A METHOD AND DEVICE FOR THE THERMAL FATIGUE TESTING OF
THICK WALLED LARGE SIZE CYLINDRICAL COMPONENTS
FIELD OF THE INVENTION
The present invention is related to the method and a device for the testing
of thermal fatigue testing of thick walled large size cylindrical components
such as tubes and pipes. Pressure bearing tubes and pipes with huge
thicknesses are used in the boiler fabrication. These tubes and pipes are
subjected to differential heating during service. The cyclic stresses induced
during differential heating causes thermal fatigue, one of the damage
mechanisms of boiler components and severely affects the service life of
boiler components. More particularly the present invention discloses a
method and a device for the testing of thermal fatigue testing of thick walled
large size cylindrical components by simulating the damage mechanism on
the testing component and helps to predict the service life of component by
validating the service conditions using experimental trials.
BACKGROUND OF THE INVENTION
The large size thick walled tubes and pipes are used in the fabrication of
boiler components. During service the components are subjected to high
temperature. When they are heated inside by the steam, inner
circumference of the component is heated suddenly. The sudden heating
causes the immediate vicinity of inner circumference to reach very high
temperature leading to thermal expansion. At the same time, the
temperature at outside circumference is different. This difference is very
high when the component is suddenly heated or suddenly cooled. Such a
sudden heating or cooling of component occurs when boiler is started after
shut off or sudden cooling for repair works. During heating, inside surface
experiences sudden expansion which is prevented by the colder outside
surface of the component leading to thermal strains. Similarly during rapid
cooling, inside surface is suddenly

cooled and this is prevented by the nearby hotter outer surface leading to
thermal strain. The thermal strain reaches a plastic state due to very high
temperature differential and number of cyclic operations leading to
permanent damage. The damage further progresses leading to crack in the
component thereby reduces the life of the component.
There are thermal fatigue testing systems available which are applicable for
specimen level testing. The miniature specimens are either cylindrical or
hour glass type specimen prepared out of material to be tested. There are
some special wedge type specimen are used in case of turbine component,
where also specimens are prepared out of turbine blade material. More over
specimen level testing is simple than the component level testing. However
thermal fatigue depends on mainly the internal restraints offered by the
component. The internal restraints and other related conditions on a
specimen level testing is simple and is complicated on the component level
testing. Hence, there exists a difference always in results between specimen
and component level testing. It is therefore the component level testing of
pressure vessel is proposed in the invention. Thick walled boiler tubes and
pipes are considered as specimen for the testing in the proposed device and
testing method. The dimensions considered is not the reduced dimension,
instead only length is reduced to be used in the device. Also detailed data
collection and automatic control of testing parameters is proposed in the
invention.
PRIOR ARTS
US 7559251 B2-Themethod and an device for forming thermal fatigue
cracks on a non-magnetic pipe. The pipe was heated using induction coil and
cooled by means of water and nitrogen with pressurizing motor. The tensile
and compressive loads can also be applied through the flanges attached at
the end of the pipe. Thereby thermal fatigue cracks were formed for the
performance demonstration of NDT. The method of thermal cycle analysis,

control of heating and cooling time details are not available and the main
interest is to prepare a sample specimen for the NDT requirements. Also the
specimen is positioned horizontally, during cooling this may lead to non-
uniform heating around the circumference.
CN 103234739 B-A thermal fatigue equipment and test method proposed
for cylinder head. The test system consists of basic test stand, high and low
double loop liquid cooling system thermostat, diesel supply and flame
heating systems, and data acquisition and control systems. A dummy
cylinder head assembly is fixed over the actual cylinder wherein cooling
arrangement is provided. This type system can only be used for the internal
combustion engine cylinder heads, may not be applicable for other
components.
US 5,967,660–is related to the accelerated thermal fatigue testing of
engine combustion chamber. The method involves directly impinging flame
heating on the combustion chamber and cooling it suddenly using
pressurized water jet. Flame heating cannot be employed for the thick
walled component and also flame heating causes non-uniform heating of
uneven surfaces. This method is mainly applicable for low temperature
differentials and not applicable high temperature heating.
US 7,985,370 B2- The invention is related to a device for forming
longitudinal thermal fatigue cracks. In this invention, the cooling is controlled
directionally around circumference of the pipe by providing additional tubular
cooling member. Inside the pipe notches were created so as to create the
longitudinal cracks on the pipe. Also opposite ends of the pipe was
restrained using tension bars. The data collection techniques are not
available. Also the main intention of the system is to demonstrate the NDT
performance for the nuclear application.
US 8,360,632 B2–This invention is related to thermal fatigue system in
which heating and cooling is provided using air and cooling gas respectively.
Air is heated first using a heating coil and it is circulated through the testing

specimen and cooling is also provided using nitrogen or carbon dioxide gases
in order to maintain uniform heating and cooling of the specimen. This
cannot be used where high thick components are used for testing, as sudden
cooling and heating may not be possible.
All of these inventions are related to the testing method and a device for the
thermal fatigue testing of pipe and engine combustion chamber component.
In general the testing systems are tailor made for different applications. The
heating system using induction heating method is applicable to large size
component. Flame heating and hot air heating appears to be difficult and
leads to non-uniform heating in case of thick walled large size component.
Also heating and cooling takes more time rather than sudden heating and
sudden cooling. In most of the inventions, the method of data collections
and parameter control instruments are not available which is an important
requirement for the testing device.
Hence, the thermal fatigue testing system for the thick walled pipe is not
readily available and has to be customized. The present invention is aimed at
developing a system with advanced data collection and control facilities so
that both the circumferential and longitudinal thermal fatigue cracks are
simulated on the testing component. This requires both the external and
internal restraints are induced and controlled as per the testing requirement.
The thermal cycle and plastic deformation data can be stored and processed
for the further analysis.
OBJECTS OF THE INVENTION
The object of the invention is to develop a simple testing device and method
to test the thick walled tube and large size pipe for the thermal fatigue
testing of pressure vessel component.

Another object of the invention is to develop testing device and method to
simulate both the circumferential and longitudinal thermal fatigue cracks
using induction heating and water cooling system.
A further object of the invention is to develop a device and method for
thermal fatigue testing that ensures detailed data collection and storage of
the same during the testing and automatic control of testing parameters and
restraint conditions.
A still further object of the invention is to develop a device and method for
thermal fatigue testing that ensures simple construction and low cost.
The detailed data collection and storage of the same during the testing and
automatic control of testing parameters and restraint conditions is evolved.
The simple construction and low cost device for the thermal fatigue testing is
another important feature of the invention.
SUMMARY OF THE INVENTION
According to the invention, a new device (A) for the testing of thermal
fatigue and testing method for the thick walled tube and pipe component (1)
is disclosed. The testing device (A) is constructed in such a way that both
external and internal restrains can be incorporated on the testing component
(1). The external and internal restraints are in turn induces longitudinal and
circumferential cracks on the testing component. The test considers the
original dimension of the component (1) and not the reduced dimension for
the testing component. Hence for the thick walled tube and pipe, the
thickness and diameter of the component (1) is as per the application
requirement, only length of the component is reduced to suit the testing
device.

The thick walled tube or pipe with length of furnace used in the device (A).
The ends of the circular component (1) is closed using dummies (2,2). The
dummies (2,2) are welded with suitable inlet (5) and outlet (4) provisions
along with the bolting arrangements (3). Thermocouple (6) is spot welded
with component (1). The testing system consists of housing arrangement in
which induction cylindrical furnace (11) is installed firmly. The device (A)
also houses furnace controller (12), high frequency data logger (13) with
personal computer (14), tension bolts (9) to induce external restraint on the
testing component.
The testing tube or pipe with dummies (2,2) and thermocouple (6) installed
on it, is inserted in the cylindrical furnace and is bolted with the test rig. The
tension bolts (7) offer external restraint to the testing component (1) in the
longitudinal direction. The water inlet (5) and outlet (4) connections are
given to the testing component. There is a drain cock (9) available in the
inlet (5), as the testing component is kept in the vertical position. Drain cock
(9) helps in draining excess water available in the testing component after
testing is over. Displacement sensors (10,10) are also positioned at both the
ends of the testing component (1). This helps in monitoring elongation and
contraction of the testing component during heating and cooling operations,
thereby ensuring the sufficiency of restraints. Thermocouple (6) is helpful in
monitoring the temperature of testing component (1) and gives feed back to
the furnace controller. The thermal cycle and number cycles undergone by
the testing component is obtained from the thermocouple (6). The
thermocouple (6) and displacement sensors (10,10) are connected to the
data logging system (13) which is connected to the personal computer (14)
in the test device. The personal computer (14) stores all the testing
parameters, thermal cycle, number of cycles, displacement experienced by
the testing component, etc. This helps in data analysis during testing.

The furnace (11) is started using controller (12) and after the set
temperature is reached, the furnace controller (12) gives warning alarm and
the current to the furnace (11) is tripped. At this time, water is allowed
through the inlet hose (5). This lead to the sudden cooling of inside
circumference of the testing component (1). The water comes out of the
outlet (4) hose after cooling the testing component. Now the inlet hose (5)
is closed and the water available inside the testing component is drained out
using drain cock (9) available in the inlet hose (5). The complete draining is
possible as the testing component is kept in vertical position and draining
takes place by gravity. After complete draining, the drain cock (9) is closed
and furnace (11) starts heating the component to the preset temperature
and cycle continues. The circumferential restraint is internal and is
happening due to the temperature differential during sudden cooling
operation. The testing device is strongly configured using structural beams
and supported by the strong legs. Different size of testing components (1)
can be housed in the testing device (A) accordingly induction heating system
will be adjusted.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 – The schematic view of the preparation of testing component
Figure 2 – The schematic view of the thermal fatigue testing device
Figure 3- The schematic view of the thermal cycle obtained after the testing
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
According to the invention, there is disclosed a method and testing device
for the thermal fatigue setting of cylindrical thick walled component. The
testing device consists of fixed rigid frame, testing component, furnace,
furnace

controller, thermocouple, displacement sensors, data acquisition system,
onboard personal computer and water supply for the testing. The thick
walled testing component is closed at both ends using dummies welded with
water inlet and outlet. The testing component is positioned inside the
furnace and is bolted with the device frame. Water inlet and outlet hoses are
connected. The induction furnace heats up the testing component and the
temperature of the specimen is monitored using thermocouple. After the
specimen has reached its pre-set temperature, water is allowed through the
inlet hose which suddenly cools the testing component and leaves the
component through outlet. The various testing parameters such as
temperature, cooling time, number cycles are recorded using data
acquisition system and is recorded in the onboard personal computer. The
constructional details pertaining to the thermal fatigue testing device for the
thick walled cylindrical components is explained with reference to the
accompanying drawings.
The following are the different parts that comprise the thermal fatigue
testing device for the thick walled cylindrical components.
1) Testing component
2) Welded dummy
3) Locking bolts
4) Water outlet
5) Water inlet
6) Thermocouple
7) Tension bolt
8) Water inlet check valve
9) Drain cock
10) Displacement sensor
11) Induction furnace
12) Furnace controller
13) Data acquisition system

14) Personal computer
15) Fixed frame
16) Furnace support
The testing component to be used in the testing device is shown in Figure 1.
The thick walled tube or pipe (1) is closed at its both ends using dummy (2)
with welding. At one end of the testing component, the welded dummy (2)
consist of locking bolts (3) and nuts with water out let valve (4). The other
end of the testing component (1) consists of welded dummy (2) and water
inlet valve (5). The thermocouple (6) is fixed on the testing component (1)
using spot welding technique. To test this testing component (1), the
thermal fatigue device is proposed and is shown in Figure 2.
The testing component (1) is positioned inside the induction heating furnace
(11) which is positioned on the furnace support (16). The testing component
is rigidly fixed with frame (15) using locking bolts (3) and tension bolts (7).
The furnace (11) heats up the testing component (1) to the pre-set
temperature in the furnace controller (12). Once the temperature of the
testing component (1) to the pre-set temperature, furnace controller (12)
gives warning signal and pressurized water inlet is allowed to the testing
component (1) through water inlet check valve (8). Water suddenly cools the
testing (1) component and leaves the testing component through water
outlet valve (4). Then the water inside the testing component (1) is released
using the drain cock (9). Again heating and cooling cycle continues as per
the requirement. During this heating and cooling cycle, the expansion and
contraction of the testing component (1) is monitored using displacement
sensors (10) provided at both the ends of the testing component (1). The
testing parameters are captured using the data acquisition system (13) and
the data analysis and monitoring is carried out using onboard personal
computer (14). The thermal fatigue testing history of the testing component
is shown in Figure 3.

WE CLAIM
1. A device for the thermal fatigue testing of thick-walled large cylindrical
components comprising:
a thick-walled tube and pipe component (1) positioned inside an
induction heating furnace (11), the combined setup positioned on the
furnace support (16), and rigidly fixed with the frame (15) using locking
bolts (3) and tension bolts (7), the testing component (1) selected on
actual dimension in the width or circumferential direction and with
reduced dimension in the longitudinal direction;
the longitudinal ends of the circular component (1) being closed by
dummies (2,2);
the said dummies (2,2) are welded with suitable inlet (5) and outlet (4)
along with bolting arrangement for sending water inside the jacket;
the said water inlet (5) are provided with check valve (8) for controlling
water;
the testing component (1) being housed in a setup (A), when the
furnace is heated using a furnace controller (12), a high frequency data
logger (13) with personal computer (14) for data acquisition and
monitoring purpose, the system connected with a thermocouple (6) for
temperature control and displacement sensors (10) provided at both
ends for monitoring expansion and contraction;
a drain cock (9) provided at inlet (5) for draining water after the testing
is over.
2. The device as claimed in claim 1, wherein a thermocouple (6) is spot
welded with component (1) and connected with data acquisition system
(13) for recording the temperature of testing component (1) and giving
feedback to the furnace controller (12).

3. The device as claimed in claim 1, wherein a plurality of displacement
sensors (10,10) are provided at both ends of components (1) and
connected to the data logging system (13) and personal computer
(14) for monitoring elongation and contraction of the testing
component during heating and cooling operation.
4. The device as claimed in claim 1, wherein the inlet hose (5) is
provided with water inlet check valve (8) for allowing water inside the
component (1).
5. The device as claimed in claim 1, wherein the inlet (5) is provided
with a drain cock (9) for draining water from the system by gravity.
6. A method for the thermal fatigue testing of thick-walled large size
cylindrical component comprising:
heating the furnace using controller for reaching the set
temperature;
allowing the furnace controller fill it gives warning alarm for tripping
the current to the furnace;
allowing the water to pass through the inlet (5) hose.