FIELD OF THE INVENTION
The present invention generally relates to a four legged parallel sided device for
supporting conveyor gallery structure disposed at lower attitude in a coal handling plant
of a thermal power plant. More particularly, the present invention relates to a weight
optimized four legged parallel sided device for conveyor gallery system in coal handling
plant.
BACKGROUND OF THE INVENTION
Coal Handling Plant (CHP) is the lifeline of a coal fueled power plant. The function of a
CHP is to receive, process, store, and feed the coal bunkers consistently during
operation of the power plant. It consists of various structural components for example
conveyor galleries, trestles and junction towers. Conveyor galleries carrying eeal coal
from coal yards to the bunkers in the boiler area of a thermal power plant. These
galleries run from ground level to bunker level which is generally between 45 to 85
metres high. A typical system designed to carry coal is normally an inclined conveyor
system with single or double conveyors on a single gallery. They are supported by
vertical supporting structures called trestles, which may be two legged trestles or 4
legged trestles.
The four legged trestle is one of the important components in the coal handling plant.
The four-legged trustle can either be employed independently (i.e., using only four
legged trestles) or in combination with two legged trestles for supporting the conveyor
galleries. These trestles can be of various heights and width depending on the specific
technical requirement.

The existing structural arrangement for four legged trestle employed to support
galleries at relatively lower height has two frames each consisting of four legs,
connected by plurality of horizontal as well as inclined bracings, the legs being built up
sections made up of flat sections for example, I beams, channels, angles etc. Further,
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 require multiple welding which in turn
increases the fabrication and erection time. In addition to this the prior art design does
not cater for the important parameter of weight optimization of the structural members
in order to reduce the total weight of the device.
At lower heights, since the wind load acting on the structure in lateral direction and the
wind load transferred from the supported gallery are relatively small, the device can be
designed as a straight structure with parallel columns or in other words, top width and
bottom width of the trestle should be the same and they are equal to the width of the
gallery being supported. For the same reason, wind load acting on the structure along
the length of conveyor and wind load transferred from adjacent two legged trestles are
moderately low, which interalia allows reducing the size of the longitudinal dimension
(breadth) of the trestle smaller than that of the prior art trestle.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a weight optimized four
legged parallel sided trestle device for supporting conveyor gallery structure 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
parallel sided trestle device for supporting conveyor gallery structure for coal handling
plant, in which is fabricated with optically determined structural members including
application of a joining sequence to produce a device with reduced weight.
A still another object of the invention is to propose a weight optimized four legged
parallel sided trestle device for supporting conveyor gallery structure for coal handling
plant, which is enabled to withstand heavy wind load conditions.
A further object of the present invention is to propose a weight optimized four legged
parallel sided trestle device for supporting conveyor gallery structure for coal handling
plant, which can operate at relatively lower heights from ground.
A still further object of the present invention is to propose a weight optimized four
legged parallel sided trestle device for supporting conveyor gallery structure for coal
handling plant, which prevents excessive deflection of the device by de-limiting the
stresses to an acceptable safe limits under severe wind load conditions.
Yet another object of the present invention is to propose a weight optimized four
legged parallel sided trestle device for supporting conveyor gallery structure for coal
handling plants adopted in thermal power plant, which is formed of standard pipe
sections and reduced welding.
SUMMARY OF THE INVENTION
Accordingly there is provided a weight optimized four legged parallel sided trestle
device made of circular pipe sections, for conveyor gallery system of coal handling
plant, the device comprises at least two sets of frames both in longitudinal and

transverse directions with four legs and each leg comprises four columns laced together
both horizontally and vertically. The two parallel frames placed across the length of the
conveyor acting as lateral frames and the other two parallel frames are located along
the length of conveyor and acting as longitudinal frames, subjected to the technical
requirements. Both sets of frames consist of horizontal bracings, and inclined bracings.
The device is divided into segments placed at intervals by horizontal bracings. The
number of segments varies depending on the height of the structure.
The inventive device is made of pipe sections for supporting a conveyor gallery
structures, which addresses the problems of optimizing the device to ensure maximum
utilization of material, reduction in welding requirement, elimination of built up sections,
and reducing the overall weight of the system.
Standard pipe sections are employed in the device which 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 tubular 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.

According to the present invention, the input technical parameters for the inventive
device are processed through a module of the system is developed which is enabled to
calculate the load acting on the device. Accordingly, the constituent members including
the forming process is determined such that the overall weight of the device is reduced,
and code provisions including the stability of the structure is maintained. The device is
then fabricated based on the selected members and the welding sequence.
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 typical segment of four legged parallel sided
trestle device.
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 the overall isometric view of the four legged parallel sided trestle device
for conveyor gallery structure in accordance with a preferred embodiment of the
invention. P & Q are two frames across the direction of coal flow (lateral frames) and
they are formed with bracings between legs A and B, C and D respectively. These
frames (P, Q) impart stability for the structure against the deflection across the length
of

the conveyor. Bracings between the legs A and D, and between the legs B and C,
respectively form the frames R and S, which are arranged along the length of conveyor
(longitudinal frames) in order to prevent deflection along the length of the conveyor.
The following are the input technical parameters considered for designing the device:-
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 device contains 16 columns (1 to 16) with four columns
in each of the legs (Fig.1). The frames P and Q consist of plurality of horizontal bracings
(17), inclined bracings (18) and cross bracings (19). Each cross bracing (19) joins each
of 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
multiple inclined lacings (23), where the inclined lacing (23) follow a single lacing
pattern. The device is divided into segments by the horizontal bracings (17) at
particular intervals. Each segment is further divided into four sub-segments at equal
intervals by the horizontal lacings (22). The number of segments depends on the height

of the structure. Figure 2 and figure 3 show various bracings and lacings of the typical
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 member and 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 a pipe section is
lesser than that of the flat members, therefore total wind load acting on the device (for
the same dimension) made of pipe sections will have less wind load acting when
compared to the prior art devices formed with flat members. For example, for an
average solidity ratio (ratio of the solid area) 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 is seen in the reduction of wind load along the conveyor direction.

The major loads that act on this device 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 parallel sided trestle of height 22m supporting double
conveyor gallery can be taken to further explain the inventive device. The dimensional
parameters considered are as follows :-
Basic Parameters
Top width
Bottom width
Total Height
Height of the first segment
Breadth
Column spacing
Risk Coefficient (Probability Factor); kl
Terrain, Height and Structure Size Factor; k2
Topography Factor; k3
The module developed incorporates a logic which takes into account the above
parameters. Self wind (wind load acting on the structure) is calculated from the above
said parameters. The members are grouped according to their function and location and
the logic allows selection of members such that each group has a particular section size.
The parameters considered for load application are as follows :-

Effective length of galleries being supported
Dimensions of the gallery
Coefficient of frictional drag
Wind load transferred from two legged trestles
Loads transferred from supported galleries
For a given set of above parameters, the following table indicates a comparison
between the prior art device and the optimized device of the invention :-


From the above table it is seen that, all section property (i.e., 1 to 8) are built-up
sections in the prior art, where as in the present invention, none of the sections are
built-up, rather, all members are made up of standard pipe sections. The table also
indicates the welding requirement in a prior art device due to the built-up sections. It
may be further noticed that the present invention is a weight optimized device
(comparing total weights) without any built-up sections which in turn reduces the
welding requirement hence reduction in fabrication and erection time.

WE CLAIM:
1) A weight optimized four legged parallel sided device for conveyor gallery system in
coal handling plant, the device comprising :
• four legs each consisting of a plurality of columns;
• two parallel frames P and Q spaced apart across the coal flow direction of
the conveyor;
• two parallel frames R and S placed along the direction of the conveyor;
wherein the columns constituting each leg are spaced apart at predetermined
intervals;
wherein the columns constituting each leg are laced together by a plurality of
horizontal as well as inclined lacings, and
wherein the frames P and Q connect the two columns of two adjacent legs across
the direction of the conveyor, the width of the frames P and Q being constant along
the height of the device wherein the frames R and S connect two columns of two
adjacent legs along the direction of the conveyor, the width of the frame R and S
being constant throughout the height of the device.
2) The device as claimed in claim 1, wherein the frames P and Q consists 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, the bracings provide stiffness for
the device against lateral deflection.
3) The device as claimed in claim 1, wherein the frames R and S consists of a
plurality of horizontal and inclined bracings, the bracings provide stiffness for the
device against longitudinal deflection.

4) The device as claimed in claim 1, wherein standard pipe sections are used to
reduce the wind load acting on the device.
5) The device as claimed in claim 1, wherein the standard pipe sections reduces
welding requirement by eliminating built-up sections.
6) The device as claimed in claim 1, wherein the device is enabled to withstand
heavy wind load conditions.
7) The device as claimed in claim 1, wherein the space between the columns is
protected from all sides to allow installation of ladder, pipes and cables for the
conveyor galley system.

ABSTRACT

The invention relates to weight optimized four legged parallel sided device for
conveyor gallery system in coal handling plant, the device comprising : four legs
each consisting of a plurality of columns; two parallel frames P and Q spaced apart
across the coal flow direction of the conveyor; two parallel frames R and S placed
along the direction of the conveyor; wherein the columns constituting each leg are
spaced apart at predetermined intervals; wherein the columns constituting each leg
are laced together by a 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 the conveyor, the width of the frames P and Q being constant along
the height of the device and wherein the frames R and S connect two columns of
two adjacent legs along the direction of the conveyor, the width of the frame R and
S being constant throughout the height of the device.