The Marlin stainless steel AC motors from Lafert have a much longer life expectancy than conventional varieties, resulting in fewer failures: up to 364 days so far, versus 114 for standard types.
Hours previously spent stopping production to install new motors at the site had also consequently been cut, the company said.
Two different sizes of stainless steel motors (2.2kW and 3kW) were installed in January 2014 on extruders on different production lines as part of plans to reduce engineering costs.
They replaced modified normal-style finned motors equipped with special shaft-mounted water deflector discs and double-lipped bearing seals, which had been installed earlier to replace failing standard motors.
Hot and steamy
The application is particularly demanding. The motors, which drive a rotating knife, have to operate in a hot and steamy environment where they can gather product material, calling for a high pressure hose wash-down.
The original, standard, motors had a survival expectation of between 30–40 days before failure. This resulted in an hour’s extruder downtime and two hours motor maintenance involving motor removal, installation of a new unit and seal and bearing replacements. Sometimes motors would also fail due to water getting into the multi-component terminal boxes.
Even modified motors, which had water-deflecting discs, only had an extended life of 114 days.
Both standard motor types had cooling fins, which trapped product material, and a paint finish. High pressure wash-downs cleaned the motors but foreshortened their work cycles and promoted paint flaking.
The two Marlin motors do not have the cooling fins and have been working continuously without failure for 241 days and 375 and rising (as at February 17, 2015). Compared to the original motors’ maintenance costs, they have saved £4,250 and against the modified motors they have saved £1,750.
These savings do not include savings from uninterrupted production. For one product line where there are two extruders a machine stoppage meant a 50% loss of production, while on the other line with six extruders production would be cut by a sixth.
“I think the main thing was the downtime saved,” Dale Bradford, Weetabix reliability engineer responsible for the upgrade, told FoodManufacture.co.uk.
The new motors’ IP66 rating enabled them to withstand high pressure hose wash-down cleaning, while their smooth body had no crevices to harbour dust and make cleaning fiddly.
They have a single-piece terminal box, which minimises any risk of water ingress, as does the durable Viton seal, reducing the potential for electrical and mechanical failures.
Weetabix did look at alternative smooth-bodied motors from other manufactures than Lafert but they had coatings and were therefore susceptible to flaking issues, it said.
Also, they had multi-part terminal boxes, inferior seals, potentially problematic drain holes and they came with non-standard mountings which would have meant re-engineering machinery, the company added.
Bradford said he was only responsible for projects at the Corby plant, but he would release news of the motors to other sites, which he hoped would adopt the solution.
“The Lafert Marlin stainless motors are proving extremely reliable and hygienic with their smooth, easy-to-clean bodies,” he said.
“Having experienced no failures so far giving us significant savings we are planning to progressively replace all the currently installed motors on our extruders.”