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Ageing automation equipment: retrofit or remanufacture?

27 June 2011

If you expect automation equipment nearing the end of its operational life to continue working reliably, you risk the double whammy of reduced productivity and increasing production costs. So, what do you do? Throw it all away and start again? Paul Hickman has a better idea

There are three distinct phases in the product life cycle of automation equipment, early-life phase, useful-life phase and the wear-out phase. Each has unique qualities requiring different support strategies. However, for equipment operating in the wear-out phase it is possible to ‘push’ the device back into the useful-life phase, thus extending the overall length of operational benefits to the end-user.

In the useful-life phase the unit, be it a drive, motor, control equipment or HMI screen, is in standard production and spares are freely available. During this phase operators can expect a fairly low but constant failure rate and a high level of machine availability.

The useful-life phase is characterised by lower production costs because there are fewer machine failures. And when supported by a planned maintenance regime, no unexpected costs are incurred. Spares usage can be accurately calculated, maintained and budgeted for. Manufacturers need only carry the spares they need, which, in turn, reduces inventory costs.

Typically, the wear-out phase for a product begins around eight to ten years after launch. Drives and motors, for example, will go into the service-phase ten years after launch, while HMIs will go into service within five years.

In the wear-out phase, we begin to see the characteristics of increasing failure rate, which, in turn, leads to increasing downtime and production costs. Spares usage is likely to increase as will costs. Repair of equipment becomes increasingly risky and less cost-effective.

A chain of failures
The increased risk comes from the repair of individual components within a unit in order to return it to operation. Other components within the unit will have similar lifespans to that of the failed component, so there’s a high probability that another component will subsequently fail in relatively short succession. Continuing to repair a unit during its wear-out phase will result in ‘multiple repeat’ failures of that unit. Maintenance staff will recognise this as a well-known effect of ageing systems and for the end-user it simply results in higher operational costs.

During the wear-out phase, end-users are faced with the possibility of significant capital reinvestment to return production machines to their previous levels of availability. The author is aware of one major end-user who recently faced a capital reinvestment bill approaching £20m for the replacement of more than 1,500 drives, motors, HMIs and power supply equipment at one of its plants. Though an extreme case, any user facing such a demand on his equipment budget will be keen to seek an alternative solution to the problem of ageing equipment nearing the end of its serviceable life.

Remanufacture
An approach put forward by this author is to remanufacture. Remanufacture (or reman’ as the author’s company terms it) can effectively extend the useful life of a product – in this case, a piece of automation equipment. An important point to bear in mind with this option is the fact that the machine wiring and software systems remain unaffected by the change of unit, so the user reduces his risk of unscheduled downtime while at the same time enjoying minimal system disturbance.

What’s more, reman’ can offer fast exchange time with the process being carried out by the end-user during a planned shutdown, thus avoiding production losses. Indeed, large-scale unit exchange can be planned and staggered to meet the needs of production schedules.
Reman’ involves the stripping down and cleaning of units, with wearable parts being replaced with original manufacturers’ specified components. The service provided by the author’s company, for example, will see units being upgraded such that their performance and reliability is on a level with that of new equipment. Once this process is completed, a functional operation test may be carried out in accordance with company quality procedures, and a warranty offered on all remanufactured parts.

In Rexroth’s case, this warranty is two years. However, a further option, called Reman’ +5, offers end-users a further five years of the unit’s service life. This option not only extends the product lifetime, but also guarantees component parts.

For the end user the benefits of reman’ include no re-engineering costs, as the service involves a like-for-like product replacement, and there’s no need to re-training operators to use or maintain new equipment. Furthermore, end users are likely to benefit from reduced manufacturing costs and improved equipment uptime - with no increase in spares requirement - which should put a ceiling on capital expenditure.

End of the line
Clearly, there comes a time when reman’, despite all its benefits, is no longer viable. An optimum point exists – perhaps when replacement spare parts are no longer available - beyond which retrofit is the only solution.

The key issue for end-users, however, is cost. Investing in new product may well be the cheaper option in terms of unit cost alone, but it is important to take associated costs into account. New products will often mean system re-engineering, new wiring, production downtime, replacement of all spares and retraining, with the added risks associated with the debugging of new software. Reman’ avoids these associated costs and with its extended warranty sees your system enjoying a new lease of life.

Paul Hickman is with Bosch Rexroth
 


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