I. Project Background: First Batch Procurement and Trial Use In early 2023, a municipal sanitation department in Changde City (hereinafter referred to as 'Changde Municipal') launched its first public tender to procure a batch of Dongfeng Yizhan-style sewage treatment vehicles, aiming to address urban river and domestic sewage treatment needs. According to the tender announcement, the total budget for this batch was capped at approximately RMB 1.707 million, with three units planned for procurement at an estimated unit price of around RMB 500,000. Chengli Special Purpose Vehicle Co., Ltd. (hereinafter referred to as 'Chengli') won the bid based on its Dongfeng chassis combined with a Yizhan-style body design and the CLW5180 model’s official type-approval parameters, delivering three Dongfeng Yizhan-style sewage treatment vehicles. After commissioning the first batch, Changde Municipal provided the following feedback: • Treatment efficiency met baseline requirements: Under typical domestic sewage treatment conditions, daily processing capacity reached approximately 80 cubic meters, satisfying routine operational demands. • However, several shortcomings were identified: – Insufficient sealing performance of the Yizhan-style body under adverse weather conditions (e.g., heavy rain or strong winds), posing risks of secondary contamination; – Marginal chassis power during full-load operation—particularly noticeable when climbing slopes or transporting over long distances; – Short maintenance intervals: Some hydraulic components exhibited leakage within six months. Statistical data showed that these vehicles processed approximately 29,000 cubic meters of sewage throughout 2023, yet accumulated over 45 days of downtime due to repairs—significantly impacting overall operational efficiency. II. Identified Issues: Requirement Upgrades and Tender Refinements Based on practical experience with the first batch, Changde Municipal revised its procurement strategy for the second batch in 2024, implementing targeted improvements to the tender specifications: • Enhanced Chassis Power: Minimum engine output raised to no less than 180 horsepower to ensure adaptability to complex road conditions. • Improved Body Sealing: The Yizhan mechanism must comply with enhanced air-tightness testing standards and be equipped with an automatic rain-protection system. • Extended Maintenance Intervals: Hydraulic systems and critical components must carry a minimum two-year warranty and support remote fault diagnostics. • Unit Budget: Capped at approximately RMB 626,000 per unit, with a total budget of about RMB 1.878 million (for three units). Changde Municipal explicitly stipulated in the tender documents: 'Bidders must provide case studies of similar municipal projects completed within the past three years; all delivered vehicles must pass acceptance testing conducted by provincial-level inspection agencies.' Leveraging operational data from the previously delivered three units and its optimized CLW5180GSSD6 model proposal, Chengli successfully re-bid and secured the contract, delivering three upgraded Dongfeng Yizhan-style sewage treatment vehicles at a unit price of approximately RMB 528,000 (per publicly disclosed tender information). III. Upgrade Solution: How Chengli Special Purpose Vehicle Met the New Requirements To meet Changde Municipal’s upgraded requirements, Chengli implemented the following enhancements to the CLW5180GSSD6 model: • Chassis Upgrade: Equipped with a Dongfeng Tianlong D320 cab, Yuchai 200-horsepower engine, and Fast Gear 8-speed transmission—delivering a 15% increase in power output while improving fuel economy. • Enhanced Body Sealing: The Yizhan-style body features dual-layer sealing strips plus a hydraulic locking mechanism, and has passed IP65-rated waterproof testing—ensuring reliable operation even during heavy rainfall. • Optimized Hydraulic System: Critical hydraulic valve assemblies upgraded to imported brands; an