Lakeside - Screw Pumps - Brochure

Lakeside Bulletin 217Revised August 2004? Wastewater Plant Lift Stations ? Land Drainage? Return Activated Sludge ? Industrial Applications? Storm Water PumpingProven designbacked byyears of reliableoperation.Lakeside Screw PumpsLakeside Screw Pumps are an efficient means of lifting large quantities of water or wastewater at lowheads. For municipal wastewater treatment plants, screw pumps offer a variety of applications rangingfrom return activated sludge to stormwater pumping.Lakeside Screw Pumps are widely accepted by engineers because of their proven design and trouble-freeoperation. Lakeside began manufacturing screw pumps in 1969 and since then has installed more than1,200 screw pumps. Lakeside offers both open and enclosed screw pumps for additional flexibility.Open Screw PumpsLakeside?s screw pumps, which are patterned afterthe Archimedean screw, consist of a tube with spiralflights set in an inclined trough. The entireassembly consists of the spiral screw, an upperbearing, a lower bearing and a drive arrangement.Each of these elements is simple and basic indesign. Open screw pumps are normally placed intoa concrete, semicir-cular ?open? trough. The troughmay be constructed at an angle of inclination of 22°to a maximum of 40°.Enclosed Screw PumpsEnclosed screw pumps utilize the same operatingprinciples as open pumps, but are enclosed in a tuberather than in an open trough. Two types ofenclosed pumps are available using either rotatingor station-ary outer tubes. Pumps available includestyles that will operate at a maximum angle of 45°producing the shortest horizontal space requirementfor a given lift.Type CThe Type C screw has two convoluted flights thatare welded to the rotating outer tube and the lowerhearing is mounted above water level. This designmay be built at inclinations of 38° or 45°.Lakeside Screw Pumps are widely accepted by engineersbecause of their proven design and trouble-free operation.Type SThe Type S is an open screw operating in an outerstationary tube. The top of the stationary tube maybe fixed or mounted on a pivot joint to allow raisingthe lower end. The pivot design may also be used tovary flow rate.2Screw Pump AdvantagesLakeside screw pumps offer many advantages over other types of pumps. Specifically, screw pumps providegreater freedom from clogging and high operating efficiencies over a greater range than other pumps. Inaddition, they offer variable pumping capacity while operating at a constant speed.(% of Capacity)10 20 30 40 50 60 70 80 90 100102030405060708090100fill point(max. pump cap.)capacityefficiencyEfficiency - %Liquid Depth - % of "f"fdeliverypointfill point?H??H?water levelCentrifugal PumpScrew PumpLift? High Efficiency Pumping Lowers Costof Electric Power.Screw pumps provide efficient pumping over awide range and operate economically down to30 percent of maximum design capacity. The highefficiency pumping results in lower electrical costsover the entire life of the equipment.? Only Minimal Maintenance and UpkeepRequired.Slow operating speeds reduce friction that dam-ages parts and causes heat generation. Only peri-odic maintenance is needed for oil changes andgreasing.? Screw Pump Installation Eliminates Needfor Wet Well, Reduces Head.Screw pumps do not require a wet well, pumphouse or piping. The screw pump can fit into achannel that is only slightly lower than influentline. This means there is no need for a large wetwell to avoid on and off pump operation. By elimi-nating wet wells, the total pump head is reducedwhich in turn lessens total power requirements.? Screw Pumps Handle Large ObjectsSo Pumps Won?t Clog.Screw pumps require no prescreening and passany debris as large as the gap between screwflights. The screw pump will not clog because itrejects large objects.? Variable Capacity Reduces Initial Costs.The pump?s built-in variable capacity automati-cally adjusts the pumping rate and power con-sumption to the depth of liquid in the inlet cham-ber while operating at a constant speed. The vari-able capacity saves money on initial cost byeliminating the need for elaborate variable speedelectrical controls.Typical open screw pump performance3Proven Design, Simple OperationBearingsBearing construction is critical to the life of any screw pump. Lakeside engineers have designed and devel-oped the best screw pump hearings available.Upper Bearing AssemblyThe upper bearing assembly is the same forboth open and enclosed screw pumps. Theassembly consists of a split housing fittedwith dual bearings and seals. One bearing,designed specifically for thrust loads, car-ries the thrust from the pump: The otherbearing carries radial loads. The upper shaftis held into the bearing housing by a uniquesplit collar and locking halter design. Thesplit outer housing allows easy internalinspection and access to the bearings. Thecomplete bearing assembly is fully self-aligning in any plane.Split HousingThrust BearingSplit CollarLocking HalterRadial BearingBronzeBushingDual SealsCam DesignSealsFigure A - The upper bearing features a splithousing that allows access to the bearings.Figure B - Lower bearing assembly for open screwpumps and Type S enclosed screw pumpsLower Bearing AssemblyThere are two types of lower bearings. The firsttype (Figure B) is used on both open screw pumpsand Type S enclosed screw pumps. This assemblyis specifically designed to compensate forinstallation misalignment, operate under wa-ter and achieve long life without constant atten-tion. This sleeve bearing is automatically and con-tinuously greased when the pump operates. Thebearing compensates for expansion and contrac-tion of the pump due to temperature fluctuationsand automatically maintains bearing alignment asthe pump deflection changes due to varying loads.The bearings rocker-type base assures uniformdistribution of radial load the full length of thebushing. The bushing rotates with the shaft so thatwear distributes over tile entire outer cir-cumference. Finally, the design allows for visualinspection of the lubrication system and recov-ers spent grease to prevent environmentalcontamination.4The second type of lower bearing (Fig-ure C) is used on Type C enclosed screwpumps. This bearing consists of rollersthat support a forged, hardened ring that ismounted on the outer rotating tube. Toprovide for expansion, contraction andvariation in deflection, the rollers aremounted in a cradle which is supported ona self-aligning thrust bearing. Thisarrangement carries the radial load andprovides positive tracking of the rollers atall times.DriveThe V-belt drives connect the motor to the speedreducer. The V-belts act as a shock absorber in thedrive system to protect the speed reducer from pos-sible shock loads and provide for easy speedchanges in the field. Back stops are standard oneach speed reducer to prevent high speed reverserotation if the pump is shut down while fullyloaded. The constant speed drive eliminates theneed for complex variable speed electrical controls.To meet the requirements of any project. Lakesideprovides shaft-mounted, concentric and parallelshaft drive arrangements.Figure C - Lower bearing assembly forType C enclosed screw pumps.Lakeside?s V-belts act as a shock absorber inthe drive system.Adjustable Self-Aligning FrameHardened SteelRollers5Designing A Screw Pump To Fit Your NeedsScrew Pump SelectionBecause of the many styles andindividual advantages of each typeof screw pump, the most appropri-ate selection is dependent uponspecific application factors.Lakeside engineers are readyand available to discuss ad-vantages, pros and cons ofopen or enclosed screwpumps, as well as makedefinite recommendations tobest suit your specificrequirements.fill pointlift?H?delivery pointwater levelCapacity of a Screw PumpThe capacity of a screw pump varies withthese engineering factors:? Diameter of the screw? Speed of the screw? Number of flights mounted on thetorque tube? Angle of inclination of the screw? Level of liquid in the influentchamber? Ratio of the diameter of the torquetube to outside diameter of thescrew flights? Clearance between screw flightsand troughBy making adjustments in these performancefactors, pump capacity can increase. However, ifsubstantial capacity increases are required, it maybe more cost-effective to use multiple screws.To design a screw pump of the proper size, the fol-lowing information is needed:? the maximum flow to be pumped in gpm? the max mum lift required in feetTo achieve the best efficiency, other engineering fac-tors to be considered are:? inclination of the screw? screw speedScrew SpeedMaximum speed is calculated as the highest rev/minat which liquid will not overflow into the next lowerchamber. If the screw speed is increased beyond itsmaximum, lower efficiency and wasted energy willresult. Loss of efficiency will also result if the screwspeed is reduced by more than 30 percent of the cal-culated maximum.6Inclination of the ScrewLakeside designs open screw pumps with standardinclinations of 30° and 38°. Lakeside can modify theangle of inclination to between 22° and 40° whennecessary to achieve a specific combination ofcapacity and lift.Increasing the angle of inclination lowers the capac-ity of the screw approximately 3 percent for eachdegree of increase. A screw at 30° therefore, will havea greater maximum capacity than one inclined at 38°.Conversely, increasing the angle of inclinationincreases the maximum lift available. A screw at 38°will have greater available lift than one inclined at30°.Selection of a screw pump requires determining anangle of inclination that satisfies both lift and capac-ity of the specific application. However, certain de-sign adjustments can be made that allow the pump toobtain the same output volume at steeper angles. Forexample, increasing the number of flights or thespeed of the screw (within limitations).Number of FlightsScrew pumps are available in single, double or triplehelix designs. Output capacity increases about 25percent for each helix added. For example. the ca-pacity of a two flight screw would be approximately125 percent of the same screw with one flight. Thethree flight screw provides the most capacity in theleast space.One FlightThree FlightsTwo Flights7Enclosed screw pumps are capable of operating at 45° inclinations.Motor HorsepowerScrew pump power requirements are based on ca-pacity and lift with consideration to efficiencies ofthe motor and gear reducer.Pump capacity varies directly with the pump speedin the upper end of the operating range. Lift is thevertical distance from the filling point to the deliverypoint. Good design practice dictates selecting themotor so that the pump requirements do not exceed90 percent of the motor nameplate HP.Screw Pump ApplicationsWastewater Plant Lift StationsBecause screw pumps are non-clogging, they offerhigh reliability and handle most objects in rawsewage influent.Return Activated SludgeThe spiral lift is a gentle lift that reduces breakupof activated sludge floc.Storm Water PumpingScrew pumps are ideally suited for widely rangingstorm flows because of the large capacity. They cantake discharge from storm drains or act as standbyunits to bypass storm flows.Land DrainageScrew pumps are particularly useful for pumpinglarge volumes of water over levees.IndustrialScrew pumps can also be used for pumping wherelow shear requirements are important.Screw pumps are non-clogging so they canhandle most objects inraw wastewater influent.The screw pumps gentle spiral lift reduces breakup of floc when handling return activated sludge.Sturdy grating or covers and handrails are suggested safetyprecautions.SafetyAs with all rotating equipment, every precautionshould be taken to prevent people, vehicles, etc.,from entering the pumping area. A few precautionsinclude covering the pit with sturdy grating, erect-ing handrails or barriers between the trough andthe service stairs and arranging the control equip-ment so that the screw cannot start accidentally.Lakeside Equipment CorporationLAKESIDEWater Purification Since 19281022 E. Devon ? P.O. Box 8448 ? Bartlett, IL 60103 ? 630/837?5640 ? FAX: 630/837?5647 ? E-mail: Sales@Lakeside-Equipment.com