90 kW Two-Stage VFD Compressor for a Machinery Plant in Jinan

A machinery manufacturer in Jinan was struggling with its ageing compressed-air system. The old fixed-speed compressors were inefficient, and the electricity bill rose month after month. The machines had no demand-based control, so they consumed power even when the plant was not running at full load.

Reliability was also a problem:

• Pressure fluctuations under long, high-intensity operation affected the precision of production equipment.
• Overheating in summer led to unplanned shutdowns that disrupted schedules and delayed deliveries.
• Frequent breakdowns pushed up maintenance costs and needed constant attention from staff.
• High noise and heat in the compressor area made the working environment uncomfortable and caused problems during environmental compliance reviews.

The plant installed a 90 kW SIND DUALLUBE-VPM series two-stage, permanent-magnet variable-speed screw compressor:

• Two-stage compression with interstage cooling. This lowers specific power compared with the single-stage machines it replaced.
• Variable-speed control. Motor speed follows actual air demand, so the compressor no longer runs at full power during light-load periods.
• Efficient cooling. The cooling system keeps core components within temperature limits during long, continuous duty. This prevents the summer overheating trips seen with the old machines and reduces heat released into the workshop.
• Electronic controller with condition monitoring. It tracks operating parameters in real time and warns maintenance staff of abnormal readings before they turn into breakdowns.

• About 30% lower electricity costs after the new compressor went into service.
• Constant discharge pressure, keeping production equipment running smoothly.
• No more summer overheating shutdowns and better on-time delivery.
• Lower noise and less heat in the workshop, supporting the plant’s environmental compliance.
• Predictive alerts that reduce emergency repairs and manual monitoring.

Replacing several inefficient fixed-speed units with one two-stage variable-speed machine improved cost, reliability and working conditions in a single step.