2014: Development of design for transportation method for Asian road conditions
Lisa Magnusson in Collaboration with ABB Hanoi, Vietnam
When an international high-tech company wishes to relocate their manufacturing to a developing country it often causes a positive expansion but the company needs a deeper knowledge of how to adapt products’ design so that the production is suitable for the country of manufacturing.
Due to the poor infrastructure which is typical for developing countries, such as Vietnam, one of the challenges with the production is the transportation on Vietnamese roads with extreme road conditions.
One company affected negatively of these unfamiliar road condition common for Asian countries is ABB who have a global production of electrical components as distributions transformers in Hanoi. Some of ABBs products’ becomes defected after transport and leaking mineral oil, a problem that have not been faced in Europe. The reason of the leaking is due to a combination of concentrated stress areas in the construction along a weld sealing the mineral oil tank, and the fact that the product is not adapted to the transportation conditions present in the country of manufacturing.
See fig 1 >
Transport of transformers is not an easy task and today the big issue is related to the design of a so called fin-wall tank construction, for distribution transformers (Figure 1) which becomes sensitive to impacts such as vibrations and harmonics created during transportation on roads with bad road conditions.
The degree project was aimed to explain the transportation conditions and to suggest a solution to the oil leaking problem of the distribution transformers of ABB in Hanoi. The degree project resulted in general advices of possibilities to prevent the existence of the problem, and one design improvement of the distribution transformers of ABB was developed. The design improvements result was a steel frame with consoles attached underneath the fin-wall section of the transformer for support.
Transport aggravates the stress situation to failure and the transformer leak. The main problem is in the structure and not only due to the transport. Therefore, it was important to reduce the stresses in the construction either by change the design of the transformer to a construction without high stress concentrations or to add an external solution to support the current structure furthermore during transport, to spread out the load incurred evenly on the support.
Consoles for support
Figure show a 4MVA distribution transformer (DTR) of ABB with the added solution attached (welded) underneath the fin-wall section, and onto the tank bottom. The solution support the transformer during transport, adds extra support for vertical road impacts and stabilise the construction. It also spreads out the existing stress concentration evenly to the support.
See fig. 2 >
The design improvements, the added solution is a steel frame consisting of flat bars and consoles, see Figure 3.
See fig. 3 >
The positions and the dimensions of the consoles are adaptable to different sizes of distribution transformers. For example the frame for a 4MVA distribution transformer have 4 consoles placed on the long side of the transformer and on the short side are 2 consoles placed. The flat bar on the long side is longer than the flat bar on the short side. The flat bars are attached with spot weld underneath the fin-wall sections and the corners are welded together and forms the frame.
A solution with enough space
The frame is attached after the transformer is assembled and before it is subjected to pressure test and before painting. The shape of the console allows to reach behind and paint and if the weld along the inside would crack then it is enough space to re-weld.
See fig. 4 >
Easy to attach onto transformers with lashing lugs
Under the fin-walls on the short side of a 4 MVA DTR there is a small shelf with consoles for the lashing lugs used during transport. With an adjustable frame it is possible to place the support consoles on the end of each long side of the bottom tank, in this way the consoles are not in the way of the lifting lugs.
Hela rapporten kan läsas på http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-10500
See fig. 5 >
Figure 1: Distribution transformer of ABB with four assembled fin-wall sections forming the transformer tank.
Figure 2: Final design solution attached underneath the fin-wall sections of the transformer.
Figure 3: Supporting frame with flat bars and consoles.
Figure 4: The shape of the consoles allows enough work space behind the frame.
Figure 5: A 4MV have lashing lugs on the short side of the bottom tank but the dimensions of the consoles can be easily adjusted and positions anywhere along the flat bar, and attached on the edge to not interfere with the lifting lugs.