Model SS. Part No. 5905011 Agna - Aerobic Mixer.
B. Substitutions: Under provision of Section 01600.
2.02 MIXER DRIVE MOTOR
A. Each mixer shall be equipped with 50 horsepower at 900 RPM speed electric motor connected for operation on a 460 volt, 60 cycle, three phase service.
B. The motor shall be vertical P base design, totally enclosed, fan cooled (T.E.F.C.), and generally rated for severe duty. Submerged motors are not acceptable.
C. The motor shall in all cases equal or exceed standard NEMA specifications. The motor winding insulation shall in all cases equal or exceed NEMA Class F design and shall be non-hydroscopic.
D. A minimum service factor of 1.15 shall be furnished.
E. All motor end bells shall be deep registered and Permatex sealed.
F. All through bolts, nuts and screws shall be of type 18-8 stainless steel.
G. A stainless steel nameplate shall be provided with each motor, and shall be securely fastened thereto. The voltage, speed, phase, insulation class, amperage, service factor, wiring diagram, motor serial number, and manufacturer's name and address shall be stamped thereon or otherwise permanently marked.
2.03 MOTOR BEARINGS
A. Motor bearings shall be regreaseable. Sealed bearings are not acceptable. Top bearing shall be shielded on the bottom side only. Bottom bearing shall be open.
B. The top and bottom motor bearings shall be of the combined radial and axial thrust type and shall be packed at the factory with CHEVRON SRI-2 grease or an approved equivalent.
C. The lower motor bearing inner race shall be locked to the motor shaft via a special washer and locking nut arrangement. The shaft shall be threaded just below the lower bearing and shall have a keyway cut into the motor shaft. This key shall accept a tab from the I.D. of the locking washer, and the locking nut shall have recesses to accept a tab from the O.D. of the locking washer to prevent the nut from backing off. Snap ring type bearing retainers will not be acceptable.
D. Immediately above the lower bearing shall be provided a slinger that rotates with the motor shaft to protect the bearings from condensation that may form and run down the motor shaft.
2.04 MOTOR SHAFT
A. The mixer motor shall have a one piece motor shaft continuous from the top motor bearing, through the lower bearing and down to and through the impeller.
B. The mixer motor shaft shall be 3.5" in diameter and manufactured from 17-A PH stainless steel. The maximum allowable full length shaft run out shall be limited to 0.006 inches T.I.R.
C. The mixer motor shaft shall operate freely without contacting any bearings or bushings other than the motor bearings, and the motor shaft deflection shall be limited to 0.060 inches within two shaft diameters of the center of the impeller hub.
2.05 MOTOR BASE ASSEMBLY
A. The motor shall be securely mounted onto a solid 304 stainless steel base which is integral with the motor base extension. All submersed wetted motor mounting base components to be constructed of 304 stainless steel.
B. The motor base shall contain a machined recess to permit the use of a free running, anti-deflection insert. The anti-deflection insert shall not require lubrication. The provision for this insert shall be located in the lower extremity of the motor base extension immediately above the impeller.
C. The motor end bell alignment pilot on the motor base shall be machined concentric with the machined recess that houses the free running, anti-deflection insert.
D. The upper portion of the motor mounting base, immediately below the lower motor bearing, shall include two independent acting air seals. One seal shall contact the rotating motor shaft extension and shall not require scheduled lubrication or maintenance. The second seal shall consist of one stationary and one moving component. These two seals shall be capable of sealing off the flow of air from the suction action of the pumped flow and prevent back flow of liquid during impeller reversal. The lower end of the motor base extension shall be provided with a rotating backflow seal that will prevent grit from being introduced into the anti-deflection insert reservoir, but shall allow liquid to contact the shaft. The backflow seal shall not require scheduled lubrication or maintenance.
2.06 FLOTATION
A. Each unit shall be equipped with a modular float constructed of 14 gauge, 304 stainless steel, foamed full of polyurethane foam of the closed cell type, and shall be totally sealed to prevent the foam from being in contact with the external environment.
B. The float shall have 2160 lbs. reserve buoyancy, shall be 114-5/8" in diameter and 16" thickness.
C. The center structure of the float shall be integral to the float cover and shall transmit all mooring stress from one mooring line to another. The center structure shall also contain rigid vertical support gussets that connect the top and bottom alignment flanges that support and connect the motor support base and the submerged impeller volute assembly.
D. All connecting bolts shall be 316 stainless steel and have drilled heads, and shall be safety wired in place with stainless steel safety wire.
E. The surfaces of all mating flanges, from the motor support base through the float and impeller volute, shall be machined flat and smooth.
F. No shoulder bolt connection, spacer sleeves or other type point load connections either in tension or compression will be acceptable.
2.07 IMPELLER
A. The impeller shall be a two-blade marine type, 23.5" in diameter and be a precision casting of 316 stainless steel.
B. The impeller shall be designed to pump the liquid from near the surface and direct it down toward the basin bottom.
C. The impeller shall be streamlined to prevent cavitation and reduce drag and shall have 180° trailback blades to insure non-clog operation.
D. The impeller shall be capable of being reversed to cause back flow liquid movement without causing damage to the mixer chassis and without causing upflow liquid damage to the motor bearing and windings.
E. The impeller shall be securely attached to the motor shaft in such a manner so that reversal operation for liquid backflushing will not loosen its connection; therefore, impellers requiring the threading of the shaft for attachment will not be allowed.
F. The impeller shall be "pitch balanced" to insure equalization of load under full flow operation. Each blade's pitch and rake shall not vary more than 2.0 percent from the other.
G. No liquid spray or other liquid leakage upward onto the surface of the motor support surface or floatation chassis will be allowed at any time.
2.08 INTAKE VOLUTE ASSEMBLY
A. The impeller shall operate in a volute made of 304 stainless steel plate with a minimum volute diameter of 24".
B. No plastic, fiberglass, carbon steel or cast iron materials shall be acceptable.
C. The volute shall be machined to align concentrically with the motor base and float without shims or external adjustment.
2.09 BALANCING
A. The entire rotating assembly including the motor rotor, shaft and impeller shall be dynamically balanced within 2.0 mils peak-to-peak horizontal displacement measured at the upper and lower motor bearing.
B. Measurements shall be taken at a frequency equivalent to the motor RPM. Transducer pickup points shall be at the motor bearings on the motor frame perpendicular to the motor shaft. Measurements shall be taken with the motor in a vertical, shaft down position and with the motor or the entire power section mounted on resilient pads. Certified copies of the balance inspection shall be supplied upon request.
2.10 MOORING
A. To allow for water level variation, a two (2) restrained mooring frames shall be utilized. One triangular (Delta) mooring frame shall be fastened to the bottom of the mixer float, and will consist of 304 stainless steel mooring arms to which are attached removable U-bolts of 304 stainless steel being 5/8" in diameter. These U-bolts shall fit around three (3) posts diameter, which shall permit the unit to rise and fall with the varying water level. Mooring arms attached to side skins of the float are not acceptable.
B. A 304 stainless steel "J" bolt shall be utilized to connect the frame to the flotation unit. A minimum of three (3) connections are required.
C. The design of the mooring frame shall be such that it can support the entire unit while at rest on the mooring post stops during low water level.
2.11 ELECTRICAL SERVICE CABLE
A. Each unit shall be furnished with sufficient feet of AWG #2 four conductor, continuous length (non-spliced) underwater electric service cable.
B. The mixer manufacturer shall furnish the cable, with the motor end sealed into the moor terminal box, and wired for 460 volt service. The mixer manufacturer shall be responsible for this watertight seal and electrical connection. The other end of the cable will be wired into the power supply by the installing contractor.
C. Only flexible type copper stranded cable with four individually jacketed conductors bound together with a non-wicking filler and sheathed in a TPE, PVC, neoprene or approved equal over jacket will be approved.
D. Provide plastic cable floats spaced 7 to 8 feet apart.
PART 3 - EXECUTION
3.01 MIXER TEST
A. The mixer manufacturer shall perform the following inspections and tests on each mixer before shipment from the factory:
1. Propeller, motor rating, and electrical connections were checked for compliance to the purchase order.
2. All mixers are vacuum tested to establish sealing integrity. All mixers are momentarily energized to determine correct rotation and current draw (prior to immersion).
3. All mixers are run dry and/or immersed to deter mine correct shaft rotation, thrust direction, and power consumption.
4. After immersion test(s), all mixers are inspected for oil seepage and/or water infiltration, insulation defect(s), and motor resistance (Ohms).
B. Inspections and tests performed shall confirm the mixer(s) listed have met all established quality assurance standards set for similar materials. All mixers shall be warranted against defects in design, workmanship, and material.
3.02 FIELD QUALITY CONTROL
A. Perform field inspection and testing under provisions of Section 01400.
B. Manufacturer's Field Services: Furnish factory-authorized service representatives to inspection during installation, to assist in adjusting and testing, to supervise initial operation, and to make final adjustments as necessary to assure satisfactory operation.
3.03 COMMISSIONING
A. Start-up and commission aerators under provisions of Section 01650.
3.04 DEMONSTRATION
A. Perform mixers system demonstrations for Detention Basin and furnish instructions to Owner's personnel under provisions of Section 01650.
B. Furnish 20 hours of classroom and on-the-job instructions, exclusive of travel time.
C. Equipment demonstrations and instructions are in addition to other Manufacturer's Field Services specified in Article 3.02.
END OF SECTION
