Carrier AquaEdge 19XR Series Start-up, Operation And Maintenance Instructions Manual

Also see for AquaEdge 19XR series: Installation instructions Start-up, operation and maintenance instructions

Contents

12LUBRICATION CYCLESummaryThe oil pump, oil filter, and oil cooler make up a package locatedpartially in the transmission casing of the compressor-motor as-sembly. The oil is pumped into a filter assembly to remove foreignparticles and is then forced into an oil cooler heat exchanger wherethe oil is cooled to proper operational temperatures. After the oilcooler, part of the flow is directed to the gears and the high speedshaft bearings; the remaining flow is directed to the motor shaftbearings. Oil drains into the transmission oil sump to complete thecycle (Fig. 8 and 9).DetailsOil is charged into the lubrication system through a hand valve.Two sight glasses in the oil reservoir permit oil level observa-tion. Normal oil level is between the middle of the upper sightglass and the top of the lower sight glass when the compressoris shut down. The oil level should be visible in at least one ofthe 2 sight glasses during operation. Oil sump temperature isdisplayed on the HMI default screen. During compressor oper-ation, the oil sump temperature ranges between 125 and 165°F(52 and 74°C).The oil pump suction is fed from the oil reservoir. An oil pres-sure relief valve maintains differential pressure in the system atthe pump discharge. A range of 18 to 40 psid (124 to 172 kPad)is normal. This differential pressure can be read directly from thedefault HMI screen. The oil pump discharges oil to the oil filterassembly. This filter can be closed to permit removal of the filterwithout draining the entire oil system. The oil is then piped tothe oil cooler heat exchanger. The oil cooler uses refrigerantfrom the condenser as the coolant. The refrigerant cools the oilto a temperature between 120 and 140F (49 and 60C).As the oil leaves the oil cooler, it passes the oil pressure transducerand the sensor for the refrigerant expansion valve on the oil cooler.The oil is then divided. Part of the oil flows to the thrust bearing,forward pinion bearing, and gear spray. The rest of the oil lubri-cates the motor shaft bearings and the rear pinion bearing. The oiltemperature is measured in the bearing housing as it leaves thebearings. The oil then drains into the oil reservoir at the base of thecompressor. The control measures the temperature of the oil in thesump and maintains the temperature during shutdown. This tem-perature is read on the HMI default screen. See the Controls Oper-ation and Troubleshooting Manual for details.During the chiller start-up, the oil pump is energized and provides40 seconds of lubrication to the bearings after pressure is verifiedbefore starting the compressor. During shutdown, the oil pumpruns for 60 seconds to ensure lubrication as the compressor coaststo a stop.Ramp loading can be adjusted to help to slow the rate of guidevane opening to minimize oil foaming at start-up. If the guidevanes open quickly, the sudden drop in suction pressure can causeany refrigerant in the oil to flash. The resulting oil foam cannot bepumped efficiently; therefore, oil pressure falls off and lubricationis poor. If oil pressure falls below 15 psid (103 kPad) differential,the controls will shut down the compressor.The oil pump is a gerotor-style pump with external filters. Agerotor pump has two rotors, one inside the other; their centerpoints are offset with respect to each other. This type of pumpprovides a smooth continuous flow. It is also quieter than otherdesigns. See Fig. 10 and 11.BearingsThe 19XR compressor assemblies include a combination of radialand thrust bearings. The low speed shaft assembly is supported bytwo journal bearings. For 19XR2-E the bearings are located be-tween the motor rotor and the bull gear — overhung rotor design.The 19XR6-7 is fully supported with bearings located on each endof the low speed shaft. The bearing closer to the bull gear includesa smaller babbitted thrust face, designed to handle axial forces.For Frame 2 19XR compressors the high speed shaft assembly issupported by two journal bearings located at the transmission endand mid-span, behind the labyrinth seal. The transmission side ofthe midspan bearing also contains a tilting shoe type thrust bearingwhich opposes the main axial forces tending to pull the impellertowards the suction end. The impeller side face of the midspanbearing includes a babbitted thrust face, designed to handlecounter-thrust forces.For 19XR Frame 3, 4, 5, C, E, 6 and 7 compressors the high speedshaft assembly utilize rolling element bearings (radial and thrust).Machines employing rolling element bearings can be expected tohave higher oil pressure and thrust bearing temperatures thanthose compressors using journal bearing design.Oil Reclaim SystemThe oil reclaim system returns oil lost from the compressor hous-ing back to the oil reservoir by recovering the oil from 2 areas onthe chiller. The guide vane housing is the primary area of recovery.Oil is also recovered by skimming it from the operating refrigerantlevel in the cooler vessel.PRIMARY OIL RECOVERY MODEOil is normally recovered through the guide vane housing on thechiller. This is possible because oil is normally entrained with re-frigerant in the chiller. As the compressor pulls the refrigerant upfrom the cooler into the guide vane housing to be compressed, theoil normally drops out at this point and falls to the bottom of theguide vane housing where it accumulates. Using discharge gaspressure to power an eductor, the oil is drawn from the housingand is discharged into the oil reservoir.SECONDARY OIL RECOVERY METHODThe secondary method of oil recovery is significant under lightload conditions, when the refrigerant going up to the compressorsuction does not have enough velocity to bring oil along. Underthese conditions, oil collects in a greater concentration at the toplevel of the refrigerant in the cooler. Using discharge gas to powereductors, this oil and refrigerant mixture is skimmed from the sideof the cooler and is then drawn up to the guide vane housing.There is a filter in this line. Because the guide vane housing pres-sure is much lower than the cooler pressure, the refrigerant boilsoff, leaving the oil behind to be collected by the primary oil recov-ery method.