UPM drives improvement at paper plant

Shotton, UK –  UPM has completed an extensive low voltage AC drive refurbishment programme at its Shotton Paper’s recycled fibre (RCF) plant (RCF): failures of drives from three suppliers previously accounted for over 5% of downtime at the facility.

The RCF is a critical process, feeding the main paper machines which produce more than 500ktpa 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 11 kV feeds to the 690 V 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.

“Our account manager was excellent and supported us in a very active and hands on way, making some valuable suggestions that ultimately resulted in a visit to meet the actual product manager and designers of the drive in Helsinki,” explains Ray von der Fecht, head of automation team.

“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 kW to 560 kW. 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.

“We have now completed this Focus Improvement programme and have not suffered a drive failure since,” says von der Fecht.

“Due to process changes, the focus on the plant is much more intense, especially as the plant has fewer shutdowns. The refurbishment program was done in a timely manner ahead of this more demanding availability requirement,” says Steve Thomson, area automation supervisor.

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

“We have raised the skill level of our own engineers. They can confidently strip down and repair units, replacing fans, capacitors and the like in accordance with approved maintenance schedules. That is a big plus.

“We do routine checks for cleanliness and general preventive maintenance in house and have a support contract with ABB for major maintenance schedules.

“Since the refurbishment we have seen a marked increase in the reliability of the drives installation which helps overcome excessive downtime and the high cost of repairs we were experiencing previously.”