FIELD OF THE INVENTION
[01] The present invention relates to a method for testing high strength friction
grip (HSFG) bolt used in structural connection being adopted in boiler
5 supporting steel structure to transfer the loads effectively. Moreover, the
present invention also relates to the method for testing the HSFG bolts by using
configured test rig and universal testing machine. The present invention
provides reduced number of variants of HSFG bolts for making easiness of
purchase and erection. 10
BACKGROUND OF THE INVENTION
[02] Background description includes information that may be useful in
understanding the present subject matter. It is not an admission that any of
15 the information provided herein is prior art or relevant to the presently claimed
subject matter, or that any publication specifically or implicitly referenced is
prior art.
[03] The Boiler furnace is a hanging mass suspended from the pressure part
20 support level beams (PPSL). These PPSL beams are supported by Main Boiler
support level called MBSL welded beams. These MBSL beams are supported by
ceiling girders which are transverse to boiler axis, connecting the boiler main
columns through girder pin assembly. In few cases, ceiling girders are seated
on cross girders which are connecting the boiler main columns along boiler
25 axis. The boiler columns are part of framed structure with horizontal beams
and vertical bracings. Therefore, the low carbon steel with yield strength of
250Mpa is used in the general structure and 350Mpa steel is used in boiler
columns, heavily loaded beams, welded beams and cross girders of ceiling
girder system. The ceiling girders are designed for the maximum depth of 4.5m
3
with hybrid steel. Therefore, the flanges of the ceiling girders are high tensile
steel yield strength of 410 MPa and web with standard yield strength of 250
MPa steel. Hence the High Strength Friction Grip (HSFG) Bolt is used in all the
structural connections to transfer the loads effectively.
5
[04] In General, a conventional boiler structure requires for 1,50,000 of HSFG
Bolts and a fully bolted structure requires for 4,50,000 of HSFG Bolts for
structural connections. In Table 2 of IS3757 standard, bolt variants are given
for a length from 40 mm to 300 mm in an interval of 5mm up to 100 and 10mm
10 interval from 100 to 300. In existing Boiler structure design, there are about
12 number of variants of 8.8 grade HSFG bolts are used in a boiler steel
structural connections. The 12 number of bolt variants are M24x60, M24x70,
M24x80, M24x90, M24x100, M24x110, M24x120, M24x130, M24x140,
M24x150, M24x160 and M24x170. These huge number of bolts with different
15 variants are required at site, right from the erection of boiler columns.
[05] Therefore, it is found difficult in the procurement of these huge quantum
of bolts and timely supply to site as and when required and also, in site, when
the particular variant of bolt is not available, the nearby variant will be used
alternatively using additional washers and this results in the shortage of
20 replaced bolts in later stage.
[06] Hence, there is a huge requirement to overcome above mentioned issues
such as reducing number of the HSFG bolts variants and a method for testing
the extended thread HSFG bolts is suggested to overcome said issues and
25 other.
4
OBJECTS OF THE INVENTION
[07] In view of the foregoing limitations inherent in the state of the art, some of
the objects of the present disclosure, which at least one embodiment herein
5 satisfy, are listed herein below.
[08] It is therefore, the primary object of the invention is to provide alternate
arrangement of HSFG bolts and a method for testing HSFG bolts by using a
test rig uniquely designed for this purpose. 10
[09] Another object of the present invention is to make easiness of purchase
and also site erection, by using reduced numbers of variants in HSFG bolts.
[010] Still another object of the present invention is to propose a test rig
15 designed for testing HSFG bolts for boiler supporting steel structure. [011] Yet another object of the present invention is to provide extended thread
dimension given in HSFG bolts as per Table 1.
20 [012] These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following
detailed description taken in conjunction with the accompanying drawings in
which a preferred form of the present invention is illustrated.
25 SUMMARY OF THE INVENTION
[013] One or more drawbacks of conventional system/method for testing the
HSFG bolts which are required in a huge quantity for structural connection
needed for boiler supporting steel structures and other problems are overcome,
30 and additional advantages are provided through the system in the present
disclosure. Additional features and advantages are realized through the
technicalities of the present disclosure. Other embodiments and aspects of the
5
disclosure are described in detail herein and are considered to be part of the
claimed disclosure.
[014] The present invention is directed to a method for testing the HSFG (High
5 Strength Friction Grip) bolts by using configured test rig, the method
comprising the steps of: clamping the test rig bolted with two bolts, in the
universal testing machine (UTM) fixed at top and bottom of the testing
machine; applying the tensile load to perform testing; and plotting the curve
on load vs time by using UTM. The bolts are clamped in the UTM performing
10 tensile test to take the testing result by plotting the curve of yield strength,
tensile strength, bolt failure load and others which are much improvised than
the requirement. The test rig is configured by using two number of item 1
plates, two number of item 2 plates and four number of item 3 plates welded
and assembled by using two extended thread HSFG bolts, nuts and washer. 15 The extended thread HSFG bolts are required for structural connection in boiler
supporting steel structure.
[015] In the embodiments of the present invention discloses the configuration
of test rig comprises: two number of item 01 plates bolted with two parts of
welded item 2 plates and item 3 plates assembly by using extended thread
20 HSFG bolts, nuts and washer through two holes for tightening the assembly,
wherein each part of welded plates (item 2 and item 3) are configured by
welding one number of item 2 plate in between of two number of item 3 plates.
[016] In said aspect of the present invention, the method may include the
following features:
25 (i) the bolts are clamped in the UTM performing tensile test to take the testing
result by plotting the curve of yield strength, tensile strength, bolt failure load
and others which are much improvised than the required value,
6
(ii) the percentage elongation of the bolt is measured after the bolt failure
happens.
[017] The preferred embodiment of the present invention is having other
features and advantages which are disclosed in the appended dependent
5 claims.
[018] Other objects, features, and advantages of the present disclosure will
become apparent from the following detailed description. It should be
understood, however, that the detailed description and the specific examples,
10 while indicating specific embodiments of the invention, are given by way of
illustration only, since various changes and modifications within the spirit and
scope of the invention will become apparent to those skilled in the art from this
detailed description.
[019] Various objects, features, aspects and advantages of the inventive
15 subject matter will become more apparent from the following detailed
description of preferred embodiments, along with the accompanying drawing
figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
20
[020] The illustrated embodiments of the subject matter will be best
understood by reference to the drawings, wherein like parts are designated by
like numerals throughout. The following description is intended only by way of
example, and simply illustrates certain selected embodiments of apparatus that
25 are consistent with the subject matter as claimed herein, wherein:
[021] Figure-1 illustrates the high strength Friction grip (HSFG) bolt figure as
given in IS 3757 standards accordance with an embodiment of the present
subject matter.
30
7
[022] Figure-2 illustrates the test rig for designed exclusively for carrying out
the shear failure test, in accordance with an embodiment of the present subject
matter.
5 [023] Figure-3 illustrates the 25mmx150mmx150mm plate which denotes item
03 plate used for configuring the test rig, in accordance with current
embodiment of the present subject matter.
[024] Figure-4 illustrates the 25mmx150mmx360mm plate which denotes item
10 01 plate used for configuring the test rig, in accordance with current
embodiment of the present subject matter.
[025] Figure-5 illustrates the 25mmx150mmx300mm plate which denotes item
02 plate used for configuring the test rig, in accordance with current
15 embodiment of the present subject matter.
[026] Figure-6 illustrates the test rig clamped in universal testing machine, in
accordance with an embodiment of the present subject matter.
20 [027] The figures depict embodiments of the disclosure for purposes of
illustration only. One skilled in the art will readily recognize from the following
description that alternative embodiments of the structures and methods
illustrated herein may be employed without departing from the principles of
the disclosure described herein.
25 DETAILED DESCRIPTION OF THE INVENTION
[028] The detailed description of various exemplary embodiments of the
disclosure is described herein with reference to the accompanying drawings. It
should be noted that the embodiments are described herein in such details as
30 to clearly communicate the disclosure. However, the amount of details provided
herein is not intended to limit the anticipated variations of embodiments; on the
8
contrary, the intention is to cover all modifications, equivalents, and alternatives
falling within the spirit and scope of the present disclosure as defined by the
appended claims.
5 [029] It is also to be understood that various arrangements may be devised
that, although not explicitly described or shown herein, embody the principles
of the present disclosure. Moreover, all statements herein reciting principles,
aspects, and embodiments of the present disclosure, as well as specific
examples, are intended to encompass equivalents thereof.
10
[030] The terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of example embodiments.
As used herein, the singular forms “a”, “an”, and “the” are intended to include
the plural forms as well, unless the context clearly indicates otherwise. It will
15 be further understood that the terms “comprises”, “comprising”, “includes”,
“consisting” and/or “including” when used herein, specify the presence of stated
features, integers, steps, operations, elements and/or components, but do not
preclude the presence or addition of one or more other features, integers, steps,
operations, elements, components and/or groups thereof.
20
[031] It should also be noted that in some alternative implementations, the
functions/acts noted may occur out of the order noted in the figures. For
example, two figures shown in succession may, in fact, be executed
concurrently or may sometimes be executed in the reverse order, depending
25 upon the functionality/acts involved.
[032] Unless otherwise defined, all terms (including technical and scientific
terms) used herein have the same meaning as commonly understood by one of
9
ordinary skill in the art to which example embodiments belong. It will be further
understood that terms, e.g., those defined in commonly used dictionaries,
should be interpreted as having a meaning that is consistent with their meaning
in the context of the relevant art and will not be interpreted in an idealized or
5 overly formal sense unless expressly so defined herein.
[033] The present invention is directed to a method for testing the extended
thread HSFG (High Strength Friction Grip) bolts by using configured test rig,
the method comprising the steps of: clamping the test rig bolted with two bolts,
10 in the universal testing machine (UTM) fixed at top and bottom of the testing
machine; applying the tensile load to perform testing; and plotting the curve
on load vs time by using UTM. The bolts are clamped in the UTM performing
tensile test to take the testing result by plotting the curve of yield strength,
tensile strength, bolt failure load and others which are much improvised than
15 the requirement. The test rig is configured by using two item 1 plates (01),
two item 2 plates (02) and four item 3 plates (03) welded and assembled by
using two extended thread HSFG bolts (05), nuts (06) and washer (07). The
extended thread bolts are required for structural connection in boiler
supporting steel structure.
20
[034] In the embodiment of the present invention, the solution to the prior art
problem is arrived by extending the thread in the HSFG bolts. The bolts are
shown in the figure-1 along with the table-1 for manufacturing of the extended
thread HSFG bolts. The bolt variants are reduced to 4 numbers namely
25 M24x70mm, M24x90mm, M24x130mm & M24x170mm with extended threads.
The thread dimension ‘b’ given in the normal HSFG bolts is extended to a
certain length to accommodate smaller plate thickness and is given in Table 1.
10
A typical extended thread HSFG Bolt comprises with a Bolt Head (01), a Shank
Portion (02) and a Threaded Portion (03) as shown in Figure 1.
[035] In order to carry out the mechanical tests, a test rig was exclusively
configured, detailed and fabricated as shown in figure 2. The materials used to
5 design the test rig was IS 2062 E 250. The test rig is made up of five numbers
of 25mm plates. Item 01 is the 360mm long 25mm plate and two numbers of
Item 01 plates are used in the formation of test rig. Similarly, Item 02 is also
two numbers of 25mm plate and it is of the length 300mm. Item 03 is also 25
mm plates and is of 4 numbers. The two number of item 03 and one number
10 of item 02 is welded together. After welding, the plates underwent the process
of stress relieving to strengthen the weld. Item no. 01 plate as mentioned
earlier is connecting the top and bottom piece as shown in figure-4. Two
numbers of 26mm diameter holes (Item 04) were inserted in these after
keeping in position as shown in the figure-4. The three plates were bolted
15 together with M24x170 extended thread HSFG bolts (Item 05, 06 & 07) and
torque tightening was done to the specified torque of 910Nm as shown in
figure-6. The test rig as explained above was tested in Universal Testing
Machine (item-08) and is shown in figure 6. The test rig should withstand the
shear load of 340kN.
20
[036] In the above embodiment of the present invention as shown in figure-1,
illustrates the extended thread bolts. The Figure.1 is illustrated along with the
details of Table.1. The bolt variants are reduced to 4 numbers namely
M24x70mm, M24x90mm, M24x130mm & M24x170mm with extended threads.
25 A typical extended thread HSFG Bolt is shown in Figure 1 is illustrated with Bolt
Head (1), Shank Portion (2) and Threaded Portion (3).
11
[037] Moreover, the present invention is shown in the figure 2, wherein the
test rig is configured in such a manner that it is used for keeping the extended
thread HSFG bolts M24X170 (Item 05, 06 and 07) for mechanical test and
shear failure test by using Universal Testing Machine. Item 05 is the Extended
5 Thread HSFG Bolt, Item 06 is the nut used for tightening the assembly, and
Item 07 is the washer used in the nut end side of the bolt.
[038] In another embodiment of the present invention, the figure-3 illustrates
the item no-3 and item no-4 as illustrated above. Moreover said figure
10 illustrates the 25mmx150mmx150mm plate.
[039] Moreover, in the embodiment of the present invention as shown in
figure-4 and figure -5, illustrate the item no-01, item no-02 and item no-03 as
illustrated above. Figure-3 illustrates the 25mmx150mmx150mm plate which
15 denotes item 03 plate measurement dimension. Figure-4 illustrates the
25mmx150mmx360mm plate which denotes item 01 plate measurement
dimension. Figure-5 illustrates the 25mmx200mmx300mm plate which denotes
item 02 plate measurement dimension.
20 [040] Moreover, in the embodiment of the present invention as shown in
figure-6, illustrates the test rig bolted by using extended thread (M24X170)
bolts, clamped with testing machine (universal testing machine) which is used
to test the tensile strength and compressive strength of materials.
25 [041] One embodiment of the present invention, the testing results by using
test rig bolted with HSFG bolt (M24X170) are illustrated in the table-2 to table- 6 which plays an important role in the establishment of the required objectives.
The table 7 result is taken from torque testing machine (not shown).
12
[042] The details of shear failure test and mechanical test is described herein.
The test rig and 5 extended thread bolts were subjected to mechanical tests.
The test rig was subjected to tension load. As per the design, the extended
thread HSFG bolt should not fail under shear up to a load 340kN. The extended
5 thread HSFG bolt didn’t fail for the design values as mentioned above. The
tensile test, yield strength, percentage of elongation, bolt joint failure under
shear test and head soundness test were conducted and the test values
exceeded the required capacity in all the tests conducted. The observed test
values are given in Table 2 to 7. The maximum length of M24x170 Bolt variant
10 alone is taken for test as the other variants which are shorter in length than
M24x170 shall follow the M24x170 test results.
[043] Table 1 illustrates the four variant of HSFG Bolts configured according to
the present invention. Table 1 explains the dimension of a bolt. ‘l’ is the total
15 length. ‘b, is the thread portion length. ‘lg’ is the shank portion of the bolt.
Table.1
Test Results:
20
[044] Table 2 illustrates the one variant of HSFG Bolt (M24X170) and testing
results according to the present art. Table 2 of IS3757 standard, bolt variants
are given for a length from 40 mm to 300 mm in an interval of 5mm up to 100
and 10mm interval from 100 to 300. Table 2 explains the yield strength of a
25 bolt. Yield strength is the maximum stress that can be applied before it begins
to change shape permanently.
13
Table.2
Sl.
No.
Bolt
Designation
Nominal
Cross Sec.
Area
(mm2)
Load at
Yield
(Kg)
Actual
Yield
Strength
During
Test
(N/mm2)
Required
Yield
Strength as
per table 3
of IS 1367
(part3): 2002
(N/mm2)
Test
Result
1 M24 x 170 353 31200 867 640 OK
5
[045] Table 3 illustrates the one variant of HSFG Bolt (M24X170) developed
and testing results according to the present invention. Table 3 explains the
ultimate tensile strength of a bolt. Ultimate Tensile strength is measured by
10 the maximum stress that the steel can withstand while being stretched or
pulled before breaking.
Table.3
Sl.
No.
Bolt
Designation
Nominal
Cross
Sec. Area
(mm2)
Load at
Ultimate
(kg)
Actual
Ultimate
Strength
during
test
(N/mm2)
Required
Ultimate Tensile
Strength as per
table 3 of IS
1367 (part3):
2002 (N/mm2)
Test
Result
1 M24 x 170 353 37702.9
0
1047.77 800 OK
[046] Table 4 illustrates the one variant of HSFG Bolt (M24X170) developed
15 and testing results, according to the present invention. Table 4 explains the
elongation of a bolt. The bolt is forced to stretch and elongate. This
stretching/elongation is maintained by the head of the bolt and the nut on the
joint thereby maintaining the joint at the desired tension
14
Table.4
Sl.
No.
Bolt
Designation
Initial
Gauge
Length
(mm)
Final
Gauge
Length
(mm)
Elongation
(%)
Required
Elongation
as per
table 3 of
IS 1367
(part3):
2002
(%)
Test
Result
1 M24 x 170 170 192 12.94 12 OK
5 [047] Table 5 illustrates the one variant of HSFG Bolt (M24X170) developed
and testing results by using test rig according to the present invention. Table
5 result is taken by testing the test rig. In the Universal testing machine, the
test rig is clamped in the top and bottom. The tensile load is applied. The load
vs time curve is plotted by the UTM. The maximum applied load on the test rig
10 is noted as the UTM capacity was 400 kN. Table 5 explains the details of failure
of the test rig. The test rig should withstand a load of 340 kN as per the design.
During testing, the 396 kN was applied and no failure was observed.
Table.5
Sl.
No.
Bolt
Designation
Maximum
Applied
Load
(kN)
Minimum Failure
Load (as per
requirement)
(kN)
Remarks Test
Result
1 M24 x 170 396.73 340
The Maximum
failure load of the
specimen could
not be reached,
Since the UTM
machine have
maximum capacity
OK
15
of 400 Kn. No
failure / fracture
observed in the
test rig
[048] Table 6 illustrates the one variant of HSFG Bolt (M24X170) developed
and testing results by using test rig and testing machine, according to the
present invention. Table 6 explains the failure of the bolt. As per code, the bolt
5 should withstand a load of 282.4 kN whereas in testing the bolt failed at 337.46
kN.
Table.6
Sl.
No. Bolt Designation Failure Load
(kN)
Minimum
Failure Load
(kN)
Test Result
1 M24 x 170 337.46 282.4 OK
[049] Table 7 illustrates the one variant of HSFG Bolt (M24X170) developed
10 and testing results, according to the present invention. Table 7 explains the
Torque test of the bolt. The maximum torque to be applied in the bolt is 1100
Nm whereas a maximum torque of 1368 Nm was applied and no failure is
observed. Moreover, Table 7 result is taken from the torque testing machine
(not shown). A torque wrench is used to clamp the nut and a hydraulic load is
15 applied for tightening the bolt. The maximum applied load is taken for the
calculation of torque.
Table.7
Sl. No. Bolt Designation Failure Load
(N/m)
Minimum
Failure Load
(N/m)
Test Result
1 M24 x 170 1368 1100 OK
16
The technical advantages of the present invention is illustrated in below:
TECHNICAL ADVANTAGE
5 [050] One of the advantages of the present invention is to reduce the variety
number (4) of HSFG bolts used in the structural connections of the supporting
steel structure in a thermal power plant.
[051] Another advantage of the present invention is that while testing those
bolts, the result parameters are improvised than the required value.
10 [052] Still another advantage of the present invention is that the testing value
of one variety of bolt tabulated in the detail description.
[053] Still another advantage of the present invention is that the usage of four
varieties of extended HSFG bolts provides more flexibility during erection of
structural members.
15 [054] Still another advantage of the present invention is achieving the cost
savings by reducing number of bolts required for structural connections of the
supporting steel structure.
[055] Thus, the present invention is having above advantages which are
reduced time during erection, procurement and supply which reduces the
20 construction cost indirectly.
[056] Furthermore, each of the appended claims defines a separate invention,
which for infringement purposes is recognized as including equivalents to the
various elements or limitations specified in the claims. Depending on the
context, all references below to the “invention” may in some cases refer to
25 certain specific embodiments only. In other cases, it will be recognized that
references to the “invention” will refer to subject matter recited in one or more,
but not necessarily all, of the claims.
17
[057] Groupings of alternative elements or embodiments of the invention
disclosed herein are not to be construed as limitations. Each group member
can be referred to and claimed individually or in any combination with other
members of the group or other elements found herein. One or more members
5 of a group can be included in, or deleted from, a group for reasons of
convenience and/or patentability. When any such inclusion or deletion occurs,
the specification is herein deemed to contain the group as modified thus
fulfilling the written description of all groups used in the appended claims.
10 [058] Furthermore, those skilled in the art can appreciate that the terminology
used herein is for the purpose of describing particular embodiments only and
is not intended to be limiting of the present disclosure. It will be appreciated
that several of the above-disclosed and other features and functions, or
alternatives thereof, may be combined into other systems or applications.
15 Various presently unforeseen or unanticipated alternatives, modifications,
variations, or improvements therein may subsequently be made by those
skilled in the art without departing from the scope of the present disclosure as
encompassed by the following claims.
20 [059] The claims, as originally presented and as they may be amended,
encompass variations, alternatives, modifications, improvements, equivalents,
and substantial equivalents of the embodiments and teachings disclosed
herein, including those that are presently unforeseen or unappreciated, and
that, for example, may arise from applicants/patentees and others.
25 [060] While the foregoing describes various embodiments of the present
disclosure, other and further embodiments of the present disclosure may be
devised without departing from the basic scope thereof. The scope of the
18
present disclosure is determined by the claims that follow. The present
disclosure is not limited to the described embodiments, versions or examples,
which are included to enable a person having ordinary skill in the art to make
and use the invention when combined with information and knowledge
5 available to the person having ordinary skill in the art.

WE CLAIM:
1. A method for testing the extended thread HSFG (High Strength Friction
Grip) bolts by using configured test rig, the method comprising the steps
of: - clamping the test rig bolted with two bolts, in the universal testing
machine (UTM) (08) fixed at top and bottom of the testing machine; - applying the tensile load to perform testing; and
- plotting the curve on load vs time by using UTM (08). 10
2. The method as claimed in claim 1, wherein the extended thread HSFG
bolts (05) are clamped in the UTM (08) performing tensile test to take
the testing result by plotting the curve of yield strength, tensile strength,
bolt failure load and others which are much improvised than the
requirement/ required value. 3. The method as claimed in claim 1, the percentage elongation of the
extended thread HSFG bolt is measured after the bolt failure happens.
4. The method as claimed in claim 1, wherein the test rig configured by
using two item 1 plates (01), two item 2 plates (02) and four item 3
plates (03) welded and assembled by using two extended thread bolts
(05), nuts (06) and washer (07); wherein the size of item 1 plate (01)
is 25mm thickness, 150mm breadth and 360mm long, the size of item
25 2 plate (02) is 25mm thickness, 150mm breadth and 300mm long and
the size of item 3 plate (03) is 25mm thickness, 150mm breadth and
300mm long.

5. The test rig as claimed in claim 1 and claim 4, wherein the configuration
of test rig comprises: - two number of item 01 plates (01) bolted/connected with two parts
5 of welded item 02 plates (02) and item 03 plates (03) assembly by
using extended thread HSFG bolts (05), nuts (06) and washer (07)
through two holes (item 04) for tightening the assembly, wherein
each part of welded plates (item 2 and item 3) are configured by
welding one number of item 2 plate (02) in between of two number
of item 3 plates (03).