When was the last time you checked on your drive?

VARIABLE SPEED drives are considered by some to be a “fit and forget” device. While it’s true that drives are highly reliable and typically require less maintenance compared to other devices, it’s important to remember that they still require some degree of looking after to maximise their lifespan and ROI.

Modern drives are highly complex electronic devices, and all but the most basic maintenance is best left to a trained and accredited professional. However, there are still things you can do as an operator or end user to keep your drive in good working order. Everyone knows that heat and dust are a drive’s two biggest enemies, and together they account for the vast majority of premature device failures. Both heat and dust, as well as other contributing factors, can very often be mitigated to at least some extent. But in order to do so effectively, you first have to know what you’re dealing with, and that means regularly checking your drive and the environment around it.

A drive has no moving parts other than a cooling fan or pump, and there is usually no outward sign that any failure is imminent. Without regular inspections or monitoring it may not be apparent that its condition has deteriorated. And because drives are generally so reliable, it can be all too easy to neglect your asset and leave it sitting in a corner for year after year, without meeting even its most basic maintenance requirements.

Despite having very few moving parts, a drive still has a lot going on inside it. Components will inevitably age and wear over time and may need regular checking and/or replacement throughout the drive’s life. The conditions in which the drive is operated can also have a significant impact on reliability and longevity, and this needs consideration right from day one – or better still, before the drive is installed.

Drives often operate around the clock, and an unexpected failure can have serious knock-on effects. Most motors are fed directly from the drive, so if the drive is out of action, the motor will be unable to operate. Very few applications have a bypass capability, and attempting to bypass can cause process issues if the motor is not normally run at full speed. In short, if a drive on a critical application goes down, then it can take the whole application – or process line, or even plant – with it. This is why it’s so vitally important to look after your drive properly.

Minimum requirements for effective drive care

Checking the environment around the drive is vital, as this will give some indication of how much attention you need to pay to keeping it maintained in the years ahead, and how frequently. For some drives an annual inspection will be sufficient, but if a drive is operating in a particularly dirty, hot, or humid environment, then it might be prudent to check more frequently.

The nature of the application will also make a difference. The day-to-day operation of for instance a pump or fan tends to be fairly predictable and stable. However, applications with a high cyclic load such as centrifuges may have very high start currents and involve quick deceleration, which will inevitably put more stress on components.

Sometimes the risks to the drive can be hidden from view. For example, if an air conditioning unit in a  switch room fails, then unless you’re carrying out regular checks you may not realise the increased in ambient temperature until a drive alarms or even fails..

The all-important first year

The first year of a drive’s life is arguably the most important. After a year you’ll have a much better idea of how often you need to be checking it, and what its general maintenance needs are likely to be. Again, as an operator there’s not a whole lot you can or should do to the drive, aside from checking it to see that nothing is amiss. Filters should typically be replaced each year (or in accordance with the environmental conditions) regardless of where and how the drive is operating.

At ABB, our engineers have tools that can measure how the environment around a drive is likely to affect its operation before it is installed. We also have the capability to remotely monitor the drivetrain, which can provide a baseline figure for how the drive and driven load should be operating. From this we can easily see any performance drift and take the necessary steps to find out what’s causing it.

Year two and beyond

Even a well-cared for drive is not indestructible. As time goes by, various components will need maintaining or replacing. Reputable manufacturers will publish a maintenance plan outlining what actions should be carried out and when. In ABB’s case this information can be found in the product manual or on the internet, setting out recommended maintenance actions from Year 1 to Year 18, or even beyond. These recommendations generally assume that the drive is working in a clean and stable environment, and so maintenance or replacement intervals may vary based on actual operation.

A Service Level Agreement (SLA) with your drive manufacturer can help ensure your asset stays fighting fit throughout its lifecycle stages. Each agreement is tailored to the specific needs of the customer and/or the asset, but they can include regular preventive maintenance checks, pre-agreed maintenance intervals tailored to the application’s needs, emergency and non-emergency on-site response, or remote condition monitoring. In ABB’s case, agreements can also include sending a drive to our Drive Service Workshop in Coalville for more substantial repairs or reconditioning.

In conclusion

Drives are remarkably reliable devices. But that doesn’t mean they’re fit and forget. As with anything, if you don’t look after it and maintain it, then an eventual failure is almost inevitable. Ultimately, achieving lifespans of 20+ years is not difficult – it’s merely a case of staying on top of what your drive needs and when. 
Knowing, as they say, is half the battle.

For more information about ABB’s OneCare Service Level Agreement for drives, motors or generators, search for “ABB Motion OneCare”.

Andrew Pearson is product manager – motion service UK at ABB

www.abb.com