FIELD OF INVENTION
The present invention relates to a process of standardization of major portion of
economizer tube for manufacturing of economizer coils of a high pressure steam
generator.
BACKGROUND OF INVENTION
The function of an economisers in steam generating units to absorb heat from flue
gases and add this as sensible heat to the feed water before the water enters the
evaporative circuit of the boiler.
Earlier the economisers were introduced mainly to recover the heat available to flue gas
that leaves the boiler and provision of this additional heating surface increased the
efficiency of steam generation, saving in fuel consumption, thus the name “Economisers
“christened.
Counter flow arrangement is normally selected so that heating surface requirement is
kept minimum for the same temperature drop in the flue gas. Economiser’s coils are
designed for horizontal placement which facilitate draining of the coils and favours the
arrangement in second pass of boiler.

An economiser’s assembly usually have multiple layers and each layer will have multiple
circuit, ranging from three to four. Each circuit will have unique configuration and
unique length. Usually the total length of each circuit exceeds the raw material length.
For example-the raw materials length purchased will vary from 10000mm to 12150mm,
but the length of individual circuit vary from 9000mm to 11000mm. Hence, it is
necessary to weld each circuit tubes in order to develop the tubes before bending. This
welding is done in butt welding machines. Also, the bending machine can handle tubes
of length up to 7200mm only. Hence the remaining portion of circuit has to be bent
separately and weld with already bent major portion to form a circuit.
The length and butt joint location in major portion of the circuit varies within the circuit
based on the bend location and attachment location. With this constraints the major
portion of all circuits will not be same. Also, it is very difficult to measure the length of
72metre tube, handle, loading it in machine for each circuit. Also the cycle time
increases if bending is done circuit wise. Therefore it is necessary to find an alternate
method to standardize the length of major portion of all circuits in single pattern to
attain easiness in handling, loading in machine and bending the circuit’s assembly wise.
And if bend is done on circuit wise it will be costlier and time consuming process.
Labour requirements also are potentially increased because a number of human
resources can only produce batches of products. In this, additional drawback is that
very large number of defected piece will produce. Operator comfort will also decrease.
So that it will result in more number of defective piece with the lager extent of safety
standard compromise. Terminology, technical specification will automatically increase.

Grading, sampling and control of product will increase and result in automatic cycle
time increasing. Codes of good practicing will reduce up to lager extent. It will also
increase the other additional machine movement to handle variety of tubes length.
As in chart-1, the raw materials length used to make circuit will vary from 10000mm
to 12150mm, but the length of individual circuit vary from 9000mm to 11000 mm.
Hence, it is necessary to weld each circuit tubes in order to develop the tubes before
bending. This welding is done in butt welding machines. Also, the bending machine can
handle tubes of length up to 7200mm only. Hence the remaining portion of circuit has
to be bent separately and weld with already bent major portion to form a circuit.
The length and butt joint location in major portion of the circuit varies within the circuit
based on the bend location and hanger tube (calculate from drawings) attachment
location. With these constraints the major portion of all circuits will not be same. Also,
it is very difficult to measure the length of 72metre tube, handle, loading it in machine
for each circuit. Also the cycle time increases if bending is done circuit wise.
In fig -1, Item number 01, 02, 03 are different circuit made by adding of various tubes
length of 1-A, 1-B, 1-C, 1-D …..Through butt joint. These all three circuit has different
total length and no any correlation either in sequence of tube of different circuit or total
length.
And if bend is done on circuit wise it will be costlier and time consuming process.
Labour requirements also are potentially increased because a number of human

resources can only produce batches of products. In this additional drawback is very
large number of defected piece will Produce. Operator comfort will also decrease. So
that it will result in more number of defective piece with the larger extent of safety
standard compromise. Terminology, technical specification will automatically increase.
Grading, sampling and control of product will increase and result in automatic cycle
time increasing. Codes of good practicing will reduce up to lager extent. It will also
increase the other additional machine movement to handle variety of tubes length.
By above difficulties and economics issues, we chose the unique method for constant
length for all variants.
Prior art
Extensive search have been made in net and it has area found that no such relevant
portion found.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a process of standardization of
major portion of economizer tube for manufacturing of economizer coils of a high
pressure steam generator which is capable of creating and implementing a standard
pattern of length for major portion of all circuits in an assembly.
Another object of the invention is to propose a process of standardization of major
portion of economizer tube for manufacturing of economizer coils of a high pressure

steam generator which is able to facilitate easiness in loading of tubes on bending
machine and bend the tubes based on assembly requirement eliminating disadvantage
of circuit wise bending.
A still another object of the invention is to propose a process of standardization of
major portion of economizer tube for manufacturing of economizer coils of a high
pressure steam generator which is capable of reducing cycle time of manufacturing a
product and thus improves volume of production.
SUMMARY OF THE INVENTION
The bending machine can handle maximum of 72m at a time and accordingly the
different circuit length of the economizer coils are studied and the two constrains will be
taken into account 1. The minimum distance of 150 mm from hanger tube to joint
location and 2. The minimum distance of 1000mm between the bend portion and joint
location. By calculating the total length required for each coil and the supplied length of
each tubes, the first circuit will be made as 72 m irrespective of the circuit length so
that for any circuit, the first will be the 72 m length tube only and the remaining length
of the circuit will be taken by the tube joints which will come only less than 72 m .It is
therefore an object of invention to propose an improved simplified standard length of
coil tube. So that variation in length of tube will reduce and handling and movements of
tube will easy to improve of productivity because of less number size and less number
of movements. It is made simpler way to avoiding complicated Movements of tubes in

operations and eliminating disadvantage of prior art. Benefits of this is especially
advantageous (1)when new products, changes to old products or upgrades are
required. Producing large quantities of a product often is more cost effective. (2)
Reductions in time and cost per product are amplified by the flexibility of these systems.
(3) Labour requirements also are potentially reduced because a smaller number of
workers can produce batches of products. (4) In this additional benefit is very less
number of defected piece will Produce. (5) Operator comfort will also increase. So that
it will result in more number of defect free piece with the lager extent of safety
standard followed. (6) Terminology, technical specification will automatically reduce.
Grading, sampling and control of product will reduce that will result in automatic cycle
time reduction. Codes of good practicing will improve up to lager extent. (7) It will also
reduce the Machine movement to handle variety of tubes length (8) Another Object of
invention is to propose an improved bend so that it can be manufactured easily from
the available material to bend in simplified way, which is capable to operate in standard
length.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Chart-(1) Economizer assembly before arriving a standardized pattern for bending.
Chart-(2) Economizer assembly after arriving a standardized pattern for bending.
Fig-(1) unstandardized pattern of all three circuits before improvement.

Fig-(2) standardized pattern arrived out of constraints locations of all three
circuits according to invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
In standardization of coil, there are four circuit which have different total length. We
standardized the partial part, which are equal length in all circuit.
According to chart no-2, the supplied raw materials length are noted down first and
supplied relevant Drawings for economizer coils are studied. The length of each circuit
noted down and no of butt joints to make full length is so chosen in such a way that the
joint location (09) will not come less than 150mm (a) to hanger tube (08). This is to
repair the welding easily in future in case any failure. Also the joint should not come
1000mm (b) from bend (07) to joint (09). This distance is maintained to avoid the joint
failure during bending if the joint falls in the jaw portion of the bending machine.
Distance of hanger tube from one end is calculated and accordingly to satisfy the above
conditions length of circuit is taken as 72metre because the bending machine can
accommodate only 72metre length.
Now, irrespective of circuit length it is possible to make a joint as per drawings with
multiples of 72metre. The excess length in each circuit over and above multiples of

72metre will be welded for the bottom portion of circuit as per the requirement given in
the drawing.
The process as explained above each circuit are made and assembly of minimum three
circuit as called one economizer coils and there are 59 or 74 economizer coils are
connected in series depending upon dimension of second pass in the steam generator
and according to capacity of the steam generator.
This is further explained with Figure 2 and accordingly, Item number 04, 05, 06 are
different circuit made by adding of tubes length of X1,X2, X3, X4 …..through butt joint.
These all three circuit has equal total length and sequence of tube in all three circuit are
same and unique.
By above process, we follow in any one circuit and similar fashion we can do it for other
circuit. By standardizing the length of each circuit, number of variant’s in tube length,
now 3 to 5 variants are sufficient to make circuit length. Each circuit length will be
equal to each other.
Now, we know that each circuit has unique total length and unique hanger tube (range,
where butt joint location cannot locate.)
In circuit one, we noted these constrains position and in similar fashion second and
third also. These constrains position are measured from any end point of circuit
separately. These all constrains position data impose on any one single circuit and then

find out the tubes length and position where butt joint made, should not fall (locate) in
the range of constrains position.
By this method, we find out the various length of tubes which fit all the circuit and their
end position of tubes (butt joint location) which should not fall in the range of
constrains.

WE CLAIM
1. A process of standardization of major portion of economizer tube for manufacturing
of economizer coils of a high pressure steam generator, the said process
comprising;
inspecting and noting down length of supplied raw materials;
studying the drawings of economizer coils to assess the requirement;
noting down the length of 72 metre of a circuit in order to be accommodated in a
bending machine;
arranging to make total circuit length in multiple of 72 mm when excess length of
each circuit above multiples of 72 m is welded for bottom portion of circuit as per
requirement, wherein the number of 72m-pices are welded as butt joint such that
joint location (09) does not come less than 150 mm (a) from hanger tube (08)
wherein minimum distance of 1000 mm is maintained between bend (07) to joint
(09) to avoid joint failure during bending when different circuits (04, 05, 06) are
made by adding tube length X1, X2, X3, X4 through butt joint when all circuits are
made accordingly with each circuit having equal total length.