US3003321A

US3003321A - Steam turbines

Info

Publication number: US3003321A
Application number: US639780A
Authority: US
Inventors: Warth Laurence Hugo Frederick
Original assignee: English Electric Co Ltd
Current assignee: English Electric Co Ltd
Priority date: 1955-01-31
Filing date: 1957-02-12
Publication date: 1961-10-10
Anticipated expiration: 1978-10-10

Description

Oct. 10, 1961 H. F. wARTH 3,003,321

STEAM TURBINES I Filed Feb. 12, 1957 2 Sheets-Sheet 1 FIG. 1

INLET# IUI CONDENSER COLD FIG.2

Oct. 10, 1961 L. H. F. wAR-rH 3,003,321

STEAM TURBINx-:s

Filed Feb. 12, 1957 2 sheets-sheet 2 FIG.3

WINLET Resv.

.v-wif REDUCING v.

lsoLATlNG v.

United States Patent 3,003,321 STEAM TURBINES Laurence Hugo Frederick Warth, Rugby, England, asslgnor to The English Electric Company Limited, London, England, a British company Filed Feb. 12, 1957, Ser. No. 639,780 Claims priority, application Great Britain Jan. 31, 1955 1 Claim. (Cl. 60-64) The present patent application is a continuation in part of the patent application Ser. No. 558,960, now abandoned, of Laurence Hugo Frederick Warth, assignor to The English Electric Company Limited, tiled on January 13, 1956.

I'he invention relates to condensing steam turbines the shafts of which have to be sealed where they pass through the housing against the flow of air into or the flow of steam out of the housing.

This sealing is usually effected by means of steam packed glands having pockets to which steam from an external source is applied as a sealing medium when the internal pressure of the turbine is below atmospheric pressure. In condensing turbines the sealing of these glands usually requires continual adjustment of valves in operation to allow for variations in the internal pressure of the machine, and this is done either by hand or automatically by means of special valves.

According to the present invention, I provide sealing means for the shaft of a steam turbine having at least one turbine housing, a rotor shaft journalled therein, and a main turbine condenser, comprising in combination: a source of sealing steam, glands mounted on the ends of the said turbine housing and extending Voutwardly therefrom sealing the said rotor shaft with respect to the said housing, pockets being arranged in the said glands at different distances from the interior of the said housing, those pockets which are arranged nearer to the said housing being in direct fluid communication with the said main turbine condenser, and those pockets which are arranged further away from the said housing being in iluid communication with the said source of sealing steam, venting means in uid communication with the said glands, and additional pockets provided in the said glands, outwardly of the said pockets in fluid communication with the said source of sealing steam, the said venting means being in fluid communication with the said additional pockets. Preferably, it comprises a source of sealing steam, glands mounted on the ends of the said housing sealing the said rotor shaft with respect to the said housing, and venting means, pockets being arranged in the said glands, at least one of the said pockets being in fluid communication on the opposite side of the said source of sealing steam and with the said venting means.

A needle valve is provided between a main isolating valve'- and a regulating throttle valve in the pipes connecting the source of sealing steam to the associated pockets in the glands at both ends of the turbine.

A pressure gauge is connected to the said pipe downstream of the said needle valve, and this enables the operator to adjust the said needle valve with ease and accuracy When starting up the turbine.

The regulating valves in the pipes leading from the source of sealing steam to the associated gland pockets are initially set in conjunction with the said needle valve (without water yet liowing through the condensers) to give the correct ow of steam to each gland, and to maintain a pressure of, say, 20 p.s.i.g. at the gauge. The regulating valves are then locked in position. Subsequently, when starting up, the operator has only to adjust the needle valve to maintain the reading of the said pressure gauge at the pressure adjusted previously.

This arrangement has proved particularly advantageous Patented Oct. 10., 1961 'ice for multi-housing turbines where one needle valve only has to be 'adjusted instead of four or six valves as in the previous arrangements.

In order that the invention may be clearly understood and readily carried into elect, two embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 diagrammatically shows a simple arrangement for a single housing turbine,

FIG. 2 shows a detail of FIG. l on a larger scale,

FIG. 3 diagrammatically shows an arrangement for a multi-housing turbine.

Referring rst to FIG. 1, the single-housing turbine 1 has a shaft 2 passing through a gland 3 at the high pressure end, and through a gland 3 `at the low pressure end of the turbine housing.

The gland 3 at the high pressure end has three consecutive pockets; the pocket 11 in the middle of the gland is connected by a pipe 12 to the main condenser 13 of the steam turbine which has conventional means for producing sub-atmospheric pressure in the condenser 13 indicated diagrammatically as a spray of cold water and a pump for the condensate.

The pocket 14 nearer to the cylinder 1 is connected by a pipe 15 to an intermediate stage of the turbine so as to reduce leakage losses from the high pressure end of the turbine to the condenser.

The pocket 6 farther away from the housing 1 is connected on top to a vent condenser denoted 5 as -a whole and to be described in more detail later with reference to FIG. 2, and on the bottom to a pipe 7 which is counected to a source of sealing steam (not shown) with an isolating valve 10, a strainer 16, a needle valve 17 and a regulating valve 8 having locking means 18 arranged in said pipe 7 in succession.

From the said pipe 7 a pressure gauge 19 and a branch pipe 7 branch oif between the said needle valve 17 and regulating valve 8. This pipe 7 leads through another regulating valve 8 having locking means 18' to a pocket 26 in the gland 3 at the 10W pressure end of the housing 1, nearest to this housing. Another pocket 4 farther away from the housing 1 is connected to a vent condenser 5 corresponding to the vent condenser 5 of the gland 3 at the high pressure end of the cylinder 1.

Cooling water is supplied by pipe 21 to a pipe coil 20, and yis discharged by pipe 22 (FIG. 2). Steam enters by pipe 25 and is condensed, discharging at the bottom into a tundish 24 and hence to drain. The body is vented at 23 to atmosphere. The said pipe 25 is connected to the top of pocket 6 at the high pressure end of housing 1 or to the pocket 4 at the loW pressure end (FIG. l).

Preparatory to starting up the turbine plant according to FIG. l, the regulating

valves

8 and 8 are initially set in conjunction with the needle valve 17 to give the correct ow of steam to each gland 3, 3', and to maintain a pressure of, say, 20 p.s.i.g. at the gauge 19. This setting is carried out at light load and without water liowing through the vent condensers, so that wisps of steam at the vent can be used as an indication of correct sealing. The regulating

valves

8, 8 are then locked in position by the locking means 18, 18', respectively.

Subsequently, when starting up, the operator has to adjust only the single needle valve 17 to maintain the reading of, say, 20 p.s.i.g. on the gauge 19 in order to keep satisfactory sealing conditions at the glands 3, 3'.

The pressure in the pockets 6 of the gland 3 will then be above atmospheric pressure by virtue of the pressure drop of the surplus steam flowing to the vent condenser 5, which itself is at atmospheric pressure.

Referring now to FIG. 3, the high pressure housing 1 and the low pressure cylinder 101 of a multi-housing turbine have their

shafts

2 and 102 respectively passing 3 t outside through glands 3, 3' Iand 103, 103', respectively. 'Ihe gland 3` onthe high pressure end of the high pressure housing 1 has four

poclets

6, 11, 9 and 14, the last mentionedpocliet beingnearestltoathe housingl. 'Ihe gland 3f, at the exhaust end of the highpressure housing 1` has two pockets 6', 11', the last mentionedv oneV being nearest to the housing-1. Y Y

TheV low pressure housingj101 is built symmetrically, the two low pressure stagesbeing at-the-ends, 'where glands 103 and 103' have pockets-104, 126 and 104', 126 respectively, therpockets 126 and V126' beingnearest to the housing 101. Sealing steam is admitted through astrainer 16, isolating valve and needle valve 17 to a pipe 7 having from which low pressure steam is tapped oi and passed through pipe 113 to a heater (not shown).

The pockets 6 and 6' of the high pressurehousing are connected, at points opposite the connection of these pockets to the sealing steam pipes 7, 7', and to vent

condensers

5, 5 ofthe kind described hereinabove with reference to FIG. 2.

The pockets 104, 104' of the low pressure housing 101 are likewise connected to vent condensers 105, 105' respectively of this type. The pockets 9, V14 at the high pressure end of the high pressure housing'l are connected to the exhaust end of the saidhousing 1V and to anintermediate stage of the said high pressure housing 1,-respectively, the saidV intermediate stage being vtapped and connected to a heater (not shown) by a pipe 115.

The operation and starting up of the gland system of this plant is similar to that described hereinabove in detail with reference to FIG. 1.v It will, however, be noted that aV single needle valve 17 serves here for adjusting the supply and pressure of sealing steamto all four glands 3, 3', 103103' of both thev high pressure 4 housing 1 and the low pressure housing 101. The advantage of the invention as regardsV simplicity of operation is accordingly even greater than in the single housing turbine plant according to FIG. 1.

With this arrangement, areducing Valve 27 in line with an isolating valve 30 arranged in a by-pass 29 bridging over the isolating valve 10 and needle valve 17 is used to maintainY the pressure of 20 p.s.i.g. except for starting up and shutting down. An impulse connection 28 connects the reducing valve 27 Withrthe line 107. The actual changeover from needle valve 17 to reducing valve 27 or conversely is carried out by opening or closing the isolating valve 30. This arrangement is of particular use when the pressure of the steam supply varies considerably.

What I claim'as my invention and desire t-o secure by Letters Patent is:

Sealing means for the shaft of a steam turbine having Y a housing having a high pressure end and a low pressure end, a rotor shaft journalled therein, and a main turbine condenser, comprising a combination: a source of sealing steam, a gland mounted on the highpressure end of said turbine housing and extending outwardly therefrom sealing the s'aid rotor shaft with respect to the said housing, annular pockets being arranged Vin the said gland at different distances from the interior of the said housing, one of said pockets which is arranged furthest from the said housing'being in direct uid communication with said source ofrsealing steam, an intermediate pocket being in uid communication with said turbine condenser, and venting means in fluid communication with a pocket which is arranged further from the housing than said intermediate pocket.

References Cited inthe file of this patent 'UNrTED STATES PATENTS 1,246,039 Baumann Nov. 13, 1917 1,450,421 Kavanaugh et al. Apr.V 3, 1923 1,757,212 Parsons et al. May 6, 1930 1,759,074 Van Rijswijk May 20, 1930 1,910,811 Peterson May 23, 1933 2,236,274 Riceet al. Mar. 25, 1941 2,332,150 Huff Oct. 19, 1943