Soft starters are cure for "excessive torqueing"

Edited by the Engineeringtalk editorial team Dec 16, 2003

Fairford soft starters are being used to overcome problems associated with excessive torque on startup with a number of 15kW mixer motors at Kernow Coatings in Cornwall.

Fairford soft starters are being used to overcome problems associated with excessive torque on startup with a number of 15kW mixer motors at Kernow Coatings in Cornwall.

Previously DOL starting had caused a high shock loading to the mixer mounting frames and was affecting both the overall reliability of the mixing process and causing some concern over safety.

Kernow Coatings, part of the Sensitisers Group, is located in Penryn Cornwall.

The company is one of the largest specialist coaters and converters of design and graphic film and paper in the UK.

Kernow lighting filters are used widely in the television and film industries, and the company also provides the widest range of UK manufactured materials for use in the inkjet and toner fusion digital imaging materials market.

Kernow has a total of six coating machines and a dedicated thermo stabilising unit, developed and built by its own staff.

Each machine has a different combination of features, enabling both aqueous and solvent coatings to be performed on film and specialist papers, including lamination of pressure-sensitive adhesives.

The lacquers used in the coating process, both water-based and solvent, are mixed by the mixing machines in a formulaic process lasting 1-8h and in some instances continually mixed at low speed until used.

The mechanism that performs the process comprises a vertically mounted 15kW electric motor driving through a vertical shaft, which is itself connected to the main mixer shaft.

As a means of ensuring rigidity in the mixer drive train, the motors are vertically mounted on welded steel tube frames that are lowered into the mixture using a pulley system and runners.

Generally this arrangement works well.

However, under some operating conditions with certain types of higher viscosity lacquers, problems were encountered with the frames twisting, under high loading from initial start up.

The Senior Maintenance Engineer at Kernow Coatings suspected that this problem was due to excessive output torque from the motor on startup.

Believing that a solution to the problem could be achieved using a soft starter, the Maintenance Engineer contacted his local BSL Branch office for advice on suitable units.

BSL personnel recommended a unit from Fairford Electronics, and, following a site visit; one of the company's soft starters was installed.

This provided a simple and cost effective solution, overcoming excessive torque on startup and ensuring a smoothly ramped start up, allaying any safety concerns and providing improved overall long-term reliability.

Following this success, Fairford soft starters have been installed on the drive motors of all the remaining mixers.

"The mixing process is a lot more reliable since we fitted the Fairford starters", said the Maintenance Engineer at Kernow Coatings.

"As a result, we are benefiting from greater continuity and certainty in our production process".