Mill gearbox upgrade contract is renewed

The contract for the refurbishment of coal pulverising mills at Drax power station has been extended.

David Brown Power Plant Gears based at Eagle Works, West Bromwich has firmly established its credentials to be regarded as a centre of excellence for mill gearbox maintenance following the announcement that the contract for the refurbishment of coal pulverising mills at Drax power station has been extended.

David Brown won the contract, published in the European Journal, against stiff international competition in 2005 and has just completed the first 12-month period successfully.

The project involves taking responsibility for the site's 65 coal pulverising mill gearboxes and partnering Drax Power to maintain them on a rolling basis and subject to annual review could run until 2009.

The newly signed contract will see Eagle Works continue to maintain the gearboxes and guarantee 60000 hours between refits for each unit.

David Brown Power Plant Gears' refurbishment centre also adds value to the equation by possible redesign to accommodate harsh conditions and mill-added influences brought about by years of operation.

Specialist knowledge is also being applied to develop an advanced condition-monitoring programme to contain these problems.

The gearboxes were originally built by David Brown around the time of the plant's commissioning in 1974.

Ordinary maintenance requires approximately one gearbox every 6 weeks to be stripped and sent to West Bromwich but extraordinary maintenance, sometimes necessitated by the harsh operating conditions, meant that some 13 units were processed last year.

The standing of David Brown Power Plant Gears is further enhanced by the number of original drawings in its possession relating to plant installed all over the world during its 75 year history.

The plant at West Bromwich has been involved in the production and maintenance of coal mills on all continents and is witness to the wide array of characteristics that feature in their design.

A notable example is the choice of induction hardening/profile grinding now being applied to recently constructed mills.

Commenting on the contract David Brown Power Plant Gears Customer Support Manager Len Phipps said: "We are proud of our expertise in this area".

"I think it's fair to say that it is unrivalled and the fact that we have retained this extremely prestigious contract is further proof of that".

"Eagle Works already services around a quarter of all this specialist work carried out in the UK and that's a figure, which we intend to increase".

"High profile contracts like Drax boost our credentials no end".

Talking about the practical aspects of the contract he went on to add: "The particular design of these mills means that the demands placed on the gearboxes are high, but the interesting part, and one which we are actively investigating is how no two pulverising mills have the same characteristics after 30 years in operation and this means that each of the gearboxes has its own set of vibrational and thermal characteristics too".

"It's an aspect we have to take into account constantly".

David Brown Power Plant Gears has analysed data obtained from the refurbishment and repairs of the units passing through Eagle Works over the past two years and is beginning to build up a picture of how the gearboxes are affected by the particular conditions within the power station.

The company believes that this will be invaluable in monitoring performance in future and assessing work priorities.

The project involves both the original gearbox design engineers and black belt Six Sigma-calibre engineers who visit the Drax Power site to examine how the gearboxes are performing and to assess conditions.

David Brown Power Plant Gears' commitment evidently goes far beyond maintaining the units, however demanding that task might be, but extends increasingly into the area of asset management in order for its customers to obtain the best value from their investment over their projected lifetime.

Staff at Drax Power dismantle the mills while David Brown Power Plant Gears collects, transports and strips the gearboxes.

The formal procedure requires Eagle Works to produce an inspection report supported by photography which is received by the client.

Test runs are also performed at West Bromwich prior to dispatch of the gearboxes.

Under the terms of the contract, turnaround time from the receipt of instructions to proceed with work to completion is six weeks, although typically David Brown Power Plant Gears is exceeding these terms in the interests of flexibility in order to be able to meet the client's requirements should unscheduled maintenance be required on another of the 64 units.

As the contract progresses both Drax Power and David Brown Power Plant Gears are finding ways of working more closely and effectively.

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