Manufacturer and repairer of electric motors and components Marthinusen & Coutts (M&C) has commissioned a new burn-off oven at its 9 500 m² facility in Cleveland, Johannesburg.

This is one of several significant recent investments, which M&C MD Richard Botton says has established the company as one of South Africa’s leading repairers of large rotating machines from 9 MW and higher.

M&C decided to invest in the oven after monitoring the subcontractors it had used to conduct burn-out of stator windings, over the years.

“M&C has successfully implemented a cold-winding removal process that has been used on several large stators, bigger than 5 MW, with excellent results.

“This cold removal process is, however, time-consuming and extends the delivery time of the motor. “For this reason, the company investigated the specifications of burn-off ovens in consultation with local and international customers, suppliers and technical experts and compiled a detailed and accurately specified standard for its new burn-off oven.”

The oven has a maximum operating temperature of 380 °C, internal dimensions of 3 m wide, 3.5 m high and 3 m deep, and is housed by 225-mm-thick walls in a 3.5 m × 4 m × 3.5 m enclosure with two stainless steel swing doors.

It is directly fired from a WG40 Weishaupt gas burner, harnessing a gas valve check system. A 12-m-high, 300-mm-diameter flue creates a negative suction of a two inch water gauge to keep the enclosure under negative pressure, while a secondary afterburner features a refractory insert in its stack to maintain 1 100 °C. The oven includes explosion relief doors in its combustion chamber and in its oven roof.

The control panel features a Brain Child VR18 human-machine interface, a paperless recorder temperature controller with software networking and a security lock-out facility for the main and afterburner. Customer product protection is ensured through a programmable process controller, an oven temperature protection controller and a paperless 18-channel chart recorder. Oven temperature is controlled using actual motor core temperatures. Mist pulsating water spray nozzles have been fitted to the roof of the oven and are controlled from the oven temperature controller, with water supplied from a local 2 000 ℓ reservoir to ensure ongoing supply in the event of a water shortage.

The burn-off oven supplier has also manu- factured a smaller, but similar, burn-off oven for M&C’s Welkom branch.

Other recent investments include the purchase of a new 32 t balancing machine, which is the third-largest in South Africa; a new facility, in Benoni, which houses M&C’s Pro Power Generation division; an 80 t crane; two computer numerically controlled lathes; and the commissioning of a specialised rotational curing facility for large machines, which ensures even distribution of the resins within the windings, resulting in better insulation and better heat distribution.

These improvements have contributed to doubling the size of the company in the space of five years, says Botton.

“M&C has grown and will continue to grow. The company has substantially increased its market share in terms of providing maintenance and repair services for rotating electrical equipment. “Owing to the increased volumes of the past few years, M&C has bought the 12 000 m² facility, in Benoni, to supplement its Cleveland operation and is already refurbishing large machines, turbo rotors and power generators at the facility,” he conludes.

To subscribe to Engineering News's print magazine email subscriptions@creamermedia.co.za or buy now.