Title of Invention

A DEVICE CALLED BOOSTER PUMP RING WITH FLOW ADJUSTMENT TO ENHANCE LIFE OF SHAFT SEAL OF REACTION TYPE HYDRO TURBINE RUN BY WATER HAVING HIGH SILT CONTENT

Abstract

This invention relates to a device to enhance life of shaft seals of reaction type hydro turbines run by silt laden water comprising of a pump ring (09) having radial holes drilled into it to constitute pumping holes, springs (13) mounting plungers (15), diaphragm plugs (17) to adjust flow of water, an additional labyrinth (14) adapted on inner diameter of shaft seal cover and on the outer diameter of booster pump ring, the said device constituting an intermediate booster pump chamber between shaft seal and top cover (04), the said device when adapted with shaft seal (02) for sucking clean filtered cooling water supplied to the shaft seal, the said filtered water pressure being boosted up through booster pump ring to attain higher pressure at the discharge chamber located on the top of the labyrinth (18) between shaft (01) and top cover (04) than the top cover water pressure to guide water flow down the labyrinth (18) on shaft flange outer diameter to prevent any entry of slit particles in the shaft seal and also booster pump area, thus ensuring enhanced life of shaft seals.

Full Text

A DEVICE TO ENHANCE LIFE OF SHAFT SEALS OF REACTION TYPE HYDRO TURBINES RUN BY SILT LADEN WATER FIELD OF INVENTION This invention relates to device using a booster pump ring for enhancing the life of shaft seais of reaction type hydro turbines run by silt laden waters. More particularly, the invention relates to an improved method of sucking the clean filtered cooling water supplied to the shaft seal, boosting up the pressure in the pumping holes and discharging at a higher pressure against the Ingress of silt of the raw river water. BACKGROUND OF THE INVENTION WITH PRIOR ART DIFFICULTIES In a typical Francis type hydroelectric turbine, a shaft seal/shaft gland is a major item of the turbine which seals the turbine against 3 the high pressure river water which drives the turbine; thus preventing flooding and subsequent stoppage, of the turbine. The shaft seal is positioned above the turbine runner and shaft coupling on the top cover. It consists of a sealing element of rubber or carbon or asbestos- resin composite which presses against a cylindrical stainless steel sleeve which rotates along with the shaft. Filtered river water is forced through the sealing elements and the rotating sleeve to serve the following purposes. 1. To lubricate the rubbing surfaces. 2. To cool the surfaces heated up due to rubbing. 3. To keep the rubbing surfaces free of silt particles carried by the river water. This is achieved by forcing clean filtered water at a pressure higher than the pressure of water in the top cover below the shaft seal. 4 The quantity of clean filtered water required for the shaft seal is a very small percentage of the total requirement of cooling water required for generator air coolers, turbine and generator bearing coolers and the transformers. The pressure at which cooling water is to be supplied is decided by the pressure, which the copper alloy tubes of the coolers can safely sustain. This pressure is generally in the range of 5 kg/sq. cm. Since the cooling water to shaft seal is at a pressure of 5 kg/sq. cm, the pressure in the cop cover below the shaft seal should in no case exceed 5 kg/sq. cm to prevent flow reversal and ingress of siit particles into the shaft seal. This is achieved by suitably designing the labyrinths fitted on top cover and runner. In high head turbines operated by silt laden water, the labyrinths wear out faster, and the pressure in the top cover below the shaft seal soon exceeds the pressure of cooling water supply to shaft seal. This results in reversal of flow; causing ingress of silt particles into 5 the shaft seal, leading to wear of the sleeve fitted on the shaft. In the existing practice a rubber lip type shaft seal is used through which the sealing takes place by two layers of rubber lip seal with cooling water forced through between the rubber lip and the rotating shaft sleeve. The cooling water lubricates and cools the rubbing items viz. the rotating shaft sleeve and rubber lip seals. Also the cooling water being at a higher pressure than the pressure below the shaft seals in the top cover, it prevents the silty water from entering into the shaft seal, when the labyrinth is healthy. This arrangement of shaft seal functions satisfactorily when the peripheral rubbing velocity between the shaft sleeve and the rubber lips is low and the silt content in the river water is low. But this seal does not function satisfactorily when either the peripheral velocity is high or silt content is high. 6 In another prior art reference a carbon ring type shaft seal is used in which the sealing takes by two layers of carbon rings (in segments) pressed radially inwards by garter springs with cooling water forced through between the carbon rings and the rotating shaft sleeve. The cooling water lubricates and cools the rubbing items viz. the rotating shaft sleeve and the carbon rings. Also the cooling water being at a higher pressure than the pressure below the shaft seal in the top cover, it prevents the silty water from entering into the shaft seal. This seal can work satisfactorily when the peripheral velocity is high but gets worn out when silt content Is high. The present invention has proposed to solve the aforesaid difficulties of prior art. 7 OBJECTS OF THE INVENTION One object of this invention is to enhance the life of shaft seal for reaction type hydro turbines run by silt laden water. Another object of the invention is to reduce the pressure of water below shaft seal by sucking in the filtered water supplied to the shaft seal. A still another object of the invention is to prevent ingress of silt particles into shaft by boosting the water pressure in the pumping holes to a value higher than pressure of water in the top cover below the shaft seal. A further object of the invention is to restrict the increased discharge through the pump ring when the turbine accidentally goes to runaway speed. Yet another object of the invention is to adjust the flow through pump ring to match site conditions. 8 SUMMARY OF THE INVENTION In the present invention, for enhancement of life of shaft seals of reaction type hydro turbines, ring with pumping holes is placed below the shaft seal, to suck in the filtered water supplied to the shaft seal. The pumping hole boost up the pressure of water coming out from the shaft seal and discharge it down through the labyrinth gap on shaft flange outer diameter, into the space below top cover. Thus, in spite of wearing of the main labyrinths and increase of water pressure in the space between top cover and runner, the raw unfiltered water containing silt particles is not able to enter the shaft seal, as the discharge pressure of the pumping holes would be higher than the raw water pressure which is built-up even with worn-out labyrinths. According to the invention there is provided a device to enhance life of shaft seals of reaction type hydro turbines run by silt laden water comprising of a pump ring being an annular shaped disc made out of 9 plate having radial holes drilled into it to constitute pumping holes, springs loaded plungers operated through retaining screw, diaphragm plugs provided in the threading on the outer end of the radial pumping holes to enable part of the holes totally plugged or filled with the diaphragm plugs to adjust flow of water, an additional labyrinth being adapted by way of stainless steel deposition on inner diameter of shaft seal cover and bronze deposition on the outer diameter of booster pump ring, the said device constituting an intermediate booster pump chamber between shaft seal and top cover (04) when adapted with shaft seal pressing against a stainless steel sleeve of a shaft for sucking clean filtered cooling water supplied to the shaft seal, the said filtered water pressure being boosted up through pumping holes of booster pump ring to attain higher pressure at the discharge chamber located on the top of the labyrinth between shaft and top cover than the top cover water pressure to guide water flow down the labyrinth on shaft flange outer diameter to prevent any entry of silt particles in the shaft seal and also booster pump area, thus ensuring enhanced life of shaft seals. 10 DESCRIPTION OF THE INVENTION The outage of turbines due to failure of shaft seal is very high in hydel projects of Himalayan region, where the silt content in the river waters is very high. This problem becomes even more acute In case of high head turbines. Detailed investigations into the problem revealed that the main turbine labyrinths between runner and top cover wear out very fast due to high silt content. Once the labyrinths wear out, the pressure in the top cover increases. When the top cover water pressure increases to a value higher than the pressure of cooling water to shaft seal, flow reversal takes place. With flow reversal, the silt laden raw river water enters into the space between the rotating shaft sleeve and the sealing element of rubber sheet and /or carbon rings. The silt particles having a high quartz content wear off the shaft sleeve to such a limit that the turbine pit gets flooded by water from the top cover below shaft seal. 11 The solution to this problem lies In preventing entry of silt particle Into the shaft seal. This Is a two pronged solution. I) To prevent the top cover water pressure after labyrinth from building up. ii) To force down cooling water through shaft seal at a pressure higher than top cover pressure. For the first case, use of hard stainless steel or stainless steel with hard coatings enhanced the useful life of labyrinths by a small amount. Shifting of the labyrinth radially inward from the outer diameter of runner to somewhere closer to runner discharge diameter enhanced the life of labyrinths a bit at the cost of a heavy top cover, but the problem still persists. 12 The other approach of forcing down cooling water through shaft seal at a pressure higher than top cover water pressure is limited by the safe working pressure of the copper alloy tubes of the turbine and generator coolers. When the above two approaches have not been able to solve the persisting problem of the industry fully, creating an intermediate booster pump chamber between shaft seal and top cover was adapted to enable the cooling water to shaft seal discharging into an intermediate chamber. This intermediate chamber becomes the suction chamber of a pump which would boost up the shaft seal discharge water pressure to a pressure higher than the top cover water pressure even after labyrinth wear. The discharge of this booster pump is to be directed against the top cover water. The ring forming partition of the booster pump suction and discharge chamber become the pump itself. 13 The present invention will be better understood from the following description with reference to the accompanying drawing in which:- Figure 1 represents a rubber lip type shaft seal of a prior art practice 1. Figure 2 represents detail of prior art practice 1 of the rubber lip type shaft seal. Figure 3 represent a carbon ring type shaft seal prior art practice 2. Figure 4 presents detail of prior art practice 2 of the carbon ring type shaft seal. Figure 5 represents overall arrangement of turbine with booster pump below shaft seal according to the present invention. Figure 6 represents enlarged view of shaft seal with booster pump according to the present Invention. 14 Figure 7 represents a plan view of shaft seal with booster pump ring according to the present invention. Figure 8 represents enlarged view of booster pump of the present invention. Figure 9 represents plan view detail of booster pump ring of the present invention. Figure 10 represents enlarged view of throttling at runaway speed according to the present Invention. Figure 11 represents plan view detail of booster pump ring at throttling according to the present invention. Figure 12 represents the seal with electric pump for low speed turbine according to the present invention. 15 Figures 1 and 2 show the existing rubber lip type shaft seal of reaction type hydro turbines. The sealing element (02) presses against a ss sleeve (05) which rotates along with the shaft (01). The sealing takes place by two layers of rubber lip seal (02) pressing against the stainless shaft sleeve (05) and cooling water Is forced through between the rubber lip and the rotating shaft sleeve. The cooling water lubricates and cools the rubbing items viz. the rotating shaft sleeve and rubber lip seals. Also, the cooling water is at a higher pressure than the pressure below the shaft seal in the top cover (04) and prevents the silt laden water from entering into the shaft seal. This arrangement of shaft seal functions satisfactorily when the peripheral rubbing velocity between the shaft sleeve and the rubber lips is low and the silt content in the river water is low. Labyrinth (03) is employed to reduce pressure in the top cover below the shaft seal. 16 This seal does not function satisfactorily when either the peripheral velocity is high or silt content is high. Figures 3 and 4 show another existing carbon ring type shaft seal. In this arrangement, the sealing takes place by two layers of carbon rings (in segments) (07) pressed radially inwards by garter springs (08) Cooling water is forced though between the carbon rings (07) and the rotating shaft sleeve (05). The cooling water lubricates and cools the rubbing items, the rotating shaft sleeve and the carbon rings. Also, the cooling water being at a higher pressure than the pressure below the shaft seal in the top cover (04), it prevents the silt laden water from entering into the shaft seal. 17 This arrangement of shaft seal functions satisfactorily even when the peripheral velocity is high. But if the water has higher silt content this arrangement is not satisfactory. As such, shaft sealing has remained an area of concern with frequent maintenance requirements. The proposed invention presents an effective answers to address this difficulty. Figure 5 to 12 show in detail the adaptation of the booster pump with booster pump ring with shaft seal and throttling to solve the difficulties of prior art as discussed above. Inside the shaft sealing cavity, on the shaft flange, the pump ring (09) is placed. This is a disc manufactured out of plate of suitable thickness and has radial holes drilled in it. It is placed on the shaft flange in an annular spigot fitted groove below the shaft seal 18 housing. The filtered clean cooling water which is supplied at the rubber lips of the shaft seal (02) finds its way down the shaft sleeve (05) to the cavity below the shaft cover. The radial holes act as pumping holes and this water is pumped to attain a higher pressure at the outer diameter of the pump ring. The discharge chamber of booster pump ring is located on the top of the labyrinth (18) between shaft (01) and top cover (04). The water pressure in this discharge chamber would be sufficiently higher than the top cover water pressure. This would ensure that water necessarily flows down the labyrinth on shaft flange outer diameter and thereby prevents entry of silt particles even into the booster pump area leave aside the shaft seal. Additionally, a labyrinth (14) has been provided on the outer diameter of booster pump ring. This labyrinth (14) is adapted by way of stainless steel deposition (11) on inner diameter of shaft seal cover and bronze deposition (12) on outer diameter of booster pump ring and both machined to give fine running clearance. This labyrinth minimizes partial recirculation i.e., 19 discharge water of booster pump leaking back into the suction chamber area where there is low pressure. The radial pumping holes are provided with threading/tapping on the outer end so that some of the holes can be either totally plugged or filled with diaphragm plugs (17) to adjust flow requirements. Safeguards for runaway speed: The discharge through the booster pump ring would be dependent on speed. At higher than normal running sped, the rubber iip would be heated more due to the increase in peripheral rubbing speed. There could be an increase in discharge through booster pump ring leading to more cooling water being sucked in between the rubber lips and shaft sleeve. However, to thwart-off any eventuality of starvation of shaft seal due to excessive discharge at runaway speed a special safeguard has been provided. 20 The radial pumping holes are connected vertically to anther series of radial holes located just above them and fitted with spring loaded plungers (15) and retaining screw (16). The spring (13) is so constructed that during normal speed running of the turbine, the plungers do not block the water passage. If and when the turbine accidentally goes to run-away speed, the plunger will overcome the spring force due to higher centrifugal force and would partially block the passage of water though the hole. This will prevent increased suction of cooling water through the shaft seal at the higher speed. The increased suction could have led to starvation of cooling water to shaft seal. Any increase of discharge through the pumping holes is restricted and therefore, the shaft seal is not starved of cooling water and is safeguarded at runaway speed condition. The pumping holes are also fitted with plugs with diaphragm holes drilled in them, a number of which can be taken off to control the total pumping effect. 21 Adaptation for low speed turbine: In case of turbines where the rotational speed is low, the head developed in the pumping holes may not be higher than top cover water pressure to prevent flow reversal and entry of silt into the shaft seal. For such cases, instead of a shaft driven booster pump ring with pumping holes, an electrically operated booster pump will be installed as shown in figure 12. Its suction pipe will be connected to the chamber formed below shaft seal and above the disc which will form a labyrinth (14) on the outer diameter with the shaft seal cover. The discharge of the booster pump is connected to the chamber formed below the rotating disc. In this way, top cover water containing silt laden water is prevented from entering the shaft seal. Augmentation of worn-out labyrinths: In high head turbine operated by very high silt laden water the main labyrinth between top cover and runner wear out very fast, leading to increase of top cover water pressure. The shaft mounted booster pump would oppose the ingress of top cover water to a large extent. However, 22 during floods, the wear of laybyrinths become excessive and the turbine cannot be stopped for labyrinth replacement on account of generation loss. In such situations an electrically operated pump would augment the capacity of shaft mounted booster pump ring and postpone labyrinth replacement to a leaner period. For such a case, the suction and discharge pipes of the electrical pump would be connected as shown in figure 12. The invention as herein described with an illustrative embodiment should not be read and construed in a restrictive manner as various modifications, alterations and adaptations are possible within the scope and ambit of the invention as defined in the encompassed appended claims. 23 WE CLAIM 1. A device to enhance life of shaft seals of reaction type hydro turbines run by silt laden water comprising of a pump ring (09) being an annular shaped disc made out of plate having radial holes drilled into it to constitute pumping holes, springs (13) mounting plungers (15) operated through retaining screw (16), diaphragm plugs (17) provided in the threading on the outer end of the radial pumping holes to enable part of the holes totally plugged or filled with the diaphragm plugs to adjust flow of water, an additional labyrinth (14) being adapted by way of stainless steel deposition (11) on inner diameter of shaft seal cover and bronze deposition (12) on the outer diameter of booster pump ring, the said device constituting an intermediate booster pump chamber between shaft seal and top cover (04), the said device when adapted with shaft seal (02) pressing against a stainless steel sleeve (05) of a shaft (01) for sucking clean filtered cooling water supplied to the shaft seal, the said filtered water pressure being boosted up through pumping holes of booster pump ring to 24 attain higher pressure at the discharge chamber located on the top of the labyrinth (18) between shaft (01) and top cover (04) than the top cover water pressure to guide water flow down the labyrinth (18) on shaft flange outer diameter to prevent any entry of siit particles in the shaft seal and also booster pump area, thus ensuring enhanced life of shaft seals. 2. A device to enhance life of shaft seals as claimed in claim 1 wherein the intermediate chamber acts as a suction chamber of the booster pump, the booster ring forming partition of the booster pump suction and discharge chamber being the pump itself. 3. A device as claimed in claim 1 wherein the SS deposition (11) and bronze deposition (12) provide fine running clearance on machining. 25 4. A device as claimed in claims 1 and 3 wherein the additional labyrinth (14) minimise partial reclrculation of discharge water of booster pump leaking back into the suction chamber area. 5. A device as claimed in claim 1 wherein safeguard for runaway speed are provided through centrifugal throttling by connecting radial pumping holes vertically to another series of radial holes located just above them and fitted with spring mounted plungers and retaining screws so that during normal running speed of the turbine the plungers do not block the water passage and in accidental runway speed, the plunger will overcome the spring force due to higher centrifugal force and partially block the passage of water through the holes to prevent increased suction of cooling water through the shaft seal at the higher speed and thus to safeguard the shaft seal not starved of cooling water. 6. A device as claimed in the preceding claims wherein in case of turbines with low rotation speed, instead of a shaft driven booster 26 pump ring with pumping holes, an electrically operated booster pump is installed as shown in figure 12, by connecting the suction pipe to the chamber formed below the shaft seal and above the disc to form a labyrinth (14) on the outer diameter with the shaft seal cover, the discharge of the booster pump being connected to the chamber formed below the rotating disc, thus preventing top cover water containing silt laden water to enter the shaft seal. 7. A device to enhance life of shaft seals of reaction type hydroturbines run by silt laden water as herein described and illustrated. Dated this 9th day of April 2007 This invention relates to a device to enhance life of shaft seals of reaction type hydro turbines run by silt laden water comprising of a pump ring (09) having radial holes drilled into it to constitute pumping holes, springs (13) mounting plungers (15), diaphragm plugs (17) to adjust flow of water, an additional labyrinth (14) adapted on inner diameter of shaft seal cover and on the outer diameter of booster pump ring, the said device constituting an intermediate booster pump chamber between shaft seal and top cover (04), the said device when adapted with shaft seal (02) for sucking clean filtered cooling water supplied to the shaft seal, the said filtered water pressure being boosted up through booster pump ring to attain higher pressure at the discharge chamber located on the top of the labyrinth (18) between shaft (01) and top cover (04) than the top cover water pressure to guide water flow down the labyrinth (18) on shaft flange outer diameter to prevent any entry of slit particles in the shaft seal and also booster pump area, thus ensuring enhanced life of shaft seals.

Documents:

00563-kol-2007-abstract.pdf

00563-kol-2007-claims.pdf

00563-kol-2007-correspondence others 1.1.pdf

00563-kol-2007-correspondence others.pdf

00563-kol-2007-description complete.pdf

00563-kol-2007-drawings.pdf

00563-kol-2007-form 1.pdf

00563-kol-2007-form 18.pdf

00563-kol-2007-form 2.pdf

00563-kol-2007-form 3.pdf

00563-kol-2007-gpa.pdf

563-KOL-2007-(13-01-2012)-ABSTRACT.pdf

563-KOL-2007-(13-01-2012)-AMANDED CLAIMS.pdf

563-KOL-2007-(13-01-2012)-AMANDED PAGES OF SPECIFICATION.pdf

563-KOL-2007-(13-01-2012)-CORRESPONDENCE.pdf

563-KOL-2007-(13-01-2012)-DESCRIPTION (COMPLETE).pdf

563-KOL-2007-(13-01-2012)-DRAWINGS.pdf

563-KOL-2007-(13-01-2012)-FORM 1.pdf

563-KOL-2007-(13-01-2012)-FORM 2.pdf

563-KOL-2007-(13-01-2012)-OTHERS.pdf

563-KOL-2007-(13-01-2012)-PETITION UNDER RULE 137.pdf

563-KOL-2007-CORRESPONDENCE 1.1.pdf

563-KOL-2007-CORRESPONDENCE 1.2.pdf

563-KOL-2007-EXAMINATION REPORT.pdf

563-KOL-2007-FORM 18.pdf

563-KOL-2007-FORM 3.pdf

563-KOL-2007-GPA.pdf

563-KOL-2007-GRANTED-ABSTRACT.pdf

563-KOL-2007-GRANTED-CLAIMS.pdf

563-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

563-KOL-2007-GRANTED-DRAWINGS.pdf

563-KOL-2007-GRANTED-FORM 1.pdf

563-KOL-2007-GRANTED-FORM 2.pdf

563-KOL-2007-GRANTED-LETTER PATENT.pdf

563-KOL-2007-GRANTED-SPECIFICATION.pdf

563-KOL-2007-OTHERS.pdf

563-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-00563-kol-2007-fig12.jpg

abstract-00563-kol-2007-fig8.jpg