Heavy Transformer Assembly Systems

ABB, as a worldwide manufacturer of large power distribution transformers, selected Doerfer Company's Omni-directional Wheelift® Technology for a system that could boost their current 80 ton capacity in-floor rail system and allow them to handle a new product line of transformers weighting up to 145 tons.

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In planning a consolidation of their North American heavy transformer manufacturing, ABB's early evaluations identified many challenges in the need to rework their plant to allow the use of air bearings as used in most of their plants worldwide. Expanding the in-floor rail system of their current plant was not desirable and the current use of air pallets by many of their plants was problematic due to floor cracks, expansion and construction joints, the threat of dust being kicked up during usage, maintaining floor surface quality vehicular traffic areas, and other issues that tend to creep in over time, driving the inexpensive initial price of air pallets to be a costly and unreliable long-term solution. Overhead cranes, in-floor rails, and door openings increasingly became limiting factors as product sizes continually grew and the realization that flexible processes were required to serve their global markets.

With their ever increasing product weights and sizes, the Wheelift® technology quickly became the preferred performance solution that could drive man-hour saving process changes throughout the facility. This strategy led to consideration of a family of Wheelift Transporters using generic platforms (skids) and identical components throughout each weight classification. In the end ABB purchased two transporters of the larger size and uses them with all skid sizes.

Wheelift technology is a viable alternative in capacities up to about 250 tons. Above that range Wheelift can offer a hybrid transporter that is a combination of air bearing pallet with Wheelift axle assemblies that will be a completely self-contained transporter, carrying its own large compressor as well as generating its electric power for the electric all-wheel drive motors and supporting systems.

For ABB's first application, the Wheelift transporters were to have four, six, or eight 15" diameter (380 mm Ø), on-center rotation axle assemblies. With their zone based fluid equalizing suspension, the axles in each zone have interconnecting fluid lines for load sharing. The load in each zone is computer controlled and capable of accommodating off-center loading. The fluid suspension system assures that every wheel carries only its specific share of the load, regardless of slopes and irregularities in the floor surfaces. Floor loading is dispersed with ground pressure loads distributed over a wide footprint.

Process-driven features include a flat deck at 21 inches in height (530 mm) that allows the transporter to lower and drive under transformer skids, then effortlessly lift and carry them to assembly positions during manufacturing. The transporters have a 4% slope capability, 6 inches vertical travel (150 mm) for self-loading and surface compliance, easy access to the power package, system monitoring, and both wireless and pendent hand-held controllers.

The heavy steel skids are insulated tunnel construction with load carrying side members and end caps. The Transporter chassis allows a universal worldwide pallet design to be used, driving economies for bulk purchases and design amortization.

CHALLENGE: For a planned expansion to larger transformers than their current in-floor rail system could handle, ABB sought a viable alternative to upgrading their old plant to the quality needed to support air bearings. The people at ABB's, South Boston, Virginia plant, accepted the challenge to be the first to install a self-loading Wheelift wheeled transporter that can handle their new range of transformers within their old and new manufacturing spaces that were severely compromised with uneven surfaces, room-to-room thresholds, rail tracks, expansion joints, gaps at the autoclave doors, along with being able to effortlessly negotiate congested aisles around fixed machinery locations.

SOLUTION: Purchase wireless, low profile, electrically self-powered, all-wheel drive transporters and several sizes of ground isolation heavy duty skids with common "tunnel spaces" that allow the transporters to drive under, lift and carry transformers to the next assembly or process location.

BENEFIT:

• Provides absolute load control
• Reductions in air-borne particulates and ongoing facility maintenance costs
• Faster travel, driving productivity, facility utilization, and safety
• Unlimited process flexibility
• Unrestricted movement across severe floor irregularities, drain grating, ramps and asphalt surface between buildings
• Provides autoclave loading and outdoor pad staging capabilities

HYBRID 800 TON TRANSPORTERS:

While the Wheelift's transporters offer many unique advantages for heavy load assembly across a broad range of industries, it is recognized that as load ranges go up in the assembly of high density loads such as transformers and generators, where weights can range from 400 to 1000 metric tons, the base of those loads are just too small to get enough wheel modules under them to support that kind of weight. Air bearing transporters have proven their capability in the heavy transformer industries across Europe and China.

First of all, air bearing transporters are relatively inexpensive to purchase, and when the plants have adequate epoxy coated floors, air bearing transporters can be very effective; however, contending with the large diameter air supply hoses when moving long distances is challenging. The hoses are heavy to handle and they must be reconnected often, all requiring time and extra personnel that could better be used elsewhere — thereby, making the next step in technology, the desirability of having a hybrid, fully self-contained Wheelift style transporters, but with air bearings under the center load deck.

Having a fully self-contained transporter with the Wheelift style precision, is not practical with current air bearing transporters, but is very practical with a HYBRID configuration of adapting the ultra heavy load carrying capacity of air bearings with the precision control of fluid equalizing suspension wheeled transporters. With this hybrid transporter carrying its own large capacity air compressor, it is totally self-contained.

A HYBRID 800 metric ton Wheelift transporter designed specifically for transformer and generator assembly would have all of the same proven precision omni-directional travel capability currently being enjoyed by other industries yet provide the large capacity self-contained air source required for efficient air bearing travel. The transporter would have omni-directional Uniload® axle assemblies under both ends for traction and would share a large part of the load. As an 800 metric ton transporter, the center portion of the transporter would have ten 60 inch diameter (1520 mm Ø) air bearings rated at 85 metric tons each.

The modular Wheelift chassis provides high load carrying capacity along with a degree of process flexibility not attainable through other technologies. Wheelift Transporters and AGVs enable manufacturing flexibility for configurable work processes facilitating new design freedoms benefiting worldwide niche markets. **Wheelift Transporters and AGVs are manufactured in Iowa and are custom engineered to application specific requirements. Chassis and fixtures are available with load capacities to 500+ tons and deck heights as low as 18.5". Power options include diesel, LP gas, battery, or umbilical cord. Computerized all electric omni-directional drives are standard with individual axle ratings of 15, 20, or 25-US ton.

Wheelift® is a Doerfer Companies technology. Doerfer engineers and builds application specific manufacturing machinery and systems. Operating from four North American locations with over 700,000 sq. ft. and 500+ employees, Doerfer offers expanded technical and manufacturing resources, is NQA-1 certified, and follows ISO 9001 standards.

SUMMATION: Applying Wheelift's unique precision travel capability to a HYBRID combination air bearing/wheel transporter whose Uniload axle assemblies provide precision, fully autonomous travel, along with the ability to be its own large combination engine-driven air compressor/generator power plant supplying the pneumatic power needed for heavy capacity air bearings, means that it will bring a degree of "flexible manufacturing" to the transformer industry that could not be possible otherwise.

TRADEMARKS

The following terms that are used through this website: Wheelift^®, Uniload^®, SynchroSteer^®, StackAxle^®, TrackAxle™ and OmniAxle^™ are all trademarks that are exclusively licensed to Doerfer Companies.