Designing more durable products is a key strategy of the Circular Economy to save materials and reduce the amount of waste to handle at the End of Life of the product. However, the design of more durable products needs to be supported by methods for assessing and verifying durability aspects. Although internal protocols are typically implemented by manufacturers, also depending on their business strategy, there is a lack of standardised methods allowing the comparison of products on the market.
The overall objective of this study is to improve the technical background related to the assessment and verification of the durability of products. General principles for the technical assessment of the durability of products have been developed and applied in this study to the analysis of household washing machines (referred to as washing machines):
1. Durability aspects associated to the use of washing machines and existing testing methods are reviewed;
2. A testing procedure for assessing and verifying the durability of washing machines is further developed;
3. The procedure is applied to two models of washing machines on the market, and the results analysed;
4. Lesson learnt and recommendations are provided for further improvement and application of assessment guidance and testing procedure.
The methodological steps applied in this study successfully allowed:
• Understanding the durability needs of the product, and identify technical problems which can disrupt the delivery of key functions;
• Analysing stress conditions, design aspects and misuses that could produce failures of key parts and loss of function(s)/sub-function(s) during the operation of the product;
• Identifying key aspects and/or correction measures to avoid / delay possible failures during the lifetime of the product and thus increasing its longevity;
• Developing further knowledge about how to assess and verify the durability of the product.
The approach could be tailored and applied to other products for which a durability assessment has to be carried out, for regulatory or research purposes. Moreover, this can also serve as input for the work carried out by CEN/CENELEC JTC10 under Mandate 543 and aimed at the development of general standard methods on material efficiency aspects of Energy-related Products under Ecodesign.
The output of the analysis of washing machines was in particular oriented to the improvement of a procedure for testing the durability of the product. As lesson learnt it was recognised that the testing procedure should:
• Focus on the testing of the entire product under conditions closer to real life operations (the use of a fixed unbalance is avoided; stresses due to washing and rinsing cycles are integrated);
• Reduce the length of the testing (by applying Accelerating Life Testing);
• Cover mechanical stresses, as main cause of damages, as well as functionality aspects as loss of performance (washing performance parameters are monitored).
Moreover, a balance has to be sought between the desirable lifetime target for the testing procedure (e.g. the average lifetime of the product) and a practical length that can be applicable for verification purposes.
This complex task resulted in a series of test cycles which impose realistic thermal and mechanical stresses to washing machines and which are executed many times mimicking a specific lifetime period of the device in a shorter period of time. The procedure was executed in a trial with two washing machines for a simulated usage period of two years. The coverage of the first two years of use of washing machines can allow identifying early failures, malfunctioning and loss of performance in worst performing products, as well as any potential sources of failures. This is in particular useful for regulatory purposes, since the testing of a representative lifetime of 12 years could require about 6 times the time and resources required by the application of this procedure.
The procedure has appeared to be suitable for laboratory testing and to be realistic in the sense that the induced stresses caused thermal and mechanical wears and tears typically found in washing machines during their lifetime.
As follow-up of this study, it is recommended to apply the testing procedure to a larger sample of devices and for longer periods of time, to understand if and how the functional performance is decreasing after the first 2 years of use of washing machines, as well as if and when minor problems encountered during the operation of the device could become major failures. This would help understanding better what makes sense to monitor and how long in the procedure, especially if this is intended to be applied in the future for regulatory purposes. Further developments should address the monitoring of noises and of possible movements of the machine. Alignment with the final output of the ongoing revision of the Commission Regulation (EU) No 1015/2010 and of the Commission Regulation (EU) No 1061/2010 (and related standards) should be moreover sought.
However, it should be noted that, in practice, the testing procedure has already taken a considerable amount of time (in total 697 h for one person for two washing machines in parallel). If this were to be refined and applied for verification / monitoring purposes, this is deemed too long and ways to shorten the testing time would be needed. The saving of time could be alternatively invested to test the product for a duration representative of longer lifetimes and/or tracking the functional performance along different moments of the lifetime.