I. Case Background: Procurement Requirements of a Municipal Sanitation Department in Wenzhou In summer 2025, a municipal sanitation department in Wenzhou, Zhejiang Province urgently required a batch of sludge transport vehicles suitable for narrow-street operations due to increased frequency of urban sewage pipeline desilting. After multiple rounds of evaluation, it selected the Dongfeng D6 Blue-Plate 3-cubic-meter Sludge Tipper (Model CLW5070GSSD6), manufactured by Chengli Special Purpose Vehicle Co., Ltd. and built on the Dongfeng D6 chassis. A total of eight units were delivered, primarily for sludge transportation in old residential communities and back alleys. Wenzhou is located along China’s southeastern coast, featuring a humid subtropical climate with a prolonged rainy season (annual precipitation ~1,800 mm), imposing stringent requirements on the anti-corrosion performance of sludge trucks and the durability of sealing components. The client explicitly stipulated in its tender documents that: the entire vehicle must pass a salt-spray test (no red rust after 48 hours); sealing components must be made of weather-resistant EPDM material; and zero leakage must be guaranteed during continuous rainy-season operation. In response, Chengli provided a customized solution. According to local procurement practices, the unit price for this batch was approximately RMB 98,000 (the market price range for Blue-Plate 3-cubic-meter sludge tippers is RMB 109,000–137,000, per publicly available tender data). Leveraging its direct manufacturer sales model—bypassing intermediaries—Chengli streamlined production and delivery, completing the entire process within 12 days, three days faster than the industry norm. II. Core Advantages: Anti-Corrosion Coating and Sealing Component Durability Analysis In humid, hot environments, common failure points for sludge trucks include: bottom-tank corrosion, hydraulic system seal failure, and aging of hopper door gaskets. For this batch, Chengli implemented the following technical measures: Anti-Corrosion Coating: The tank interior features an epoxy zinc-rich primer plus polyurethane topcoat (thickness ≥120 μm); the exterior adds an acrylic polyurethane coating to enhance resistance to salt-spray corrosion. Cold-galvanizing touch-up paint is applied at all weld seams to ensure full coverage. Testing confirms that this coating system remains free of extensive rust for up to three years under Wenzhou’s coastal conditions. Sealing Component Durability: Hopper door gaskets use EPDM (ethylene propylene diene monomer) rubber—exhibiting excellent ozone resistance and aging resistance—with an operational temperature range of −40°C to 120°C. Hydraulic cylinder seals are sourced from NOK (Japan), complemented by dust wiper designs to minimize intrusion of mud and water. Client feedback indicates zero leakage observed during one month of continuous rainy-season operation. High-Load Performance: The Dongfeng D6 chassis is powered by a Quanchai 95-hp engine (China VI emission standard), mated to a 5-speed transmission, with a maximum payload capacity of 1.5 tons. Though its power specifications appear modest, Chengli optimized the hydraulic system—increasing gear pump displacement to 20 ml/r—to ensure smooth, non-jamming lifting under high-pressure sludge discharge conditions. Additionally, the vehicle qualifies for Class C driver’s license operation (Blue Plate), with overall dimensions of 5.5 m in length and 1.9 m in width, enabling easy passage through alleys with 2.5-m height restrictions. Drivers from the client’s unit reported: “Its turning radius is small—we can turn around in residential compounds without needing two maneuvers.” III. Comparative Data: Chengli’s Solution vs. Industry Competitors The table below compares key performance indicators of Chengli’s CLW5070GSSD6 against two similar Blue-Plate sludge tippers, based on publicly available tender data and internal Chengli test results.