A real-world test under humid conditions: A case study of sewer cleaning truck procurement by a municipal sanitation department in Quanzhou, Fujian Province. Located on the southeast coast of China, Quanzhou experiences an annual average humidity exceeding 80%, with a rainy season lasting up to six months—posing heavy demands on urban drainage network cleaning. Last year, a municipal sanitation department procured a batch of 5 m³ blue license plate sewer cleaning trucks via public tender to address rainwater and sewage pipe cleaning needs in older residential neighborhoods. According to the fleet management supervisor of this department, after comparing multiple suppliers, Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as 'Chengli') was ultimately selected—the Dongfeng single-cab blue license plate sewer cleaning truck (model CLW5070GSSD6). The supervisor admitted: 'In Quanzhou’s hot-humid climate, vehicles are especially vulnerable to rust and aging of sealing components. In previous procurements, rust spots appeared on chassis within two years, and hydraulic systems frequently leaked oil. By contrast, this batch from Chengli has operated for approximately eight months and has performed beyond expectations.' I. Fleet Management Supervisor’s Evaluation: Anti-Rust Coating and Sealing Component Durability Are Critical 'This batch of 5 m³ sewer cleaning trucks is primarily deployed for intensive operations before and after the rainy season. Chengli emphasized its anti-corrosion process specifically designed for coastal climates upon delivery,' the supervisor explained. This Dongfeng single-cab sewer cleaning truck (blue license plate, 5 m³; reference unit price per publicly disclosed tender documents: approx. RMB 105,000) features full-chassis cathodic electrophoretic coating, complemented by high-temperature spray coating on the superstructure—effectively resisting salt fog corrosion. 'In the past, we spent about RMB 3,000 annually on chassis anti-rust treatments; now, this batch requires virtually no additional maintenance, resulting in direct cost savings.' Moreover, sealing component durability is especially critical in hot-humid environments. Sewer cleaning trucks routinely handle sewage and silt; if hydraulic cylinder and pipeline joint seals lack corrosion resistance, oil leakage failures easily occur. The CLW5070GSSD6 model supplied by Chengli (MIIT Announcement No.: CLW5070GSSD6) employs imported nitrile rubber seals in its hydraulic system—offering superior resistance to oil and acids/alkalis compared to standard rubber. According to feedback from the supervisor, during three consecutive months of intensive rainy-season operation (averaging five working days per week), not a single instance of hydraulic leakage occurred across this batch. In contrast, another brand procured concurrently began exhibiting leakage after roughly three months—highlighting a clear reliability gap. II. Dispatch Flexibility: Balancing Blue License Plate Advantages with 5 m³ Capacity The primary advantage of blue license plate sewer cleaning trucks lies in their operability with a Class C1 driver’s license and exemption from urban driving restrictions. Narrow roads in Quanzhou’s historic urban core prevent access by large-scale cleaning vehicles, whereas the 5 m³ capacity of blue license plate models perfectly meets routine cleaning requirements. A total of six Dongfeng single-cab sewer cleaning trucks were delivered to this municipal sanitation department; each vehicle cleans approximately 15 manholes per day, covering about 30% of the jurisdiction’s drainage network. 'Dispatch is highly flexible—we don’t need to assign larger vehicles. One compact truck plus one driver suffices to cover an entire district,' added the supervisor. 'The superstructure volume of Chengli’s trucks is precisely 5 m³; the tank is fabricated from stainless steel—corrosion-resistant and lightweight—ensuring compliance with blue license plate reg