16% Lower Specific Energy at a Shanghai Die-Casting Plant

The client is a die-casting company in Shanghai. It covers design, mould making, die casting and precision machining, and exports to Japan, Germany and the United States.

Its compressed air station had three fixed-speed screw compressors, two running and one on standby. The machines still worked, but their efficiency had fallen well behind current standards. Combined, they ran at a specific energy of 0.123 kWh/m³. With die-casting cells demanding air continuously at high load, the station had become a hidden cost burden.

The company faced a dilemma. Keeping the existing equipment meant long-term high electricity bills and emissions. Scrapping the whole station would waste assets that still had service life left.

An energy audit of the station confirmed that the plant’s continuous, high-load demand profile offered significant savings potential. The upgrade focused on the main supply. The duty compressors were replaced by a 100 kW SIND DUALLUBE-VPM series two-stage, permanent-magnet variable-speed screw compressor:

• Two-stage compression. This gives lower specific power than the single-stage fixed-speed units.
• Permanent-magnet variable-speed drive. Output follows real-time air demand, which removes most of the unload and idle losses of the old machines.
• Continuous-duty design that supports uninterrupted production.

The rebuild lifted the station from below the current Grade-1 standard to benchmark level.

The savings appeared immediately after commissioning:

• 16.3% lower specific energy consumption than the previous station (baseline 0.123 kWh/m³).
• About 180,000 kWh of electricity saved per year.
• About CN¥150,000 (≈US$21,100 at CN¥7.1/US$) saved in electricity costs per year.

The plant avoided a full station replacement and gained a measurable drop in operating cost, with lower carbon emissions in line with its green-manufacturing goals.