I. Procurement Background: Starting with the First Batch of 3 Units In winter 2023, a municipal sanitation department in Tianjin (hereinafter referred to as the 'Procuring Party') issued a public tender for 3.308 m³ sewage treatment vehicles to address sludge removal from aging urban pipelines and pumping stations, as well as emergency sewage treatment needs. A total of five enterprises participated. Chengli Special Purpose Vehicle Co., Ltd. won the bid with its EHY5045TWCE6 model—featuring complete official announcement parameters (verifiable via MIIT Announcement No.) and a configuration comprising a 3 m³ sewage tank, high-efficiency vacuum pump, and winter anti-freeze package—at an approximate unit price of RMB 120,000 (based on publicly available tender information) and delivered the first batch of three units. These vehicles are built on Dongfeng light-duty truck chassis, fully compliant with China VI emission standards. Key configurations include: effective tank capacity of approximately 3 m³; overflow prevention device; self-priming and self-discharging system; and electrically heated anti-freeze piping. The Procuring Party prioritized Chengli’s advantage of 'direct factory sales without intermediaries' and its commitment to 'local production in Suizhou, zero-inventory delivery, and standard-model delivery within 7–15 days.' Actual delivery was completed within 12 days, meeting expectations. II. User Feedback: Winter-Exposed 'Freezing Point' Issues From December 2023 to January 2024, Tianjin experienced prolonged sub-zero temperatures, with minimum ambient temperatures dropping to –15°C. During actual operations, the Procuring Party identified the following core issues: • Difficult Cold-Start Performance: Upon early-morning deployment, extended engine preheating times were observed; some vehicles required 3–4 repeated starts before achieving normal operation, negatively impacting emergency response speed. • Poor Low-Temperature Hydraulic Stability: Increased hydraulic oil viscosity at low temperatures caused sluggish actuation of the power take-off (PTO) and hydraulic pump, reducing sewage suction efficiency by approximately 15%. • High Winter Maintenance Costs: The original equipment lacked full-vehicle electric heating insulation; operators had to install additional thermal insulation blankets manually, and antifreeze replacement intervals were shortened. The project manager of the Procuring Party commented: 'Given Tianjin’s winter operating conditions—vehicles must remain outdoors for at least eight hours daily—anti-freeze performance is non-negotiable. Although the initial batch fulfilled basic operational requirements, overall efficiency was compromised.' This feedback directly triggered subsequent requirement iterations. III. Requirement Upgrade: Mandatory Technical Specifications for the Second Procurement In autumn 2024, the Procuring Party launched a new procurement initiative, with a budget capped at approximately RMB 148,000 (in line with local procurement practices). However, the technical tender document explicitly introduced three mandatory requirements: • Anti-Freeze Starting System: Standard installation of a low-temperature preheating device (e.g., engine jacket heater or fuel-fired heater) capable of ensuring single-start success at –20°C. • Low-Temperature Hydraulic Stability: Use of low-temperature-specific hydraulic oil (e.g., L-HV 32#) and addition of thermal insulation layers or electric heat-tracing to hydraulic lines. • Winter Maintenance Plan: The supplier must provide a comprehensive winter operation manual, including recommended service intervals for antifreeze, lubricants, and battery maintenance. Upon learning of these requirements, Chengli’s technical team promptly implemented targeted upgrades to the EHY5045TWCE6 model: • Installation of an intelligent fuel-fired heater (optionally powered by either 220 V external supply or onboard 12 V DC), ensuring engine coolant temperature rises abo