Government procurement case of the EHY5045TWCE6 sewage treatment vehicle (3308 model) in Haikou: A high-load solution for hot and humid environments. I. Pain Points of Aging Equipment: 'Incompatibility' in Hot and Humid Conditions. As a tropical coastal city, Haikou experiences year-round high temperatures and humidity, frequent rainy seasons, and heavy precipitation. A municipal sanitation department is responsible for sewage pumping, drainage, and temporary treatment across multiple low-lying urban areas. Its legacy equipment consisted primarily of standard chassis retrofitted with basic sewage pumps. After three years of operation, these units revealed several critical shortcomings: Severe corrosion: Chassis-to-tank connection points, valves, and piping—continuously exposed to salt-laden air—exhibited blistering and peeling of conventional anti-corrosion coatings within one year, leading to seal failure and sewage leakage, causing secondary pollution. Seal component aging: Under persistent hot and humid conditions, standard rubber seals (e.g., suction port and discharge valve gaskets) rapidly hardened and cracked, resulting in frequent 'leaks, spills, and drips'; maintenance frequency escalated from once per month to once per week. Unstable high-load operation: During the rainy season, equipment was required to operate continuously for 8–12 hours; aging vehicles suffered frequent shutdowns due to inadequate engine and hydraulic system cooling and excessive oil temperature, severely compromising emergency response efficiency. Regulatory compliance limitations: The original equipment met only China IV emission standards, failing to comply with Haikou’s urban environmental restrictions and thus prohibited from entering core operational zones. Following local procurement practice, the department launched an open tender at the end of 2025, with a budget capped at approximately RMB 885,000, seeking two 3308-model sewage treatment vehicles featuring rust/corrosion resistance, high-seal durability, and suitability for sustained high-load operation. The specified model was Chengli Special Purpose Vehicle’s EHY5045TWCE6. II. New Requirements Research Process: Rigorous Operating Conditions Driving Technical Upgrades. Prior to tendering, the department assembled a technical team to conduct on-site inspections and performance comparisons of mainstream market products. Key evaluation criteria included: Chassis and upper-structure corrosion resistance: Requirements stipulated electrophoretic primer + polyurethane topcoat for chassis frame, tank, and piping; critical fasteners to be stainless steel or galvanized; salt-spray test reports mandatory. Seal component durability: Suction port, discharge valve, and manhole cover gaskets required fluorocarbon rubber (FKM) or silicone rubber, with operating temperature range of −20°C to +120°C, supported by accelerated aging test data. High-load operational performance: Engine and hydraulic systems must incorporate forced cooling devices; oil temperature must remain ≤85°C after ≥10 hours of continuous operation; onboard fault self-diagnosis capability required. Announcement & registration compliance: Must meet China VI emission standards, possess complete official announcement documentation, and support nationwide registration, annual inspection, and commercial operation. Following multiple rounds of on-site demonstrations and technical proposal evaluations, Chengli Special Purpose Vehicle’s EHY5045TWCE6 solution emerged as the top choice. Its technical specifications (per MIIT announcement data) are as follows: Item / Specification Chassis Model EQ1045SJ3CDF Gross Vehicle Weight (kg) 4,495 Effective Tank Capacity (m³) 3.3 Sewage Pump Flow Rate (m³/h) 80 Maximum Suction Depth (m) 7.5 Emission Standard China VI Corrosion Protection Full-vehicle electrophoretic primer + polyurethane topcoat; stainless-steel piping Seal Material FKM oil-resistant sealing rings; silicone rubber manhole cover gaskets Co