The path to an unbreakable plant: the challenge of availability and wear management
The desire for an ‘unbreakable plant’, loosely translated as ‘100% availability’, inevitably leads to the consideration of when and how components subject to wear should be replaced. This requires recognising which components are subject to which type of wear – and over long periods of time.
It is undisputed that moving components sooner or later reach the end of their wear reserve. In some cases, this can happen after just a few days or weeks, while other components only reach their limits after several years. In this context, it is important to take a look at the entire production plant and also consider those parts that may not have been the focus of an initial analysis. Electronic components are often regarded as ‘wear-free’ and therefore uncritical! However, this assessment often proves to be inaccurate over the years and decades. Technology is constantly evolving and the introduction of more energy-efficient alternatives, for example, means that existing systems quickly become obsolete.
An illustrative example of this is the evolution of hall lighting: from incandescent lamps to metal halide lamps and fluorescent tubes, the technology has now evolved to LEDs, with each step being accompanied by significant potential savings. Taking these aspects into account is crucial to ensure the long-term availability and efficiency of production facilities. The situation is similar with other critical components such as robotics, safety equipment, industrial controls and PCs for industrial automation. The latter systems must also be critically scrutinised on an ongoing basis from a cyber security perspective in order to protect them from wilful interference by maliciously motivated ‘attackers’. As experience shows, control systems that were initially considered virtually wear-free are by no means ‘unbreakable’ during operation. They can fail unexpectedly – even if this is not immediately obvious.
In order to prevent such failures, there have been various ways of implementing ‘early detection’ in control systems for a number of years: Switching cycle counters are one example of a proven technology that can be used to reliably predict the end of life of electrically switching components. It is crucial that these warnings are taken seriously and that repairs are carried out in good time during planned shutdowns. A frequent obstacle here is the conflict between rational decision-making and emotional perception: As no acute fault has occurred at the time of the warning message, many tend to follow the ‘never change a running system’ principle. The feeling says ‘It’s still running’, although the mind knows that the failure is already foreseeable. However, if the affected components are replaced in good time, system availability can be increased in the long term. However, this is offset by higher spare parts and labour costs. This dilemma can be compared with the example of the tread depth of car tyres: Here, too, tyres are replaced as a precautionary measure as long as there is still sufficient wear reserve. While legal regulations in the automotive sector stipulate the replacement of tyres, in industry it is up to each company to weigh up the costs of unplanned downtime against the costs of preventive maintenance. Ideally, these costs are already recorded in a total cost of ownership (TCO) analysis and regularly reviewed. One aspect that is often overlooked and should not go unmentioned at this point is the specified service life of safety components. Just as the legislator stipulates a minimum tread depth for car tyres, there are also specifications in various standards for safety technology according to which safety-relevant components must be replaced regularly. These time specifications are not ‘recommendations’, but mandatory requirements that must be taken into account during maintenance. In order to successfully implement the above-mentioned measures for early detection and preventive maintenance, a functioning discontinuation management system is therefore essential. When a component reaches the end of its service life and it is only then realised that spare parts are no longer available, it is often already too late. In such a case, there is a risk of an unplanned and potentially lengthy plant shutdown, which is expensive and problematic.
A planning manager who has opted for standardised monitoring of the installed components at an early stage has a clear advantage here. This strategy helps to significantly reduce costs and simplify the supply of spare parts. However, anyone who has to work with a large number of different component manufacturers – and this is the case in most modern systems – is faced with an almost impossible task:
Where to start? Which problems should be tackled first? Unfortunately, management often only receives vague statements from maintenance such as ‘everything is old’ or ‘everything has to be removed’. This type of feedback usually prevents targeted problem solving and strategic planning.
In order to address this challenge systematically and effectively, INspares has taken up the topic of obsolescence management, taking into account the manufacturer-neutral EN 62402 standard for obsolescence management. A comprehensive database was developed in which the installed control components were catalogued and supplemented with the relevant data, such as the obsolescence data. This data can then be synchronised following an inventory of the installed components in the company.
This gives maintenance staff access to the current documentation of the components at any time and, for the first time, a clear overview of the discontinuation status of the system components. This makes it possible, for example, to recognise at an early stage which components could experience bottlenecks in the supply of spare parts in the future. This sound basis of information can then be used to make strategic decisions about conversions, retrofits or even the replacement of components in order to keep the systems truly ‘unbreakable’ in the long term – i.e. to maximise their availability and operational reliability.
