FIELD OF THE INVENTION
The present invention generally relates to a four legged inclined trestle system
for supporting conveyor gallery structure of coal handling plant in a thermal
power plant. More particularly, the present invention relates to a weight
optimized four legged inclined trestle system for supporting conveyor gallery
systems erected at a higher height from the ground level in coal handling
plant.
BACKGROUND OF THE INVENTION
Coal Handling Plant (CHP) is the lifeline of a coal fuelled power plant. The
function of a CHP is to receive, process, store, and feed the coal bunkers of
the power plant. A CHP consists of various structural components for example,
conveyor galleries, trestles and junction towers. Conveyor galleries carry coal
from coal yards to the bunkers in the boiler area of a thermal power plant.
These galleries run from ground level to the bunker level at a height of
approximately 45 to 85 meters. A typical system designed to carry coal is
generally an inclined conveyor system with single or double conveyors on a
single gallery. They are supported by vertical supporting structures called
trestles. These may be two legged trestles or four legged trestles.
The four legged trestle is one of the important components in a coal handling
plant. They can either be employed as independently (i.e., using only four
legged trestles) or in combination with two legged trestles for supporting
conveyor galleries. These trestles can be of various height and width
depending on the technical requirement.

The prior art four legged inclined trestle has two frames and consists of four
legs, connected by plurality of horizontal as well as inclined bracings, all of
them are of built up sections made up of flat sections for example, I beams,
channels, angles. Further, the wind force acting on a structure is one of the
most important factors which govern the design of a vertical structure. The
wind load acting on an uncladded structure is directly proportional to the
exposed area and force coefficient for the members in the exposed region.
Higher force coefficient for flat members increases wind load acting on the
structure. Moreover, the built up sections call for more welding requirements
which in turn increases the fabrication and erection time. In addition, the prior
art design is not based on optimizing the structural members in order to
reduce the total weight of the structure.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a weight optimized
four legged inclined trestle system for supporting conveyor gallery structure
erected at a level higher than the ground level for coal handling plant, which
eliminates the disadvantages of prior art.
Another object of the present invention is to propose a weight optimized four
legged inclined trestle system for supporting conveyor gallery structure erected
at a level higher than the ground level for coal handling plant, which selects
and adapts constituting structural members including the joining sequence to
reduced weight of the system.

A still another object of the invention is to propose aft weight optimized four
legged inclined trestle system for supporting conveyor gallery structure for
erected at a level higher than the ground level coal handling plant, which can
withstand heavy wind load conditions.
Yet another object of the present invention is to propose a weight optimized
four legged inclined trestle system for supporting conveyor gallery structure for
erected at a level higher than the ground level coal handling plant, which is
operable at various heights from ground.
A further object of the present invention is to propose aft weight optimized
four legged inclined trestle system for supporting conveyor gallery structure
erected at a level higher than the ground level for coal handling plant, which
prevents excessive deflection of the system by delimiting the stresses to safe
limits under severe wind load conditions.
A still further object of the present invention is to propose aft weight optimized
four legged inclined trestle system for supporting conveyor gallery structure
erected at a level higher than the ground level to coal handling plant, which is
fabricated primarily with standard pipe sections to reduce welding
requirements.
SUMMARY OF THE INVENTION
Accordingly there is provided aft weight optimized four legged inclined trestle
system made of circular pipe sections, for conveyor gallery structure erected at
a level higher than the ground level for coal handling plant, the system
comprising at least two sets of frames each set disposed in longitudinal and
transverse directions with four legs, each leg comprises four columns which

are laced together both horizontally and vertically, the two frames forming a
first set of frame, placed across the length of the conveyor called constitute
lateral frames whereas the other set of frames disposed along the length of
conveyor or longitudinal frames, wherein each set of frames consists of
horizontal bracings, and inclined bracings, and wherein the system is
configured in multiple segments and joined by horizontal bracings at regular
intervals. The number of segments vary depending on the height of the
structure.
According to the present invention, the input technical parameters for the
innovative systems are processed in an apparatus to develop a mathematical
model to calculate the load acting on the system so as to optimize the
constituent members including forming a welding process such that overall
weight of the system is reduced, and code provisions including the stability of
the structure is maintained. The system is then fabricated from the selected
members following the formulated welding procedure.
Standard pipe sections are employed in the proposed arrangement of Trestles.
Pipe sections are preferred over standard flat sections because of the following
reasons,
i. The force coefficient of circular sections are almost 30% less when
compared
to flat sections which results in huge reduction in wind load acting on the
structure,
ii. The load carrying capacity increases because of increase in moment of
inertia,
iii. Circular section may have as much as 30 to 40% less surface area than that
of an equivalent rolled shape and thus reduces the cost of maintenance, cost
of painting.

iv. There is no better section than the tabular one for torsional resistance,
v. Tubes are of special interest to architect from an aesthetics view point,
vi. The external surface of the tube does not permit the collection of moisture
and dust thus reducing the possibility of corrosion.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The accompanied drawings describe the invention in detail and illustrate the
features, aspects, and advantages of the present invention. Reference
numerals and alphabets are used for locating the component of the system.
The invention may be readily understood and carried into practical effect
based on the following description taken in conjunction with the accompanying
drawings, wherein:
Figure 1 shows an enlarged view of a single segment of four legged inclined
trestle system of the invention.
Figure 2 shows a front view of the enlarged segment of figure 1.
Figure 3 shows a side view of the enlarged segment of figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Figure 1 shows an overall isometric view of the four legged inclined trestle
system for conveyor gallery structure in accordance with a preferred
embodiment of the invention. P & Q are two frames located across the
direction of coal flow (lateral frames) and they are formed with bracings placed
between legs A and B, C and D respectively. These frames (P.Q) impart
stability for the system against deflection across the length of the conveyor.
Bracings between the legs A and D, B and C, form the frames R & S
respectively which are arranged along the length of the conveyor

(longitudinal frames) in order to prevent deflection along the length of the
conveyor.
1) Top width - Centre to centre distance between two legs (across the
direction of coal flow) at the top of the trestle which is equal to the gallery
width.
2) Bottom width - Centre to centre distance between two legs (across the
direction of coal flow) at the bottom of the trestle.
3) Height of the structure
4) Height of the first segment
5) Trestle breadth - Centre to centre distance between two legs along the
length of the conveyor.
6) Column spacing - Centre to centre distance between two columns in one
leg.
According to the invention, the structure contains sixteen columns (1 to 16)
with four columns in each of the legs (Fig.I). The frames P and Q consist of
plurality of horizontal bracings (17), inclined bracings (18) and cross bracings
(19). The cross bracing (19) joins the inclined bracing (18) at its midpoint
making an angle of 90 degree in between. Plurality of horizontal bracings (20)
and inclined bracings (21) form the frames R and S. Four columns in each leg
are tied together by a plurality of horizontal lacings (22) and inclined lacings
(23), wherein the inclined lacings follow a double lacing pattern. Plurality of
bracings in the horizontal plane (24) provides additional stiffness for the

system against torsional away. The system is configured as multiple segments
joined by horizontal bracings (17) at particular intervals. Each segment is
further divided into four sub-segments at equal intervals by horizontal lacings
(22). The number of segments depends on the height of the system. Figure 2
and Figure 3 show various bracings and lacings of a single segment shown in
figure 1.
A table (from IS 875 Part III code Table 28) is provided below to compare the
Force- coefficients (which, when multiplied by exposed area and design wind
pressure gives the total wind load on that particular structure and it depends
upon the face of the member on which wind force acts) for flat sided members
and members with circular cross sections.

It can be seen from the above table that, the force co-efficient of the pipe
section is less than that of the flat members, therefore total wind load acting
on the system (for the same dimension) made of pipe sections, have less wind
load acting when compared to the prior art systems forward with flat
members, For example, for an average solidity ratio (ratio of the solid area
(area which restricts the flow of wind) to the total enclosed area) of 0.3 and
given topographical condition, the percentage reduction in wind load acting on
the structure is approximately 29%.

The bracing pattern followed in the frames P and Q has an additional
advantage of having lower exposed area and contributing lesser into solidity
ratio due to reduction in length of the bracing members compared to X or
cross-type bracing. The cumulative effect will be seen in the reduction of wind
load along the conveyor direction.
The major loads that act on this system is the self weight, dead load if any i.e.,
pipes, cables etc., live load, wind loads and loads from the conveyor.
While the illustrative embodiments of the disclosure has been described above,
it will be recognized and understood that various modifications can be made to
the embodiments and the appended claims are intended to cover all such
modifications which may fall within the spirit and the scope of the disclosure.
For example, a typical four legged inclined
trestle of height 70m supporting double
conveyor gallery of length 24m can be taken
to explain the process of this proposed
system. The dimensional parameters
considered are as follows :-



The logic generated takes into account the above parameters and generate the
solid model. Self wind (wind load acting on the structure) will also be calculated
from the above said parameters. The members are grouped according to their
function and location and the logic to select the property is given in such a way-
that each group has a particular section size.
The parameters considered for load application are as follows :-

For a given set of above parameters, the following table gives the comparison
between the system of prior art and the optimized design with pipe sections.



From the above table it is seen that, all section property (i.e., 1 to 11) are built-
up sections in the existing design where as in the present invention, none of the
sections are built-up, all members are made up of standard pipe sections. The
table also indicates the welding requirement in the conventional design
(existing) due to the built-up sections. It may be further noticed that the present
invention is a weight optimized arrangement (comparing total weights) without
any built-up sections which in turn reduces the welding requirement hence
reduction in fabrication and erection time. So the above said structural
arrangement with pipe sections is better than the existing structural
arrangement

WE CLAIM.
1) A weight optimized four legged inclined trestle system for supporting
conveyor gallery systems erected at a higher height from the ground level
in
coal handling plant comprising:
• at least four legs each leg consisting of plurality of columns;
• a first set of frames P and Q spaced apart across the direction of the
conveyor (coal flow) at regular intervals;
• a second set of frames R and S placed along the direction of the
conveyor subjected to the technical requirements;
wherein each of plurality of the columns are spaced apart based on the
load acting, and the columns are laced together with plurality of horizontal
as well as inclined lacings, wherein the frames P and Q connect the two
columns of two adjacent legs across the direction of conveyor, the width of
the frames decreasing along the height of the system and wherein the
frames P and Q consist of plurality of horizontal, inclined and cross
bracings, the cross bracings joining the inclined bracings at its mid point at
an angle of 90 degree to provide stiffness for the system against lateral
deflection.
2) The system as claimed in claim 1, wherein the frames R and S connect the
two columns of two adjacent legs along the direction of the conveyor.
3) The system as claimed in claim 2, wherein the frames R and S consist of
plurality of horizontal and inclined bracings, the bracings providing stiffness
for the system against longitudinal deflection.

4) The system as claimed in claim 1, wherein the bracings in the horizontal
plane provides stiffness for the system against torsional sway.
5) The system as claimed in claim 1, wherein standard pipe sections are used
to reduce wind load acting on the system.
6) The system as claimed in claim 5, wherein the standard pipe sections
reduces welding for fabricating the system.
7) The system as claimed in claim 1, wherein the space in between the
columns is protected from all sides to allow installation of ladder, pipes,
cables for the system.

ABSTRACT

The invention relates to a weight optimized four legged inclined trestle
system for supporting conveyor gallery systems erected at a higher height
from the ground level in coal handling plant comprising ÷ at least four legs;
each leg consisting of plurality of columns a first set of frames P and Q
spaced apart across the direction of the conveyor (coal flow) at regular
intervals; a second set of frames R and S placed along the direction of the
conveyor subjected to the technical requirements; wherein each of plurality
of the columns are spaced apart based on the load acting, and the columns
are laced together with plurality of horizontal as well as inclined lacings,
wherein the frames P and Q connect the two columns of two adjacent legs
across the direction of conveyor, the width of the frames decreasing along
the height of the system and wherein the frames P and Q consist of plurality
of horizontal, inclined and cross bracings, the cross bracings joining the
inclined bracings at its mid point at an angle of 90 degree to provide stiffness
for the system against lateral deflection.