Electrical Product Pathfinder Group Electric kettles

Transcription

1 Electrical Product Pathfinder Group Electric kettles Identifying failure drivers and opportunities for life extension. Version 4 December 2013

2 About this project This work aims to provide simple and accessible guidance on how to reduce return rates and improve brand value by building more durable products. Between September 2013 and March 2014 WRAP is working with a consortium of specialists to develop these outputs through targeted research and engagement with industry and other bodies. This document is the first step in this process and presents the consolidation of evidence around perceived failure rates and opportunities that will be further expanded upon from November About the Electrical Product Pathfinder Group How to use this deck 1. Please view in Slide Show to activate hyperlinks. 2. To access the slide s content either browse one page at a time or use the navigation bar below to jump between the main sections. Throughout the deck there are links to external sources of interest. 3. We would like to encourage on the contents of this deck and your thoughts on the identified failure points, drivers and resolutions. Please click the links on each page to contribute. WRAP is helping the electrical and electronic product sector to cut costs, reduce resource use, and build reputation for corporate responsibility. The EPPG aims to: identify the most significant changes in the supply and sale of electrical and electronic products in the UK that would use less material resources, reduce cost and reduce business risk, while improving profit; implement changes on key products, measure the benefits and distil good practice; and share insight on consumers understanding and attitudes to product lifetime. Short-Term Failure Long-Term Failure Best Practice Opportunities

3 Purchase Short-Term Key Failure Points Failure Failure Point Why product is being returned Leaks from water level window or at base (short term and longer term). Leaks elsewhere are less common Leaking spout Will not switch off Lid not closing or not open-able (both short and long term) Too noisy Driver Why failure has occurred Expected Life Design and method of connections between kettle body and window and how they are bonded This occurs with plastic kettles that have separate poorly attached spouts to bodies. Failure to switch off at correct time can be due to a variety of design flaws Poor design, unsuitable choice of materials (e.g. wrong grade), voids in mouldings, etc. Many possible reasons. Rapid heating of water will create noise as bubbles form and collapse. The noise level is affected by many factors; power rating, scale build-up, shape and surface of hotplate, etc. Notes Statistical data available from Which based on 7904 kettles of 19 brands Many comments on Internet of early kettle faults, mostly leaks, lid problems and switching on / off issues A small survey of 20 shortterm and longer term kettle failures, 30% due to leaks, 20% due to lid problems, 25% were on/off switch related, 10% were too noisy and elements failed in 10% - this was consistent with the Which survey of 7500 members. Information from a kettle OEM indicates that taste of water, pouring issues (dribbles), element failures & switch off time (too early or late) were problems that they have solved. Short-Term Failure Long-Term Failure Best Practice Opportunities

4 Purchase Long-Term Key Failure Points Failure Point Why product is being replaced Elements failing (Today, these are mostly concealed tubular elements below a flat plate but thick film elements are also used, but are uncommon) Plastic failures - handles Plastic failures lids, bodies, etc. On/off switch failure (most kettles boil water but a small number are designed to heat to specific temperatures. This summary describes kettles for boiling only Base and plug electrical connection failure with cordless models Driver Why failure has occurred End of Life Various possible causes. Damage due to impact, oxidation/corrosion, production faults causing hotspots, deterioration of electrical connection, scale build-up Poor design causing high strain. Fatigue due to unsuitable cleaners for type of plastic Poor design and material choice. Most kettles now use polypropylene but this is not ideal for all plastic kettle parts. Have a finite life but will be shortened by contamination from leaks Arcing occurs when kettle lifted before power shuts off. This erodes contacts Notes Results of Which survey of 7500 members; 29% problem with element, 29% kettle stopped working, 22% problem with pouring or leaks and 10% problems with auto switch-off. A few reports of base / plug failures reported. May be due to lifting kettle before power is shut off causing arc damage to contacts Previously reported Which surveys identified noisy kettles (30%), leaks (20%), lid problems (15%) unclear water level gauges (11%) so the proportions of fault type are changing as designs have changed. Short-Term Failure Long-Term Failure Best Practice Opportunities

5 Best Practice Component Specification Kettles must meet EU safety standards Buyers need to decide on their expected kettle lifetime which they should specify to suppliers. If, for example, a kettle is expected to survive 1, 2 or 3 years under reasonably heavy use conditions, this means that the kettle must operate at least 2,920, 5840 or 8,760 times for a 1, 2 or 3 year lifetime, assuming 8 uses per day. It is not possible to specifying components in order to guarantee a reliability as this is mainly due to materials choice, design and manufacturing quality. Therefore testing will be needed to confirm reliability over the specified lifetime and to ensure that design flaws that cause early failures have been eliminated. Knowledge gained from this R&D will be beneficial to all future kettle designs Design Kettle designs are a compromise between low cost, simple construction and reliability, whereas, the materials used are close to the limits of their performance. All new designs should be thoroughly tested before sales occur. Type and design of bonds between plastic parts is critical to obtain permanent bonds that do not leak Moving parts of lid opening mechanism must be designed to not distort, wear or fracture during normal lifetime (and when exposed to steam) Avoid separate plastic pouring spouts Testing Standards There are no durability standards for kettles Test standards exist for adhesive bonds and for switches, but none found for ultrasonic welded bonds Several safety standards for controls and for connection between base and cordless kettle Typical UK user behaviour (i.e. number of uses per day) is not published User Instruction Descale regularly and provide instructions on how to do this without damaging kettle List types of cleaning chemicals that are suitable and those to avoid If scale filter is fitted and is needed to ensure kettle switches off, then provide instructions on cleaning and warning that it must be replaced if removed An option is to state on package or instructions call our helpline before returning this product if you have a problem if a helpline is available, as this could prevent returns due to customers not understanding user instructions

6 Opportunities Failure Mode Cause Early/ Late Water level window joint leaks Leaks from base Failure of bond between kettle body and transparent plastic insert. Adhesives unsuitable in steam, so ultrasonic welding is used for plastic to plastic. This requires suitable joint shape and good welding process control. Windows in metal kettles need to be clamped with gaskets suitable for C cycling Depends on design and materials used. Could be due to either seal failure between concealed element plate and body or from plastic welds if this method is used Early Opportunity Resolvable by good joint design, use suitable polymer materials and a joint shape that makes achieving good watertight bonds by welding easy to do. Good welding process control is also needed to maintain quality. Suitable gaskets (silicone) for metal kettle bodies Polymer seals are often used. These must function over the wide temperature range and account for thermal expansion differences between materials used. Proprietary patented designs are available. Ultrasonic welding, if used, must be carried out correctly ( extensive Implementation Mechanism Kettle designers must follow good design practice and factory carry out research into bonding process by testing assembled kettles (at both maximum and minimum fill) to ensure no early defects occur. Institute quality control checks in factory Cost Implications Cost for redesign and R&D. Should have no minimal material or parts costs guidance is available) Ensure reliability by testing new kettle designs over the specified lifetime, e.g. 9,000 cycles if a minimum of 3 years specified (see next item combine this issue with other reliability testing) Cost for R&D. Proprietary kettle seals may be more expensive. Beware of counterfeits

7 Opportunities Failure Mode Cause Early/ Late Does not switch off Will not switch on Deactivation mechanism fault. There are several potential reasons, e.g. blockage of steam pipe, excessive water collecting around bimetallic strip, heat distortion of plastic parts, lid open or possibly due to scale filter removed by user and excessive erosion of switch contacts Arc or heat damage to power switch. This will eventually occur as the types of switch contact used in kettles are unlikely to survive > ca.25,000 actuations. Lifetimes will however, be shorter if contacts are contaminated by leaks or during kettle assembly Late Opportunity There are two main manufacturers of kettle control switches, but beware of counterfeits which would infringe patents. All parts of the deactivation mechanism (control, steam pipe, etc.) should be reliable for the required number of cycles (e.g. 9,000 actuations if 3 years is specified). Some faults caused by user - avoid by clear user instructions The types of switch contacts that are used in kettles are of a type that should survive at least 20,000 actuations, but will degrade faster if contamination occurs. Beware of counterfeit controls. Do not contaminate during assembly and avoid leaks into base Implementation Mechanism Specify that switch-off must operate reliably for required number of actuations. Test kettles at minimum fill as well as maximum fill (cool to ambient between tests). Provide clear user instructions Specify minimum kettle lifetime. For example, 9000 cycles if 3 years are specified. Cost Implications R&D required to obtain reliable designs; includes testing kettles to ensure that they switch off reliably at all fill levels and for expected lifetime. Should be no parts or materials costs as kettles should survive more than 10,000 cycles and many do Based on examination of switch contacts from modern kettle controls, there should be no extra cost as these should survive at least 20,000 switch cycles which should be sufficient for >5 years use (based on 8 uses per day)

8 Opportunities Failure Mode Cause Early/Late Opportunity Implementation Mechanism Lid will not close or open Too noisy Locking mechanism parts worn, distorted or damaged due to incorrect choice of grade or poor polymer processing Has several contributory causes including the potable water s composition which affects scale build up Early Use suitable type of dimensionally stable rigid plastic (e.g. PPO, PA, POM), that does not distort in steam or with use. Also requires a suitable moulding process. Avoid stress concentration points in mouldings. Use concealed flat base elements The surface finish will affect the noise level and a textured surface that produces many small bubbles by increasing nucleation will be quieter. All types of kettle should be descaled as this also affects noise levels Implement good engineering design and thoroughly test for durability before sales Specify maximum noise level, e.g. at 70 75dB (note that vacuum cleaners are typically 75dB) and measure with a decibel meter. Provide descaling instructions at location that will be seen by user (e.g. attached to power cord or handle) Cost Implications Some R&D and testing costs. Small additional costs for slightly more expensive plastics ( 0.01/kettle) Small additional cost for low-noise surfaces

9 Opportunities Failure Mode Cause Early/ Late Opportunity Implementation Mechanism Cost Implications Leaks between spout and body Failure of seal material Sealing this bond with plastic kettles is difficult. Material must comply with food contact materials regulation. Best option is to produce spout and body as one moulding. Metal kettle spouts can be brazed or welded. Design plastic kettles without separate spout No additional cost to new kettle design as these will need new injection mould tools anyway Element failure Impact damage, excessive scale causing overheating or failure of electrical connections. Can be due to manufacturing defects. Impact damage should not occur. Provide descale instructions. Avoid leaks from base to prevent corrosion and overheating of electrical connections. Use reputable brands that can demonstrate reliability. Thick film elements are less affected by corrosion and are more energy efficient but can be damaged by bending or impact. Impact damage most likely during element and kettle transportation and construction so precautions needed. Element defects can be detected using X-ray imaging with automatic image analysis. Avoid internal leaks into base. Elements should survive required number of use cycles, test new designs to confirm Negligible

10 Opportunities Failure Mode Cause Early/ Late Opportunity Implementation Mechanism Cost Implications Plastic parts fail Poor design not able to withstand stresses in use. Use of unsuitable cleaning chemicals Mainly late Designs should be robust enough for normal expected use so plastic must be sufficiently thick, avoid stress concentration points Implement good engineering design. Provide user instructions Should be very small Base connection to cordless kettle fails Arc damage due to lifting kettle before power off, but likely to be due to safety cut-out switch not functioning (or not fitted) Arcing of connector should not occur if cutout operates when kettle lifted. The main two kettle controllers products include these cut-outs but beware of counterfeits Monitor quality of control mechanism, beware of counterfeits. None

11 Standards BSI BS Methods of Measuring the Performance of Household Electrical Appliances Part 1: Electric Kettles and Jugs BIS IS 367 Electric kettles and jugs for household and similar use - Includes Amendments 1-3 GOST 7400 Domestic electric tea-kettles and electric samovars. Specifications Methods for Measuring Performance of Electric Kettles and Jugs for Household and Similar Use - First Edition; IEC Amendment 1:1992; Amendment 2: 05/2004 AENOR UNE METHODS FOR MEASURING THE PERFORMANCE OF ELECTRIC KETTLES AND JUGS FOR HOUSELHOLD AND SIMILAR USE Household cooking and liquid-heating appliances - Seventh Edition; Update No. 1: June 2013 (text mentions CSA C22.2 NO "endurance") BSI EN Safety standard: Requirements for Products heating Liquids Standard Test Method for Durability Assessment of Adhesive Joints Stressed in Peel (may be useful to assess durability ASTM D (201 of water level sight window bonds to avoid leaks) ASTM D (200Standard Test Method for Determining Durability of Adhesive Joints Stressed in Shear by Tension Loading BS EN Appliance couplers for household and similar general purposes Part 1: General requirements Appliance couplers for household and similar general purposes Part 2-4: Couplers dependent on appliance weight BS EB for engagement (connection between cordless kettle and base) BS EN Automatic electrical controls for household and similar use Part 1: General requirements ( Kettle on/off controls) Automatic electrical controls for household and similar use Part 2-9: Particular requirements for temperature sensing BS EN controls