FIELD OF INVENTION:-
The present invention relates to a device for fatigue testing of Teflon hoses
under simulated conditions. The invention particularly relates to a device where
in a Teflon hose is rigidly coupled to electromagnetic exciter and subjected to
apply a thermal, pneumatic and dynamic mechanical fatigue stresses
simultaneously and continuously and the parameters are monitored.
BACKGROUND OF INVENTION:-
In a large generator stators, winding is cooled using mainly distilled water
flowing through its hollow copper conductor. So it has electric circuit formed by
winding conductors, dielectric circuit - Insulation of winding and winding
isolators from stator body/earth - and cooling water circuit. So for electrical
isolation of winding from water headers and in turn stator body/earth, water
from header is passed into winding through very high resistance (insulation
resistance) of Teflon hoses. The Teflon hose is provided with special nuts,
washer and sealing '0' ring arrangement at both its ends and connected to
winding through a threaded nipples on header and winding bar. These Teflon
hoses are also provided with special bend/profile so that they are connected to
winding and header with minimum mounting stresses on it. Any failure of these
Teflon hoses or leakage of water through water tight joints of these Teflon hoses
during actual operation of generator at site results in a serious forced shut down
of unit resulting in disruption of power generation. Thus insulating Teflon hose is
one of the critical components in all the above three circuits and reliability of its
functioning with respect to these is of utmost significance. As such these are
rigorously tested time to time on sample basis for their performance and
reliability under accelerated ageing, especially thermo-mechanical in nature, to
which it is subjected during actual operation. This is to ensure that proper raw
materials are being used at input stage, right manufacturing processes followed
and quality norms are consistent and continually in place.
In the existing device(s) available for fatigue testing of Teflon hoses directly or
indirectly have the following disadvantages.
One disadvantage/limitation of the known device is that it employs open
loop pressure and temperature control. As such temperature and pressure
has to be controlled manually while the subject device uses commonly
available closed loop PID controllers.
Another disadvantage of the prior art device is that the water is not in
circulation but it is in static condition. This does not simulate the actual
working conditions for testing.
A further disadvantage of the prior art device is that the water in
circulation was not saline water but plain water. As such any leakage in
the Teflon Hose/its joints is difficult to detect online during the test but
gets detected only after completion of test at helium leak test stage and
there too exact location is difficult to identify/locate.
- An yet further disadvantage of the prior art device is that the water in
circulation was not saline water but plain water. Hence if there is trace of
leakage there will not be visible corrosion in spring washers behind
tightening nuts and leakage cannot be detected there.
- A still further disadvantage of the prior art device is that it does not have
anti corrosion tank and pump motor bearing which leads to frequent
break down and malfunctioning.
A still another disadvantage of the prior art device, is that it did not have
in-built automatic data acquisition, display, storage and plotting
arrangement.
In view of above the prior art system was difficult to handle and results may not
be reliable.
So it is envisaged to develop a device which enables to carry out the required
fatigue test on sample of Teflon Hoses with conformity and reliability.
OBJECTS OF THE INVENTION:-
It is therefore, an object of the present invention to propose a device for fatigue
testing of Teflon Hoses which eliminates the disadvantages of prior art.
Another object of the present invention is to propose a device for fatigue testing
of Teflon hoses which is simple and compact.
A further object of the present invention is to propose a device for fatigue testing
of Teflon hoses which saves cost and a direct means of fatigue testing of Teflon
hoses under simulated condition.
An yet further object of the present invention is to propose a device for fatigue
testing of Teflon hoses which circulates saline water for pin pointed detection of
any small invisible traces of leakage in the Teflon hose sample under test.
SUMMARY OF THE INVENTION:-
A device for fatigue testing of Teflon hoses comprising a test sample (16) of
Teflon hose, first open end of which is clamped to an outlet line of water pump
and the 2nd end of which is clamped with a discharge water line (12), forms an
interconnecting close loop of water circulation from a tank through a pump via a
pressure transmitter and one control valve, tightly coupled to an electromagnetic
exciter(6) and one electromagnetic exciter subjects Teflon hose to a
predetermined level of vibration for a fixed duration of time and one 50 litre-
water tank provided with a water heater, a temperature sensor, a temperature
indicator and one inlet and one outlet high pressure and temperature hose pipe
are also connected with water tank to circulate high temperature and pressure
water into the test loop and one pump (2) along with an attached electrical
motor (17) to create high pressure in the testing loop and a pressure gauge and
a control valve are also provided in the water flow line and one computer (4) and
Industrial Software for data acquisition and the interface communication link
between PID Controllers in the control panel; characterized in that the test
sample of Teflon hose in the close loop is subjected to circulate hot and
pressurized saline water and a predetermined level of vibration from the
electromagnetic exciter coupled with said hose for a fixed duration of time
extending to tens of hours to check and detection of any leakage of the Teflon
hose wherein pressure and temperature information/data are continuously
acquired electronically, stored and displayed in the form of graphical plots on
CRT screen of the device.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS:-
Fig. 1 shows a sketch of device and other equipments.
Fig. 2 shows a photo view of complete test set-up including the devices other
equipments required for test.
Fig. 3 shows a photo view of inter connection joints.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF
THE INVENTION:-
As shown in figure. 1, the present invention consists of an equipment for closed
loop control of temperature, flow and pressure of salted water circulating/
flowing through a sample of Teflon hose rigidly coupled to electromagnetic
exciter (6). The electromagnetic exciter (6) subjects Teflon hose to
predetermined level of vibrations for a fixed duration of time extending to tens of
hours. Pressure information/data is continuously and accurately monitored
electronically, stored and displayed in the form of graphical plots on CRT screen
(4, fig. 2).
A PUMP UNIT (2)
A high pressure triplex plunger type pump (2) is provided in set up. It has
sufficient flow rate handling capacity and sufficient discharge pressure. This
pump is having brass construction and is fitted with electric motor (17 of figure.
1) with sufficient rating compatible with required flow and pressure of water.
This pump is also having Teflon coated bearings to withstand salt water in case
of leakage of water to bearings.
SS TANK (3), HEATER (10)
One 50 litre-capacity SS tank (3) made up of stainless steel. Its inner tank is
lined with corrosion free coating and is capable to store saline water. The gap
(18 in fig.l) between inner tank and outer tank is filled with glass wool. It has
provision of separate pipe fittings (13 of fig. 1) for close loop water circulation as
well as filling of fresh water and draining out of water. It is provided with glass
type of water level indicator. The tank is provided with in built indirect heating
arrangement with two heater (10 of fig. 1) assemblies and PT100 based
Thermostat for temperature sensing (11 of fig. 1) and one temperature indicator
(19 of fig. 1).
The system is completely equipped with a high pressure and high temperature
flexible hoses (12 of fig. 1) - interconnecting tank outlet (13 of fig. 1), - pump
intel (14 of fig. 1), pump outlet (15 of fig. 1) through a control valve (20) and a
pressure gauge (21) and Teflon hoses (16 of fig. 1) under test by means of
clamps (22) for closed loop water circulation.
Water circuit has been provided with a pressure transmitter (21 of fig. 1),
pressure measurement is provided by pressure transmitter (21) and pressure
control by PID Controller and voltage to frequency converter base drive. This
provides a high level pressure control and stability in close loop control system.
DATA ACQUISITION ARRANGEMENT:-
It consists of
a) Computer (4 of fig. 2)
b) Industrial Automation Software.
c) Interface and communication link between control panel (1 of fig. 2) and
computer (4).
CONTROL PANEL AND POWER CONTROLLER:-
This power controller (1) distributes main power to various units, that is, pump
motor (19), heaters (10) refrigeration type cooler pressure transmitter (21) PID
Controller switching, indication and protection devices. This panel also provides
4-20 mA control/measurement signal to PC for logging of temperature and
pressure data.
The use of salt is made in circulating water to further indicate and confirm the
pinpointed location of leakage in Teflon hose sample under test by way of
corrosion spring water or other test assembly (1 & 2 of fig. 3).
TEST PROCESS:-
The Teflon Hose sample (16) is observed closely for any physical damage during
the testing and their status noted. The sample is subjected to test for
predetermined hours. These are checked for any physical damage/visible crack
observed during and after completion of testing. Initially salt deposition would be
found at number of location on associated pipes joints/connection assembly
other than Teflon hose joints/connection assembly. These leakages are plugged
by tightening of interconnecting joints. The salt deposits removed, nipple cleaned
shining clean, assembly of Teflon Hose under test checked. Throughout during
testing no salt deposition should be found on the nipples of Teflon hose that is
subjected to fatigue test. This indicates that there is no apparent leakage
through any Teflon Hose joints during extreme test conditions of vibration,
pressure and temperature. Teflon hose sample (16) is checked by commonly
available He(Helium) leak test technique for healthiness before and after
subjecting it for this fatigue test. (In case of even a very small trace of leakage
of salt water, traces of water gets evaporated leaving behind a visible salt
powder deposit and this is advantage in this device. In absence of this, leakage
is detected only after completion of test at helium leak test stage and there too
exact location is difficult to identify/locate. The visual indication of salt deposit at
the location of leakage in test assembly other than sample under test is shown in
Figure-3 in Annexure-I).
Further investigation can be carried out to ensure that there is no visible
corrosion in spring washers behind tightening nuts and same are intact indicating
there is no leakage of water (salt water) even to spring washer which is tightly
sealed by rubber "O" ring. Here also it is the use of salt water that leads to
corrosion of spring washer and helps detect the however small leakage is there
which otherwise would be very difficult to make out.
WE CLAIM:-
1. A device for fatigue testing of Teflon hoses comprising:-
- a test sample (16) of Teflon hose, first open end of which is clamped to
an outlet line of water pump and the 2nd end of which is clamped with a
discharge water line (12), forms an interconnecting close loop of water
circulation from a tank through a pump via a pressure transmitter and one
control valve, tightly coupled to an electromagnetic exciter;
- one electromagnetic exciter subjects Teflon hose to a predetermined level
of vibration for a fixed duration of time;
- one 50 litre-water tank provided with water heaters, a temperature
sensor, a temperature indicator and one inlet and one outlet high pressure
and temperature hose pipe are also connected with water tank to circulate
high temperature and pressure water into the test loop;
- one pump (2) along with an attached electrical motor (17) to create high
pressure in the testing loop and a pressure gauge and a control valve are
also provided in the water flow line;
- one computer (4) and Industrial Software for data acquisition and the
interface communication link between PID Controllers in the control panel;
characterized in that the test sample of Teflon hose in the close loop is subjected
to circulating hot and pressurized saline water and a predetermined level of
vibration from the electromagnetic exciter coupled with said hose for a fixed
duration of time extending to tens of hours to check and detect any leakage in
the Teflon hose wherein pressure and temperature information/data are
continuously acquired electronically, stored and displayed in the form of
graphical plots on CRT screen of the device.
2. The device as claimed in claim 1, wherein the use of definite quantity of
salt in circulating water to indicate any leakages in Teflon hose sample
that is under test.
3. The device as claimed in claim 1, wherein the use of salt in circulating
water to indicate pinpointed location of leakage in Teflon hose sample
under test.
4. The device as claimed in claim 1, wherein the water storage tank is made
of anticorrosion storage stainless steel sheet metal.
5. The device as claimed in claim 1 and 4 wherein the water storage tank is
covered with an outside steel jacket and some insulated materials are
filled in gap between the water tank and the jacket.
6. The device as claimed in claim 1, wherein one inbuilt heating coil and
refrigeration unit are provided for heating and cooling of circulating water
under closed loop PID Temperature Control.
7. The device as claimed in claim 1, wherein one inbuilt pump motor is
installed with drive control for speed control through the voltage to
frequency control giving very fine, stable and accurate speed control
hence fine pressure control in a closed loop PID Control.
8. The device as claimed in claim 1, wherein one integrated PC based data
acquisition is provided for data storage, display in given format, storage
and retrieval and provides standard analog signal outputs to be connected
to control digital data acquisition/processing system without any additional
hardware for converting data into suitable standard analog output signal.

A device for fatigue testing of Teflon hoses comprising a test sample (16) of
Teflon hose, first open end of which is clamped to an outlet line of water pump
and the 2nd end of which is clamped with a discharge water line (12), forms an
interconnecting close loop of water circulation from a tank through a pump via a
pressure transmitter and one control valve, tightly coupled to an electromagnetic
exciter(6) and one electromagnetic exciter subjects Teflon hose to a
predetermined level of vibration for a fixed duration of time and one 50 litre-water
tank provided with a water heater, a temperature sensor, a temperature
indicator and one inlet and one outlet high pressure and temperature hose pipe
are also connected with water tank to circulate high temperature and pressure
water into the test loop and one pump (2) along with an attached electrical
motor (17) to create high pressure in the testing loop and a pressure gauge and
a control valve are also provided in the water flow line and one computer (4) and
Industrial Software for data acquisition and the interface communication link
between PID Controllers in the control panel; characterized in that the test
sample of Teflon hose in the close loop is subjected to circulate hot and
pressurized saline water and a predetermined level of vibration from the
electromagnetic exciter coupled with said hose for a fixed duration of time
extending to tens of hours to check and detection of any leakage of the Teflon
hose wherein pressure and temperature information/data are continuously
acquired electronically, stored and displayed in the form of graphical plots on
CRT screen of the device.