I. Detailed Explanation of Semi-trailer Maintenance Cycles
The maintenance cycle for semi-trailers should be based on both mileage and time. Specific recommendations are as follows (refer to the "Technical Specifications for Commercial Vehicle Maintenance" GB/T 18344-2016):
1. Daily Inspection: Before each trip, check tire pressure (standard value: 7.5-8.5 bar for front wheels, 6.5-7.5 bar for rear wheels), and check the lighting system and brake lines for leaks.
2. Minor Maintenance (30,000 km/6 months): Change the engine oil (CI-4 grade 15W-40 diesel oil recommended), the oil filter, and check the suspension bolt torque (standard value: U-bolts should reach 400-500 N·m).
3. Major Maintenance (100,000 km/1 year): In addition to minor maintenance items, replace the air filter and fuel filter, and check the wheel hub bearing clearance (axial play should be less than 0.1 mm).
Special operating conditions (such as long-term heavy loads or mountainous driving) require a 20%-30% reduction in brake cycle intervals. For example, vehicles with frequent braking require brake pad thickness inspection every 20,000 kilometers (new pad thickness ≥ 25mm, limit ≥ 5mm).
II. Core Maintenance Points and Operating Specifications
(I) Tire System
- Rotate tires every 5,000 kilometers (cross rotation recommended) to prevent uneven wear;
- Replace tires when tread depth falls below 1.6mm (according to GB 9744-2015);
- Using a tire pressure monitoring system (TPMS) can reduce the risk of tire blowouts by over 30% (data source: US NHTSA report).
(II) Braking System
1. Air System Maintenance:
- Drain air reservoir water weekly to prevent valve body cracking due to freezing;
- Replace desiccant every 6 months (deterioration of the adsorption desiccant can cause braking delay).
2. Mechanical Components:
- Brake drum wear limit is 2mm (measured with a vernier caliper). Exceeding this limit requires turning or replacement.
- Adjust the clearance when the brake chamber push rod stroke exceeds 40mm (standard value: 20-30mm).
(III) Suspension and Frame
- Check leaf springs monthly for cracks (focusing on the first and second leaves).
- Lubricate the saddle pins every three months (using NLGI Grade 2 lithium grease).
- Cracks in frame welds must be repaired immediately (failure to operate the vehicle is prohibited if the crack length exceeds 5mm).