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Critical Turnaround 350kW Fan Repair & Test

Industry – UK Flooring Manufacturer

Our client reported concerns on operations of a large extraction fan, one of our External Sales Engineers attended site to assess the situation & take condition monitoring readings which confirmed vibration was at unacceptable levels and advised that the unit was removed for overhaul.

The unit is the sole extraction fan weighing 5 tonnes for a flooring production factory which couldn’t operate safely without the fan in use. The plant was therefore shutdown until the fan could be reinstalled.

The Condition Monitoring analysis determined that both the motor and fan bearings were not showing any signs of damage – the vibration was propagating from the impeller end of the fan. Given the criticality and short timescale of the repair, the overhaul of the rotating element was undertaken to cure the vibration issue.

The fan was delivered to our workshop facility and the front cover was removed to find that the impeller was fractured on the front shroud. Closer inspection identified further cracking and fractures on the impeller vanes. The impeller was separated from the shaft, pressure cleaned prior to MPI testing. Magnetic Particle Inspection was carried out on the impeller which located over 80 further faults to the welds & blades of the vanes.

All cracks were then terminated by a drilled hole to stop the crack from propagating prior to the welding of the blades.  The rotating element was then dynamically balanced to G2.5 @ 1450rpm.

The impeller was re-drilled and the covers were refitted with a new seal which had been specified to suit the 250 °C operating temperature.

The unit was painted internally & externally, the fan reassembled & the unit placed in our test cell where the motor & fan shafts were LASER Aligned to minimise vibration.

The 350kW motor was connected to our Control Panel Inverter and the unit was run up to full speed witnessed by our client. Once bearing temperatures had stabilised full condition monitoring results were taken. Vibration had reduced from RMS values of over 10mm/s to below values below 1.5mm/s.


The time taken from the unit arriving in our workshop to it being back on site was less than 3.5  days. After delivery of the fan to the clients premises, our engineers attended site to carry out Laser Alignment of the fan drive to the motor before the unit was commissioned. The unit has run on site without any problems for over 6 months.

For more information on our repair capabilities for all types of Rotating Equipment, please contact a member of our Repairs Team on +44 (0)161 864 4678 or via email.