December 2021

20 | Plant & Works Engineering www.pwemag.co.uk Annual Buyers’ Guide 2022 Maintenance Matters Focus on: Seals, Bearings & Lubrication M ost commercial and industrial operations will rely on electric motors and for many organisations it is standard practice to store working spares so that, in the event of a motor failure, downtimes can be minimised by swapping out the failed motor with a working spare. For this reason, it is essential that stored motors remain operation-ready, and this does require correct management and regular servicing. Firstly, it is important to keep stored motors protected from vibration and extremes of temperature and weather, so outdoor storage is not advisable. Ideally, electric motors should be stored indoors in a clean and dry environment. While a climate-controlled environment is the best option for storing electric motors, in some instances, this may not be possible. In such cases, the motor may need to be palletised outdoors. If this is the only option, the motor should be covered loosely with a waterproof covering, ensuring that air can circulate to help minimise condensation. It is also important to try and protect lower IP motors from pest intrusion. Ensure that all openings – cable entries, air vents, grease pipes etc. – are suitably covered or sealed during storage. Exposed surface areas could also be coated with a corrosion inhibitor which will need to be removed before the motor goes back into service. Protecting bearings To protect from vibration indoors, it is also a good idea to store motors in locations that are not near any ambient vibration areas. Bearings in stored motors have been known to fail due to fretting or false brinelling as a result of environmental vibrations, which induces small scale motion of the bearings. Even minimal ambient vibration will cause motor bearings to wear over time. Storing motors on materials that can help absorb vibration is, therefore, good practice. Regular shaft rotation also helps to reduce bearing wear on any one point of the bearings, helping to prolong their life. The AEMT advises that shafts are rotated at least once a month, with the shafts of larger motors turned more often. While it is generally acknowledged that shaft turning is necessary on stored equipment, AEMT members have reported that, in practice, the task is rarely actioned often enough. So regular shaft rotation should be made someone’s responsibility, as part of a store’s maintenance schedule. Ensuring adequate lubrication For grease lubricated motors, the shelf life of the grease in the bearings should be a consideration. If the motor employs sealed bearings, it is very likely that if not in operation for an extended period – say two years – the grease inside the bearing will separate and will not work optimally when required to start turning again. Motors that utilise re-greaseable bearings should be regreased on average every year or so when in storage, to help prolong bearing life and ensure that the motor is fit for service when needed. Any moisture or dampness in the air will eventually find its way into a Karl Metcalfe, technical support at the AEMT, offers some advice on how to ensure stored electric motors are properly maintained to make sure they are ready for operation when required. Don’t ignore your stored motors