Dorin Factory Tour Details the Company’s CO₂ Compressor Production and Testing Processes

Italian manufacturer Dorin gave NaturalRefrigerants.com a behind-the-scenes tour of its Florence, Italy, manufacturing facility, highlighting its CO₂ (R744) compressor production and testing processes.

For strong quality assurance, Dorin conducts leak detection and operational tests on every CO₂ compressor before shipping it out of the factory, said Giacomo Pisano, CO₂ Business Development Manager at the company.

Dorin offers a series of transcritical CO₂ compressors to cover all possible market applications, including mobile air-conditioning, supermarkets and industrial processing, with a new 750HP 8-cylinder unit to be launched in 2025.

“Our unique production process control runs every single compressor through a real operating CO₂ loop at 25bar [363psi] suction pressure and 80bar [1,160psi] discharge for 25‒30 minutes,” Pisano told Marc Chasserot, Founder and CEO of ATMOsphere, during the factory tour. ATMOsphere is the publisher of NaturalRefrigerants.com.

As part of the tour, Pisano outlined several quality control measures Dorin takes to ensure every compressor is fully functioning when it reaches the customer.

Traceability: Each compressor represents a handcrafted item, with a single operator assembling it from start to finish.

• “With one operator completely assembling a unique piece of equipment, it gives him pride when he signs off on it,” Pisano said. “Moreover, the single assembler system allows us to trace issues and correct flows using [laser marking] beamers and barcodes.”

Leak testing: Dorin uses helium gas for its fine particle size to conduct refrigerant leak tests in an automated process.

• Testing occurs in a vacuum chamber and lasts for 2 to 2.5 minutes with the pressure on the discharge side of the compressor at 165bar (2,393psi) and on the crankcase side at 110bar (1,595psi).
• “Pushing a helium mixture with dry air into the compressor housing helps us to see the leaks better and quicker,” Pisano said. “We guarantee a maximum refrigerant leakage rate of 3g [0.1oz] per year.”

Operational tests: Conducting operational CO₂ loop testing on every compressor creates a manufacturing bottleneck and increases costs for Dorin.

• “Our CO₂ numbers are increasing, with the factory dedicating two production lines solely to CO₂ compressors,” Pisano said.
• To address the testing bottleneck, Dorin is building a new area in the factory with multiple test stations.
• According to Pisano, testing the drive gear reliability and effectiveness of a newly developed 900HP CO₂ compressor, which Dorin plans to release in a couple of years, costs the company €500 ($529) a day. To offset that cost, Dorin is designing a CO₂ chiller heat pump for the compressor to provide comfort heating and cooling to the entire factory, plus heating for production processes.

Compressor design: Dorin’s CO₂ compressor design enhances reliability and extends the CO₂ application envelope, Pisano explained in a presentation at the 2024 Refrigerating Engineers and Technicians Association (RETA) Conference. The event was held October 21‒24 in Grapevine, Texas.

• “An external discharge manifold isolates the high-temperature, high-pressure CO₂ from the drive gear,” Pisano said. Transcritical laboratory tests show that an external manifold decreases compressor oil temperature and increases the oil residual viscosity compared to the standard internal design. “The external manifold gives better performance and reliability with no wear detected on the wrist pin,” Pisano noted.
• To support reliability during high ambient temperature operation, Dorin has created an internal refrigerant passage inside the compressor crankcase that restricts oil from entering the refrigerant circuit. “Between the refrigerant passage and another element we are not ready to disclose, we have reduced the oil in the circuit by a factor of five compared to a similar-sized compressor manufactured by a competitor,” Pisano told NaturalRefrigerants.com at the RETA conference.