Technotrans : Using highly efficient pumps in temperature control units is worthwhile and can be subsidised

01.08.2019
Category: gwk, 2019

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Especially in view of the ongoing debate about climate change, it is increasingly necessary to think about alternative, efficient technologies and to act accordingly. This also applies to the technology used for compact temperature control units as the integrated pumps play an important role for the total energy consumption of the units and, thereby, for their CO₂ emissions.

For many years, rotary pumps with peripheral impeller technology have been used in temperature control units. This pump type is characterised by its compact design and low initial costs. A disadvantage of this pump technology, however, is the relatively low level of efficiency and its low flow rate at process-typical pressure loss values.

Due to a change in the process requirements caused by mould circuits that are connected in parallel, the requirements that need to be fulfilled by the temperature control units have clearly changed in recent years. Combined with efforts to become more efficient, another rotary pump type, the centrifugal pump, becomes increasingly important. This pump type is characterised by a high base efficiency and its high flow rates combined with a low level of energy consumption. Since this pump is more expensive than a peripheral pump and requires more space, the highly efficient centrifugal pump technology has, so far, only played a minor role for standard temperature control units.

However, due to the growing environmental awareness and protection of our climate, efficiency is increasingly becoming an important purchase criterion. In addition, the legal provisions for reducing CO2 emissions, e.g. the Ecodesign Directive and the new issue of ISO 50003, including the requirements concerning the auditing of energy management systems, have become considerably stricter. Global players, such as Daimler, VW, BMW, BOSCH, etc., have committed themselves to achieving CO2 neutrality and demand the same level of commitment from their suppliers.

As an additional incentive, the German Federal Ministry for Economic Affairs and Energy established a new investment programme at the beginning of this year. It aims at promoting measures for reducing CO2 emissions and provides subsidies to cover up to 40 % of the eligible investment costs for replacement pumps or new pumps that fulfil certain criteria in terms of their efficiency.

If designed properly, centrifugal pumps, unlike peripheral pumps, fulfil the criteria of this programme so that they are perfectly eligible for subsidies in terms of an investment in this technology.

Apart from the potential funds, the energy cost savings that can be expected as well as the higher flow rates clearly speak in favour of using centrifugal pumps in standard temperature control units.

A comparison of the characteristics of two commercially available pumps (Figure 1) shows the immense benefits of a centrifugal pump in terms of its efficiency. The centrifugal pump used for the example requires nearly 65 % less energy than the peripheral pump while providing an 11 % higher flow rate.

Based on 6,800 hours of operation in three shifts and an electricity price of € 0.16/kWh, the centrifugal pump leads to annual savings of € 598.40 or 2.01 tons of CO₂.

Another example (Figure 2) shows the cost saving potential and flexibility of a speed-controlled centrifugal pump. At 100 % speed, the centrifugal pump can provide 3.5 times the flow rate of a peripheral pump while having the same level of energy consumption. As a result, it can replace several devices that are equipped with standard peripheral pumps. Alternatively, the energy demand can be reduced by approx. 65 % at a lower speed but with the same flow rate.

This example shows annual savings of € 337.28 or 1.13 tons of CO2 based on 6,800 hours of operation in three shifts and an electricity price of € 0.16/kWh.

gwk offers a highly efficient series with centrifugal pumps as an alternative
With its protemp series, which is based on the enersave technology, gwk offers highly efficient units with stainless-steel centrifugal pumps that cover a wide range of temperatures and capacities. protemp units are available for a temperature range from 95°C to 140°C, a heating capacity from 9 kW to 50 kW and a flow rate of up to 440 l/min.

The centrifugal pumps that are used for this series have been specially adapted to the requirements of the gwk units, and their minimum efficiency index (MEI) is significantly higher than what is required by the Ecodesign Directive. Due to the efficiency of the centrifugal pumps, the criteria of the financial support program are fulfilled so that an investment in the protemp series is eligible for subsidy.

The various models of the protemp series are available with a modern variable pump version to ensure their demand-responsive adaptation to varying production conditions. A perfectly coordinated system of pump hydraulics, motor and frequency inverters, with power reserves, allows for a continuous boost function with the permanent utilisation of the maximum pump speed, without any notable increase in wear. By using the OPC UA interface, the speed can even be predefined from the injection-moulding machine controller or any other controller connected in the OPC UA network via the EUROMAP 82.1 protocol.

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