Identifying the right levers – Analysing energy consumption in the foundry

Actions to optimise the consumption of energy and resources in the foundry should be rooted in an extensive analysis of the different loads. Such analyses help identify the biggest consumers of energy and resources and can serve...

Actions to optimise the consumption of energy and resources in the foundry should be rooted in an extensive analysis of the different loads. Such analyses help identify the biggest consumers of energy and resources and can serve as a useful basis to analyse costs, the returns on investments and to prove the effectiveness such measures.

Utility bills are the most accessible source of data for initial investigations of energy demand and related costs. As a rule energy bills are based on calendar months. They show the total energy used during the respective month, and frequently also how much energy was used during times at higher or lower tariff rates. Additionally, many utilities provide their customers today with load profiles for 15 minute intervals, thus allowing much more detailed analyses.

High energy demand for the melting process

Most die casting operators in Europe purchase electrical energy and gas to meet their primary energy needs. What almost all foundries have in common is that, irrespective of the type of alloy used for casting, 50% of the energy goes towards the melting processes. In many foundries, and in particular in aluminium foundries, allocating usage to the respective energy source is easy, because gas is used exclusively for melting in large, centralised melting furnaces and the energy used for the melting process can be determined by analysing the invoice.
Metering campaigns can be carried out to structure the analysis of the internal energy demand of foundries – a service which Frech also offers its customers. Such metering campaigns can be performed at different degrees of resolution, i.e. the analysis can focus on specific sections of the production process, a representative machine or entire casting cell, or, at a maximum level of detail, capture every single energy load in the foundry.

Distribution of energy demand

Such metering campaigns help to show that the production cells in total account for around 25 to 35% of energy demand, i.e. they are the second biggest users of energy in the foundry. These are followed by air compression equipment, the third biggest consumer, requiring 10% to 20% of energy. Processes such as simple finishing operations of castings or machining, lighting equipment, IT and small consumers account for the rest of the energy consumed in he foundry. This distribution will not always be exactly the same for each and every foundry, nevertheless with some shifts of emphasis it can be applied to most foundries, as the amount of energy required for melting and for the generation of compressed air are linked to the number of production cells and their respective output.

Expert knowledge required

If metering needs to be performed in connection with die casting cells, it is not advisable to use the services of metering service providers who are not a familiar with high-pressure die casting operations. The variety of different machine states and process conditions often leads to errors during the metering process itself or to the misinterpretation of meter readings. To give an example, some loads in the production cell, such as the die casting machine, trimming press, spraying equipment or extraction robots have a cyclical load profile which follows that of the production cycle. In the case of  other equipment, such as machine, holding and dosing furnaces or heating and cooling devices, however, the load profile cycles are completely different and in some cases do not follow the production cycle at all. In these cases it is therefore vital to take the actual status of the device into account in the analysis, as well as all relevant operating parameters, and to select a specifically adapted mode of analysis for the load profiles. To illustrate this it is sufficient to point to the influences of the different types of casting processes. Die castings cells which are used for the production of structural components have energy and resource consumption patterns which are entirely different to those of machines used to cast cylinder crankcases. For such applications, the heat balance as well as cycle time are significant influencing factors on energy and resource usage. Frech offers metering services to enable detailed analyses and comparisons of production machinery and cells. The metering results can then serve as the point of departure for different optimisation schemes.

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