US3537265A

US3537265A - Apparatus for condensing sealing fluid from gland structures

Info

Publication number: US3537265A
Application number: US751172A
Authority: US
Inventors: Ralph D Brown
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1968-08-08
Filing date: 1968-08-08
Publication date: 1970-11-03
Anticipated expiration: 1987-11-03
Also published as: DE1939606A1; ES370150A1; BE737038A; FR2015319A1; NL6911872A; CH512047A; GB1210368A

Description

Nov. 3, 1970 R. D. BROWN 3,537,265

APPARATUS FOR CONDENSING SEALING FLUID FROM GLAND STRUCTURES Filecl Aug. s, 1968 9 lg H1,

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7 /TI 52 L ,74 53 WITNESSES EN OR W v Rfllph D. Bro n ATTORNEY United States Patent 01 fice 3,537,265 Patented Nov. 3, 1970 3 537,265 APPARATUS FOR CONDENSING SEALING FLUID FROM GLAND STRUCTURES Ralph D. Brown, Springfield, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 8, 1968, Ser. No. 751,172 Int. Cl. F01n 3/04 US. C]. 6094 4 Claims ABSTRACT OF THE DISCLOSURE The invention comprises a condenser arrangement for a turbine gland sealing system in which a small individual condenser is located near each turbine unit in the system for condensing condensible vapor after it is employed to seal the shaft of the turbine units. The condensers are of the direct contact type in which a condensing liquid is intermingled with the condensible vapor conducted thereto to condense said vapor in an economical and space saving manner.

BACKGROUND OF THE INVENTION The present invention relates to turbine power plants and particularly to apparatus for obtaining a vacuum at the locations where turbine rotor shafts extend through the turbine end walls in order to prevent leakage of fluid out or air into the turbines along the shafts.

Fluid utilizing machines, for example steam turbines, have housing structures provided with openings in the end walls thereof through which a rotor shaft extends. To minimize the leakage of air into and steam or other motive fluid from the turbine to atmosphere, the end walls of the turbine housings are provided with sealing gland structures. The gland structures define annular spaces about the shaft which function to seal the end wall openings when a sealing gaseous fluid (usually a condensible vapor) is directed to the gland structures. The sealing fluid flows through the annular spaces to a region maintained at a lower pressure value than that of the atmosphere, for example, a gland condenser. The gland condenser condenses the fluid to form a condensate which may be further employed for useful purposes.

Presently, sealing fluid condensing arrangements employ a single gland fluid condenser to which all of the sealing fluid is piped from the gland structures. The sealing fluid is condensed and the resulting condensate is directed to the hot well of a main turbine condenser, while any air or other incondensible gas is ejected to atmosphere. The single gland condenser is of the surface heatexchange type, such as a tube and shell structure, designed to direct boiler feedwater through the tubes, the sealing fluid and air mixture entering the shell for direction around the tubes.

The present design, as broadly described above, has several disadvantages. First of all, the present design is expensive because the gland condenser must be designed to withstand the pressure of a boiler feed pump, and sized to pass a large portion of the total turbine feed water flow and handle the sealing fluid from all of the glands.

Secondly, the location of the gland condenser is determined by the boiler feed piping which requires long runs of costly pipe between the turbine glands and the gland condenser. This results in uneven vacuum conditions between the glands due to varying piping pressure losses, the distance between the condenser and one gland being different from that of another gland and so on with no two of the glands having the same length of gland piping.

Thirdly, the diameter of the pipe forming the long runs must be large to minimize pressure losses since the difference in pressure between the condenser and glands (i.e., the allowable pressure drop) is only a few inches of water, the pressure in the condenser and pipe being slightly below atmospheric to prevent leakage of the sealing fluid to atmosphere.

BRIEF SUMMARY OF THE INVENTION The present invention provides a small direct contact type gland condenser for each turbine unit with each condenser being disposed in close proximity to its associated turbine and glands. This reduces considerably the amount of large diameter piping needed to conduct the sealing fluid from the glands to the gland condensers. With such an arrangement, the actual cross sectional area piping requirement is substantially reduced in comparison to the piping required for a surface type heat exchange condenser. The reduced pipe diameter and lengths of piping produces savings in both cost and space. The cost of the smaller piping and reduced length is considerably less than that of the large diameter piping, it is easier to handle and provides installation flexibility unobtainable with the large pipes employed in present gland fluid condensing system.

Further, with the present invention, the separate gland condensers can be individually evacuated with respective small electrical air pumps which may be further hydraulically interconnected to provide continued evacuation in the event of failure of one or more of the air pumps.

THE DRAWING The invention, with its object and advantages, will become more apparent from reading the following detailed description in connection with the accompanying drawing in which:

FIG. 1 is a schematic diagram of a prior and presently used gland steam condensing system construction;

FIG. 2 is a schematic diagram of a gland steam condensing system arranged in accordance with the principles of the invention.

PREFERRED EMBODIMENT More particularly, FIG. 1 shows a diagrammatic view of the present (i.e., the prior art) method and construction for condensing a condensible vapor, such as steam, employed to seal turbine glands. Accordingly, the invention may be employed in conjunction with a turbine power plant system employing any condensible vapor, steam being the most common example, though the invention is not limited thereto. Hereinafter, the terms steam and water will be employed for simplicity and facility of understanding.

Specifically, FIG. 1 shows a closed cycle steam turbine power plant system 10 employing, for purposes of illustration, a high pressure turbine unit 3 and two

low pressure units

1 and 2 connected in tandem by shafts 4 and suitable shaft couplings 5 to drive a suitable load, for example an electrical generator 6. The turbine units are shown as centrally fed, double opposed-flow type turbines through the invention is not limited thereto.

Hot motive steam for driving the units 1 to 3 is provided by a steam generator 8 connected to the high pressure (HP) unit 3 by a suitable supply conduit 9. The steam produced by the steam generator is directed through the conduit 9 to the HP unit, and after expansion therein, is directed to the low pressure (LP)

units

1 and 2 through a reheater 12 and

main conduits

13 and 14. The main conduit '14 has

parallel branch conduits

16 and 17, re-

spectively connected to the

LP units

1 and 2.

The

LP units

1 and 2 may be of the same size and type, and, as mentioned above, may be of the well-known central admission, double opposed flow type. Accordingly,

with reference to the LP unit 1 for example, the steam is admited thereto at the center by the branch conduit 16 and thence divides, with one half of the steam flowing to the right for expansion through the right-hand expansion portion and the other half of the steam flowing through the left-hand expansion portion for expansion therethrough. After the steam is expanded through said portions, it is then directed therefrom in two streams as indicated by

arrows

21 and 22. The other LP unit 2 is operated in the same manner as unit 1 and need not be further described.

The steam directed from the

LP units

1 and 2 is vitiated or spent steam and is condensed in

turbine condensers

24 and 25 having tube bundles respectively indicated by 24A and 25A. The turbine condensers 24 and 25 may be constructed in the manner of the condensing structure shown and described in U.S. Pat. 3,194,021 issued July 13, 1965 to C. C. Peake et al. and assigned to the present assignee, or in the manner of other suitable structures. For example, the condensers may be provided with

hot well structures

26 and 27 as shown. In any case, the resulting condensate is withdrawn from the

hot well structures

26 and 27 by

condensate pumps

28 and 29, and returned to the main boiler, i.e., the steam generator 8 through a gland condenser 30 and

conduits

31 and 32.

The ends of each of the

turbine units

1, 2 and 3 are provided with glands 34 through 39, only schematically shown in the figures, each of the glands being an annular shaped structure disposed about the shafts 4 as they extend through the end walls of the units, for example, as shown and described in copending application Ser. No. 695,793, filed Ian. 4, 1968 by the present inventor and assigned to the present assignee.

All of the glands 34 to 39 are connected to the gland condenser 30 by a main conduit 41 having branch conduits 44 through 49 connected between the main conduit 41 and the respective glands. The gland condenser is further connected to the hot well 26 of the turbine condenser 24 by a conduit 43.

A condensible sealing fluid, usually steam, is directed to the glands 34 to 39 by suitable conduit means (not shown) to seal the turbines, for example as shown in the above-mentioned copending application. The steam is drawn through the glands and to the gland condenser 30 by the vacuum maintained therein by an air ejector or air pump 42 connected to the condenser.

Therefore, the gland condenser is large and of sufficient capacity to condense the steam from all of the glands and, likewise the air pump is large and of suflicient capacity to evacuate the large condenser.

In the gland condenser 30, the sealing steam is condensed and the resulting condensate is withdrawn from the condenser through the conduit 43 by the pump 28, directed to the steam generator 8 via the

feedwater conduits

31 and 32.

The gland condenser 30, as schematically represented in FIG. 1, and as presently used in systems for condensing condensible vapors employed to seal gland structures, is a large size vessel and structure of the surface heat exchange type which must be designed to withstand the feed pump pressure to the boiler 8 and dimensioned to handle the boiler feedwater flow. These requirements, in turn, require a large, expensive gland condensing structure requiring further, as mentioned above, a large and costly air pump or ejector for reducing the pressure therein.

. As further seen from FIG. 1, the location of the gland condenser 30 is primarily determined by the

feedwater conduits

31 and 32. This requires the main gland conduit 41 to be quite long with the consequent pressure losses produced thereby. The

gland conduits

41 and 44 to 49 must also have a large internal area cross section and diameter because of the limited allowable pressure drop or differential existing between the glands and the gland condenser, the pressure in the gland condenser 30 and conduit 41 being sub-atmospheric to effect the flow of sealing steam. This limited pressure drop requires an extremely low velocity flow of the sealing steam which results in the diameter of the conduits being quite large. Thus, the gland conduit is not only long, but must have a large internal diameter to minimize friction losses therealong.

In accordance with the invention, FIG. 2 shows a gland condenser arrangement in which the gland structure of each of the turbine units is provided with a relatively small, condenser of the direct contact type. Thus, the

glands

34 and 35 of the LP unit 1 are provided with their own condenser 51, said glands being connected thereto by conduits 44 and 45 respectively. Similarly the LP unit 2 is provided with its own gland condenser 52, its

glands

36 and 37 being connected thereto by

conduits

56 and 57 respectively. The HP unit 3, like the

LP units

1 and 2, is similarly provided with its own gland condenser 53, the

glands

38 and 39 of the HP unit being connected to the condenser 53 via

conduits

58 and 59 respectively. For simplicity of illustration and for comparison purposes, like numerals designate like components in FIGS. 1 and 2.

The gland condensers 51 to 53, shown schematically as a liquid spray type, have nozzle structures 61 to 63 connected to the pressure side of the

pumps

28 and 29 via conduits 65 to 67 respectively, the pump 29 shown serving two gland condensers, namely, the

condensers

52 and 53.

The bottom portion of the condenser 51 is connected to the hot well of the turbine condenser 24 via a conduit 71 while the lower portion of the

condensers

52 and 53 are connected to the hot well 27 via

conduits

72 and 73 joining a common conduit 74.

Vacuum conditions are created in the gland condensers 51 to 53 by individual

electrical air pumps

75, 76 and 77 shown connected in fluid communication with the top portion of the respective gland condensers. The gland condensers and air pumps may be further interconnected by

conduits

78 and 79 extending respectively between the

air pumps

75 and 76 and between 76 and 77.

The condensible vapor for sealing the glands 34 to 39 is directed to and through said glands, and then conducted to the respective gland condensers 51 to 53 by virtue of the vacuum conditions created therein by operation of the respective air pumps 75 to 77 and the condensation of the steam. In the condensers, the vapor is condensed by being contacted directly with a portion of the water directed from the

turbine condensers

24 and 25 by the condensate pumps 28 and 29. The water from the turbine condenser is relatively cool, having performed a heatexchange operation with the cooling fluid directed through the

tubes

24A and 25A extending through the

condensers

24 and 25.

The use of separate gland condensers allows said condensers to be disposed in close proximity to their respective turbines and gland structures thereby requiring a piping cross sectional area substantially less than that shown in the prior construction of FIG. 1. The lenthy conduit 41 (FIG. 1) is eliminated, resulting in the elimination of the uneven vacuum conditions between the glands caused thereby. Further, the separate gland condensers, as shown in FIG. 2, are not required to handle the boiler feedwater and to withstand feedwater pump pressure, thereby providing a condenser structure that is considerably less costly to make and install than that of the prior construction of FIG. 1. The pure Water condensate produced by the separate condensers 51 to 53 is, however, utilized in the feedwater system by being directed to the

turbine condensers

24 and 25, and thence to the steam generator 8.

With the three air pumps 75 to 77 interconnected by

conduits

78 and 79, the failure of one pump will not disable the system for reducing the pressure within the gland condensers. For example, if the air pump 77, associated with HP unit 3 and its gland condenser 53 failed, the remaining

air pumps

75 and 76 would continue to reduce the pressure in the condenser 53 by virtue of the interconnecting

conduits

78 and 79 and thereby maintain continued functioning of the

glands

38 and 39 of the HP unit. In a similar manner, the glands of the LP units could be maintained operative with the operation of the HP unit air pump 77 with failure of the LP

unit air pumps

75 or 76 or both.

In the prior construction, as shown in FIG. 1, the vacuum system is entirely dependent on the one air pump 42. A second, standby pump could be provided in the FIG. 1 construction, but the cost thereof would be substantial since such pumps are necessarily large in order to provide the required degree of Vacuum in so large a vessel as that forming the gland condenser 30. With the present invention, small expensive electric pumps can handle the vacuum system even with one or more disabled.

Although only one embodiment of the invention has been shown it will be obvious to those skilled in the art that the invention is not so limited, but is susceptible to various other changes without departing from the spirit thereof.

What is claimed is:

1. In a multi-unit turbine power plant having a plurality of turbine units, each of said turbine units having gland structure for sealing each unit along a turbine rotor shaft when a condensible vapor is directed to said gland structure,

apparatus for condensing said vapor comprising at least one condenser for each turbine gland structure, said condensers being located in close proximity to their associated gland structures,

conduit means connecting said gland structures to their associated condensers,

conduit means for directing a condensing liquid of high purity to each of said condensers, said liquid being of the same substance as said condensible vapor,

said condensers being of the type in which said condensible vapor is directly contacted by said condensing liquid to condense said vapor and form a homogeneous liquid mixture,

means for withdrawing the resulting mixture from said condensers for useful purposes,

said power plant including at least one higher pressure turbine unit and at least one lower pressure turbine unit,

means for conducting motive fluid to the lower pressure unit from the higher pressure unit,

a main condenser associated with said lower pressure unit for receiving vitiated motive steam therefrom and for condensing said steam to form substantially pure water,

conduit means for directing said water to the gland condensers as the condensing liquid for condensing the condensible vapor,

the condensible vapor being steam employed in the gland structures, and

the withdrawing means including conduit structure for directing theresulting water mixture to said main condenser from the gland condensers.

2. The apparatus recited in claim 1 in which the main condenser is provided with a hot well, and

the conduit means for directing the water to and from the gland condensers being connected between said hot well and the gland condensers.

3. In a multi-unit turbine power plant having a plurality of turbine units, each of said turbine units having gland structure for sealing each unit along a turbine rotor shaft when a condensible vapor is directed to said gland structure,

apparatus for condensing said vapor comprising at least one condenser for each turbine gland structure,

said condensers being located in close proximity to their associated gland structures,

conduit means connecting said gland structures to their associated condensers,

said condensers being of the type in which said condensible vapor is directly contacted by said condensing liquid to condense said vapor and from a homogeneous liquid mixture,

at least one air pump for each of said gland condensers,

and

conduit means connecting said air pumps to their associated gland condensers,

said air pumps being efiective to reduce the pressure in said gland condensers.

4. In a multi-unit turbine power plant having a plurality of turbine units, each of said turbine units having gland structure for sealing each unit along a turbine rotor shaft when a condensible vapor is directed to said gland structure,

apparatus for condensing said vapor comprising at least one condenser for each turbine gland struc ture, said condensers being located in close proximity to their associated gland structures,

conduit means connecting said gland structures to their associated condensers, conduit means for directing a condensing liquid of high purity to each of said condensers, said liquid being of the same substance as said condensible vapor,

at least one air pump for each of said gland condensers,

conduit means connecting said air pumps to their associated gland condensers,

said air pumps being eifective to reduce the pressure in said gland condensers, and

conduit means interconnecting said air pumps so that the reduced pressure within the gland condensers can be maintained by one or more of said air pumps with the failure of one or more of said air pumps.

References Cited UNITED STATES PATENTS 3,003,321 10/1961 Warth 60-95 X 3,194,021 7/1965 Peake et al. 6095 FOREIGN PATENTS 728,512 11/ 1942 Germany.

CARROLL B. DORITY, 111., Primary Examiner US. Cl. X.R. 6095