Case Study of Nanning’s Government Procurement of Dongfeng Single-Cab Sludge Suction Trucks (Blue License Plate, 5 m³): A Practical Analysis from Successful Trial Use to Contract Renewal and Expanded Procurement. In southern Chinese cities, the sludge removal pressure brought by the rainy season is an annual challenge for municipal sanitation departments. As a typical humid subtropical climate zone, Nanning experiences concentrated rainfall from May to October each year, resulting in heavy workloads and high operational frequency for clearing silt from urban drainage networks, rivers, and low-lying areas. In 2022, a district-level municipal sanitation department in Nanning procured 15 units of Dongfeng single-cab blue license plate 5 m³ sludge suction trucks via public tender for the first time. After two years of high-load operation, in 2024 the department renewed its contract and ordered an additional 20 units of the same model. This 'contract renewal and expanded procurement' case not only validates the vehicle’s reliability under hot-humid conditions but also provides valuable reference for other cities procuring sludge suction trucks. I. Case Background: From Initial Procurement to Contract Renewal and Expansion 1. Initial Procurement in 2022: 15 Units of Dongfeng Single-Cab Blue License Plate 5 m³ Sludge Suction Trucks In 2022, a district-level municipal sanitation department in Nanning planned to procure a batch of blue license plate sludge suction trucks based on local drainage network cleaning requirements. Blue license plate vehicles (gross vehicle weight ≤ 4.5 tons) can be operated with a Class C1 driver’s license and are exempt from urban traffic restriction policies—making them ideal for operations in narrow streets and residential communities. Following multiple rounds of tender evaluation, the department selected the 5 m³ sludge suction truck built on a Dongfeng single-cab chassis and equipped with Chengli’s proprietary superstructure. The first batch of 15 units was delivered. According to publicly available tender information, the unit price of these vehicles was approximately RMB 120,000, with the total budget kept within RMB 2.07 million. Upon delivery, the vehicles were primarily deployed for main-pipe desilting before the rainy season, emergency post-rain疏通 (unclogging), and routine maintenance operations. 2. User Feedback: High-Load Performance Under Hot-Humid Conditions Nanning’s summer features high temperatures and abundant rainfall, with relative humidity consistently exceeding 80%—posing stringent demands on the anti-corrosion performance and sealing component durability of sludge suction trucks. During the two-year usage period from 2022 to 2024, the district’s municipal sanitation department reported the following key performance indicators: • Excellent Anti-Corrosion Coating Performance: The tank body and piping adopt Chengli’s standard automotive corrosion-protection process. An epoxy resin anti-rust coating is applied internally to the tank, while cathodic electrophoretic primer plus topcoat is used externally. After continuous operation across two rainy seasons, no significant rusting occurred on the tank or piping; only minor surface oxidation was observed on some fasteners—a normal wear phenomenon. • Good Sealing Component Durability: Sludge suction trucks require frequent opening/closing of the rear tank lid and suction pipe valves during operation, placing high stress on sealing components under hot-humid conditions where rubber parts tend to age rapidly. Users reported that rubber seals—including the tank mouth gasket and suction pipe interface gaskets—showed no leakage or cracking over the two-year period. Only one set of primary seals per vehicle was replaced prior to the 2024 rainy season, at a cost of approximately RMB 800 per unit. • Stable High-Load Operational Performance: During the rainy season, each vehicle averages 8–10 hours of daily operation, removing roughly 30–40 cubi