Service Life Analysis of Connecting Rod Bolts in Air Compressor

Key role of connecting rod bolts in reciprocating air compressor

connecting rod bolts are the key fasteners of the core moving parts of reciprocating air compressor, which undertake the transmission task of periodic repeated fluctuating load in piston-connecting rod-crankshaft system. The stability of its pre-tightening force directly affects the operation safety and vibration level of the whole machine.

Main Factors affecting fastener life

• mechanical Fatigue: High frequency reciprocating motion leads to stress circulation, which is easy to produce micro cracks at the root of the thread or the rod;
• preload attenuation: thermal expansion and cold contraction, fretting wear and plastic deformation will reduce the effective clamping force;
• environmental corrosion: accelerate surface deterioration under wet, oily or dusty conditions;
• installation error: asymmetric stress distribution caused by torque deviation or improper lubrication.

Regular replacement cycle recommendations

based on typical working conditions (continuous operation, medium load, good maintenance), connecting rod bolts are recommendedthe preventive replacement cycle is 12-18 months or 6000-8000 hours in total.. High load, frequent start and stop or old unit should be shortened to 6-12 months. Repeated use of removed bolts is strictly prohibited-even if the appearance is intact, the microscopic fatigue damage is irreversible.

Mechanical Fatigue Analysis Guide practice

in modern maintenance practice, the state assessment can be carried out by combining vibration spectrum analysis and bolt elongation measurement. For key units, it is recommended to introduce S-N curve (stress-life curve) to carry out customized fatigue life prediction, and establish a Bolt service file to track the historical load spectrum.