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An extensive low-voltage AC drive refurbishment programme has been carried out by ABB on a series of drives used throughout UPM Shotton Paper’s recycled fibre plant (RCF).

The RCF is a critical process, feeding the main paper machines that produce more than 500,000 tonnes of newsprint per annum.

Any stoppage on the RCF affects the entire production.

To improve the overall performance of its installed drives base, reduce downtime and lower the cost of repairs, UPM initiated a Focus Improvement Team.

The team was tasked with identifying reasons for low-voltage AC drives downtime from three different manufacturers.

ABB were invited to join the team in an effort to get to the heart of the investigations into its drives.

At first there was concern that the power supply network may be causing spurious spikes that were damaging the drives’ semiconductors.

Engineers from ABB in Sweden applied a network-analysis tool to look at 11kV feeds to the 690V motor-control centres feeding the drives.

The tests confirmed that the network was stable and UPM were able to eliminate this potential cause early from its investigations.

UPM was invited to Helsinki, home of ABB’s drives manufacturing, where in-depth discussions were held with the designers of the drives.

Ray von der Fecht, head of automation team, said: ‘After very constructive discussions it was agreed that the next failure would be returned to the factory for a full analysis.’ The ABB drives were suffering from dry solder joints on the power semiconductor units.

Although this was natural degradation and a common occurrence with drives generally, it was happening outside of normal warranty.

However, ABB offered to support UPM with replacement units.

Using ABB’s service workshop at St Neots, Cambridgeshire, UK, the refurbishment, phased in over six months, included replacing power semiconductor modules and fans in 36 drives ranging from 160 to 560kW.

Any additional components identified as faulty during this upgrade were replaced after agreement with UPM Shotton.

Up to four drives at a time were refurbished at ABB’s St Neots drive workshop, during short-time shutdowns of various parts of the plant.

The workshop is a member of the ABB Global Drives Service Workshop network and repairs and refurbishes ABB drives to the latest factory standards using certified original parts and procedures.

Two standby drives were supplied to site to cover those being refurbished.

Each drive was upgraded in a day and the batch of drives were tested and returned to the Shotton site the following week.

UPM has now completed this Focus Improvement programme and has not suffered a drive failure since.

During the programme, UPM sent its engineers to the ABB service workshop where they were trained on the latest drives maintenance techniques.

Since the refurbishment UPM have seen a marked increase in the reliability of the drives installation, which helps overcome excessive downtime and the cost of repairs.

In 2007, more than five per cent of UPM’s total downtime was due to drive failures across all three of its suppliers.

However, since ABB’s upgrade the company has confidence that production will be well supported by ABB drives.

ABB Automation Tech – Drives and Motors

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