BOCK® CO2 Compressors Reduce Vibration, Facilitating CO2 Adoption in Food Retail

While CO2 offers great potential as an energy-efficient, environmentally friendly alternative to traditional synthetic refrigerants, it is not without its challenges. One such challenge can be vibration. A recently released whitepaper from Danfoss, “Danfoss BOCK® CO₂ Compressor Reduces Vibration for Optimal Transcritical Supermarket Refrigeration Performance,” details how BOCK® HGX compressors were able to reduce vibration and deliver a significantly smoother and quieter performance at one supermarket site. By reducing vibration, BOCK compressors are making it easier for the food retail industry to implement CO2.

Vibration can cause damage to racks, piping, and structural components and result in reduced compression cycle effectiveness and excess energy consumption. A supermarket in Ohio was experiencing abnormal and excessive compressor and rack vibration in its refrigeration system, a transcritical booster system with low-temperature (LT) and medium-temperature (MT) suction groups on one rack. As authors Karthikeyan Somasundaram and Jeffery Miller describe, the test, conducted as part of a retrofit installation, involved multiple BOCK HGX compressors, along with a variable frequency drive (VFD), a gas cooler, high pressure valve and flash gas bypass valve.

Using a calibrated vibration meter, Danfoss application engineers captured measurements at multiple locations on the rack and at various points on individual compressors and common piping lines.

Results: 

• Compared to existing compressors, Danfoss BOCK HGX compressors achieved vibration reductions ranging from 48.3% to 97.7% at various points and capacities.
• The average vibration reduction across all capacity combination and direction vectors was 83%.
• The BOCK lead compressor employing the VFD achieved a wider frequency range—from 35-70Hz compared to the original compressor’s 40-60Hz range—resulting in a larger capacity range in the suction group without added vibration. 

The vibration reductions also resulted in less noise and less shaking of the pipes and other rack components. In addition to the improvements in safety and reliability of the operating components, the environment of the area was much more pleasant for maintenance personnel.

“We are encouraged by the test results that affirmed the operational and sustainability benefits of BOCK compressors for transcritical CO2 refrigeration systems,” said Chris Brown, application engineering manager at Danfoss. “Danfoss BOCK HGX compressors can deliver the energy savings and environmental benefits of CO₂ safely and reliably in a wide range of supermarket refrigeration sites, removing a critical barrier to increased adoption of CO2 across the industry.”