Project Background: Sewage Treatment Vehicle Procurement Requirements under Zhangzhou's Humid and Hot Climate. In 2025, a municipal sanitation department in Zhangzhou City, Fujian Province, issued a public tender for a batch of sewage treatment vehicles to support urban drainage network maintenance and river remediation. Located on the southeast coast, Zhangzhou features a subtropical monsoon climate, with an annual average humidity exceeding 80%, concentrated rainfall from May to September, and annual precipitation surpassing 1,500 mm. This humid and hot environment imposes stringent requirements on vehicle corrosion resistance, sealing system durability, and high-load operational reliability. After comprehensive evaluation, the procuring entity selected sewage treatment vehicles from Chengli Special Purpose Vehicle Co., Ltd.—the Dongfeng Yizhan series—model numbers CLW5070GSSD6 (blue license plate, 5 m³ capacity) and CLW5180GSSD6 (yellow license plate, 12 m³ capacity). Since their phased delivery beginning in August 2025, these vehicles have operated stably for over six months during Zhangzhou’s rainy season, receiving positive feedback from the client. Key Requirements: Corrosion-resistant coating, sealing components resistant to aging under humid and hot conditions, and fault-free continuous operation during the rainy season. Solution Analysis: How Chengli’s Dongfeng Yizhan Series Addresses Humid and Hot Environmental Challenges 1. Anti-Rust Coating: Full-Life-Cycle Corrosion Protection from Chassis to Tank To address Zhangzhou’s high-salinity fog and high-humidity climate, Chengli employs a multi-layer anti-rust coating system on the Dongfeng Yizhan sewage treatment vehicles. The chassis utilizes OEM electrophoretic primer plus polyurethane topcoat, offering salt fog resistance exceeding 1,000 hours (per industry-standard testing). The tank and piping systems are coated with epoxy zinc-rich primer plus acrylic polyurethane topcoat, achieving a minimum thickness of 120 microns—ensuring rust-free performance during prolonged exposure to wastewater and rainwater. 2. Sealing Component Durability: Weather-Resistant Rubber and Precision Engineering Leakage-prone areas—such as connections between the sewage tank and pumps/valves—are reinforced using ethylene propylene diene monomer (EPDM) rubber seals. EPDM offers superior ozone and UV resistance compared to standard nitrile rubber, extending seal service life by 3–5 years under humid and hot conditions. Additionally, all flange joints feature dual O-ring sealing combined with stainless-steel fasteners, preventing gap expansion caused by thermal expansion and contraction. Real-world testing under simulated Zhangzhou rainy-season continuous spray conditions confirmed zero leakage across the entire sealing system. 3. High-Load Rainy-Season Performance: High-Flow Pumps and Intelligent Control System During Zhangzhou’s rainy season, daily operating time for sewage treatment vehicles often exceeds 10 hours. Chengli equips this model series with standard high-flow sewage pumps from Wilo or equivalent brands, delivering up to 60 m³/h flow rate and 30 m head—enabling rapid dewatering and sludge removal. An intelligent control system continuously monitors pump temperature, current draw, and liquid level; automatic overload protection prevents motor burnout. Client feedback confirms uninterrupted 72-hour operation during Typhoon Passage in September 2025, with no shutdowns or failures. One-Stop Procurement: Multi-Model Configuration Reduces Management Costs This procurement involved not a single vehicle type but a diversified fleet tailored to distinct operational scenarios: the blue-license-plate 5 m³ model (CLW5070GSSD6) is optimized for narrow streets and community sewer cleaning, while the yellow-license-plate 12 m³ model (CLW5180GSSD6) serves main roads and pumping station transfer operations.