Indian Patents. 272639:A DEVICE FOR ELONGATING STEAM TURBINE PARTING PLANE STUDS

Title of Invention	A DEVICE FOR ELONGATING STEAM TURBINE PARTING PLANE STUDS
Abstract	Present invention relates to a device for elongating steam turbine parting flange dtuds having oxygen acetylene flame obtained through a conventional blowpipe for heating up the air, a SS tube in the form of a coil; an arrangement for directing the hot air via an outlet to the inner co-axial hole of the steam turbine parting flange stud.

Full Text	2 A DEVICE FOR ELONGATING STEAM TURBINE PARTING FLANGE STUDS FIELD OF INVENTION The present invention relates to a device for elongating steam turbine parting flange studs and, more particularly, to energy efficient device and method, which can be used to heat a steam turbine parting plane stud without causing any damage to the studs during the dismantling and assembly process of steam turbine casing. BACK GROUND ART: The present invention is addressed to solving complex problems involving bolting systems required to operate at high temperatures for an extended operating time. Conventional bolting systems used to form high temperature joints, used particularly in steam turbines and similar joints, have the acute disadvantage that they become considerably weaker when the operating temperature increases. It is necessary in such a bolting system that components are designed to clamp the joint firmly without damaging the most expensive part, the main turbine casing. In some cases the clamped part may be an expensive valve body or any other component. While the present invention is not so limited, a bolting system for a main steam turbine casing has been chosen for the purpose of disclosing the present invention. At elevated temperatures of the order of 500 C to 550C, bolting parts, studs typically tensioned in a threaded tapped hole, often fail because of an improper selection of stud material. The studs soften, stretch and become loose. Other problems occur because the stud is subjected to differential expansion causing the clamped part to become loose when the stud expands faster than the clamped part and similarly the stud becomes over stressed when stud expansion is slower than the clamped part. In the latter circumstance conventional studs stretch permanently under the clamping force because the force is too great. In order to achieve proper tightness of the parting flanges of a steam turbine casing, the 3 parting flange studs are tightened in two steps, viz. (1) co(d or hand tightening and (2) tightening to a predetermined level or final tightening. The second step that is tightening up to a pre determined level is obtained as per the recommendations of the turbine manufacturer using devices mentioned by them. The principle of working of these devices can be classified into two classes: ? Device which heat the studs thereby elongating them and the heated/ elongated studs are hand tightened to a predetermined level, when the studs cool down the required level of tightness is achieved. ? Devices, which elongate the studs by means of pull force (hydraulic jack) and thereafter tightening of the studs to the predetermined level. Once the piece on the stud is released the studs achieve the acquired degree of tightness. The limitations of these devices can be outlined as follows: -(A) Devices using the heating principle :- Presently three types of devices are used to heat the steam turbine parting flange studs. They are listed below with their main disadvantages / limitations 1) Electrical heaters are inserted in the central co-axial hole of the studs. The studs are heated using low voltage high amperage current. The main disadvantage of this system is that in case of any sparking in the heaters the studs are damaged. The damage caused to the stud is very difficult to assess and such studs are likely to fail during operation of the steam turbine which may in turn lead to major breakdowns / accidents. The proper maintenance of these heaters under actual working condition is also a matter of concern. 2) Oxygen Acetylene Flame: The second method in use is heating of the studs by means of oxygen acetylene flame. The main disadvantage / limitations of this system are 4 0) Damage to the studs due to cutting by the oxy acetylene flame 0) The Oxygen Acetylene flame cannot be used in studs, which are fitted in blind holes. 3) Heating rods The third method used to heat the studs is by means of heating them by inserting red-hot mild steel rods. The mild steel rods are heated in turn by using Oxygen Acetylene flame. The main disadvantages of this system are 1) High-energy wastage due to heat loss in the process of heating the rods. 2) Time consuming process due to two step heat transfer and manual handling of the rods. 3) Safety concern due to manual handling of the red hot rods. 4) Devices using the "Pull" principle: Steam Turbines where these devices are used have specially designed studs and cap nuts. Provision is made to attach a specially designed hydraulic jack, which is attached to the stud. The main limitation of this device is that it can work only on those studs, which have provision for fixing of the jack. It cannot be used on the vast numbers of steam turbines, which do not have this provision. The device invented by us uses the heating principle. The device ensures that no damages are caused to the studs and is more energy efficient than some of the processes outlined above. SUMMARY OF THE INVENTION The present invention relates to a device for elongating steam turbine parting flange studs and, more particularly, to energy efficient device and method, which can be used to heat a steam turbine parting flange stud without causing any damage to the studs used in dismantling process and assembly of steam turbine casing. Therefore as disclosed herein a device for elongating steam turbine parting flange studs comprising of, a SS tube in the form of a coil, through which compressed hot air, heated by conventional blowpipe using oxygen acetylene flame, is directed into the central coaxial hole of the steam turbine parting plane flange stud. 5 The main objectives of our invention is to find energy efficient device which can be used to heat a steam turbine parting flange stud without causing any damage to the studs or cap nuts. The purpose of heating the Steam turbine parting flange studs is to achieve a predetermined level of elongation of the studs so that the cap nut can be further tightened without straining the threads, to arrive at the required degree of tightness which is achieved once the studs cool down. Another object of the present invention is to provide a device, which is simple to use so that it finds wide usage in turbine maintenance practice. It should have high level of safety. It should be a low cost device. As per another exemplary embodiment of the present invention the device is further developed to be simultaneously used to heat a number of studs, thus reducing the overall time required for dismantling / assembly of turbine casing. This will also help reduce energy consumption. This device can also be used to heat similar types of studs having co axial bore e.g. coupling bolts, which are hot tightened. It is another object of the present invention to provide a bolting system that will maintain a predetermined clamping force while in use at elevated temperatures; over a long time period without damage to the bolted parts. As per another exemplary objective of the present invention to use the device heat antifriction bearings mounted on shaft using interference fits with some modifications. The bearings will not be damaged because the heating medium will not harm the bearing body. Another object of the present invention is to provide a device so as to increase the life of studs and cap nut, having a simple construction, low cost with no maintenance and easy to use. These together with other objects of the invention, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which 6 there are illustrated preferred embodiments of the invention. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIG. 1 is a diagram showing the device fitted in position with the steam turbine as per the present invention. FIG. 2 is a diagram showing the test device used as first test set up as per the present invention. FIG. 3 is a table showing the test results of the first test set up as per the present invention. FIG. 4 is a diagram showing the test device used as second test set up as per the present invention. FIG. 5 is a table showing the test results of the second test set up as per the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS As per the main objectives of our invention a device which can be used to heat a steam turbine parting flange stud without causing any damage to the studs or cap nuts, so that the cap nut can be further tightened without straining the threads, to arrive at the required degree of tightness which is achieved once the studs cool down. The device works on the principle of thermal elongation of the studs. The idea is to heat the studs using a medium, which causes no harm to the studs. In order to do this compressed air is passed through a SS tube in the form of a coii. The oxygen acetylene flame obtained through a conventional blowpipe heats up the air, which is passed through the coil. The heated air is direct to the inner hole of the as can be seen in the fig 1. The outlet of the tube is designed in such a manner that the air path is not blocked by any dirt / etc which may be present at the blind hole where the tube rests. Holes are also provided at some internals on the portion of the tube, which goes inside the stud. These holes serves the purpose of providing hot air for uniform heating and for creating .7 turbulence in the air flowing at of the stud for better heat transfer. The SS coil (1) is enclosed by a Mild Steel tube (2) which is thermally insulated by asbestos packing (3) Under a cladding cover (4) this insulation reduces the loss of heat there by saving energy. A handle (5) is provided for safe handling of the device. The device is fitted with a flow control valve on the air inlet side and a thermo dial measuring the temperature of the outlet air or the heated stud. The temperature of the hot air depends on the rate of airflow and the heat input of the blowpipe with the help of valve the temperature of the outlet air, which can be controlled there by controlling the rate of heating of the stud. This coil helps in having better control over the functioning of the device. Through this modification certain mechanical parts (Bearings, Coupling) having interference fits can be heated up to exactly the required temperature. The advantages being better temperature control and no damage to the components because air as used as heating medium. Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skid in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled. 8 We Claim:- 1. Oxygen acetylene flame obtained through a conventional blowpipe for heating up the air, a SS tube in the form of a coil; an arrangement for directing the hot air via an outlet to the inner co-axial hole of the steam turbine parting flange stud. 2. The device as claimed in claim 1, wherein, the arrangement for directing the hot air is designed in such a manner that the air path is not blocked by any dirt / etc which may be present at the blind hole where the tube rests. 3. The device as claimed in claim 1, wherein, the SS coil is enclosed by a Mild Steel pipe which is thermally insulated by asbestos packing under a cladding cover, which reduces the loss of heat there by saving energy. 4. The device as claimed in claim 1, further comprises of a handle for safe handling of the device 5. The device as claimed in claim 2, wherein the outlet tube is provided with holes at some intervals on the portion of the tube, which goes inside the stud, which serves the purpose of providing hot air for uniform heating and for creating turbulence in the air flowing inside / through the stud for better heat transfer. 6. The device as claimed in claim 1, wherein, a flow control valve is fitted on the air inlet side and a thermo dial measuring the temperature of the outlet air of the heated stud. 7. The device as claimed in claim 1, wherein, regulating the flow of air controls the temperature of the stud and the SS coil helps in having better control over the functioning of the device. 8. The device as claimed in claim 1, further comprises of a thermo dial for measuring the temperature of the outlet air of the heated stud. 9 9. A device for elongating steam turbine parting plane studs, substantially such as herein described with particular reference to the accompanying drawings. To, The Controller of Patents, The Patent Office, Kolkata. Present invention relates to a device for elongating steam turbine parting flange dtuds having oxygen acetylene flame obtained through a conventional blowpipe for heating up the air, a SS tube in the form of a coil; an arrangement for directing the hot air via an outlet to the inner co-axial hole of the steam turbine parting flange stud.

Full Text

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A DEVICE FOR ELONGATING STEAM TURBINE PARTING FLANGE STUDS FIELD OF INVENTION
The present invention relates to a device for elongating steam turbine parting flange studs and, more particularly, to energy efficient device and method, which can be used to heat a steam turbine parting plane stud without causing any damage to the studs during the dismantling and assembly process of steam turbine casing.
BACK GROUND ART:
The present invention is addressed to solving complex problems involving bolting systems required to operate at high temperatures for an extended operating time. Conventional bolting systems used to form high temperature joints, used particularly in steam turbines and similar joints, have the acute disadvantage that they become considerably weaker when the operating temperature increases. It is necessary in such a bolting system that components are designed to clamp the joint firmly without damaging the most expensive part, the main turbine casing. In some cases the clamped part may be an expensive valve body or any other component. While the present invention is not so limited, a bolting system for a main steam turbine casing has been chosen for the purpose of disclosing the present invention.
At elevated temperatures of the order of 500 C to 550C, bolting parts, studs typically tensioned in a threaded tapped hole, often fail because of an improper selection of stud material. The studs soften, stretch and become loose.
Other problems occur because the stud is subjected to differential expansion causing the clamped part to become loose when the stud expands faster than the clamped part and similarly the stud becomes over stressed when stud expansion is slower than the clamped part. In the latter circumstance conventional studs stretch permanently under the clamping force because the force is too great.
In order to achieve proper tightness of the parting flanges of a steam turbine casing, the

3
parting flange studs are tightened in two steps, viz. (1) co(d or hand tightening and (2) tightening to a predetermined level or final tightening.
The second step that is tightening up to a pre determined level is obtained as per the recommendations of the turbine manufacturer using devices mentioned by them. The principle of working of these devices can be classified into two classes:
? Device which heat the studs thereby elongating them and the heated/ elongated
studs are hand tightened to a predetermined level, when the studs cool down the
required level of tightness is achieved.
? Devices, which elongate the studs by means of pull force (hydraulic jack) and
thereafter tightening of the studs to the predetermined level. Once the piece on
the stud is released the studs achieve the acquired degree of tightness.
The limitations of these devices can be outlined as follows: -(A) Devices using the heating principle :-
Presently three types of devices are used to heat the steam turbine parting flange studs. They are listed below with their main disadvantages / limitations
1) Electrical heaters are inserted in the central co-axial hole of the studs.
The studs are heated using low voltage high amperage current. The main
disadvantage of this system is that in case of any sparking in the heaters
the studs are damaged. The damage caused to the stud is very difficult to
assess and such studs are likely to fail during operation of the steam
turbine which may in turn lead to major breakdowns / accidents. The
proper maintenance of these heaters under actual working condition is
also a matter of concern.
2) Oxygen Acetylene Flame:
The second method in use is heating of the studs by means of oxygen acetylene flame. The main disadvantage / limitations of this system are

4
0) Damage to the studs due to cutting by the oxy acetylene flame
0) The Oxygen Acetylene flame cannot be used in studs, which are fitted in blind holes.
3) Heating rods
The third method used to heat the studs is by means of heating them by inserting red-hot mild steel rods. The mild steel rods are heated in turn by using Oxygen Acetylene flame. The main disadvantages of this system are
1) High-energy wastage due to heat loss in the process of heating the rods.
2) Time consuming process due to two step heat transfer and manual handling of
the rods.
3) Safety concern due to manual handling of the red hot rods.
4) Devices using the "Pull" principle:
Steam Turbines where these devices are used have specially designed studs and cap nuts. Provision is made to attach a specially designed hydraulic jack, which is attached to the stud.
The main limitation of this device is that it can work only on those studs, which have provision for fixing of the jack. It cannot be used on the vast numbers of steam turbines, which do not have this provision.
The device invented by us uses the heating principle. The device ensures that no damages are caused to the studs and is more energy efficient than some of the processes outlined above.
SUMMARY OF THE INVENTION
The present invention relates to a device for elongating steam turbine parting flange studs and, more particularly, to energy efficient device and method, which can be used to heat a steam turbine parting flange stud without causing any damage to the studs used in dismantling process and assembly of steam turbine casing. Therefore as disclosed herein a device for elongating steam turbine parting flange studs comprising of, a SS tube in the form of a coil, through which compressed hot air, heated by conventional blowpipe using oxygen acetylene flame, is directed into the central coaxial hole of the steam turbine parting plane flange stud.

5
The main objectives of our invention is to find energy efficient device which can be used to heat a steam turbine parting flange stud without causing any damage to the studs or cap nuts. The purpose of heating the Steam turbine parting flange studs is to achieve a predetermined level of elongation of the studs so that the cap nut can be further tightened without straining the threads, to arrive at the required degree of tightness which is achieved once the studs cool down.
Another object of the present invention is to provide a device, which is simple to use so that it finds wide usage in turbine maintenance practice. It should have high level of safety. It should be a low cost device.
As per another exemplary embodiment of the present invention the device is further developed to be simultaneously used to heat a number of studs, thus reducing the overall time required for dismantling / assembly of turbine casing. This will also help reduce energy consumption. This device can also be used to heat similar types of studs having co axial bore e.g. coupling bolts, which are hot tightened.
It is another object of the present invention to provide a bolting system that will maintain a predetermined clamping force while in use at elevated temperatures; over a long time period without damage to the bolted parts.
As per another exemplary objective of the present invention to use the device heat antifriction bearings mounted on shaft using interference fits with some modifications. The bearings will not be damaged because the heating medium will not harm the bearing body.
Another object of the present invention is to provide a device so as to increase the life of studs and cap nut, having a simple construction, low cost with no maintenance and easy to use.
These together with other objects of the invention, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which

6
there are illustrated preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 is a diagram showing the device fitted in position with the steam turbine as per the present invention.
FIG. 2 is a diagram showing the test device used as first test set up as per the present invention.
FIG. 3 is a table showing the test results of the first test set up as per the present invention.
FIG. 4 is a diagram showing the test device used as second test set up as per the present invention.
FIG. 5 is a table showing the test results of the second test set up as per the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As per the main objectives of our invention a device which can be used to heat a steam turbine parting flange stud without causing any damage to the studs or cap nuts, so that the cap nut can be further tightened without straining the threads, to arrive at the required degree of tightness which is achieved once the studs cool down.
The device works on the principle of thermal elongation of the studs. The idea is to heat the studs using a medium, which causes no harm to the studs. In order to do this compressed air is passed through a SS tube in the form of a coii. The oxygen acetylene flame obtained through a conventional blowpipe heats up the air, which is passed through the coil. The heated air is direct to the inner hole of the as can be seen in the fig 1. The outlet of the tube is designed in such a manner that the air path is not blocked by any dirt / etc which may be present at the blind hole where the tube rests. Holes are also provided at some internals on the portion of the tube, which goes inside the stud. These holes serves the purpose of providing hot air for uniform heating and for creating

.7
turbulence in the air flowing at of the stud for better heat transfer. The SS coil (1) is enclosed by a Mild Steel tube (2) which is thermally insulated by asbestos packing (3) Under a cladding cover (4) this insulation reduces the loss of heat there by saving energy. A handle (5) is provided for safe handling of the device.
The device is fitted with a flow control valve on the air inlet side and a thermo dial measuring the temperature of the outlet air or the heated stud.
The temperature of the hot air depends on the rate of airflow and the heat input of the blowpipe with the help of valve the temperature of the outlet air, which can be controlled there by controlling the rate of heating of the stud. This coil helps in having better control over the functioning of the device.
Through this modification certain mechanical parts (Bearings, Coupling) having interference fits can be heated up to exactly the required temperature. The advantages being better temperature control and no damage to the components because air as used as heating medium.
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skid in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

8
We Claim:-
1. Oxygen acetylene flame obtained through a conventional blowpipe for heating up
the air, a SS tube in the form of a coil; an arrangement for directing the hot air via an
outlet to the inner co-axial hole of the steam turbine parting flange stud.
2. The device as claimed in claim 1, wherein, the arrangement for directing the hot
air is designed in such a manner that the air path is not blocked by any dirt / etc which
may be present at the blind hole where the tube rests.
3. The device as claimed in claim 1, wherein, the SS coil is enclosed by a Mild Steel
pipe which is thermally insulated by asbestos packing under a cladding cover, which
reduces the loss of heat there by saving energy.
4. The device as claimed in claim 1, further comprises of a handle for safe handling
of the device
5. The device as claimed in claim 2, wherein the outlet tube is provided with holes
at some intervals on the portion of the tube, which goes inside the stud, which serves the
purpose of providing hot air for uniform heating and for creating turbulence in the air
flowing inside / through the stud for better heat transfer.
6. The device as claimed in claim 1, wherein, a flow control valve is fitted on the air
inlet side and a thermo dial measuring the temperature of the outlet air of the heated
stud.
7. The device as claimed in claim 1, wherein, regulating the flow of air controls the
temperature of the stud and the SS coil helps in having better control over the
functioning of the device.
8. The device as claimed in claim 1, further comprises of a thermo dial for
measuring the temperature of the outlet air of the heated stud.

9
9. A device for elongating steam turbine parting plane studs, substantially such as herein described with particular reference to the accompanying drawings.

To,
The Controller of Patents, The Patent Office, Kolkata.

Present invention relates to a device for elongating steam turbine parting flange dtuds having oxygen acetylene flame obtained through a conventional blowpipe for heating up the air, a SS tube in the form of a coil; an arrangement for directing the hot air via an outlet to the inner co-axial hole of the steam turbine parting flange stud.

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Patent Number

272639

Indian Patent Application Number

1396/KOL/2006

PG Journal Number

17/2016

Publication Date

22-Apr-2016

Grant Date

13-Apr-2016

Date of Filing

26-Dec-2006

Name of Patentee

STEEL AUTHORITY OF INDIA LIMITED

Applicant Address

BOKARO STEEL PLANT, BOKARO STEEL CITY-827001,

Inventors:

#	Inventor's Name	Inventor's Address
1	ROY DEEPAK	BOKARO STEEL PLANT, BOKARO STEEL CITY-827001,
2	RAY AMITAVA	BOKARO STEEL PLANT, BOKARO STEEL CITY-827001,
3	PANDEY KRISHNA BIHARI	BOKARO STEEL PLANT, BOKARO STEEL CITY-827001,

PCT International Classification Number

N/A

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA