Puyan Roots Water Ring Vacuum System for PET Degassing

Puyan Machinery customized a Roots water ring vacuum system for a PET sheet extrusion plant in Peru, supporting high-quality plastic production in the South American market. In the field of PET sheet extrusion, the vacuum degassing system is the core link that determines product transparency and mechanical properties. Recently, Shanghai Puyan Machinery Equipment Co., Ltd. successfully delivered a Roots water ring vacuum system to a PET sheet production factory in Peru. Featuring the Puyan ZJP-300 Roots vacuum pump paired with a 2BV5121 stainless steel water ring pump and a Puyan control panel, the system fully met the customer's stringent requirements for high vacuum, moisture tolerance, and continuous operation in the PET extrusion degassing process.

Project Background: High Standards for Vacuum Degassing Systems in PET Extrusion

The Peruvian customer is primarily engaged in the production of transparent PET sheets and plates, widely used in food packaging, medical consumables, electronic trays, and industrial thermoforming. During the PET extrusion process, if moisture and low-molecular volatiles in the raw materials are not fully removed, bubbles, silver streaks, or crystalline specks will form in the sheet, severely affecting product transparency and mechanical properties.

PET extrusion degassing typically requires a vacuum level of 25–40 mbar or higher, with some high-quality sheet production lines requiring a stable residual pressure below 10 mbar. The customer previously used a single water ring vacuum pump for independent air supply, which presented the following problems: insufficient pumping speed led to incomplete degassing and occasional bubble defects in the sheet; the water ring pump's limited ultimate vacuum made it difficult to consistently reach the vacuum range required for high-quality PET sheets; and the single pump had no backup, meaning any equipment failure would shut down the entire extrusion line.

The customer explicitly requested a vacuum system with high pumping speed, high vacuum, and moisture tolerance, capable of continuously and stably providing a negative pressure environment for the extruder degassing chamber, while also adapting to continuous operation under the hot climate conditions in Peru.

Puyan Solution: ZJP-300 Roots Pump + 2BV5121 Stainless Steel Water Ring Pump + Puyan Control Panel

Based on the operating characteristics of the PET extrusion process, the Puyan Machinery technical team customized a Roots + water ring series vacuum system for the customer:

• Booster main pump: Puyan ZJP-300 Roots vacuum pump. This pump offers a pumping speed of 300 L/s and an ultimate pressure of 3×10⁻² Pa. As a booster pump, it significantly improves the pumping speed and ultimate vacuum of the backing pump. The Roots pump features a non-contact rotor design, providing smooth operation and minimal wear, making it suitable for 24/7 continuous operation on a PET extrusion line. The ZJP-300 comes standard with overflow valve protection – when the backing pump cannot meet the inlet pressure requirement, the valve automatically opens to ensure safe operation of the Roots pump.
• Backing pump: 2BV5121 stainless steel water ring vacuum pump. This pump offers a maximum gas volume of 4.66 m³/min (approx. 280 m³/h), a motor power of 7.5 kW, and an ultimate pressure of 33 mbar absolute (approx. 97% vacuum). The water ring pump uses water as the working fluid, making it particularly suitable for extracting gas mixtures containing water vapor and trace dust. The pump body and wetted parts are made of stainless steel, providing strong corrosion resistance to handle corrosive volatiles that may be generated during PET extrusion. As the backing pump for the Roots pump, it provides the required pre-vacuum for the Roots pump.
• Control system: Puyan control panel. Integrated with PLC control, it enables one-button start/stop of the system, automatic control based on upper and lower pressure limits, fault alarms, and real-time monitoring of operating status. The panel is equipped with a remote communication interface for integration with the customer's extrusion line central control system.

The entire system adopts a skid-mounted structure, with all piping connections and program testing completed at the factory. On-site installation only requires connection to the main pipeline, cooling water, and power supply, significantly shortening the installation and commissioning cycle for overseas projects.

Technical Features: Process Advantages of the Roots + Water Ring Series Combination

The series combination of a Roots pump and a water ring pump is a mature and efficient vacuum solution in the PET extrusion degassing field. The water ring pump, as the backing pump, evacuates the system from atmospheric pressure to the Roots pump's starting pressure (typically 30–50 mbar). At the same time, thanks to its moisture tolerance, it effectively intercepts water vapor and trace volatiles extracted from the extruder degassing chamber, protecting the Roots pump from corrosion. After the Roots pump engages as a booster, it further elevates the system vacuum and maintains it in the high-vacuum range, ensuring that moisture and volatiles in the PET melt are thoroughly removed. This two-stage series design leverages both the water ring pump's moisture tolerance and the Roots pump's high pumping speed and high vacuum, making it an ideal configuration for PET extrusion degassing applications.

Project Results

Since the Roots water ring vacuum system was delivered to the Peruvian customer and put into operation, the customer's production workshop has reported the following:

• Vacuum level achieved: After stable operation, the degassing chamber vacuum level consistently met the customer's process requirement of below 25 mbar, and the defect rate of bubbles and crystalline specks in PET sheets significantly decreased.
• Degassing efficiency improved: With the Roots pump engaged, the pumping speed increased substantially, the degassing chamber response time accelerated, and the extrusion line evacuation time during startup was noticeably shortened.
• Stable and reliable operation: The water ring pump's moisture tolerance effectively handled the hot, humid gases extracted from the extruder degassing chamber, with no pump failures caused by liquid ingress.
• Easy maintenance: The water ring pump uses water as the working fluid, requiring only routine replenishment and periodic inspection, without frequent oil changes, reducing the maintenance burden for the overseas customer.

The customer's production manager commented: "Puyan's Roots water ring vacuum system was installed and commissioned very smoothly. After startup, the vacuum level fully met our process requirements. The Roots pump provides fast pumping speed, and the sheet quality has significantly improved. The after-sales service response in South America has also been very timely."

Why Choose Puyan Machinery's Roots Water Ring Vacuum System?

Puyan Machinery specializes in vacuum pumps and custom vacuum systems. Our core strengths lie in on-demand customization (providing non-standard designs based on air volume, vacuum level, media, corrosion resistance requirements, etc.), our own brand with reliable quality, and rapid response (providing solutions within 24 hours). This Roots water ring vacuum system uses a series design of Roots booster + water ring backing, particularly suitable for process scenarios with dual requirements for moisture tolerance and high vacuum, such as PET extrusion degassing, rubber and plastic devolatilization, and chemical distillation. Besides PET sheet extrusion, this series of systems is also widely used in lithium battery vacuum drying, food packaging, electronic component manufacturing, pharmaceutical chemicals, and other industries. If your plant faces issues such as extrusion degassing, vacuum drying, or system instability, please contact Puyan Machinery for a customized solution.