Vilter Single Screw Compressor - Genemco

1 Vilter Single Screw CompressorThe World s Best Compressors forIndustrial RefrigerationVilter s Single Screw compressors deliver longer life, higher reliability and better energy efficiencythan twin Screw compressors and have fewer moving parts than reciprocating compressors. Thekey to the Single Screw Compressor s reliability is in its balanced design. The balanced designresults in ultra-low bearing loads with significantly decreased vibration and sound inherent balanced design advantages allows Vilter to offer the exclusive 5/15 Warranty,including 5-years on the Compressor and 15-years on the bearings. The key to the Single screwcompressor s high efficiency is Vilter s exclusive Parallex slide system allowing the compressorto run at optimum efficiency through it s full range of capacity.

2 Providing the highest reliabilityand surpassed energy The World s Best Compressors are available only from Vilter !2 Parallex slide system - It s the key to partload efficiencies far superior to twin screwcompressors. Capacity and volume slides(with an expanded volume ratio of to )move independently of each other based onload, eliminating over or under compressionand saving motor 20/20 - Microprocessor control Reliable Operation Enhance Communications Easy to Use Flexible and ExpandableOil cooling options Thermosyphon Water Cooled Liquid Injection V-PlusBlock and bleed valves are standard3 TheoryThe compression cycle begins after suction gas fills the top andbottom grooves of the main Screw at the suction end of the the Screw Compressor has two gaterotors, the compressionprocess occurs simultaneously on opposite sides of the Screw ; thetop and bottom.

3 As the main Screw rotates, it in turn drives thegaterotors. The engagement of the gaterotor with a Screw groovetraps the suction gas and begins the compression process. As thescrew rotates, the engagement of the gaterotor continues, thusreducing the initial volume of the groove and increasing thepressure in the groove. Once again this occurs simultaneously onopposite sides of the , as the main Screw rotates toward the completion of thecompression cycle, the groove aligns with a port in the housing atthe discharge end of the casing. The gas and any liquid in the grooveare radially discharged through the port into the discharge there are six grooves in the main Screw , the compressionprocess simultaneously occurs six times in two locations perrevolution of the Screw .

4 Operation at 3000 RPM results in 18,000simultaneous compression strokes at the top and bottom groovesper minute and a relatively smooth flow of discharge LoadingOne advantage of the Single Screw Compressor is the fact thatthere are no net radial or axial forces exerted on the main Screw ordrive shaft components due to the work of compression. Since thecompression process occurs symetrically and simultaneously onopposite sides of the Screw , the forces due to compression arecanceled out. The only vertical loads exerted on the main screwbearings are due to gravity. Since the discharge end of the screwis vented to suction, the suction gas pressure is exerted on bothends of the Screw resulting in balanced axial Single Screw has an inherent design advantage of reducedloading during the compression process.

5 This is due to the factthat the gaterotor tooth area decreases as the gas pressure in thegroove approaches discharge pressure. When the gaterotor firstengages with the main Screw the compression process begins. Asrotation continues, the gaterotor tooth area exposed to the gaspressure increases. The resultant force creates the axial loads onthe gaterotor assembly. Approximately half way through the stroke,or when the radial axis of the gaterotor is perpendicular to therotational axis of the main Screw , the maximum area of thegaterotor is exposed to the gas pressure. As the compression cyclecontinues, the pressure within the groove increases but the areaof the gaterotor exposed to the discharge pressure continues todecrease.

6 The lower loads transmitted to the components andbearings result in higher reliability. At the end of the stroke, thearea of the gaterotor has been reduced to zero as it disengagesfrom the main design feature of the Single Screw Compressor thatenhances reliability results from the fact that the loads on thegaterotor assemblies are well defined and isolated from the mainscrew. Since the gaterotor assemblies are independent and do notinterfere with the rest of the main Screw body, bearings can besized for maximum During CompressionSealing is accomplished by the combination of precision runningclearances and an injected liquid (coolant/lubricant) which isallowed to leak through and thus seal the clearances during thecompression process.

7 In the Single Screw Compressor , this liquidmust also have adequate viscosity to lubricate the bearings. Theliquid is swept into the groove during the suction process and alsoinjected into the compression groove during the compressionprocess to maximize sealing of the running to the rotation of the Screw , centrifugal force impels theinjected liquid to the circumferential clearance volume betweenthe Screw and the housing. This minimizes the leakage describedas cascading. Cascading is defined as the leakage from the highpressure groove past the land separating the grooves into the4trailing low pressure groove. Another inherent attribute of theSingle Screw design is that there is more surface area on the landsnear the discharge end of the groove than near the middle of thegroove.

8 This attribute also minimizes leakage from the highestpressure region of the area where the leakage is minimized is between the highpressure end of the groove to the volume behind the Screw whichis at suction pressure. This potential leak path is sealed by meansof a non-contacting hydrodynamic seal known as a viscoseal,windback seal, or labyrinth Seal SystemA shaft seal system prevents any of the process gas from leakingaround the drive shaft of the main Screw to the environment. Theoil flooded Single Screw Compressor has two seal types ; thestandard Single mechanical face seal or a triple mechanical faceseal with purge capabilities depending on the process stationary carbon face of the seal rides on a hydrodynamicfilm of oil on the rotating mating ring which is fixed on the optional triple seal allows various options including a purgeand vent to be connected to the housing thus adding a secondarysafety buffer during operation.

9 The incorporation of this seal isshown in the cross-section of the oil flooded gas rotating assembly within the gas end has two sets of typical oil flooded Single Screw Compressor consists of tworotating gaterotor assemblies and a main Screw assembly, eachhaving one pair of angular contact bearings to maintain axialposition of the assembly and a cylindrical roller bearing to supportthe opposite end. All of the bearings are pressure fed with oil, upon draining from the bearings, is drawn into the suctionof the main Screw and is discharged with the process gas andinjected oil. Since the main Screw has no loads except for gravity, Vilter Single Screw Compressor - Design and OperationBALANCED LOADINGCOMPRESSION PROCESSDISCHARGE PROCESSSUCTIONSTART OFCOMPRESSIONCOMPRESSIONEND OFCOMPRESSIONSTART OFDISCHARGEEND OFDISCHARGEThe Single screwcompressor has noradial or axial loadson the main the groove increasesto maximum, the gasflows into the intakerotationThe gas is trappedin the groove atsuction the groove volumeis decreased, thepressure in the gas continues to becompressed until it reachesthe minimum volume andmaximum pressure for gas in the groove is atdischarge pressure.

10 Themain Screw aligns with thedischarge port in thehousing and pushes thegas through the port intothe discharge of the gas that wastrapped in the groove ispushed out. The volumeof the groove is reduced DischargeDischarge PortOpeningDischarge PortOpening5the bearings are considered over designed since they aredetermined by the required shaft diameter for the appliedhorsepower. The Single Screw design does not restrict thebearing sizes for the gaterotor supports. As a result, thebearings are optimized for maximum DesignThe dual slide design on the Vilter Single Screw Compressor offersthe highest level of flexibility and performance optimization forscrew compressors. This design actually has two slides percompression side of the gas end.