PREVENTIVE maintenance routines in many companies across a wide range of industries vary in quality. Many don’t add value and, in some cases, are counter-
productive. How many times have we heard an operations team complain that “equipment is less reliable after maintenance than it was before.” So why is this the case?
Here are ten of the most common reasons which we come across as to why preventive maintenance tasks (PMs) are not fit-for-purpose.
1. Many of the PMs are time-based, for example the annual overhaul, rather than condition-based. Time-based maintenance can be described as “taking kit to pieces at regular intervals to see why it is still working”. Condition-based maintenance is often described as “letting the equipment tell you when it needs to be maintained”.
2. Too little use is made of condition monitoring techniques such as vibration analysis, thermographic cameras, oil analysis, ultrasonic leak detection, etc.
3. Where condition monitoring is undertaken, it is done by specialist contractors. More often than not, this could be better carried out in-house, after technician training. This can lead to significant cost savings, increased ownership, and improved outcomes.
4. The PMs are based on manufacturers’ recommendations. These do not recognise the equipment’s criticality, eg whether there is a stand-by, or buffer stocks. They take no account of its operating context, eg whether it operates single shift or 24/7. They ignore the environment, eg whether it is in a clean room or is exposed to dust and debris, and they take no account of the duty, ie what is being handled. Vendors also have a vested interest in selling spare parts, which is why they tend to favour time-based maintenance over condition-based maintenance.
5. PMs which could be better carried out by operators rather than technicians as part of asset care programmes. Typical tasks might include non-intrusive checks for wear, condition or leaks.
6. Generic PMs – the same PM is used for a range of similar but not identical equipment, eg all the belt conveyors have exactly the same PM although they vary in length, width, and drive motor size. Some are fixed speed, others are inverter driven, and some are horizontal and others are inclined.