CARRIER 2466190 - Caterpillar

Illustration 1 g01087064
Typical example of a turbine wheel
Illustration 2 g01087065
(1) Accumulation of deposits on the turbine wheelCertain operational practices and maintenance practices can prevent major damage to the turbocharger. This will also extend the service life of VTC254 turbochargers that are used on some G3600 engines. The accumulation of deposits on the turbocharger's turbine blades is the main failure mode of the VTC254 turbocharger on G3600 engines. Refer to Illustrations 1 and 2. The deposits can accumulate more in one area or pieces of the deposits can break loose from the blade. This causes the turbine wheel to become unbalanced. This imbalance causes the shaft to move.Once the shaft is able to move, the oil film that is between the rotating shaft and the shaft bearings degrades. This leads to failure of the shaft bearing. Once the shaft bearing fails, the blades on the turbine and on the compressor can come into contact with the turbocharger housing.Analysis of Trends in Engine Data
As deposits form on the turbine blades, the efficiency of the turbocharger is slowly degraded. The G3600 control system adjusts for changes in efficiency of the turbocharger by closing the wastegate which forces more exhaust gas through the turbocharger. This allows the turbocharger to maintain the desired manifold pressure and the desired air/fuel ratio. The general condition of the turbocharger can be determined by monitoring and by recording engine data and analyzing the trends indicated by this data. The most critical parameters that must be monitored are the following:
Inlet manifold air pressure
Operation of the wastegate
Indicated engine loadAdditionally, these other parameters must also be monitored:
Inlet air restriction
Emissions NOx
Inlet manifold air temperature
Fuel quality (fuel correction factor)
Ambient air temperature
Humidity
Barometric pressure
Turbocharger speed The number of items that are recorded determines the accuracy of the prediction of the turbocharger's condition. The data from different engines cannot be compared due to the following factors:
Different sites
Arrangement of the engines
Variations of the inlet air ducts and of the exhaust ductsComparative data must be taken under controlled conditions. The monitoring must be started with the following components in good condition:
A clean turbocharger
A tuned engine
Air cleaners
Spark plugsAnalysis of the data must take into consideration the condition of the engine and of the air filters. Incorrect analysis can result from data that is taken when the air filters are dirty or when a cylinder misfire is present. Monitoring trends for determining the maintenance intervals of the turbocharger requires careful planning and the careful collection of data. Maintenance costs for the turbocharger can be reduced as more data is collected and as experience is gained in analyzing the trends of the data.Monitoring of Vibration
Monitoring of vibration is another method of determining the condition of the turbocharger. The monitoring of vibration shows the effects of accumulation of deposits on the turbine blades. An accelerometer is mounted on the exhaust inlet of the main housing. This is done by drilling and tapping the housing. This port must be made horizontally to the shaft centerline.The measurements must be taken over a frequency range of