Heavy gears and gearboxes machined and fabricated

Gears up to 4.75 metres in diameter and 50 tonnes in weight, with face widths to 1100mm and pitches up to 40 module are machined as well as complete gearboxes up to 10,000hp and weighing over 200t.

The Gear Manufacturing operation of Sheffield-based Kvaerner EandC enjoys an international reputation, with customers in North and South America, Africa, the Pacific Rim, Europe and throughout the UK, and current contract listings exceed GBP 2 million in value.

This unique facility has the capacity for grinding gears up to 4.75 metres in diameter and 50 tonnes in weight, with face widths to 1100mm and pitches up to 40 module; it also builds complete gearboxes up to 10,000hp, weighing upwards of 200 tonnes and including housings fabricated on site.

Yet whilst mainly associated with super-large sizes, the company can also cut gears down to 150mm diameter and 4 module.

Illustrating the scale and skills of this operation, Kvaerner EandC has recently supplied a 187 tonne gearbox, with carburised and case hardened gears, to Brazil; innovatively cut a massive 10metre gear wheel in four segments and assembled them together in a perfect ring; produced double helical gears for a Spanish customer, employing a special expanding mandrel for precision machining the units in two separate halves.

Such products are utilised across a wide spectrum of engineering applications, including metals and processing, mining and quarrying, marine and offshore, power generation and heavy mobile plant.

Boasting a fully dedicated gear cutting and grinding facility, Kvaerner EandC manufactures spur, single and double helical, and internal gears, as well as spindles, shafts and other associated products.

It also produces complete reduction gearboxes and pinion housings, including change-speed transmissions complete with clutch mechanisms.

Equipped with modern production machinery, including two of the largest Maag and Liebherr models in the country, and working to all recognised international standards, the operation can handle planing up to 1.6 metres external and internal diameters, hobbing to 3.2 metres and grinding to 4.75 metres and beyond, with barrelled couplings again to 1.6 metres.

A particular speciality is fabricating composite gear wheels from high quality EN24 steel on lower grade, lightened hubs, in order to reduce cost and weight on very large diameters.

Independently certified to ISO9001 and EN29002, the gear manufacturing facility employs a total quality management system throughout the production process, from design to testing and checking.

Gear and transmission designs are generated using the latest computer-aided techniques, encompassing solid modelling, finite element analysis and clash detection, and materials are carefully selected so that each drive meets the required performance and reliability criteria.

A team of qualified technicians and inspectors is then responsible for determining that the metallurgical, ultrasonic and dimensional parameters are always in accordance with the design and manufacturing specifications.

In-house resources include full metallurgical facilities, for verifying heat treatment and metallographic structure, and non-destructive ultrasonic testing systems; whilst an on-site standards laboratory is responsible for systematically calibrating all production machinery, to ensure absolute accuracy.

After profile and pitch inspections have been carried out on automatic testing equipment, finished components are proved on precision test rigs, which check that gear sets mesh together correctly, and are then re-proved at the customer's premises.

Kvaerner EandC applies aircraft-style precision standards to gear engineering and its ability to work to extreme tolerances is particularly exemplified when cutting double helical drives.

These gears feature a circular herringbone pattern, with the right and left helixes converging around the centre spine.

Normally, a narrow gap enables cutting or grinding without running into the opposing helix, although considerable skill and precision is nevertheless required.

However, a set of steel mill pinions recently produced for Horburgh Scott in the USA were too complex to allow this, so the company machined the gears in two separate halves, employing a special expanding mandrel for one half, then shrinking this onto a shaft with the mating half, requiring an extremely high degree of accuracy for such comparatively large components.

Its capacity to design and produce complete transmission units is best illustrated by a massive 183 tonne overhead edger gearbox, which was delivered last year to CST in Brazil, at a cost of GBP 1 million, and included a gearcase that was fabricated in-house, as it was simply too large for casting.

Yet a giant 10m diameter gear wheel, part of a GBP 250,000 engineering contract for Kvaerner EandC, was too big even for the company's massive Maag 460 grinding machine.

Instead, it machined the gear in four separate segments, using conventional machinery, then mated the quadrants together with the highest degree of precision, proving that engineering and innovation can go hand in hand.
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