US2020456A - Shaft packing suitable for steam turbines - Google Patents

Description

Nov. 12, 1935. s. s. cooK 2,020,455

SHAFT PACKING SUITABLE FOR STEAM TURBINES Fi1ed.Sept. 16, 1953 3 Sheets-Sheet l ATTORNEYS Nov. 12-, 1935.. s, s, COCK 2,020,456

SHAFT PACKING SUITABLE FOR STEAM TURBINES 'Filed Sept. 16, 1953 5 Sheets-Sheet 2 H. F? TUR B/NE L. P. TURBINE L. P. TURBINE z RESERVOIR I TURBINE Jay-z.

ATTORNEYS Nov. 12, 1935. '5, s co 2,020,456

SHAFT PACKING SUITABLE FOR STEAM TURBINES Filed Sept. 16, 1933 3 Sheets-Sheet 3 5 LEAK arr TO 4 CON DIN mam 4 mama q I BY I 1 ATTORNEYS mimic mam .Ti

Patented Nov. 12, 1935 U ITED STATES' PATENT OFFICE- SHAFT PACKING SUITABLE FOR STEAM TURBINES England Application September 16, 1933, Serial No. 689,781 In Great Britain September 19, 1932 7 Claims.

The invention relates to shaft packings suitable for steam turbines and particularly to packing systems of the kind commonly known as the reservoir type, the main object of such systems being to maintain an equal pressure slightly above atmosphere in all the outer pockets of the glands so that leakage to the engine room may be reduced to a negligible quantity, consistent, however, with obtaining an indication, by such leakage, that the gland system is functioning properly.

The main object of the present invention is to provide improved or alternative forms of such packing systems. a

With this main object, the invention consists in improved shaft-packing systems suitable for steam turbines, as hereinafter described and particularly pointed out in the claims.

Referring to the accompanying diagrammatic drawings Figure 1 shows a plan view of one form of the invention applied to a cross-compound turbine unit having high-pressure and low-pressure sections;

Figure 2 being a plan view of a system of the kind shown in Figure 1 duplicated for application to a twin-screw marine installation;

Figure 3 is a similar view of a modified system in which direct connections are provided between the high-pressure and low-pressure inner gland pockets at both ends of the turbine sections, with the reservoir symmetrically placed between these cross connections;

Figure 4 shows an arrangement in which the reservoir is unsymmetrically disposed, and

Figure 5 a modification of the system shown in Figure 4, in which the want of symmetry is to some extent reduced; while finally Figure 6 shows a structural form of the invention in which the reservoir capacity is in part provided by horizontal collectors.

The same reference symbols are used in the different drawings to denote corresponding parts.

In carrying the invention into efiect, one form is shown in Figure 1 applied to a steam turbine installation having a high-pressure section, a, and a low-pressure section, b, in separate casings, through the ends of which the turbine shafts, c and d respectively, pass.

Taking the high-pressure 'turbine'by way of example, the packings at both ends are of the labyrinth type, arranged in three lengths, a a (1. with intermediate outer and inner gland pockets, a and a respectively.

A steam reservoir, e, of any suitable form is provided to which the outer gland pockets, 0. at each end of the high-pressure turbine section, a, are connected by the pipes, a and the inner gland pockets by the pipes, a].

Corresponding parts associated with the lowpressure turbine section are denoted by the letter b with the appropriate numerical suflix.

The reservoir, 6, is provided with a supply of live steam, f, controlled by a suitable valve, h, either manually or automatically operated, which likewise determines the amount of leak-off from the reservoir to the condenser by way of the pipe, 2', the control valve being ported as shown so that only the live steam supply, ,1, or the leak-off, i, can be connected to the reservoir at a given moment.

If the pipe connections are of sufiicient volume, the reservoir may be of small size or serve merely as a junction piece.

With the arrangement described, the general flow of leakage steam is from the high-pressure turbine, a, to the low-pressure turbine, b, by way of the reservoir, e. Thus, leakage steam at each I end from within the high-pressure turbine a, will pass along the packing, a to the inner pocket, a and there divide, the greater part of it flowing directly through the pipe connection, a", therefrom to the reservoir, e, and the balance passing on through the intermediate length of labyrinth packing, a to the outer pocket, a whence it passes through the connection, a to the reservoir.

A similar flow occurs in the case of the lowpressure turbine, b, but in the opposite direction. Thus, steam at each end from the reservoir, e, passes to the inner pocket, b mainly through the connection, W, a small part, however, passing through the connection, b to the outer pocket, b and thence through the intermediate length of labyrinth packing, W. The flow of the combined streams then continues through the length of packing, b to the interior of the lowpressure turbine, b, which is assumed to be at a pressure below atmosphere.

An excess or defect of leakage from the highpressure turbine, a, into the reservoir, e, compared with that required for the low-pressure glands can be readily adjusted by operating the control valve, 71., of the reservoir to connect to the live-steam supply, 1, or leak-off, 2', to condenser as required, the object aimed at by such adjustment being to maintain a pressure in the reservoir slightly above atmospheric.

It will be seen that if the pipes between the gland pockets and the reservoir have only a small resistance to the flow of steam in relation to the resistance of the length of packing between the pockets the pressures in the outer pockets of the different glands can be maintained substantially uniform by the manipulation of only a single valve.

In the case, say, of the high-pressure turbine,

since the resistance of the packing, a between the pockets is large in relation to the resistance of the inner-pocket pipe connection, a' the rate of outward flow through this packing is very small, and since the resistance of the outerpocket pipe connection, a is also small,'the pressure difference necessary to produce a flow from the outer pocket to the reservoir will be very small.

In the case of the low-pressure turbine, the rate of flow through the packing from the outer pocket, D to the inner pocket, b is also very small, and the pressure difference necessary to produce the flow of steam from the reservoir to the outer pocket through pipe, b is also very small.

A uniform pressure slightly above atmosphere is thus readily maintained in all the outer gland pockets.

In a particular application of the invention above described, applied to a twin-screw marine installation, (see Figure 2) the port high-pres- 7 sure turbine is denoted by the letter a, and the port low-pressure turbine by the letter Z), the corresponding turbines on the starboard side being denoted respectively by the letters m and n. Each set of turbines has its own reservoir, (the port reservoir being indicated at 0 and the starboard at 10) connected to all its outer and inner gland pockets, as shown in Figure 2 with a system of reference symbols similar to that of Figure 1, the two reservoirs being connected to a common control valve, h, with connections, f and i, to the live-steam supply and leak-off to the condenser as before, while a shut-off valve, 0 13 is provided in addition between the control valve, h, and each reservoir so that in the event of one set of turbines being inoperative, the whole of its gland system may be isolated from that of the other set.

According to a modified form of the invention, (see Figure 3) the high-pressure inner gland pockets, a are directly interconnected by the pipes, r, to the low-pressure inner gland pockets, b at both ends of the turbine stages, similar inter-connections, 8, being provided between the high-pressure and low-pressure outer gland pockets, a, 12 Each of these inter-connections, r, 1', in turn is connected to the reservoir, 6, by a branch pipe, T and each of the inter-connections, s, by a branch pipe, 8

With this arrangement, the resistance to trans fer of steam from high-pressure to low-pressure gland pockets is reduced to a minimum, since not only is the length of piping itself reduced, but the losses due to stopping the flow of steam on entering the reservoir and accelerating the steam on leaving the reservoir are also eliminated or greatly reduced. The direct interconnections, 1', s, serve to conduct the bulk of the leakage steam from the high-pressure to the low-pressure pockets while the branch connections, T 8 to the reservoir conduct only the steam necessary for removing a surplus or supplying a deficiency, as the case may be.

Preferably, the reservoir, e, is arranged symmetrically between the pockets at the two ends of the turbines, as shown in Figure 3, but if this is not convenient, the reservoir, e, (see Figure 4) may be placed wholly on one side of the interconnections, 1', s, in which case, in respect of the inner gland pockets, a b a branch, r passes from the inter-connection, r, therebetween at one end to the inter-connection at the other end and continues as r to the reservoir, e, and similarly for the outer gland pockets, a 22*, the branch connecting the inter-connections being lettered s and its extension s If a more symmetrical arrangement is desirturbines are inter-connected by a commonpipe,

which is in turn provided with a connection to the reservoir, the outer pockets having a similar set of connections.

Structural details of the systems above described may take various forms and in particular (see Figure 6) a considerable part of the capacity of the reservoir may take the form of a large collector pipe, t, running horizontally and so disposed between the turbine stages that the inner gland pockets, a b can be directly connected thereto by short lengths of pipe, t t running at right angles tothe axis of the collector pipe.

A horizontal collector pipe, u, of preferably smaller capacity may serve a similar function in respect of the outer gland pockets, (1, b.

The control valve, h, may either be connected to the reservoir directly or by way of a length of pipe, so that, in the latter case, it may be disposed in a suitable position for convenient manipulation.

In any of the systems described above, if one or more of the glands is or are used to pack against such a pressure as to require only a small quantity of steam for packing, a single-pocket type gland may be substituted for a two-pocket gland.

Variations may be made in the details of the systems above described, both as regards the structure of the glands and the number and arrangement of the turbines, without exceeding the scope of the invention.

I claim:

1. Shaft-packing system for the shafts ot elastic-fluid prime movers having a higher-pressure and a lower-pressure stage, comprising in combination packing for said shafts, said packing in respect of each of said stages comprising two end packings, two gland pockets spaced apart between said end packings, and a packing intermediate said gland pockets and serving as a leakage-flow path from one to the other of said gland pockets; together with a reservoir system including separate connections to said gland pockets in both said higher-pressure and said lower-pressure stages.

2. Shaft-packing system suitable for steam turbines, comprising two' end packings and two gland pockets spaced apart between said end packings, and packing intermediate said gland pockets and serving as a leakage-flow path from one to the other of said gland pockets; a reservoir system including separate connections to each of said gland pockets; a steam supply to' and a leak-off from said reservoir system; to-

gether with means for controlling said supply and said leak-off, said controlling means being such that only said supply or leak-01f can be operative at a given time.

3. Shaft-packing system for the shafts of elastic-fluid prime movers, comprising in combination a higher-pressure and a lower-pressure prime-mover stage disposed side by side, each of said stages including shafts and packing for said shafts at each end, each of said packings comprising two end packings, two gland pockets spaced apart between said end packings and a packing intermediate said pockets and serving as a leakage-flow path from one to the other of said pockets; a. reservoir system including separate cross connections between corresponding gland pockets at each end of said prime-mover stages and including also a reservoir properly disposed symmetrically between said stages and also between said cross connections; together with other connections between said reservoir proper and each of said cross connections.

4. Shaft-packing system for the shafts of elastic-fluid prime movers, comprising in combination a higher-pressure and a lower-pressure prime-mover stage disposed side by side, each of said stages including shafts and packing for said shafts at each end, each of said packings comprising two end packings, two gland pockets spaced apart between said end packings, and. a packing intermediate pockets and serving as a leakage-flow path from one to the other of said pockets; 'a reservoir system including separate cross connections between corresponding gland pockets at each end offsaid primemover stages and including also a reservoir proper disposed wholly on one side of all of said cross connections; together with connections between said reservoir proper and each of said cross connections.

5. Shaft-packing system for the shafts of twin elastic-fluid prime-mover plants, each plant comprising in combination a higher-pressure and a lower-pressure prime-mover stage disposed side by side, each of said stages including shafts and.

packing for said shafts at each end, each of said packings comprising end packings, two gland pockets spaced apart between said end packings, and a packing intermediate said pockets and serving as a leakage-flow path from one to the other of said gland pockets; each plant comprising also a reservoir system including separate connections to said gland pockets at each end of said higher-pressure and said lower-pressure stages and including also a reservoir proper; together with a direct connection between said reservoirs proper associated with said different plants and means for controlling flow of fluid through said direct connection.

6. Shaft-packing system for the shafts of elastic-fluid prime movers having a higher -pressure and a lower-pressure stage comprising in respect of each of said stages the following juxtaposed elements, namely, a first length of packing at the prime-mover end of the packing sys tem, a first gland pocket, a second length of packing, a second gland pocket and a third length of packing, together with a reservoir system including separate connections to said first and second gland pockets in both said higher-pres sure and said lower-pressure stages.

7. Shaft-packing system as claimed in claim 6, in which said connections include direct connections between the second gland pockets of said higher-pressure and said lower-pressure stages.

STANLEY SMITH COOK.

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