FIELD OF THE INVENTION
The present invention relates to a safe and reliable method of reducing the
shipping weight and dimensions of power transformers so as to increase
transportability. More particularly the present invention relates to a method of
manufacturing transformer tank to reduce transportable dimensions of large
rating power transformer to safe and economical transportation.
BACKGROUND OF THE INVENTION
Power Transformers are manufactured at the manufacturing works for installing
at various sites for their use. Different types of power transformers find
application in various areas for example, power generating stations, load centers,
and sub stations. The tank of transformer are fabricated as enclosures to house
the active parts of the transformer viz core, the windings, insulation items. The
housing accommodates the active part being immersed in transformer oil also to
provide insulation requirement, and also to as to restrict the temperature of the
transformer within required limits. During operation of the transformer, the
transformer tank is subjected to various stresses resulting from pressure,
vacuum, weight of equipment, short circuit forces. To prevent the tank from
being deformed under such load conditions, the tank is strengthened by
providing with stiffeners of different shapes and sizes. The stiffeners are
permanently welded on to the tank walls/ cover of the transformer.

The tank is designed considering all the resulting stresses and also economic
considerations such as thickness of the steel plates , stiffeners welded at various
locations on the tank wall and cover. After manufacturing and testing of the
transformer at manufacturing works, the transformer is transported to the
erection sites for installation. The mode of transport is mostly by road using
trailer. Sometimes train and ship are also used for transporting. In exceptional
circumstances, transportation by air is also urged.
Many a times transportation of the large transformer presently , is restricted due
to limitations such as capacity of road, capacity of bridges, height of the
bridges/railway bridges, over head lines, tunnels on the way. Some times, the
limitation also includes maximum weight transportable by a particular trailer. In
order to overcome these constraints of transportation, it is required to make
changes in design and routes of traveling which are often difficult and costly.
At times, while traveling through hilly areas, the Centre of Gravity of the
transformer can cause toppling of the trailer causing damage of the transformer.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a method of manufacturing
transformer tank to reduce transportable dimensions of large rating power
transformer for safe and economical transportation.

Another object of the invention is to propose a method of manufacturing
transformer tank to reduce transportable dimensions of large rating power
transformer to safe and economical transportation which further reduces the
total concentrated weight of the transformer.
A still further object of the invention is to propose a method of manufacturing
transformer tank to reduce transportable dimensions of large rating power
transformer to safe and economical transportation which allows access to wall of
the transformer tank for inspection and other investigations without modifying
the manufacture transformer.
Yet another object of the invention is to propose a method of manufacturing
transformer tank to reduce transportable dimensions of large rating power
transformer to safe and economical transportation which allows alteration in
stiffener arrangement based on individual transportation constraints of the
transformer.
A still further object of the invention is to propose a method of manufacturing
transformer tank to reduce transportable dimensions of large rating power
transformer to safe and economical transportation which caters for incorporating
new/additional design requirement of pressure, vacuum and other mechanical
forces on the tank without affecting the active part at factory works or during
operation.

A still further object of the invention is to propose a method of manufacturing
transformer tank to reduce transportable dimensions of large rating power
transformer to safe and economical transportation which provides a cushion to
rectify the damaged stiffeners due to handling of the transformer during
loading/unloading of the transformer onto/from trailer or ship.
SUMMARY OF THE INVENTION
Accordingly, there is provided a method to reduce the transportable weight and
dimensions of large rating power transformers to a permissible limit to increase
transportability of the transformers. This is achieved by providing bolted type of
stiffeners on the transformer tank cover and side plates.
As per requirement, the stiffeners can be bolted during manufacturing and
testing and removed from the tank before transportation. After reaching the
designated site, the stiffeners are again bolted on to the transformer. With this
arrangement the transportability of the transformer increases. The transport
dimensions and weight can be considerably reduced and the equipment can be
transported to sites safely and economically.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : shows the arrangement of stiffeners on the Transformer tank side
walls and cover according to the invention.
Figure 2: shows fouling of the transformer tank constituting an over-dimensional
cargo (ODC).
Figure 3: Method of removable bolted stiffeners on the tank side wall / cover.
DETAILED DESCRIPTION OF THE INVENTION
Transformer is the most important equipment used in transmission of power.
The transformer comprises of active part which includes core, windings,
insulation and other interconnecting items. The tank houses these active parts
and other associated components and it is completely full of oil. The tank of the
transformer is made of structural steel. The tank has to be made suitable for
Pressure test, Vacuum test, Leakage test that is essential for the safe working of
the transformer during various conditions of working. For this purpose the tank is
strengthened by providing several stiffeners as shown in figure 1 which are
welded on to it.

In the proposed method the stiffeners are fixed on the tank walls using bolting
arrangement which provide required rigidity to withstand forces generated on
the tank. These stiffeners are provided in such a way that these can be easily
removed during shipment or as per requirement and then reassembled on the
tank at site. Such modification does not affect the active part (housed inside the
tank) in any manner thus the performance of transformer is not affected. So, the
removal and re-fixing of the stiffeners do not affect the active part of the
transformer housed inside the tank.

WE CLAIM :
1. A method of manufacturing transformer tank to reduce transportable
dimensions of large rating power transformer for safe and economical
transportation, the transformer comprises a plurality of active components
including the interconnecting components all of which being
accommodated in a transformer tank filled with transformer oil such that
all the active components at least remain submerged in the transformer
oil to restrict rise in temperature of the transformer during operation
within a threshold value, wherein a plurality of stiffeners are welded on
the cover and side wall of the transformer tank to prevent deformation of
the tank due to several types of stresses sustained by the transformer in
operation, characterized in that the plurality of stiffeners on the cover and
side walls of the tank cover are formed with universal dimension and
detachably attachable components to allow reduction of the transportable
dimension including reduction in concentrated load of the transformer
during transportation.
2. The method as claimed in claim 1, wherein the stiffeners are attachable
through a fastening means during manufacturing and testing at
manufacturing works, wherein the stiffeners are detachable during
transportation, and wherein the stiffeners are re-attachable at erection
site upon transportation through said fastening means.

3. The method as claimed in claim 1, wherein the active components are core
windings insulation items of the transformer.
4. The method as claimed in claim 1, wherein several types of stresses
sustained during operation of the transformer are pressure, vacuum, and
mechanical forces.

ABSTRACT

The invention relates to a method of manufacturing transformer tank to reduce
transportable dimensions of large rating power transformer for safe and
economical transportation the transformer comprises a plurality of active
components including the interconnecting components all of which being
accommodated in a transformer tank filled with transformer oil such that all the
active components at least remain submerged in the transformer oil to restrict
rise in temperature of the transformer during operation within a threshold value,
wherein a plurality of stiffeners are welded on the cover and side wall of the
transformer tank to prevent deformation of the tank due to several types of
stresses sustained by the transformer in operation. The plurality of stiffeners on
the cover and side walls of the tank cover are formed with universal dimension
and detachably attachable components to allow reduction of the transportable
dimension including reduction in concentrated load of the transformer during
transportation.