I. Case Background: The 'High-Frequency Operation' Pain Point in Sludge Collection and Transportation for Municipal Sanitation in a District of Tangshan City As an industrial hub, Tangshan City faces persistent challenges in transporting urban sludge, industrial sediments, and high-moisture-content materials generated by wastewater treatment plants—long-standing difficulties for municipal sanitation departments. In 2025, the Urban Management Bureau of a district in Tangshan City planned to replace a batch of sludge transport vehicles, primarily tasked with daily transportation from local wastewater treatment plants to designated disposal sites. According to publicly released tender information, the project budget was controlled at approximately ¥502,000–¥613,000 per unit, with procurement specifying Sinotruk chassis-based 24 m³ sludge tipper trucks. Customers reported frequent issues with existing vehicles under continuous heavy-duty operation—including body corrosion, hydraulic system leakage, and insufficient chassis load-bearing capacity—resulting in average annual maintenance costs of ¥30,000–¥50,000 per vehicle, severely impacting operational efficiency. Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as 'Chengli SPV') provided a customized solution for this project, delivering multiple Sinotruk-chassis 24 m³ sludge tipper trucks, now fully operational locally. This article analyzes equipment fatigue management challenges faced by municipal sanitation units under daily high-load operations, and interprets Chengli SPV’s design philosophy for heavy-duty working conditions. II. Analysis of Daily High-Load Operating Scenarios for Municipal Sanitation Units 2.1 Operational Frequency and Intensity Sludge collection differs significantly from standard waste transportation: it involves higher frequency, shorter haul distances (typically 20–40 km), and materials with high moisture content (up to 70%–80%). For example, in the aforementioned district of Tangshan, 3–5 round trips are required daily, with total daily mileage averaging 150–200 km—and frequent entry/exit from sludge dewatering workshops and tipping platforms. This 'high-frequency, short-haul' operating pattern places exceptionally high demands on vehicle chassis suspension, hydraulic systems, and body sealing performance. 2.2 Core Contradictions in Equipment Fatigue Management Based on practical feedback from multiple municipal sanitation authorities, primary wear-and-tear on sludge transport vehicles concentrates in the following areas: • Chassis Fatigue: Under heavy-load conditions (a 24 m³ sludge load typically weighs 24–30 tons), the frame endures prolonged torsional stress, leading easily to weld seam cracking. • Body Corrosion: Acidic components (e.g., sulfides) and moisture in sludge cause severe corrosion to standard carbon-steel bodies; typical steel plates perforate within 3–5 years. • Hydraulic System Failure: Frequent lifting and dumping accelerate wear of hydraulic cylinder seals, resulting in insufficient hydraulic pressure or oil leakage. • Rear Door Sealing: Sludge leakage is a common complaint point; aging door seal strips easily cause roadside contamination. Therefore, the procuring authority prioritized 'durability under heavy-load conditions' as the top technical requirement for this project. III. Interpretation of Chengli’s Heavy-Duty Working Condition Design 3.1 Chassis Selection and Reinforcement The delivered vehicles utilize the Sinotruk HOWO chassis (model ZZ1257N464GF1), an engineering-grade reinforced variant equipped with the Sinotruk MC07.31-60 Tier VI engine (310 hp) and a 10-speed transmission. To address sludge transport-specific requirements, Chengli SPV implemented the following adaptive enhancements to the chassis: • Reinforced Frame: Features a dual-layer longitudinal beam structure (300 mm wide), with localized reinforcement plates added to improve torsional rigidity. • Optimized Rear Axle Ratio: