CHAPTER 1 DESCRIPTION OF THE CENTRIFUGE 1.1 GENERAL EQUIPMENT DESCRIPTION The ANDRITZ high performance centrifuge uses centrifugal force to separate liquids and solids. Whether the centrifuge operates as a fully contained thickener or a dewatering device, precise optimization is attainable with internal configuration options. The feed slurry is introduced to the centrifuge through a stationary feed tube and is distributed into the rotating bowl. The solids are separated from the liquid by centrifugal force. The action of a scroll conveyor, rotating at a differential speed compared to the bowl, transports the solids to cake discharge ports. The centrate flows axially back toward the feed end, exiting over adjustable weirs. The maximum overall dimensions of the centrifuge are 317 inches long by 85 inches wide (with shock absorber plate) by 90 inches high, excluding the oil lubrication unit. See Table 1-1. The centrifuge is supplied complete and includes the frame, solid bowl decanter, conveyor tile assembly, anti-vibration isolators, adjustable weirs, in-line drives and Cyclo gears, torque control and electrical controls, and an oil lubrication unit. Duplicate parts are interchangeable. All 316 stainless steel construction that requires welding is supplied with 316L grade stainless steel. Ancillary information such as brochures and illustrations are found at the end of this chapter. TABLE 1-1. CENTRIFUGE CHARACTERISTICS Length Width Height Weight with Drive Product Feed Solids Outlet Centrate Outlet 317 inches 85 inches with shock absorber plate 90 inches 50,706 lb 4-Inch ANSI Flange Flange: 57.125 x 22.5625 inches ext Flange: 57.125 x 16.1875 inches ext Southerly WWTP: D12LL Centrifuges 1-1 Chapter 1
1.2 CENTRIFUGE PERFORMANCE The D12LLU30CHP centrifuge continuously receives, flocculates, conditions, and thickens the feed sludge specified herein, and neatly discharges the thickened sludge into a hopper or conveyor. The centrifuge is designed to operate continuously or intermittently on demand. The centrifuge is suitable for thickening the specified sludges continuously for 24 hours per day, 7 days a week, and is designed to perform the required thickening operations as shown below. TECHNOLOGICAL DATA Medium to be thickened Blend ratio: Feed solids Primary and waste activated sludge 4045 % primary/ 6055 % WAS Primary: 0.30.6 %; WAS: 0.70.8 %; blend: 0.50.7 % TS CAPACTIY REQUIREMENTS Number of units 4 Hydraulic loading 1,000 to 1,500 gpm Solids loading 3,503 lb/hr DS Sludge volume index (WAS) 60120 Machine type D12LLU30CHP thickening centrifuges with Easy Pond Guaranteed cake solids 6.0 to 8.0 % Guaranteed capture rate 90 % Guaranteed polymer dosage 6.0 lb/dry ton of feed TSS PERFORMANCE TEST CONDITIONS Medium to be thickened Primary and waste activated blend Blend ratio 4045 % primary/6055 % WAS Blended feed solids 0.50.7 % TS Hydraulic loading 1,000 gpm Thickened sludge 68 % TS Polymer dosage 6.0 lb/dry ton of feed TSS Capture rate 90 % Southerly WWTP: D12LL Centrifuges 1-2 Chapter 1
TABLE 1-2. DESIGN SPECIFICATIONS SPEED MATERIALS CYCLO REDUCER Nominal absolute speed Maximum safety absolute speed For maximum density of sludge Variable relative speed Bowls Scroll Scroll flight coating Seals in contact with product Make size/ratio Lubrication 1,400 rpm 1,800 rpm 1.2 1 to 22 rpm Duplex Stainless steel 316 L REV 12 BUNA-N ZS PN 624/360-53 ELF Carter EP 100 BLOCK BEARING Lubrication ELF Carter EP 68 Oil LEVEL ADJUSTMENT Level Adjustment Plates Conical bowl overflow 602 to 652 mm 612 mm DRIVE MOTOR BOWL SCROLL Make Type Power Baldor Reliance Custom 500 HP Baldor Reliance Custom 75 HP VFD BOWL SCROLL Make Power AB PowerFlex 700 Series 500 HP BELTS XPC 3150 Set of 8 PULLEY RATIO 0.941 WEIGHT: 50,706 lb AB PowerFlex 700 Series 75 HP Southerly WWTP: D12LL Centrifuges 1-3 Chapter 1
1.3 CENTRIFUGE COMPONENT DETAILS The centrifuge components are described in the following sections. See Table 1-3 for materials of construction for centrifuge components. TABLE 1-3. MATERIALS OF CONSTRUCTION Cast parts (bowl) Stainless Steel AISI 316L Bowl Duplex (1.4470) Frame Painted Steel Cover Stainless Steel 1.3.1 Bowl The bowl consists of a horizontal cylindrical conical assembly. See Table 1-4. The bowl is manufactured from a centrifugal cast 316 or Duplex stainless steel. The bowl is machined and balanced to withstand all centrifugal forces encountered at design operating speeds with adequate safety factors. Bowl thickness in the cylindrical section is 1.14 inches and is 0.98 inches in the conical section. The bowl is thoroughly inspected for cracks, shrinkage, porosity or other defects by means of a liquid dye penetrate test as part of the construction process. The inside bowl length is 173.23 inches with an inside diameter of 44.09 inches. The bowl is supported on a cylindrical roller bearing at both ends of the centrifuge. Each end is fitted for connection to the oil lubrication unit. The pond depth in the centrifuge bowl is adjusted using weirs at the large diameter (front) end of the bowl where liquid is discharged. Cake solids are discharged from the small diameter (rear) end of the bowl, opposite from the liquid discharge. Sludge feed is introduced to the bowl through a zone that evenly distributes the feed. The internal scroll conveyor rotates at a slight differential speed from the solid bowl and is supported by greaselubricated ball bearings. The bowl is manufactured with longitudinal strips and prevents circumferential slippage of sediment solids that cause formation of a protective feed solids layer. Field-replaceable sintered tungsten carbide inserts protect the solids discharge ports. The bowl drive is supplied with a 500 hp main drive motor that delivers 2,035 maximum Gs at 1,800 maximum rpm. Southerly WWTP: D12LL Centrifuges 1-4 Chapter 1
TABLE 1-4. BOWL CHARACTERISTICS Inner diameter L/D ratio 4 Total length Nominal speed Maximum Speed 44.09 inches 173.23 inches 1,400 rpm 1,800 rpm G-Value at maximum speed 2,035 Conical part angle Equivalent surface at maximum "G"; conical bowl excluded Equivalent volume at maximum "G"; conical bowl excluded Total length of rotating assembly with pillow blocks Total rotating assembly weight with pillow blocks 11 degrees 19,773 square meters (212,835 square feet) 4,278 cubic meters (1,130,128 gallons) 263.39 inches 24,516 lb 1.3.2 Main Bearings Two main bearings support the entire rotating assembly. Pillow block bearings are supplied with cylindrical roller and are equipped with connections to the oil lubrication unit. Bearings have an AFBMA life of 100,000 hours minimum. See Table 1-5. 1.3.3 Scroll The centrifuge includes a stainless steel horizontal cylindrical-conical scroll supported by a ball bearing at the feed (front) end and ball bearings at the gearbox (rear) end and is equipped with helical flights independently mounted concentrically within the centrifuge bowl. Bearings are protected by seals and have external grease fittings for lubrication. The scroll feed zone is internally coated with flame-sprayed tungsten carbide on the wearing surfaces. The scroll is driven by a 75 hp back drive motor. See Table 1-5. The scroll edge and face of the flights are protected against abrasion with replaceable sintered tungsten carbide tile assemblies from the feed zone to the solids discharge of the scroll. Each tile assembly is affixed to the conveyor flight by an electric-welding attachment procedure. 1.3.4 Base The centrifuge is supported on a fabricated carbon steel base mounted on vibration isolators. The vibration isolators are provided to isolate the centrifuge frame from the building structure. The isolators are specifically sized for the bowl speed and service conditions so that they dampen 98% of all vibration loads in all directions. Machined surfaces are provided at all points where support loads are transferred to the base. Lifting holes in the base are provided as required for lifting the base with an overhead crane. Southerly WWTP: D12LL Centrifuges 1-5 Chapter 1
1.3.5 Casing A one-piece stainless cover is constructed to act as a protective guard from the bowl assembly also providing complete enclosure for both noise reduction and odor control. This cover is fabricated with replaceable stainless steel wear liners in both the solids and liquid discharge areas of the cover. The bowl assembly cover is bolted directly to the main frame of the centrifuge. 1.3.6 Guards OSHA-approved totally enclosed fiberglass guards are provided over belt drives and back drive components for noise reduction. 1.3.7 Feed Tube The feed tube is type 316 SS and is field replaceable. 1.3.8 Polymer/Sludge Feed Manifold A polymer/sludge feed manifold assembly is provided for the injection of polymer into the feed stream. 1.3.9 Cyclo Reducer Each centrifuge is equipped with a two-stage Cyclo reducer that controls the differential speed between the centrifuge bowl and scroll. The gear has a torque capacity to meet the expected service conditions. A torque overload control is provided to initiate centrifuge shutdown in the event of scroll overload. The gear ratio has been selected to handle the required solids loading and to be consistent with satisfactory operation. The gear unit is oil lubricated. All standard units are provided with seals of Nitrile-Butadiene-Rubber (NBR 3760). The power transmitting elements are made of bearing steel, hardened, tempered, and ground. The torque capacity of this gearbox exceeds the requirement of 220,000 inch-pounds. 1.4 CENTRIFUGE DRIVE MOTORS The centrifuge motor information is summarized in Table 1-5. 1.4.1 Main Drive Motors See Chapter 3, Centrifuge Operation. 1.4.2 Scroll Back Drive Motor See Chapter 3, Centrifuge Operation. Southerly WWTP: D12LL Centrifuges 1-6 Chapter 1
TABLE 1-5. CENTRIFUGE MOTOR DRIVE LIST BOWL DRIVE: Manufacturer: Model: Motor Data: Paint: Baldor Reliance Inverter Duty Custom Part Number 500 hp, 460 VAC, 3-phase, 60-Hz, 1793 rpm, G5012Y frame, 1.0 service factor, TEFC, 40 ºC ambient, continuous duty, oversized F-1 mounted main conduit box, separate 120 VAC space heater terminated in separate conduit box located on F2 side; 563 amps; Class F insulation; inverter spike-resistant wire; 100-ohm PT 100 RTDs, two per phase (six total) brought to a single conduit box mounted on the F2 side; a single 100-ohm RTD mounted on each bearing (two total) and wired directly to the COP; insulated bearings provided; provisions are made for mounting three accelerometers and wiring each directly back to the COP; 10:1 constant torque. RAL 5011, Andritz dark blue SCROLL(BACK) DRIVE: Manufacturer: Model: Motor Data: Paint: Baldor Reliance Inverter Duty XE Premium Efficiency ECP4404T-4 75 hp, 460 VAC, 3-phase, 60 Hz, 1185 rpm, 405T frame, 1.0 service factor, TEFC, 40 ºC ambient, continuous duty, oversized F1 mounted main conduit box with 120 VAC space heater terminated within, 86.9 amps; NEMA Design B, Class F insulation, inverter spike-resistant wire, thermistors (three total) brought to a single conduit box mounted on the F2 side, a single 100-ohm PT100 RTD mounted on each bearing (two total) and wired directly to the COP; insulated bearings provided; provisions are made for mounting three accelerometers and wiring each directly back to the COP; 10:1 constant torque. RAL 5011, Andritz dark blue EASY POND SERVOMOTOR Manufacturer: Model: Motor Data: Paint: RAL 5011 EASY POND GEAR BOX Manufacturer: Model: Data: Allen-Bradley MP Series Food Grade Motor MPL-B320P-MJ24AA Paint: RAL 6011 3.05 Nm continuous stall torque (1.5 kw), 480 VAC, 3-phase, 60 Hz, 5,000 rpm, IP 66 and IP 67 rated, 40 ºC ambient, integral 24 VDC brake Alpha-Wittenstein Two-Stage Right-Angle Gear Box SPK075S-MF2-26-1E1 Right-angle design, 25:1 gear ratio, max speed input 6,000 rpm, 94% efficiency at full load, IP 65 protection class Southerly WWTP: D12LL Centrifuges 1-7 Chapter 1
1.5 CENTRIFUGE INSTALLATION INFORMATION See Table 1-6 for a summary of centrifuge characteristics. 1.5.1 Anchor Bolts ANDRITZ supplies all anchor bolts as specified for mounting the centrifuge (refer to the foundation drawing (F804831-1, rev 6). 1.5.2 Vibration Isolation The centrifuge is mounted on Solymar isolators rated for the load and impact associated with normal operation. The centrifuge is provided with vibration monitoring for sensing vibration and will automatically shut down the centrifuge in the event of excess vibration. The equipment will not exceed the 0.24 in./s RMS required by the specification under Dry Shop Testing Conditions. 1.5.3 Noise The centrifuge is equipped with sufficient vibration absorption materials so that the average noise level measured at 3 feet around the periphery of the centrifuge does not exceed 86 dba when tested at the factory at nominal speed. 1.5.4 Fasteners All fasteners are ASTM A320 type 316 stainless steel. 1.5.5 Flexible Joints ANDRITZ supplies all synthetic rubber flexible joints for the sludge feed, centrate, and solids discharge connections TABLE 1-6. EQUIPMENT DATA SCROLL Scroll design Discharge parts For dismantling purposes: Total length of scroll with handling hoist and bowl plate Corresponding weight to lift High performance Field replaceable 156.0 inches 2,933 lb (including lifting beam) GEARBOX Type Nominal torque value Cyclo reducer 228,350 in.- lb MAIN CENTRIFUGE BEARINGS Type Lubrication FAG / SKF Oil Southerly WWTP: D12LL Centrifuges 1-8 Chapter 1
TABLE 1-6. EQUIPMENT DATA AFBMA L-10 100,000 hours minimum POND DEPTH ADJUSTMENT Type Drive Easy Pond Servomotor WEAR PROTECTION Inner bowl surface Scroll Vickers hardness of the carbide grains 2,500 to 4,000 Scroll feed chamber (distributor) Bowl discharge (diffuser) Average life span ANTICORROSION PROTECTION Integral cylinder and cone grooving Replaceable sintered tungsten carbide tiles Sintered tungsten carbide nozzles Sintered tungsten carbide nozzles 16,000 hr /2 years Frame and parts in cast iron or steel RAL 5011 Standard epoxy paint (dry coat minimum thickness) Primer Second coat Finish coat SEALS Type 12.0 mils 2.53.0 mils 4.0 / 6.0 mils 4.0 / 6.0 mils BUNA-N Maximum temperature admissible 175 ºF NOISE LEVEL Measured at nominal speed from 3 feet while empty 86 db (A) MISCELLANEOUS Minimum sludge feed pressure Minimum polymer feed pressure Wash water flow rate Air flow (to vent) 20 psi 25 psi 440 gpm for 15 minutes at each stop @ 45 to 75 psi 580885 cfm Southerly WWTP: D12LL Centrifuges 1-9 Chapter 1
1.6 CENTRIFUGE CONTROL SYSTEM Each centrifuge is supplied with a centrifuge starter panel, a centrifuge operator panel, and a servo control panel shared among the five centrifuges supplied by Andritz. All control panels are UL listed. The centrifuge starter panel (CSP) is located in the electrical room of Thickening Facility East. The centrifuge operator panel (COP) is located on operating floor of Thickening Facility West. The Servo Panel is located in the intermediate basement of Thickening Facility West. All control panels are completely assembled, prewired, and tested for proper control of the centrifuge system. All are freestanding units. For more information about the centrifuge control system, turn to Chapter 3, 3.2. Drawings of the centrifuge operating panel, centrifuge starter panel, and servomotor control panel are contained in Chapter 5, 5.6. Southerly WWTP: D12LL Centrifuges 1-10 Chapter 1