JPS62251575A - Sealing pressure controlling method using visco-seal - Google Patents

Abstract

PURPOSE:To widen the application range of a seal as well as to make the cooling of heat ever so easy, by expanding the extent of sealing pressure for a shaft seal in an way of partially leaking a sealant to the sealed fluid side of an opposed visco-seal. CONSTITUTION:Both opposed visco-seals 22 and 24 are being installed along a turning shaft 16 for a turbine 1, and a space 20 is installed anew between these opposed visco-seals and mechanical seals 13 and 15. A potassium solution is filled up inside the opposed visco-seal as a sealant 3, and at the side of a turbine 1, a screw part of the left visco-seal 24 is made to be shorter so as to cause this sealant 3 to be leaked. This leakage quantity is detected by a pressure sensor 29, operating a solenoid valve 27 by a controller 9, and cover gas pressure in a liquid tank 4 is made so as to be constant. Thus, it is made applicable even in the case where sealing cannot be done with pump pressure of the visco-seal alone.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a shaft seal that prevents leakage of sealed fluid from the rotating shaft of a steam turbine or pump, and which can be used even with chemically active substances. The present invention relates to a control method for increasing the sealing pressure of and further compensating for pressure fluctuations.

[Conventional technology]

Traditionally, "°°shaft seals" have been used, for example, in the case of steam turbine shaft seals, contact-type mechanical seals and non-contact-type labyrinth seals that reduce atmospheric pressure. Mechanical seals are contact-type seals. Therefore, the sealing pressure is high and a state close to complete sealing can be achieved, but depending on the type of fluid to be sealed, such as steam, the sealing material may corrode.
For example, if the fluid to be sealed is a chemically very active substance such as metallic potassium vapor, there are considerable restrictions such as the inability to use it for a long period of time. On the other hand, since the labyrinth seal is a non-contact type, it is not so severe in terms of corrosion caused by the sealed fluid, but due to its structure, it cannot completely prevent the leakage of steam, etc. On the other hand, the opposed visco seal has few practical examples and has a slightly higher speed. Na pump shaft seal for breeder reactors and US NA'? It is only known that A planned to use it as a space power generator. Opposing visco seals are capable of almost "complete sealing" even when the sealed fluid is a chemically very active substance, but the sealing pressure per shaft seal length is small and leakage occurs when the shaft rotation stops. There are drawbacks. It has been confirmed that when this opposed visco seal is used, leakage caused by one rotation stop can be covered by the seal system and system operating method.

[Purpose of the invention]

The present invention aims to substantially increase the sealing pressure of the opposed visco seal and to follow pressure fluctuations. Originally, Visco Seal had a rotating shaft and a fixed part (
The sealing pressure can be increased by reducing the gap (clearance) with the housing or by increasing the per-peripheral speed. However, in reality, there is a limit to this, and it cannot be increased that much.In addition to the above method, a method of increasing the sealing pressure by increasing the pump pressure of the visco seal part is to partially leak the sealant. In this case, it is necessary that the fluid to be sealed and the sealant are the same substance. However, if the seal tent can be separated from the fluid to be sealed, they may not be made of the same material. The present invention can be used in cases where this is permitted. The advantage of this method is that by flowing the sealant toward the fluid to be sealed, the sealing pressure can be several times higher than when no sealant is flowing, so the shaft seal length can be shortened, and the cover gas pressure all!
! Since the pressure is simply increased to a constant pressure, there is no need to control the cover gas pressure in response to pressure fluctuations of the fluid to be sealed, and the sealing portion can be cooled by the flow of the sealant.

This method is easiest to control when the shielded chamber is almost evacuated, and is suitable for chemically very active fluids, such as shaft seals of metallic potassium steam turbines. Furthermore, since it can be used satisfactorily even at high temperatures, its range of applications is wide.

[Structure of the invention]

Figure 1 shows an example of a sealing pressure control system for opposed visco seals in a rotating shaft seal system for a potassium steam turbine. (1B), cut the opposing visco seals (visco seals (22) and (24) with opposite threads and install them on the rotating shaft, so that the pressure (pump pressure) due to the pump action of each is applied to the center part. The Visco seals that are made are collectively called the Opposite Visco Seal, and the central part is called the Opposite part (23).This Opposite 1'fB (23) is usually not threaded)
is provided. Then, mechanical seals (13) (15) and bearings (
A zero space'' (20) is provided between the opposing visco seal and the mechanical seals (13) and (15) (not shown).
After that.

This space (20) is called a shielding chamber), the opposing visco seal is filled with potassium liquid as a sealant (3), and a gas-liquid interface (21) is created on the shielding chamber (20) side. (The length from the two opposing parts (23) is the height of the sealant (3) in the liquid tank (4), that is.

The head (b) of the potassium liquid and the liquid tank (determined by the balance between the cover gas pressure in the 0 and the pressure in the shielding chamber (20)), and the turbine (1) side are arranged so that the sealant (3) does not leak. Compared to the right visco seal (22), the left side (
Shorten the threaded part of the visco seal (24) on the turbine (1) side or increase the clearance. This leakage amount is measured by a pressure sensor (29) that measures the cover gas pressure in the liquid tank (0).
It is detected by the controller (9), and the solenoid valve (27) is activated to maintain a constant pressure.
(23)), and the liquid head (head (h)) of the sealant (3) in the liquid tank (4).
A sealant supply system is added to keep the amount constant. The liquid level (5) in this liquid tank (4) is detected, for example, by the liquid level gauges A and H in Fig. 1, and the sealant is applied to the flow 1 control valve (7) through the controller (6). (3).

If the pressure in the shielding chamber (20) is made the same as the pressure in the liquid tank (4), the position of the gas-liquid interface (21) will not change because the head (h) is constant, and the pressure in the shielding chamber (?0) can be made independent. Even if the pressure is maintained at a constant level, the gas-liquid interface (21)
However, in this case, the position of the gas-liquid interface (21) is balanced by the head (h) and shielding chamber (20) pressures and the liquid tank (0 pressure).

Under the above setting conditions (shaft rotation speed, liquid tank (0 internal pressure, constant head (h)), a constant flow rate of sealant (3) leaks. However, this leakage amount is limited to the turbine (sealed fluid). Since the sealing pressure changes according to side pressure fluctuations, it automatically controls the sealing pressure by itself below the limit as described later (Figure 2).Others (8011) (1B) (2
8) is a manual valve, (12) is a pressure reduction of 2m! valve, (14)
is lubricating oil, (19) is drain, (2B) is turbine (
The end of the shaft seal portion on the side 1) is shown, and the outflow portion of the sealant (3) is shown as (25).

[Action of the invention]

In Fig. 1, for example, if the pressure in the shielded chamber (20) is set to approximately θ atmosphere by using a vacuum pump, the position of the gas-liquid interface (21) of the right visco seal (22) of the opposing visco seal is at the liquid tank (4). It becomes stable when the sum of the internal pressure and the liquid fi (he, de (h)) balances the pump pressure of the visco seal (22). In this state, when the pressure of the sealed fluid on the turbine (1) side increases, the leakage of the sealant (3) of the left visco seal (24) decreases, and finally the leakage stops and a gas-liquid interface (not shown) occurs. The gas-liquid interface is the opposing part (23
). Therefore, since the gas-liquid interface (21) of the right visco seal (22) is stable until it reaches the opposing part (23), pressure changes in the fluid to be sealed are allowed during this time. Also, when the pressure on the turbine (1) side becomes low and finally reaches 0 atmospheres, the seat tent (3) on the turbine (1) side
The amount of leakage is maximum. This principle will be explained below.

Figure 2 shows the characteristics of the sealant leakage amount on the vertical axis and the pump pressure of the Visco seal on the horizontal axis. N2 is the rotational speed of the shaft (IB), N, <N. Point a is the pump pressure at the shaft rotational speed N, leakage amount = O, which is usually called the "shutoff pressure", and the pump pressure is When the pressure is lower than that, a gas-liquid interface is formed within the Kahisko seal. Furthermore, when the sealant (3) leaks, the pump pressure increases in proportion to the amount of leakage. Now, if we consider the opposed visco seal in Fig. 1, the first
It is assumed that the sealant (3) is completely leaked from the visco seal (24) on the left side of the figure and is initially at point b in Figure 2.

At this time, it is assumed that the pressures in each part of FIG. 1 are balanced. Here, when the pressure of the sealed fluid (pressure on the turbine (1) side) increases, the pump pressure of the left visco seal (24) must decrease because the pressure in the opposing part (23) is kept constant. , in Fig. 2, when looking at this pressure change, at first d corresponds to the sealant leakage point lb.
For example, the pump pressure at point moves to point e, the amount of sealant leakage decreases by that amount, and moves to point g, which corresponds to the pressure at point e.

In this way, the pressure balance between the opposing visco seals (7) in FIG. 1 is maintained. Namely.

Changes in the amount of sealant leakage result in automatic adjustment of the pressure balance. However, this pressure change causes the pressure of the sealed fluid to increase and the amount of leakage becomes 0, and when it reaches point a in FIG. 2, a gas-liquid interface (not shown) occurs. Looking at Chopsticks 1, the pressure is generated in the left visco seal (24), increases further, and finally when the gas-liquid interface reaches the opposing part (23), the pressure balance collapses and the sealed seal on the turbine (1) side The fluid passes through the left visco seal (24) and flows to the opposite side a! ! (
23) to the liquid tank (4) and also to the right visco seal (22), breaking the seal. Therefore, a pressure increase of 1 up to this range is allowed as a change in the pressure of the sealed fluid. On the other hand, when the pressure of the sealed fluid decreases, the second
As you can see from the figure, the amount of sealant leakage increases, the pump pressure increases, and the pressure balance is maintained, so if the sealant supply system has sufficient noise, the pressure will be balanced even if the pressure of the sealed fluid drops to θ atmosphere. will not collapse,
Therefore, this pressure fluctuation range can create a much greater sealing pressure than when the sealant (3) does not leak. However, the present invention requires a supply system or circulation path for the sealant (3). This sealant (
3), in the example shown in Figure 1, the liquid tank (4)
Liquid inside f! A liquid level controller (6) is required to keep A (head (h)) constant. This liquid level sensor is shown in Figure 1.
1 shows electrode rods for detecting the upper and lower parts by A and B, but liquid level detection may have to be done using other methods depending on the type of sealant (3).

Next, the pressure of the cover gas in the liquid tank (4) and the shielding chamber (20) will be described.

In Fig. 1, in order to keep the pressure in the liquid tank (4) constant, the pressure is detected by a pressure sensor (28), the signal is judged and processed by a controller (8), and a solenoid valve (27) is used to detect the pressure. ) to control the pressure in the liquid tank (0).On the other hand, the shielded chamber (
20) maintains a constant pressure instead of O atmospheric pressure, the pressure is accumulated by the pressure sensor (30), judged and processed by the controller (9), and the solenoid valve (lO) or the solenoid valve (1
7) to maintain the pressure in the shielded chamber (20) at a constant pressure. At this time, the pressure relationship between the liquid tank (0) and the shielded chamber (20) is to make the pressures in both parts equal (this method is (Although not shown in the figure, the pressure control becomes one line, making the control easier), or the pressure in the liquid tank (4) is made higher (this method increases the pressure in the head (h) in the liquid tank (4)). It can be lowered. However.

As shown in the figure, there is a method in which the control is performed in two series, making it more complicated. In any case, the pressure in the liquid tank (4) and the shielding chamber (20) must be controlled so that the gas-liquid interface (2) in the right visco seal (22) maintains a constant position.

The explanation so far has been made under the condition that the shaft rotation speed is constant, but when the shaft rotation speed changes, that is, when there is a large load change, start-up and stop of operation, etc., the cover gas pressure must be controlled. To do this, the rotational speed sensor (tachometer) (35) shown in Fig. 1 detects the fluctuation, and the controller (3) judges and processes this to control the solenoid valve (to) (17).
) (27) to control the cover gas pressure in the liquid tank (0) and the shielding chamber (20), and keep it at the pressure in the opposing part (23) that corresponds to the rotational speed at all times, provided that the gas-liquid interface (
The relationship between the shaft rotation speed that keeps the position of 21) constant and the pressure of the opposing part (23) is determined by the shape and dimensions of the visco seal and the sealant temperature.

Since it is uniquely determined by the position setting of the gas-liquid interface, etc., it is necessary to store it in the controller (8) in advance.

The present invention relates to a rotary shaft seal, and is not limited to turbine steam. For example, the turbine casing (2) in FIG. The liquid can be sealed.

Figure 3 shows another example of a method for causing the same sealant (3) to flow out to the sealed fluid side as shown in Figure 1, based on the idea that the pressure at the facing part is constant.In this case, the pressure at the facing part ( 23) is detected by the pressure sensor (30) and the controller (
9), the electromagnetic pump (32) is activated and its pressurizing force is kept constant. In Figure 0, the accumulator (31) absorbs the pressure noise of this system. In this case, the head at the interface of the liquid tank (service tank: 34) does not need to be constant, unlike in Figure 1.
33) is a manual valve.

〔Effect of the invention〕

The present invention has the advantage that it can be applied even in cases where the pressure difference between the sealed fluid and the sealed fluid is large and sealing cannot be achieved with only the pump pressure of the opposed visco seal, so it has a wide range of application. Advantages include that it is relatively easy to adjust the internal head, and because the sealant flows out to the sealed fluid side, it is easy to cool the heat transmitted to the seal portion and the shaft.

[Brief explanation of drawings]

Fig. 1 is a piping diagram showing an example of the shaft sealing device used in carrying out the present invention, Fig. 2 is an explanatory diagram showing the pressure characteristics of the Visco seal, and Fig. 3 shows another example of the shaft sealing device. It is a piping diagram. (1) Turbine (2) Turbine casing (3) Sea tent (4) Liquid tank (5) Liquid level (6) Liquid level controller (7) Flow rate control valve (8) (11) (18) (28
) (33) Manual valve (8) Controller (10) (17) (
27) Solenoid valve (12) Pressure reduction regulating valve <13>Cl5)
) Kaniriki At Sea At (14) it! l Lubricating oil (1
B) M rotation axis (18) Drey (20) Shielding chamber (
21) Gas-liquid interface (22) Right side visco seal (23)
Opposing part (20 Left side visco seal (25) Outflow sealant (26) Turbine side shaft seal end (29) (30) Pressure sensor (31) Accumulator (32) Electromagnetic pump (34) Service tank (3)
5) Rotation speed sensor

Claims (1)

[Claims] When sealing a fluid using a viscous seal (hereinafter referred to as opposed visco seal) that combines visco seals that are threaded in opposite directions on the same rotating shaft, the fluid to be sealed is placed at one end of this opposed visco seal. At the other end, if necessary, place an inert gas as a cover gas (if an inert gas is not required, air or other gas may be used, or a vacuum may be used), and seal in the middle, that is, within the opposing visco seal. Fluid (hereinafter referred to as sealant) is supplied from another sealant supply system to the central part (opposing part) under a set pressure, and a part of the sealant leaks to the sealed fluid side of the opposing visco seal. A sealing pressure control method using a visco seal that expands the sealing pressure of the seal and maintains the pressure of the opposing part constant by automatically following the pressure fluctuations of the sealed fluid with the amount of sealant leakage.