Interpretation of the Government Procurement Case and Winter Operation Plan for the Dongfeng Yizhan-Style Sewage Treatment Vehicle in Chengdu. In Southwest China—especially in densely populated, rain-prone cities like Chengdu—the demand for sewage treatment vehicles among municipal sanitation departments remains consistently high. Recently, a municipal sanitation department procured a batch of Dongfeng Yizhan-style sewage treatment vehicles via public tender, intended for urban drainage network maintenance and emergency response tasks. This article uses that case as a starting point and, combined with a winter operation-oriented structure, provides an in-depth analysis of vehicle selection, maintenance, freeze-prevention measures, and Chengli Special Purpose Vehicle’s service advantages—offering reference guidance for similar procurement decisions. Case Background and Vehicle Selection This procurement involved approximately five Dongfeng Yizhan-style sewage treatment vehicles, with a budget capped at around RMB 449,000 (based on publicly available tender information). The client required vehicles capable of high-efficiency suction, solid-liquid separation, and rapid emergency response, while also being suitable for Chengdu’s humid, subtropical climate and high-intensity operations during the rainy season. Ultimately, Chengli Special Purpose Vehicle Co., Ltd. delivered Yizhan-style models built on Dongfeng chassis. These feature original Dongfeng engines compliant with China VI emission standards, ensuring regulatory compliance for urban operations. The model adopts a wing-type body design to facilitate rapid equipment loading/unloading and integrates a vacuum pump, sludge dewatering system, and water storage tank. A single operation can process approximately 10 cubic meters of sewage. According to MIIT announcement parameters (e.g., model CLW5070GSSD6), the vehicle’s gross vehicle weight is controlled within the 7-ton class, meeting the requirements for blue-plate license plates and Class C driver’s licenses—reducing driver qualification requirements. Key Considerations for Winter Operations 1. Northern Winter Maintenance Guidelines (Adapted for Chengdu’s Humid Climate) Although Chengdu’s winter temperatures are milder than those in northern China, its humid environment poses stronger corrosion risks to metal components. The Dongfeng Yizhan-style sewage treatment vehicle is factory-equipped with Chengli’s proprietary anti-corrosion coating applied to the chassis, tank body, and connecting components—effectively resisting oxidation and rust under high-humidity conditions. Feedback from a district urban management bureau indicates that this coating extends tank service life by approximately 30% under high-frequency rainy-season operations. Additionally, weather-resistant rubber seals are used to prevent swelling or deformation caused by humidity, thereby minimizing sewage leakage risks. 2. Cold-Weather Starting Recommendations While Chengdu rarely experiences extreme cold, occasional sub-zero temperatures (e.g., ~0°C) still require attention during vehicle startup. Chengli recommends using winter-grade engine oil (e.g., 5W-30 or 0W-30) and ensuring full battery charge. Under severe weather conditions, optional fuel heaters or electric pre-heating systems may be installed. Based on real-world experience, the original cold-start assist system fitted on Dongfeng chassis ensures reliable engine start-up even at -15°C—ideal for Southwest China’s variable climate. 3. Freeze Prevention Measures Freeze prevention is critical for sewage treatment vehicles due to their extensive piping, valves, and pump bodies. Chengli models come standard with an antifreeze circulation system and thermally insulated piping. Users report that the system automatically circulates antifreeze—even during overnight shutdowns in winter—preventing ice blockages. Furthermore, heating elements are integrated into the tank discharge ports to avoid freezing of r