Polytech Systems, Inc

Wastewater Treatment equipment manufacturer including grit master grit washer, grit conveyor, helical skimmers, nonmetallic helical skimmers, non-metallic helical skimmers, gritmaster grit washer, rotary scum skimmers, dipping trough skimmers, flight monitoring system, DAF, Plate settlers, and Hydropneumatic systems for Water and Wastewater Treatment applications

•  S P E C I F I C A T I O N S  F O R   M O T O R I Z E D   S C U M   S K I M M E R   •

SCUM SKIMMER SPECIFICATIONS

WORM & GEAR WITH MOTORIZED OPERATOR

 

ROTATING SCUM SKIMMERS

 
  1. The rotating scum troughs shall be sized as shown on the drawings, with a wall thickness not less than 0.250-inch, with a 60-degree slot cut symmetrically about the vertical axis. The edges of the trough shall serve as a weir over which the scum will flow into the trough when the trough is rotated. The edges of the slot shall be parallel to the longitudinal axis of the pipe. At regular intervals, not to exceed 2-ft-6-in, minimum, 2-inch wide bands of the full pipe periphery shall be left in the pipe to act as stiffeners. Scum troughs shall form a continuous obstruction-free path through sedimentation tank walls so that scum can travel continuously across all sedimentation tanks and discharge into scum decant structure.

    Rotary Skimmers shall be installed as shown on drawings. Rotary Skimmer shall be as manufactured by Polytech Systems, Inc., Littlerock, California. (661) 944-0855

  2. The rotating scum troughs shall be supported by and revolve in a Type 316 stainless steel bearing/collar at each end of the trough. The collar shall provide adequate bearing for the trough for both dry and wet conditions; the collar shall be welded to a plate, which shall be fastened to the existing concrete using anchor bolts. The bearing shall be completely sealed to the wall to prevent leakage into the trough. A "D" shape watertight and replaceable seal shall be provided for each end of the trough where it rests in the support bearing. The seal shall be so constructed that it shall remain effective even with a slight misalignment of the trough and bearing; provide a positive and removable retainer to hold the seal in position over the full 360 degrees. The seal shall not be affected by grease or mild acids or alkalies, shall be readily renewable without removing the trough from the supporting brackets and shall not bind or impede the smooth action of the revolving pipe.

  3. Each scum trough shall have an electrically controlled worm gear operator.

     

    1. Worm gear operators shall consist of a UHMW ring gear and a nylon worm gear which shall engage to rotate the trough as the shaft is turned. The worm gear shall be made of cast nylon. Worms shall be 3.50 pitch diameter and 4" in length. The ring gear shall be attached to the scum pipe by 316 stainless steel bolts and shall be easily replaceable. The ring gear shall be UHWM and shall be 46 tooth with a 3" face and have a pitch diameter of 18.303.

    2. The trough supports and the worm and shaft supports shall be arranged in such a manner that a slight misalignment of the trough will not affect the gear operation or cause a leakage.

    3. The worm gear shall be supported by a bearing housing attached to the wall plate that includes UHMW bearings. No grease or oil shall be required for the operation of the ring gear and pinion operation.

    4. Provide 316 stainless steel wall sleeves to allow scum to flow through walls of adjacent tanks and pass to the scum channel of the hypochlorite contact tanks. Existing wall sleeves in the existing primary and final settling tanks shall remain in place for re-use.

    5. Furnish type 316 stainless steel anchor bolts and expansion bolts for mounting of the scum troughs. Expansion bolts shall be "Anker-Tite" by Wedg-it, "Wedge Anchors" by Phillips Drill Co, or "Kwik-Bolt" by Hilti. The length of the bolt shall be sufficient to place the wedge portion of the bolt a minimum of 1 inch behind the reinforcing steel in the concrete.

    6. Scum trough shall be constructed of type 316 stainless steel except where shown otherwise on the drawings.

     

 

ELECTRIC MOTOR OPERATOR

 
  1. The electric motor operator shall be by Limitorque Corp., Lynchburg, VA; Rotork Controls, Inc., Rochester, NY; EIM Company, Houston, Texas; or equal. The operators shall be provided by the scum trough manufacturer. The operator shall include the motor, operator unit gearing, limit switch gearing, limit switches, thermal overloads and auxiliary handwheel. The electric operator shall be designed for cold temperature applications and be supplied with low temperature lubricants.
     
    1. The scum trough drive shall be modulating. The motor shall have torque ratings and thermal capacity specifically designed for this service and shall be 480 Volt, 3 phase, 60 Hz, totally enclosed non-ventilated construction with the motor leads brought into the limit switch compartment without having external piping or conduit box. The motor shall be capable of rotating the scum trough against maximum torque load when voltage to the motor terminal is within plus or minus 10 percent of the nominal rated voltage. Bearings shall be the prelubricated anti-friction type. Motors shall be of weatherproof construction and shall have Class F insulation with 120 VAC space heaters for protection against moisture ingress and condensation when the motor is not running. Provide a grounding lug in the terminal connection compartment. A mechanical dial position indicator and a 4-20 mA position feedback transmitter shall be furnished for each drive.

       

    2. The power gearing shall consist of carburized and hardened alloy steel worms with threads ground after heat treating. The worm gear shall be of alloy bronze, accurately cut with a hobbing machine. Where required, additional generated helical gears of heat treated steel shall be used. All power gearing shall be suitably lubricated with oil or grease and shall be suitable for mounting in any position. Ball and roller bearings shall be used throughout.

       

    3. Limit switches and gearing shall be an integral part of the trough operator. The limit switch shall be totally enclosed in its own gear case and permanently grease or oil lubricated. Limit switches shall be provided at each end of travel. The switches shall be adjustable to allow the switch to trip at any point on the trough's rotation. The limit switches shall be geared to the drive mechanism and in step at all times whether the unit is in motor or manual operation.

       

    4. The trough control shall be equipped with a double torque switch. The torque switch shall be adjustable and shall be responsive to load encountered in either direction of travel. It shall operate during the complete cycle to protect the trough should excessive load be met because of obstruction in either direction of travel.

       

    5. The operator shall have a stem nut of high tensile bronze. The nut arrangement shall be of the two-piece type to simplify field replacement. The stem nut shall be capable of being removed from the top of the operator without the necessity of removing the operator from the floor stand or disassembling any of the gearing within the operator.

       

    6. A handwheel shall be provided for manual operation. The handwheel shall not rotate during electric operation, but shall be responsive to manual operation at all times except when the motor is in operation. The motor shall not rotate during hand operation, nor shall a fused motor prevent hand operation. When in the hand operating position, the unit shall remain in this position until the motor is energized, at which time the operator shall automatically return to electric operation and shall remain in the electric position until hand operation is again desired. This movement from electric to hand operation shall be accomplished by a positive declutching lever which shall disengage the motor and motor gearing mechanically but not electrically. When in hand operation, not more than 40 lobs of force shall be required for handwheel operation. An arrow shall be cast on the handwheel labeled to indicate the direction of rotation to rotate the trough. The direction of rotation to go forward shall be clockwise.

       

    7. Furnish floor stands for operators. Provide a double-nut arrangement for leveling. Do not install non-shrink grout until after the unit is tested.

       

    8. Control enclosures shall be FM certified and shall meet NEMA 3, 4, and 6 requirements. Provide space heaters in each compartment to prevent condensation by maintaining space temperature of at least 60 degrees F.

       

    9. Each operator shall be provided with integrally mounted electrical controls housed in the enclosure. The controls shall be completely factory wired to the motor, limit switches and torque switch such that the only field wiring connection required shall be for power supply and signal. All field wiring shall be to terminal strips.

       

    10. The scum troughs shall be capable of automatic remote control and local manual control. Drive shall be capable of positioning the tipped elevation of the scum trough by a 4-20 mA signal in both the forward and reverse direction.

       

    11. Provide a LOCAL-OFF-REMOTE selector switch with REVERSE-FORWARD pushbuttons at the operator. The reverse and forward pushbuttons shall rotate the skimmer continuously while the pushbutton is depressed. Provide dry 10 Amps, 120 VAC contacts for remote indication that skimmer is in the "LOCAL" mode.

       

    12. Local controls shall be located such that they are in a horizontal position and are easily accessible when standing at the operating level. Provide engraved nameplates to identify all controls. Control circuits shall be 120 Volt, single phase, 60 Hz supplied by control transformer.

       

    13. Provide and label red and green indicating lights on operator. Two red lights to indicate when skimmer is completely opened in either direction; green light, when skimmer is in normal vertical position. Both red and green lights on during operation at intermediate positions or when operator is stopped at any intermediate position. Provide separate lights for forward and reverse positions. Provide dry 10 Amps, 120 VAC contacts for each position for remote indication.
     

    Mechanized
    Skimmers
     

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    29233 106th Street East • Little Rock • CA  93543
    PH: 661 944-6970 • FX: 661 944-0813
    Email:     info@polytechcorp.us