US2636754A - Seal for hydrogen-cooled generators - Google Patents

Description

April 28, 1953 Filed Sept. 13, 1949 INVENTOR ATTORNEY Patented Apr. 28, 1953 SEAL FOR HYDROGEN-COOLED GENERATORS Rene A. Baudry, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 13, 1949, Serial No. 115,505

3 Claims. C1. 286-9) My invention relates to hydrogen-cooled polyphase generators, or other machines which have a substantially hermetically tight, hydrogenfilled housing, with the hydrogen at higher than atmospheric pressure, and having a rotatable shaft extending through the housing, with a gland seal surrounding said shaft Where it extends through said housing, and means for pumping or forcing oil through said gland seal. The oil which is supplied to the gland seal escapes partly to the air side, and partly to the hydrogen side of the seal. Heretofore, it has frequently been necessary to vacuum-treat the oil before it is supplied to the seal, in order to remove as much air and moisture as possible, from the oil, before allowing that portion of the oil which escapes to the hydrogen side of the gland seal to come into contact with the hydrogen gas in the machine, where it would give up air and moisture to the hydrogen. This has involved expensive and cumbersome apparatus to vacuum-treat the seal-oil.

Although my invention is not limited to any particular type of machine, it may be noted that, in a typical generator to which my invention is applicable, the average oil-flow is 3 G. P. M. (gallons per minute) from the air side of the seal, and 1% G. P. M. from the gas side. It is reasonable to assume that the oil flowing to the air side picks up 10% of air by volume. The air-side drain-oil would therefore contain in solution 57% cu. ft. of air per day. The oil to the gland seal will consist of 3 parts air-side oil to 1 parts gas-side oil. Therefore oil to the gland seal would have in solution air by volume. The amount of air brought to the gas side would be 1% X 6.4%=.l1 G. P. M. 01' approximately cubic feet per day. To maintain a 95% gas purity, it would be necessary to supply 400 cubic feet of make-up h drogen per day. This large amount of make-up hydrogen would usually be prohibitive. from an economic standpoint, and it is for this reason that a vacuum oil-treating system has commonly been used heretofore.

If this make-up hydrogen can be kept below 100 cubic feet per day, the vacuum-treating system can be eliminated.

It is an object of my present invention to provide for a slow, continuous leak-off of hydrogen from the area immediately surrounding the hydrogen side of the gland seal, and to use this leak-off hydrogen to wash or scrub the air-side oil which comes out of the air side of the gland seal, so that most of the air and moisture is removed from said air-side oil before it is recirculated through the seal. In this way, the rate of air-transfer, into the hydrogen-cooled machine, through the recirculation of the seal-oil, can be kept down to a figure which is low enough to admit of the use of a small amount of make-up hydrogen, which is quite satisfactory from a commercial standpoint.

A further object of my invention is to provide a novel type of orifice-Valve for controlling the amount of leak-off hydrogen, as such a valve presents certain problems because of the extremely slow rate of hydrogen-flow which must be provided, and also because of the small molecular size of the hydrogen-gas, Which makes it particularly difiicult to accurately control its flow through very small passages.

With the foregoing and other objects in view, my invention consists in the systems, combinations, structures, parts and design-methods hereinafter described and claimed, and illustrated in the accompanying drawing, the single figure of which is a diagrammatic cross-sectional simplified showing of apparatus illustrating one form of embodiment of my invention.

In the drawing, I have shown one end of a hydrogen-cooled machine, having a substantially hermetically-tight, hydrogen-filled housing or casing l, including a substantially upright bearing-bracket 2. The bearing-bracket has a bearing-receiving opening 3 therein, in which is disposed an oil-lubricated bearing 4. The casing I contains hydrogen at higher than atmospheric pressure, and this hydrogen is recirculated, within the machine, as by means of fans 5. The rotor 6 of the machine is mounted on a shaft I which extends through the bearing 4. so as to pass through the portion of the casing which is shown in the drawing.

As is usual in such machines, a gland-seal structure I l is provided being illustrated as being secured to the inside of the bearing-bracket 2, in a position suitable for providing a gas-tight seal I2 which surrounds the shaft at a point on the hydrogen side of the bearing. This gland seal i2 is provided for the purpose of preventing, as much as possible, the escape of hydrogen from the housing at the point where the shaft extends through the housing. Oil must be continuously supplied to this gland seal 12, through a suitable oil-feed pipe IS. The oil which is supplied to the seal enters the seal near its center, and flows to the surface of the shaft, at which point the oil divides and moves in both directions along the shaft, that is, both toward the air side of the seal and toward the hydrogen side of the seal, as is known in the art.

As is customary in the art, I provide a small hydrogen-chamber IE immediately surrounding the hydrogen side of the seal 12, this small hydrogen-chamber being separated from the hydrogen-filled housing, or from the main filling of hydrogen-gas within said housing, through a long and restricted clearance-space l surrounding the shaft 7, a suitable labyrinth it being provided for this purpose. In order to dispose of the seal-oil which escapes from the hydrogen side of the gland seal I2, it is necessary to drain this oil from said small hydrogen-chamber it, through a drain-hole H which leads to a combined defoaming-tank and gas-trap IS. The liquid oil is drained from this oil-tank i8 through a suitable drain-pipe l9, under the control of a float-valve 20. In accordance with my present invention, I provide the top part of the oil-tank it, above the oi1-level therein. with a continuously operating, slow-hydrogen-leak-oif passage which may be adjusted to permit hydrogen-flow at the rate of anywhere from 9 to 80 or 100 cubic feet per day, or such other amount as may be desirable in any particular machine. This leak-off hydrogen is thus drawn from the top of the gas-trap or oil-defoaming tank l8, and hence this leakoff hydrogen is drawn, through the large drainopening I I, from the small hydro en-chamber M which immediately surrounds the hydrogen side of the gland seal l2.

The slow-hydrogen-leak-ofi passage 23 preferably includes a special kind of orifice-valve 24, comprising a ring-member 25 and a plug-member 26 hav ng close tolerance 21 therebetween, Any suitable means is provided, for causing the leak-ofi hydrogen to pass axially through said tolerance 27, such means being illustrated in the form of an axially drilled hole 28 in the plug 26, and one or more communicating axial holes 29, wh ch supply the leak-off hydrogen to an annular groove 3!! in said plug 25. The hydrogen then escapes axially along the tolerance or clearance 2? between the plug 26 and the ring 27, thus reaching a space 3!, from which the hydrogen escapes through a pipe or opening 32. The rate of gas-flow through this special orifice-valve may be controlled by means of a hand-wheel 33 which adjusts the axial position of the plug 26 w thin the ring 25, so as to control the axial length of the hydrogen-passage through the tolerance 27. The ring 25 and the plug 26 can be made from a set of ring and plug gauges, which are regularly produced to close tolerances, and with which, if the nominal diametrical clearance is .001 inch, the radial clearance will be kept between .000445 and .0005 inch.

I also provide a separate drain-pipe 3 3 for withdrawing air-side oil from the air side of the glandseal l2. In accordance with my invention, this air-side oil is caused to fiow from this drain-pipe t l to a gas-trap 34', and thence downwardly through a gas-washer or scrubber 35, and thence to a drain-pipe 35 which is large enough to carry both the washed oil and the leak-off hydrogen, which is used for washing or scrubbing the airside oil, so as to remove as much as possible of the air and water-vapor therefrom.

In the particular form of embodiment of my invention which is illustrated, the hydrogen-side drain-pipe E9, the hydrogen-leak-ofi pipe 32, and the washed-oil air-side drain-pipe 35 all empty into a gas-space 31 at the top of an oil-reservoir 38. Thus, leak-off hydrogen enters said gas-space 3'! through the pipe 32, keeps said gas-space scoured of accumulated air or moisture, and passes on upwardly through the oversized air-side drain-pipe 36, and into the bottom of the gaswasher 35. The hydrogen-flow through the gaswasher 35 is thus in a direction counter to the oil-flow, so that the hydrogen removes most of the air and vapor which is dissolved in the air-side oil which comes out of the gland seal 2, with the purest oil in contact with the pure hydrogen. The hydrogen then escapes from the top of the gas-washer 35, through a gas-escape pipe 39.

A circulation of oil is provided by means of an oil-circulating pipe 4|, which extends up from a point near the bottom of the oil-reservoir 38, well below the oil-level 32 therein, and thence through an oil-pump 43, and thence to piping 4 which leads to the seal-oil input-pipes I3 at both ends of the machine.

In operation, the air-side oil, in the drain-pipe 34, carries approximately the same amount of air as heretofore, due to the passage of the sealoil through the gland-seal 12. In order to fix our ideas, let us call this air-volume 57% cubic feet per day. To give a further concrete example, let us assume that the leak-off hydrogen amounts to 100 cubic feet per day. On account of the low partial pressure of the air above the oil in the gas-washer 35, most of the air which was dissolved in the oil will be removed. In an exemplary gas-washer 35, let us assume that about 88% of the dissolved air would be removed by the flow of hydrogen, which would mean that only 12% of 57%, or less than 7 cubic feet of dissolved air per day, would finally be mixed with the scrubbed air-side drain oil. Since the oil to the gland seal would contain only about 64% of airside drain-oil, less than 64% of 7, or less than 4.5 cubic feet of air, would be carried over, by the recirculated oil, so as to contaminate the hydrogen in the small hydrogen-chamber it, during each day of operation. The addition of less than 100 cubic feet of hydrogen, to be brought into the small hydrogen-chamber it; each day, would thus maintain the required purity.

It is to be noted that this air-infiltration into the machine does not contaminate the main body of hydrogen within the machine, but only the hydrogen in the small hydrogen-chamber Hi immediately surrounding the hydrogen side of the gland seal l2. This is because the hydrogen is continuously escaping from the small chamber it, at a slow rate of the order of cubic feet per day or less, and hence a like amount of hydrogen is flowing axially along the restricted clearancespace E5 of the labyrinth seal it, in the direction from the main body of hydrogen in the machinehousing I, through said clearance-space l5, and thence into the restricted hydrogen-chamber I i. Thus the gas-pressure in the small hydrogenchamber [4 is intermediate between the hydrogen-pressure which is maintained in the main body of the space within the machine-housing i and the pressure of the surrounding atmosphere, so that practically no air can leak out of the small hydrogen-space M into the main hydrogen-space within the machine-housing. It will be under stood that the hydrogen-pressure within the main machine-housing i is automatically maintained, by suitable hydrogen-inlet and pressure-control means (not shown), as is common in the art of hydrogen-cooled generators.

While I have illustrated my invention in but a single exemplary form of embodiment, I wish it to be understood that my invention is not limited, in all of its details, to the illustrative gas-quantities, or to the particular configurations which are shown in the drawings, as many changes may be made, in the way of additions, omissions and the substitution of equivalents, without departing from the essential spirit of my invention. I desire, therefore, that the appended claims shall be given the broadest construction consistent with their language.

I claim as my invention:

1. A hydrogen-cooled machine having a substantially hermetically tight, hydrogen-filled housing, the hydrogen being at higher than atmospheric pressure, said machine having a rotatable shaft extending through the housing, a gland seal surrounding said shaft where it extends through said housing, means for supplying oil to said gland seal, means for providing a small hydrogen-chamber on the hydrogen side of the gland seal, means for causing said small hydrogen-chamber to be separated from the hydrogenfilled housing through a long and restricted clearance-space around the shaft, means for withdrawing air-side oil from the air side of said gland seal, means for causing said air-side oil to flow through a gas-washer, means for recirculating the washed air-side oil through the oil-supplying means of the gland seal, means for pro viding a continuously operating, slow-hydrogenleak-off passage from said small hydrogen-chamher to the gas-washer so as to cause a hydrogenfiow through said gas-washer in a direction counter to the oil-flow, and means for providing a gas-escape passage from the gas-Washer.

2. The invention as defined in claim 1, in combination with a hydrogen-side drain-pipe and gas-trap, said drain-pipe draining ofi oil and hydrogen from said small hydrogen-chamber to said gas-trap, and said slow-hydrogen-leak-ofi passage being provided from the upper portion of said gas-trap.

3. The invention as described in claim 1, characterized by said slow-hydrogen-leak-ofi passage including a ring-member and a plug-member having close tolerance therebetween, means for causing the leak-off hydrogen to pass axially through said tolerance, and means for axially adjusting the position of the plug-member with respect to the ring-member whereby to adjust the axial length of the hydrogen-passage through said tolerance.

RENE A. BAUDRY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,559,182 Rice Oct. 27, 1925 2,236,274 Rice et a1 Mar. 25, 1941 2,282,675 Pigott May 12, 1942 2,288,997 Eggert July 7, 1942 2,350,753 Grobel June 6, 1944 2,470,664 Sterrett May 17, 1949 2,501,304 Baudry et al Mar. 21, 1950 2,504,899 Sterrett Apr. 18, 1950

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