1-Attachment B - Tech Specs (2).pdf

IFB 2000004255

Attachment B

Technical Specifications

Mixers shall be utilized for mixing primary effluent and screened aerated wastewater. Primary effluent mixers' horsepower shall be of 2.5 – 3 HP and the screened aerated mixers' horsepower shall be 4 – 4.7 HP.

1. General and Technical Requirements:

The successful bidder shall provide the mixers on as-needed basis. The two sizes of mixers are as follows:

A. Primary effluent mixers shall be 2.5 – 3 HP and shall be able to handle solid concentration in the range of 0-1,000 mg/I. Mixer's thrust output range should be in the range of 400- 500 Newton and propeller speed shall not exceed 1150 RPM.

B. The screened aerated mixers shall be 4 – 4.7 HP and shall be able to handle solid concentration in the range of 1,000 to 15,000 mg/I. Mixers' thrust output range should be in the range of 700-800 Newton and propeller speed shall not exceed 1150 RPM.

C. The mixers shall be compatible with the existing 2” X 2” Flygt guide rail system. Mixers requiring change to guide rail system shall not be accepted. No portion of the mixers shall rest or bear on the tank bottom. Mixers requiring personnel to enter the tank to connect the mixers to the floor mounted bracket shall not be accepted.

D. The mixers shall be designed and fabricated for continuous underwater operation. The mixers shall also be capable of continuous operation in air or un-submerged for a minimum of two (2) hours without damage to any component of the mixers.

E. The mixers should be equipped with a reliable, maintenance free cooling system. mixer shall be cooled by submergence in the surrounding environment.

F. Each mixer shall be submersible with the motor close-coupled, directly connected to the propeller. Gear box designs shall not be acceptable. The propeller shall be capable of handling solids, fibrous materials, heavy sludge, and other matter found in sanitary sewage applications.

2. Materials of Construction: Mixer components in contact with the liquid shall be Type 316 stainless steel with smooth surfaces devoid of blow holes and other irregularities. All exposed fasteners, nuts, bolts, and hardware shall be of Type 316 stainless steel.

3. Mating Surface Seals: All mating surfaces where watertight sealing is required shall be machined and be fitted with a double set of nitrile rubber or Viton O-rings. No other sealing mechanism will be accepted.

4. Propeller: The propeller shall be of Type 316 stainless steel, dynamically balanced, non-clogging backward curved design. The propeller shall have three vanes and be of the diameter and of the blade angle, in degrees, as indicated. Each blade shall be laser cut and welded to the hub to ensure that the propeller is properly balanced. The propeller shall be secured to the shaft by a shaft key and hub screw. The shaft shall be Type 420 stainless steel.

5. Bearings: The shaft shall rotate on permanently lubricated bearings. The outboard, propeller end, bearing shall be an angular contact bearing. The inboard, motor end, bearings shall be an angular contact to take up the axial loads and a radial bearing to take up the radial loads. The bearings

Technical Specifications shall be pre-loaded by a bearing loading nut located on the motor end of the shaft in order to reduce shaft deflection and increase bearing and seal life. Mixers without pre-loaded bearings shall not be accepted. All bearings shall have a minimum L-10 rated life of 100,000 hours.

6. Shaft Seals: Each mixer shall be provided with two sets of lapped end face type mechanical seals running in an oil chamber for cooling and lubrication. The seals require neither maintenance nor adjustment but shall be easy to check and replace. Only the seal faces of the outer seal assembly shall be exposed to the mixed media.

Each mixer shall be provided with an oil chamber for the shaft sealing system. The oil chamber shall be designed for oil pressure compensation. The drain and inspection plugs, with positive anti-leak seals, shall be easily accessible from the outside.

7. ELECTRIC MOTORS

A. General: The multi-pole motor shall be directly connected to the propeller. The motor shall be a squirrel cage, induction, shell type design, housed in an air filled, watertight chamber.

The motor shall be designed for continuous duty, capable of sustaining a maximum of at least ten evenly spaced starts per hour. The motor shall be suitable for service in a Class 1, Division 2 environment and bear UL approval. The stator winding shall be insulated with moisture resistant Class F insulation which will resist a temperature of 155°C (311°F). The stator shall be dipped and baked three times in Class F varnish. The rotor bars and short circuit rings shall be made of aluminum.

B. Power Cable: Provide 30ft of power/control cable with each mixer, suitable for submersible application, sized in accordance with NEC requirements. Provide cable terminal box on side of motor housing, with cable entry sealed to ensure that no entry of moisture is possible into the motor/ terminal area even if the cable is damaged or severed below water level.

Cable entries providing only rubber grommet (external cable jacket) seals will not be accepted. Non-metallic Snap-On fasteners shall be provided to fix the power/control cable to the static support cable to prevent movement of the cable. The mixer manufacturer shall provide a cable support bracket suitable for supporting the entire weight of the power/control cable from a hook near the upper mast bracket.

C. Cable Entry: Cable entry seal design shall provide a watertight submersible seal.

The cable entry housing shall be an integral part of the back plate. The cable entry shall have a double set of elastomer grommets in order to ensure a redundant system in the event of a cable entry failure. Single sealing systems shall not be accepted. The cable entry shall be comprised of two cylindrical elastomer grommets, each flanked by washers and a ferrule designed with a close tolerance fit against the cable outside diameter and the entry inside diameter. The assembly shall bear against a shoulder in the stator casing opening and be compressed by a gland nut threaded into it. Interaction between the gland nut and the ferrule should move the grommet along the cable axially instead of with a rotary motion. The junction chamber and motor compartment shall be separated by a terminal board which shall protect the motor interior from foreign material gaining access into the mixer top.

Connection between the cable conductors and the stator leads shall be made with threaded, leak-proof compressed type binding posts, permanently affixed to the sealed terminal board.

D. Thermal Protection: For each phase of the motor, use a bi-metallic temperature monitor in the upper portion of the stator windings to monitor stator temperatures. Embed the

Technical Specifications temperature monitors in the stator winding coils, connected in series and coupled to the motor contactor coil providing single switch shutdown capability. Use a temperature setting of 140°C ± 5°C (284°F ± 41°F) that will automatically reset once the stator temperature returns to normal. Wire temperature monitors to the control panel, and use temperature monitors in conjunction with, and supplemental to, external motor overload protection.

E. Moisture Sensing: Equip each submersible mixer with an electrical probe to detect the presence of moisture. Design the system so that a solid-state device mounted in the control panel or in a separate enclosure sends a sensing signal (24 VDC, 0.5 µA) to the probe.

Energize a warning light, audible alarm or telemetering device at the control panel if moisture enters the mixer, as detected by the probe.

Do not use moisture detection devices other than a solid-state electrical device.

8. MONITORING RELAY: The required Mixer Supplier provides monitoring relays to monitor all motor sensors. The relays should be installed at the motor control panel and properly wired in accordance with pump manufacturer’s instructions. Relays shall mount in standard 12-pin socket bases (provided) and shall operate on available control voltage of 24-240 VAC. If relays require an input voltage that is not available in the motor control panel an adequate transformer (with fused input) shall be provided by the mixer supplier. Relays shall have a power consumption of no more than 2.8 watts and shall be UL approved. Relays shall be modular in design, with each relay monitoring no more than two motor sensor functions.

Each relay module shall include a dual color (red/green) LED to indicate the status of each monitored sensor. Green will indicate “status OK”; red will indicate a failure or alarm condition. A self-corrected fault will allow the relay output contacts to reset and cause the LED to change from a steady alarm indication to a flashing signal. The LED shall continue to flash until locally cleared, providing the operator with an indication of a potential intermittent fault. Each relay shall also include a power-on LED and both “test” and “reset” pushbuttons.

An independent fail-safe (switch on power loss) form-C output contact shall be included for each monitored sensor to provide a normally open / normally closed dry contact to initiate a remote alarm device or shut down the motor. Contacts shall be rated for 5 amps at 120 volts.

9. MAINTENANCE INTERVAL: The complete mixer unit shall be designed for operation with scheduled maintenance intervals of not less than 16,000 running hours (or 2 years whichever occurs first). This scheduled maintenance interval shall be clearly stated in the mixer manufacturer’s standard operation and maintenance manual supplied with the mixer.

10. WARRANTY: The mixer manufacturer shall warrant the mixer and motor to the Owner against defects in workmanship and materials for a period of one (1) year from date of first beneficial use or eighteen (18) months from shipment (whichever occurs first). The manufacturer’s warranty shall be in published form and shall apply to all similar units. A copy of the warranty shall be provided to the owner at startup.