Following imbalance and electrical frequency: chiller compressor in a chemical plant

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The following case study describes and explains a typical remote analysis application of imbalance and electrical frequency monitoring on a chiller compressor in chemical plant. The continuous surveillance was set up in a very effective way for the customer and analyst:

For the Customer: Easy detection, fast diagnosis and monitoring with low risk for data collection and no heavy protocol for continuous monitoring installation

For the analyst: Continuous data, instant trend data and 24/7 protection, higher confidence without any travel or measurement time spent. Comfort of data collection.

Equipment, plant overview, Context

The Chemical site is a huge chemical complex in East Asia operating 24 hours 7 days a week with a constant growing production. The equipment in question is a Chiller compressor. Due to its high criticality, customer wants to monitor the equipment for 1 month before major shutdown. Wi-care was installed on the electrical motor and the compressor close to the bearing location. From the first measurement an imbalance was detected with moderate value and an electrical frequency. The two frequencies may be linked together. I-Care suggested the installation of Wi-care wireless vibration/temperature monitoring system and the analysis/trending by its remote team to ensure no need of action before the shutdown and to evaluate the link between the two frequencies. Loose rotor bar?

chiller compressor 2

Measurement points

                      Reference                                                     Description                          



Motor Inboard Horizontal




Motor Outboard Horizontal




Motor Inboard Horizontal


Analyst diagnosis and spectrum justification

Wi-care data from July 2014.

Measurement Wi-care SN 2000 location Motor MNV




Analyst observations

We detect frequency at 1X and 2X RPM on the electrical drive which indicate unbalance and misalignment. The amplitudes are not negligible and justify more monitoring. We also detect peak at 2425 Hz and sidebands at 30 Hz which indicate electrical frequency. The levels associated to these frequencies are still acceptable. 

We recommend performing a longer vibration monitoring of the motor with vibration measurement also on the chiller. No lubrication issue on the motor.

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