Overheat and abnormal noise of connecting rod small end bush of air compressor

1. Improper radial clearance

The radial clearance of the connecting rod small end bush must be properly selected, otherwise, an accident will be caused:

Too large clearance - the knocking sound is produced during operation, and the sound can be heard in both directions of the cross head reciprocating travel. In serious cases, the bearing liner will be cracked and the lubrication will be damaged;

Too small clearance - overheating, tile burning, axle holding and other accidents.

Adjustment method of radial clearance of connecting rod small end bush:

For integral bearing bush (Bush) - if the clearance is too small, repair it slightly; if the clearance is too large, replace the bush;

For split type bearing bush, the gasket of two half of the Bush mouth can be increased or decreased to adjust the amount of Bush, and then the inclined iron can be tightened.

The contact surface between the inclined iron and the back of the tile shall be more than 70%, and shall be evenly distributed. If necessary, it shall be grinded and repaired. The contact surface of the bearing bush to the crosshead pin shall be about 50%, and it shall be scraped and grinded if necessary.

2. Improper axial clearance

The axial clearance of connecting rod small end bush can be detected with feeler gauge. When the connecting rod is leaning to one side, the axial clearance is the sum of the two sides.

When the axial clearance of the small end bearing of the connecting rod is too small, the heating, burning and even expansion will bite.

Its specific characteristics are mainly abnormal fever. It is easy to cause knocking, collision and other phenomena due to excessive cooling, and the main manifestation is abnormal sound.

3. The connecting rod assembly is skewed

If the clearance of the small end bearing of the connecting rod is correct and appropriate, but the overall assembly of the connecting rod is skewed, it will also cause failure.

For example, the connecting rod is not perpendicular to the crosshead pin as a whole, and the contact between the small head pad and the pin shaft is diagonally skewed, which is easy to cause single side knocking, poor contact of the pad surface and excessive heating. To prevent this, it is necessary to:

(1) The center line of crankshaft and fuselage slideway shall be perpendicular to each other in a 90 ° condition, and shall be adjusted properly through inspection and alignment.

(2) For the main parts such as slideway and air cylinder, it's better to align them with steel wire and fix the center.

4. Poor lubrication

The small end bearing of connecting rod shall be provided with reasonable oil groove and oil wedge to obtain normal lubrication and create necessary lubrication and cooling conditions for the friction couple.

Otherwise, it is easy to cause accidents such as tile burning and axle holding.