Process Cooling Systems for the Plastics and Rubber Industry

Do not size it from machine motor power or injection tonnage alone. Assess mould, hydraulic and auxiliary heat loads separately, along with cycle time, material, part weight, mould count, simultaneous machines and target water temperature. For an existing system, use measured flow and supply-to-return water temperature difference.

A rough material-throughput guide is 1 kW for every 7–10 kg/hour of plastic. At 500 kg/hour of PP, mould load is about 70 kW, or roughly 85–100 kW with hydraulics and auxiliaries. Final capacity depends on material, cycle time, mould temperature and simultaneous operation.

It varies by polymer: 10–40 °C for PE and PP, 8–15 °C for PET preforms, 40–80 °C for PS and ABS, 80–100 °C for PA and POM, and 80–120 °C for PC and PMMA. Chillers typically serve temperatures below 40 °C, while mould temperature controllers serve higher ranges. Also consider cycle time and ambient dew point.

Preform moulds usually require 8–12 °C water. Because this can be below the summer dew point, the mould room needs humidity control. Multi-cavity moulds also need high flow, making pump and pipe sizing as important as chiller capacity.

Raise mould-water temperature to 2–3 °C above ambient dew point, dehumidify the mould room or insulate mould plates if cold water is essential. In Turkey, summer dew points can reach 18–22 °C, so uninsulated moulds supplied with 7–10 °C water are prone to condensation.

A chiller produces central chilled water by removing process heat. A mould temperature controller regulates an individual mould or machine, can heat the fluid and may control temperatures up to 150 °C. In a central system they work together; include heat rejected by the controller in chiller sizing.

No. At low loads it can cycle frequently, destabilise temperature and shorten compressor life while raising capital and electrical-infrastructure costs. Size it from minimum, average and peak loads, then select compressor staging and buffer volume accordingly.

Savings depend on site climate, process-water temperature, operating hours and load profile. Hydraulic and mixer circuits above 30 °C can often use only a dry cooler for much of the year, while mould circuits may use partial free cooling. Calculate actual savings with hourly weather and load data.

Use glycol where outdoor pipework may freeze or the process operates at low temperature. More glycol raises viscosity, pump duty and pressure loss while reducing heat-transfer capacity. Set the concentration for local climate and size equipment for the actual mixture.

Critical plants can use N+1 redundancy. Controls sequence multiple chillers and pumps so the critical load remains covered while one unit is maintained. Base the standby capacity on critical process load and the cost of downtime.

Inverter controls adjust motor speed to current flow, pressure or condenser load, avoiding continuous full-speed operation. The control strategy must still maintain minimum evaporator flow, required process pressure and safe condenser conditions.