US 3302951 A
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Description (OCR text may contain errors)
Feb. 7, 1967 c. B. OLESEN 3,302,951
METHOD FOR SEALING A TURBINE OR COMPRESSOR SHAFT Filed Jan. 26, 1965 23 x1) 70 muuuu l 2\ i w /4 /5 E I i #43 J INVENTOR. UarsZeroBaZsZev 02am ERlC Y. MUNSON dizorlg United States Patent 3,302,951 METHOD FOR SEALING A TURBINE OR COMPRESSOR SHAFT Carsten llalslev Olesen, Finspang, Sweden, asslgnor to Stal-Laval Turbin AB, Finspang, Sweden, :1 corporation of Sweden Filed Jan. 26, 1965, Ser. No. 428,165 Claims priority, application Sweden, Mar. 31, 1964, 3,953/64 2 Claims. (Cl. 2771) This invention relates to a method for sealing a turbine or compressor shaft, an example of which is disclosed in my co-pending application for patent Serial No. 282; 781, filed May 23, 1962, now Patent No. 3,235,269.
In said application is disclosed a means and method for sealing a turbine or compressor shaft by means of an arrangement located between a chamber containing vapour of, for example heavy water (D 0) and a bearing, and it comprises a series of sealing glands, separated from each other by chambers. The described arrangement is such that air at atmospheric pressure is admitted to one of the chambers, and air mixed with oil, formed by oil leaking from the bearing to another of the chambers in one direction along the shaft, and by atmospheric air leaking from the first chamber in the other direction, is withdrawn by a fan, thereby maintaining a pressure lower than atmospheric in the secondmentioned chamber.
The present invention is characterized by the fact that in a line extending to one of the chambers, the air pressure from a fan in said line is kept constant due to the fact that a part of the air is returned to the suction side of the fan through a return line provided with a pressure-controlled regulating valve, and in addition, the pressure on the suction side is kept constant by supplying atmospheric air through a line provided with a regulating valve which is controlled by the pressure on the suction side. This provides a system of control which can maintain a constant pressure in several of the chambers with different flow rates through seals arranged around the shaft, that is, a very stable control is provided which makes it possible to supply the shaft seal with the quantities of sealing air required by the leakage variations due to changes in the clearance at the edges of the seal, at constant line pressure before and after the fan.
The view shown in the accompanying drawing diagrammatically illustrates a shaft-sealing means for sealing a shaft in accordance with the present invention.
Referring to the drawing, there is therein shown a shaft 1 for a turbine which, for example, operates on D 0 steam. A steam chamber in the turbine is designated at 2. The shaft 1 is carried in a bearing shown at 3. Between the chamber 2 and the bearing 3 is a shaft seal which surrounds the shaft 1 with a plurality of sealing points designated respectively at 4, 5, 6 and 7, the same being separated or spaced apart by means of the chambers I, II, III and IV.
Oil from the bearing 3 is sprayed into the chamber I, wherein a vacuum is maintained by means of a suction or evacuation fan 8 and from the opposite side of which air leaks in along the shaft 1 from the chamber II, which chamber is supplied with atmospheric air entering through the line shown at 9. This assures a stream of air toward the bearing through the edges of the seal at sealing point 4 which prevents oil from leaking past at this point.
Dry sealing air under above-atmospheric pressure is "ice supplied to the chamber III through a line 10. Part of this air flows into chamber II at atmospheric pressure and part flows into the chamber IV from which air and steam from chamber 2 are withdrawn through a line 11 leading to a leakage condenser 12. From here the D 0 steam is led away through a line 13 while air saturated with D 0 steam is led to a pre-dryer 14 from which D 0 is carried away through a line 15. From here the medium is led through a final dryer 16 which, in the arrangement shown in the drawing, can be a rotary air dryer of the absorption type. Dry air is sucked from the dryer 16 by a fan 17 through the line 10 and delivered into the chamber III.
After passing from the fan 17, air from line 10 is returned to the suction side of the fan through a return line 18, provided with a valve 19, controlled by the pressure in line 10. The pressure in line 10 beyond the fan can thus be kept constant. The pressure on the suction side of the fan in line 10 can also be kept constant due to the fact that air evacuated by the fan 8 through sealing points 4 and 5 is replaced with air supplied to the line 10 through line 20 which is provided with a dryer 21. The pressure on the suction side of the fan 17 in line 10 is kept constant by means of a regulating valve 22 which is controlled by the pressure in the leakage condenser 12.
If the leakage in the seal 5 increases due to wear at the edges of the seal, the air flow in the line 10 to chamber III will increase. This acts to throttle the valve 19 and the pressure in the leakage condenser 12 drops, which in turn means that the valve 22 opens to admit atmospheric air. If the leakage through seal 6 to chamber IV increases, the air flow in line 10 to chamber III increases. This acts to throttle the valve 19. The pressure in the leakage condenser 12 rises as more air is supplied through the line 11, but less air flow through line 18 results in an unchanged flow through the valve 22.
As shown on the drawing, the return air may be heated, or at least a part of it can be heated, by means of a heater connected into the line 18 from which it is led through the dryer 16. Such a heater is shown at 23 and it serves to absorb the moisture given off in the dryer by the medium in the line 10. From the dryer the medium is returned to the line 10 by way of the predryer 14.
Having thus described an embodiment of the invention, it is obvious that the same is not be restricted thereto, but is broad enough to cover all structures coming within the scope of the annexed claims.
What I claim is:
1. The method of sealing a turbine or compressor shaft by means of a sealing arrangement located between a chamber containing vapour and a bearing, and comprising the use of a series of sealing glands, which sealing glands are separated from one another by chambers I, II, III and IV in sequence from the bearing and located around the shaft, characterized in that air at atmospheric pressure is admitted to the chamber II and that air mixed with oil formed by oil leaking into the chamber I in one direction along the shaft from the bearing, and by atmospheric air leaking from the chamber II in the opposite direction, is withdrawn by a fan, maintaining a pressure lower than atmospheric in the chamber I, admitting dry blocking air into the chamber III at a pressure higher than atmospheric and which air leaks along the shaft partly to the chamber II and partly to the chamber IV, the pressure in the line leading to chamber III being kept constant due to the fact that a part of the air is returned to the suction side of a sec- "2 a and fan through a return line provided with a pressurecontrolled regulating valve, and in addition the pressure on the suction side is kept constant by supplying atmospheric air through a line provided with a regulating valve which is controlled by pressure on the suction side. 2. A method according to claim 1, characterized in that the return air or at least a part of it is heated and passes through an air dryer such as a rotary air dryer of the absorption type which absorbs moisture given off by air flowing through the air dryer to the fan.
References Cited by the Exarm'ner UNITED STATES PATENTS Van RijsWijk 27712 XR Cuny 277-3 Cuny 277--15 Warth 277-12 XR Olesen 2771 SAMUEL ROTHB'ERG, Primary Examiner.