The aim of the project, at a large plastics injection moulding plant in the South of Holland, was to save energy and reduce running costs. Delta Technics Engineering bv, Resource Data Management's (RDM’s) distributor in Holland, worked with consultant GTex and engineer VKD on a solution based on (RDM) systems. The high efficiency, user-friendly control solution that resulted is delivering savings of 40 per cent on the power costs associated with cooling the plant’s high-pressure injection moulding machines.
Modern plastics injection moulding machines require substantial inputs of mechanical cooling to harden the hot liquid plastic in the moulds once filled and keep them operating efficiently. This requires large amounts of power to ensure there is sufficient cooling available when required to match the high load. The plant in question operates 32 plastics injection machines, producing specialist containers for oil and fuel. Cooling for the injection moulding machines was supplied by a dedicated chiller linked to each, resulting in inefficiencies and poor plant-wide control. The combined power requirement of the plant, catering for plant operation and cooling, amounted to 8 Million kWh per year.
It was decided to replace the localised chillers with a single large chiller capable of providing for all the cooling needs of the plant. To further improve energy efficiency, the system was designed to harness free-cooling when ambient conditions allowed, augmenting mechanical cooling and reducing costs. Key to the new centralised approach was an effective control system able to balance the needs of moulding machines across the plant. A second key requirement was that it maximised the use of free-cooling.
An important element in the design for improved efficiency was the use of variable speed fans in the plant’s cooling towers. The control system needed to monitor and regulate these, to optimise cooling performance and energy use. Delta Technics used RDM’s The Data Builder (TDB) to design a bespoke control and monitoring system for the new cooling plant. RDM plant controllers were used to monitor the oil temperature of the plastics moulding machines and control free-cooling and fan speed, opening and closing valves that adjust input between mechanical and free cooling circuits. The control system constantly regulates and optimises the cooling delivered across the 32 machines. This ensures process quality is maintained at the highest level while minimising energy consumption.
A key aspect of the project was the ability, using RDM control and monitoring systems, to test various operating conditions in order to optimise power use without reducing quality. Max Neus, who headed up the project for Delta Technics, says: “The operators wanted to test how high they could go in terms of cooling water temperature and still deliver a high-quality product. This revealed a huge opportunity to cut power inputs and reduce costs.”
Using the RDM system, it was established that the plant could raise cooling water temperature by 7degK without impacting product quality. This resulted in a huge additional energy saving, on top of the significant savings realised from the use of a centralised system with free-cooling. Max Neus says: “Overall, the plant has been able to reduce cooling energy costs by some 40 per cent. This has given a pay-back time for the project of just six months. A fantastic result. The client is delighted and saving a lot of money.”
As a result of the successful project, the customer is now looking to apply RDM-based control and monitoring more widely at its plants. This includes applications to heating and flow control and monitoring. “We learned a great deal on this project,” says Max. “The key in working with the TDB is get clarity on the project definition. It is vital to understand the process and map it accurately. You need to pin down exactly what the client wants to achieve. When this comes together, the user-friendly RDM system can deliver a precise, elegant and energy-saving solution that would be hard to achieve by any other means.”