Why main shaft and main bearing of air compressor have excessive heating and abnormal noise?

The common fault features of the main shaft (i.e. crankshaft) and the main bearing are excessive heating and abnormal noise of the main bearing.

In order to know whether the main bearing bush is overheated, the temperature of the main bearing bush must be detected. Generally, there are several methods to detect the degree of main bearing depression as follows:

(1) Insert a mercury (or alcohol) thermometer into the temperature measuring hole of the main bearing cover. The temperature measuring hole shall be close to the main bearing as far as possible to ensure accurate temperature measurement.

This method can only be observed directly. It is not suitable for the machine with bearing seat inside the fuselage.

(2) The pressure type thermometer with live contact can be used for remote control observation, and the thermometer can be concentrated on the operating platform for reading.

However, this method has the disadvantages of lag and large error.

(3) The temperature of each main bearing bush can be checked point by point on the operation panel by using thermocouple thermometer, primary element of sheet platinum thermocouple and secondary multi-point electronic signal bridge.

When the temperature rises to the specified limit, the device can send out sound light signal or automatically stop.

The abnormal sound of the main bearing is usually manifested in the heavy and dumb impact sound produced in each rotation of the main shaft, accompanied by the vibration of the bearing pedestal and the bearing cover.

Generally, the reasons for this kind of failure are too large bearing clearance, poor fitting of inclined iron or incorrect assembly of main shaft.

The methods of detecting the main bearing sound are as follows:(1) Use a long screwdriver or a thin iron handle as a listening tool, directly touch the head of each part of the bearing, and stick the handle on the ear, then you can hear the operation sound of this part, and judge whether it is normal according to the comparison of experience and operation reality.

(2) Use the fault detector to check the operation sound. This kind of instrument is actually a semiconductor sound amplifier, which is equipped with a dry battery in the barrel. When the metal contact pin touches the surface of the machine directly, the amplified sound can be heard in the earplug. According to the experience and the actual operation, the position and nature of the fault can be judged.