Analysis of the Causes of Turbocharger Failure and Preventive Measures

A Japanese Komatsu PC220-5 excavator from a subordinate unit of our department has continuously damaged nine turbochargers in nearly two years of use.

I. Cause Analysis

Through the analysis of several on-site faults of this machine, it is known that the main reasons for the damage of the turbocharger are as follows:

1. Damage caused by insufficient lubricating oil

(1) Oil passage blockage: When the original turbocharger was damaged, during on-site analysis and diagnosis, the oil pressure in the main oil passage was measured to be normal. However, when the lubricating oil inlet pipe of the turbocharger was disassembled, almost no lubricating oil flowed out. After disassembling and inspecting the oil radiator, it was found that the radiator was basically blocked by sludge. After a thorough cleaning of the engine lubrication system, the oil lubrication was restored and the turbocharger operated normally.

(2) Damage caused by oil pump failure: In a fault diagnosis of a turbocharger failure, the measured oil pressure in the main oil passage was only 0.03MPa, and there was almost no oil in the turbocharger's oil inlet pipe. The lubrication system was inspected and no blockage in the oil passage was found. When disassembling and inspecting the oil pump, it was found that fragments of cotter pins had entered the oil pump, causing damage to the gears and housing and resulting in the failure of the oil pump. This also led to the failure of the turbocharger due to lack of oil lubrication. The damage to the oil pump this time also led to a major overhaul of the engine.

After disassembling and inspecting other damaged turbochargers, it was found that some had deposits in the middle shells, which affected the lubrication of the turbochargers.

The axle speed of the turbocharger is from tens of thousands to 200,000 revolutions per minute at high speed. All bearings must be supplied with lubricating oil to play a role in stabilization, lubrication and cooling. If the lubricating oil is insufficient or interrupted, at such a high rotational speed, the direct friction between metals will inevitably cause the components to be damaged one by one very quickly, until the turbocharger fails.

2 Damage caused by engine overheating

Due to the lack of sufficient data and experience during the engine maintenance process, one time the fuel injection volume was adjusted too much when adjusting the fuel injection pump, and the other time the fuel injection timing was adjusted too late. As a result, the engine overheated (the engine felt extremely hot after running for a while), and the cause was not found in time, which led to the damage of the turbocharger. When disassembling and inspecting the turbocharger, it was found that the wheel shaft of the turbocharger had changed color due to overheating, there was carbon residue in the middle housing, and the bearings were damaged.

During disassembly and inspection, it was also found that when the turbine impeller was exposed to high temperatures (exceeding 650 ℃), the heat was simultaneously transferred along the axial direction to the compressor. The lubricating oil burned in the middle shell and formed sediment, which then entered the friction parts along with the lubricating oil, accelerating the wear of the bearings. Meanwhile, at high temperatures, the lubricating oil thins, causing the oil pressure to drop and the lubrication to be affected, ultimately leading to the failure of the turbocharger.

In addition, due to the poor condition of the engine, it often stalls suddenly at high speed during use, and drivers frequently stop the engine while it is running at high speed. This is also one of the reasons for the premature damage of the turbocharger.

Ii. Preventive Measures

1. Install and use the turbocharger correctly

(1) When installing a new turbocharger or changing the engine oil, a certain amount of engine oil should be injected into the turbocharger. Or rotate the crankshaft several times to ensure that the turbocharger is lubricated after starting the engine but before the oil pressure is established.

(2) After the engine starts, it must be idled for several minutes to ensure that the lubricating oil pressure is established and the turbocharger is fully lubricated, preventing dry friction.

(3) Before the engine stops running, it must idle for several minutes to gradually reduce the speed and temperature of the turbocharger as much as possible. This is to prevent the turbocharger from suddenly interrupting lubrication at high speed and high temperature, which may cause dry friction of components, as well as carbonization of the lubricating oil due to high temperature.

(4) After the engine is repaired, it is necessary to ensure that the lubricating oil passage is unobstructed and has sufficient pressure. When starting the engine, a pressure gauge should be installed to measure the oil pressure. For engines without an oil pressure gauge display (warning light display), the oil pressure should also be frequently checked during normal operation to prevent errors in the oil pressure display on the engine.

2 Properly maintain and adjust the turbocharger and engine

(1) Turbochargers generally do not require periodic maintenance. However, if the lubricating oil is found to be too dirty, the oil filter element is clogged, or there are impurities in the lubricating oil, necessary maintenance of the turbocharger should be carried out to remove oil stains and impurities from it.

(2) It is necessary to prevent the lubricating oil from being contaminated and replace it regularly to avoid affecting the oil supply volume and pressure of the turbocharger, as well as to prevent oil stains from entering the turbocharger.

(3) Adjust the engine's operating parameters correctly. Improper adjustment may cause the engine to malfunction, overheat, emit black smoke, and thus contaminate and carbonize the oil.

(4) Effectively prevent any external debris from entering the turbocharger compressor through the air inlet.

3 Choose the turbocharger correctly

(1) Prevent substandard turbochargers from being put into use.

(2) The model and part number of the turbocharger must match those of the engine. If they do not match, it will affect the performance of the engine and the lifespan of the turbocharger.

4 Strengthen equipment management and the sense of responsibility of drivers

Through the above analysis of the causes of faults, it is known that the damage to the turbocharger is all related to the use and maintenance of the engine. The damage caused by the turbocharger itself has not been found yet. Therefore, the driver should be enriched with knowledge about the use and maintenance of the entire equipment, and the management of the equipment and the sense of responsibility of the driver should be strengthened.