Quicker and cheaper to refurbish large component than buy new

With the commissioning of its new spiral welder earlier in 2010 (see Spiral welding machine for equipment refurbishment, Rewinds & J Windsor (RJW) was able to offer an enhanced technical service to its customers in terms of repairs to shafts and other rotating machinery components.

Within days of the machine being ready, the company was asked by a large oil seed food processing company to repair a rotary diverter lock from a conveyor handling system. The assembly in question was made of 316L stainless steel and measured 2.5m long and 500mm diameter.

The customer established that a new unit would have cost over 20,000 and delivery was projected to be 18-22 weeks from receipt of manufacturer's drawings. In fact no drawings were available, so redrawing would have added further cost and time penalties.

However, RJW collected the rotor lock shaft assembly from site just hours after receiving the enquiry, then fully cleaned and inspected it and made detailed measurements. Analysis confirmed that the material was 316L stainless steel. Additionally an ultrasonic test was completed to ensure the shaft was structurally sound, and free from inherent flaws or cracks.

The detailed inspection had found that the drive end bearing diameter was bent and worn and the non-drive end also showed signs of wear. In this condition the shaft could soon have failed catastrophically. As a critical process component this would have led to huge downtime costs and production problems affecting not only the site but also key downstream customers.

RJW reported to its customer and outlined the following suggested procedure:

• Prepare failed non drive end diameter
• Machine true and prepare drive end diameter (full length)
• Set up in spiral welding machine and weld using 316L welding wire and externally approved welding procedures
• All stainless steel heat treatments to be covered during the process
• Set up shaft and proof machine
• A dye penetrant inspection to be completed following machining
• Finish machine and keyway DE and NDE shafts back to manufacturer's standard
• Carry out final dye penetrant inspection
• Inspect all work and deliver to customer

All work was carried during normal working hours and the unit was returned within seven working days (if required the job could have been completed in 30 hours using the RJW round-the-clock service).

It was found that the cost of the job was approximately 15 per cent of new and the delivery of seven working days was far quicker than the original equipment manufacturer's quotation.

This work was achieved during the customers scheduled downtime period and therefore no loss of production was incurred.

By following a best practice path for the repair of the machine, the customer prevented a potential plant failure and benefited from a re-engineered, fully documented job with an improved specification over the original in a fraction of the delivery time and cost.