JPH0474590B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a shaft seal device using a visco seal, and more specifically to a shaft seal that prevents leakage of sealed fluid from a rotating shaft of a steam turbine or a pump. This invention relates to a shaft sealing device using a viscoseal suitable for use with chemically active substances.

[Prior Art and Background of the Invention] Conventionally, in the case of shaft seals for steam turbines, contact mechanical seals and non-contact labyrinth seals that reduce steam pressure have been used as shaft seals. Since mechanical seals are contact type, they have the advantage of high sealing pressure and being able to achieve a nearly complete seal, but depending on the type of fluid to be sealed, such as steam, the seal material may corrode. In the case of highly chemically active substances such as metallic potassium vapor, there are considerable limitations, such as the inability to use them for long periods of time. On the other hand, since the labyrinth seal is a non-contact type, corrosion by the sealed fluid is not so severe, but due to its structure, it cannot completely prevent leakage.

In contrast to these shaft seals, there are few practical examples of Visco seals, and only a few are known to have been used, such as shaft seals for sodium pumps for fast breeder reactors and NASA in the United States planning to use them in space power generators. This is the extent of the situation. Opposed visco seals are capable of almost complete sealing even when the sealed fluid is a chemically very active substance, but have the drawbacks of low sealing pressure per shaft seal length and leakage when the shaft stops rotating. . In addition, with Visco Seal, it is possible to increase the sealing pressure by reducing the distance between the rotating shaft and the fixed part (housing) or by increasing the shaft rotation speed, but in reality there are limits to these. , and it cannot be made that large. Furthermore, it has been confirmed that leakage due to rotation stop when using this opposed visco seal can be sufficiently covered by the seal system and system operating method.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks of the opposed visco seal, and to provide control so that a good sealing state can be appropriately maintained in response to pressure fluctuations of the fluid to be sealed. An object of the present invention is to provide a shaft sealing device using a visco seal.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a shaft using a visco seal that prevents sealed fluid in a rotating device from leaking along the rotating shaft of the rotating device. In a sealing device, Visco seals are arranged along a rotating shaft and have opposite thread directions, means for supplying sealing fluid with a constant water head to opposing threaded parts of the Visco seals, and rotating equipment of the Visco seals. means for supplying inert gas to the opposite end; differential pressure detection means for detecting the pressure difference between the sealed fluid and the inert gas; and pressure detected by the differential pressure detection means for detecting the pressure of the inert gas. The invention is characterized by comprising means for controlling based on the difference.

[Function] In the shaft seal device using the Visco seal of the present invention, for example, when the pressure on the sealed fluid side increases,
The pressure difference between the pressure of the inert gas supplied to the shielded chamber provided at the opposite side of the sealed fluid side of the visco seal opposing part and the pressure of the sealed fluid is detected by the differential pressure detection means. When the pressure of the inert gas is increased and the pressure of the sealed fluid becomes lower than the pressure of the inert gas, the differential pressure is detected by the differential pressure detection means, the inert gas is released, and the pressure is lowered. The sealed fluid side and the sealed chamber side are controlled so that the pressure is always maintained in balance within the Visco seal through the sealed fluid filled in the visco seal. It effectively exhibits the characteristics of Visco Seal even against fluids, and can maintain a good sealing state.

[Examples] Examples of the present invention will be described in detail below based on the drawings.

FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to a rotating shaft of a potassium steam turbine.
Here, 1 is a potassium steam turbine, 2 is its rotating shaft, and, although not shown, for example, a generator is mounted on the right side of the figure. 3 and 4 are visco seals which are provided with screws facing in opposite directions and are incorporated on the rotating shaft 2; these visco seals 3
And by the pump action of 4, pressure is applied to the sealant of the sealing fluid supplied to the central part 5 (hereinafter referred to as the opposing part, no screws are provided in this part), and the steam from the turbine 1 side is directed to the shaft. Seal. Such a device is called an opposed visco seal, and the present invention relates to a shaft sealing device using such an opposed visco seal.

A liquid tank 6 is provided above the facing part 5 and stores potassium liquid as a sealant, and the sealant 7 is filled from the liquid tank 6 toward the facing part 5. 8 is a shielding chamber provided at the right end of the opposing visco seal, and the shielding chamber 8 includes a
Inert gas (hereinafter referred to as cover gas) is supplied while maintaining a predetermined pressure.

In such an opposed visco seal, potassium vapor, which is a fluid to be sealed, tends to leak from the turbine casing 1A side along the shaft 2, but due to the pumping action of the opposed visco seal, the left visco seal 3 and The gas-liquid interfaces 9 and 10 are maintained at the right Visco seal 4. In this case, the left gas-liquid interface 9 is such that the sum of the water head h in the liquid tank 6 and the cover gas pressure is potassium vapor. The gas-liquid interface 10 on the right side is generated at a position where the water head h and the pump pressure at the right side Visco seal 4 are balanced. I'll do what I do.

Therefore, in this example, the shielding chamber 8 and the upper space of the liquid tank 6 are communicated through the communication pipe 11, and a differential pressure detection sensor 12 is used to detect the pressure difference between the shielding chamber 8 and the turbine casing 1A. Furthermore, the communication pipe 11 is refilled with cover gas from a supply source such as a cover gas supply tank (not shown) via the solenoid valve 13.
The opening and closing operations are performed by a pressure controller 14 having a computer function.

In this way, the solenoid valve 1 is controlled via the pressure controller 14 so that the difference between the pressure of potassium vapor, which is the fluid to be sealed, and the pressure of the cover gas is always maintained at a predetermined condition.
Controls the opening and closing operations of 3. 15 is a manual valve such as a needle valve, and the solenoid valve 13 is controlled by the manual valve 15.
It is possible to adjust the flow rate when the valve is opened. 16
is a pressure reducing valve for previously reducing the pressure of gas from the gas supply source to the pressure required for supply.

Further, in the shielding chamber 8, a solenoid valve 18 and a manual adjustment valve 19 are provided in a passageway for guiding gas to a low pressure tank (not shown) via a drain reservoir 17 for controlling the pressure of the cover gas to be lowered. 20 and 21
is a mechanical seal provided between the shielded chamber 8 side and the generator side, and a bearing (not shown) is further provided between the mechanical seals 20 and 21.
A lubricating oil 22 is circulated between the two.

In addition, here, in the sealant liquid tank 6,
In order to keep the water head h constant regardless of fluctuations in the steam pressure inside the turbine casing 1A, the inner diameter of the liquid tank 6 is made as large as possible, and for example, as shown in this example, It is preferable to provide a replenishment tank 23 or the like in the tank so that the liquid level can be adjusted.

In the shaft seal device configured using the Visco seal in this way, the left gas-liquid interface 9 moves in response to fluctuations in the steam pressure on the turbine 1 side, but the permissible range of this movement is limited to the left side Visco seal. 3 from the end of the casing 1A side to the opposing part 5, and in order to maintain the gas-liquid interface 9 during this period, the pressure in the shielding chamber 8 must be adjusted so that the pump pressure does not exceed its fluctuation range. The pressure of the cover gas may be controlled in response to fluctuations in the steam pressure on the turbine 1 side.

Now, in FIG. 1, if the steam pressure on the turbine 1 side increases for some reason, the differential pressure detection sensor 12 detects the pressure between the cover gas pressure in the shielding chamber 8 and the steam pressure in the turbine casing 1. The difference is sensed and provided as an electrical signal to pressure controller 14. Therefore, the pressure controller 14 operates the solenoid valve 13 according to the pressure difference and the speed of its fluctuation based on the signal. By this operation, the cover gas is supplied to the space of the shielding chamber 8 and the liquid tank 6, and the pressure is increased, so that the solenoid valve 13 is closed when equilibrium with the steam pressure on the turbine casing 1 side is maintained.

Further, when the steam pressure on the turbine 1 side becomes lower than the cover gas pressure in the shielded chamber 8, a negative differential pressure signal is supplied from the differential pressure detection sensor 12 to the pressure controller 14, so that the pressure controller 14 Then, an operating signal is output to the solenoid valve 18 on the pressure reducing side, and the shielding chamber 8
The pressure in the space of the liquid tank 6 is reduced so that an equilibrium can be obtained between the pressure and the vapor pressure. Note that the low-pressure tank (not shown) is used to obtain a pressure lower than the expected lowest steam pressure on the turbine 1 side, and if the turbine steam and sealant are potassium, the vacuum tank and vacuum pump A combination of these is expected.

Further, the solenoid valves 13 and 18 may be of the type that uses a plurality of solenoid valves for on/off operation or the type of continuously variable operation. Furthermore, although the above is an example of a steam turbine, the application of the present invention is not limited to this, and for example, a turbine casing 1.
By filling A with liquid, the gas-liquid interface 9
Pressure control can be carried out in the same way even in cases where this does not occur, and in this case, the sealant is a liquid in the same chamber as the fluid to be sealed.

Furthermore, a sensor that directly detects the pressure of the sealed fluid and a cover gas pressure detection sensor are provided,
If the differential pressure is detected from information from both sensors, even more appropriate control can be performed.

[Effects of the Invention] As explained above, according to the present invention, it is not only applicable to cases where the pressure of the fluid to be sealed is large and cannot be sealed only by the pump pressure of the opposed visco seal, but also because it is a non-contact type. The friction loss is much smaller than that of mechanical seals. Due to its structure, it goes without saying that it can be applied to chemically active sealed fluids, and since the pressure of the cover gas is electrically controlled, the response is quick, and since a computer can be used for control, it is fine-tuned. can be controlled.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of a shaft seal device using the Visco seal of the present invention. 1...Turbine, 1A...Turbine casing, 2
... Rotating shaft, 3, 4... Visco seal, 5... Opposing part,
6...Liquid tank, 7...Sealant, 8...Shielding chamber, 9,1
0... Gas-liquid interface, 11... Communication pipe, 12... Differential pressure detection sensor, 13, 18... Solenoid valve, 14... Pressure controller,
15, 19... Manual valve, 16... Pressure reducing valve, 17... Drain reservoir, 20, 21... Mechanical seal, 22...
Lubricating oil, 23...supply tank.

Claims (1)

[Scope of Claims] 1. A shaft sealing device using a visco seal that prevents sealed fluid in a rotating device from leaking along the rotating shaft of the rotating device, comprising: a shaft sealing device disposed along the rotating shaft; Visco seals with threads in opposite directions; means for supplying a sealing fluid with a constant water head to a portion of the Visco seal facing the threads; and an inert gas at an end of the Visco seal opposite to the rotating equipment. differential pressure detection means for detecting a pressure difference between the sealed fluid and the inert gas; and controlling the pressure of the inert gas based on the pressure difference detected by the differential pressure detection means. A shaft sealing device using a visco seal, characterized in that it is equipped with means for: