JPS63230903A - Shrinkage fit thrust collar - Google Patents

Abstract

PURPOSE:To prevent the axial looseness of a thrust collar by providing an axial cold spring, at the time assembly, to a sleeve that presses down axially the thrust collar which is to be shrinkage fitted to a turbine rotor. CONSTITUTION:A thrust collar 2 that is to be shrinkage fitted to a turbine rotor 1 is pressed down by a sleeve 4. The position of the sleeve 4 is set by a shaft nut 5. A cold spring is provided to the sleeve 4 by tightening the nut 5 after bulging the sleeve by injecting a pressure medium through a pipe 14 into a pocket 13 formed between the sleeve 4 and the rotor 1. By this method, the axial looseness of a thrust collar during turbine operation can be prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is applicable to both high pressure and medium pressure under steam conditions of 5661566°C.
This invention relates to a turbine using 2Cr rotor material.

[Background of the invention]

Design of 70ONV LNG-Fired
USCPovor-PlantforKavago
a Tharw+al Power 5fation
No, 1.2EPPI Nou, 19-21.1986
shows an example of the use of a shrink-fit thrust collar in a 70ONV actual machine, about technological trends and lubricants in steam power plants, and 6-Goku Review Vol. 25, No. 2 shows an example of the use of a shrink-fit thrust collar in a nuclear turbine. This shrink-fit thrust collar for 1800 rpm is shown as an example of 700 MW.
It is necessary to improve it so that it can be applied to 3600RP-machines.

χPurpose of invention] To improve bearing characteristics of 12Cr rotor material.

The structure in which the thrust collar of Cr-Mo material is shrink-fitted is as follows:
Although this has been used in the past, due to the thermal expansion of the collar during shrink fitting, a gap inevitably exists between the rotor fillet and the thrust collar, which is left after heat removal. This gap causes the collar to loosen in the axial direction when the thrust collar is relaxed, causing fretting corrosion. The present invention aims to eliminate this structural drawback.

[Summary of the invention]

In order to prevent the shrink-fit thrust collar from loosening in the axial direction when the shrink-fit force is relaxed, a cold spring force is applied to the sleeve, which is held in the axial direction and positioned by the shaft nut, and the collar is When initially relaxed, this force is used to press the collar against the rotor fillet, eliminating axial clearance.

Even during subsequent operations, this cold spring force holds down the collar, so it will not loosen.

[Embodiments of the invention]

12Cr rotor material has the characteristic of allowing fine solids in the lubricating oil to bite into the journal surface, so a Cr-Mo-V steel sleeve is shrink-fitted to the journal part in order to improve bearing characteristics. . The same is true for thrust bearings, C
The thrust collar of r-Mo-V@ is shrink-fitted to the rotor.

4 to 6 show the structure of a shrink-fit thrust collar according to the prior art.

The thrust collar 2 is shrink-fitted so as to be in contact with the fillet 7 of the rotor 1. Furthermore, it is held down in the axial direction by a sleeve 4, which is positioned by a shaft nut 5. This shaft nut 5
is engaged with the left-hand thread 6 machined on the rotor l, and 1
Usually, it is devised so that additional force is applied by rotational force.

The shrinkage fit A of the thrust collar is selected to be such that it loosens at approximately 120% speed, so it will not loosen during normal operation, but just in case.

A key 3 is provided between the rotor 1 and the rotor 1 to prevent rotation.

However, this key 3 is necessarily smaller than the keyway 11 of the thrust collar, and cannot completely prevent the collar from loosening.

Next, when shrink-fitting the thrust collar 2, it is necessary to heat the collar to about 200° C. to expand its inner diameter and fit it into the rotor. Therefore, after heat removal, the thrust collar always contracts in the axial direction, so a gap C is generated between the fillet 7 and the collar contact surface 8.

Since the sleeve 4 is provided to press down the thrust collar, a tight fit is used in which the engagement allowance B with the rotor is approximately 0 during assembly.

Therefore, although no gap is created between the end surface 10 of the sleeve and the contact surface 9 of the collar, the engagement allowance B increases due to the centrifugal force generated in the sleeve 4 during turbine operation, causing the sleeve 4 to loosen. The sleeve 4 is assembled by tightening it in the axial direction with a nut 5, so if this tightening force is insufficient or if a foreign object is caught in the contact surface between the rotor and the sleeve, This means that no tightening force can be applied to the thrust collar 2.

In this way, the sleeve 4 loosens during turbine operation, so to prevent it from rotating, the end of the key 3 for the thrust collar is extended and slightly engaged with the sleeve 4, but this key is chamfered. Therefore, the sleeve 4 cannot be completely prevented from rotating.Therefore, the sleeve 4 is fixed to the nut 5 with a set screw 12, and the nut 5 is further prevented from rotating.

With this structure, as the rotational speed of the turbine increases, the amount of tightening of the thrust collar 2 decreases, and when a thrust collar is added due to an increase in load, the thrust collar 4 will move in the axial direction. , there is a slight possibility of movement. In general, the thrust force generated in a steam turbine is designed to reverse its working direction as the load changes so that the thrust force in both directions does not become too large. It will move left and right in the division direction between the gap and the gap 9-10, but since nut 5 is prevented from rotating, the additional effect of making it a left-handed thread will actually occur. For this reason, tail-to-tip pad type thrust bearings are generally used for shrink-fit thrust collars.

If the thrust collar 2 loosens during operation, it will cause fretting corrosion on the shrink-fit surface with the rotor after long-term operation. In reality.

In shrink-fit thrust collars that have been in operation for more than 20 years, there have been cases where the rotor has broken due to fretting corrosion.

In addition, in turbines such as large-capacity steam turbines that exert a large thrust force, it is necessary to shrink-fit a large thrust collar, which inevitably increases the stress on the inner diameter of the collar and reduces the shrink-fit allowance. This increases the risk of stress fatigue and stress corrosion on the shrink-fit surface. Therefore, a structure that can withstand many years of operation is required.

The following two points can be considered as effective means to overcome the above-mentioned drawbacks in the conventional shrink-fit thrust collar structure.

(2) Eliminate the axial gaps that occur between 7 and 8 and between 9 and 10, and apply an axial force that stably presses the thrust collar 2 against the fillet 7.

■Do not make the internal stress of the thrust collar too high to prevent fretting corrosion and SCC and extend its life.

For this purpose, the present invention provides the structures shown in FIGS. 1-3.

First, in the thrust collar shrink-fitting operation, the thrust collar 2 is pressed against the fillet 7 of the rotor as much as possible and shrink-fitted to reduce the gap between 7 and 8. Furthermore, the heating temperature of the thrust collar during shrink fit is maintained at the minimum required temperature, and while pressing the heated collar 2 against the fillet 7 of the rotor, the temperature of the collar decreases from the side closer to the fillet 7, thereby improving the shrink fit effect. It is also desirable to continue heating the sleeve-side surface 14 of the thrust collar 2 so that this effect begins to appear and gradually transfers to the sleeve side.

After the thrust collar 2 is shrink-fitted with great care in this way, the heat is completely removed. At this time, the shrink fit allowance A should be selected so that the thrust collar 2 relaxes at about 120% of the rotor rotation speed, or a smaller shrink fit should be selected in order to lower the shrink fit stress and extend the service life. It is also possible to use a fitting allowance.

Next, fit the sleeve 4, but considering the workability, the mating distance B between the sleeve 4 and the rotor should be just a conventional tight fit.
Furthermore, the nut 5 is tightened to press the thrust collar 2 toward the rotor fillet 7 via the sleeve 4. However, at this time, the thrust collar does not move because the shrink fit stress of the thrust collar is high, and the thread of the shaft nut 5 is a left-hand thread, which is the same as before. In this state, the surfaces between 9 and 10 should be in complete contact. Fine solid matter on the rotor 1 that cannot be removed by cleaning before fitting the sleeve 4 is removed from the contact surface 9-10.
It is sufficient to drop it into the rotor group 15 provided at the bottom of the rotor group 15. Incidentally, the rotor group 15 and the group 16 at the base of the fillet 7 are also effective as a measure to prevent fretting corrosion.

Next is the main point of the present invention. For this work, which applies a cold spring force to the sleeve 4,
A notch is provided on the inner surface of the sleeve 4 over almost the entire length,
When the sleeve 4 and the rotor 1 are brought into close contact with each other, a pocket 13 is formed around the entire circumference of the rotor.

Before starting work, the axial length of the sleeve 4 is accurately measured to clarify the positional relationship between the thrust collar 2 and the nut 5. Furthermore, the rotor group 16 improves workability by measuring the gap generated between the thrust collar 2 and the rotor fillet 7.

The material of the sleeve 4 is preferably Cr, since it is easy to provide a cold spring and has a large compression resistance.
- Titanium alloys with a Young's modulus that is about half that of Mo-V steel and high strength (e.g. 6 A Q -4V -T
i alloy) etc. are optimal.

The cold spring may be applied by forcibly tightening the nut 5, but in order to provide the sleeve 4 with an axial shrinkage margin with high accuracy, the cold spring may be applied by forcibly tightening the nut 5. A pressure medium (for example, compressed air, compressed water, pressure oil, etc. can be considered, but pressure oil is preferable from the viewpoint of reliability) is introduced through the external conduit 14 to inflate the sleeve 4 in the radial direction in advance. The sleeve is also shrunk in the axial direction to give the sleeve the necessary shrinkage.

While maintaining this state, a shrinkage amount can be given to the sleeve 4 by moving the nut 5 toward the sleeve by a necessary shrinkage amount calculated in advance. Thereafter, when the pressure medium in the pocket 13 is extracted, a cold spring force is applied to the sleeve 4. After this work is completed, measure the axial length of the sleeve again to confirm that the necessary shrinkage has been given to the sleeve. If the dimensions are correct, the detent 12 between the sleeve 4 and the nut 5
, and install a rotation stopper for the nut 5. For pressure medium extraction P14, the introduction pipe is removed and a closing screw is installed.

Assembly is now complete, but the thrust collar has not yet moved in the axial direction.

The cold spring force applied to the sleeve 4 starts working at the first opportunity when the rotor rotates upward and the shrinkage fit of the thrust collar 2 relaxes.

That is, when the force of the cold spring force of the sleeve 4 that pushes the thrust collar toward the fillet 7 overcomes the frictional force caused by the tightening pressure, as the rotor rotates up and the shrinkage fit of the thrust collar decreases. , the thrust collar 2 is smoothly moved in the axial direction, and the end face 8 of the thrust collar and the rotor fillet 7 are brought into close contact. As a result, the cold spring force of the sleeve 4 is relaxed and the outer diameter is restored, and the contact pressure between the rotor fillet 7 and the thrust collar one end surface 8 and between the thrust collar one end surface 9 and the sleeve end surface 10 is averaged. .

It is desirable that this force exchange be performed at a speed exceeding the rated rotational speed.

Furthermore, once the above-mentioned force is exchanged, during subsequent operations, the areas 7-8 and 9-10 are always in close contact, and the thrust collar does not wobble in the axial direction as in the conventional structure. Never again.

Even if the thrust collar 2 moves due to excessive thrust force applied under abnormal operating conditions, the cold spring force acts to push the thrust collar 2 back to its normal position when the rotation increases thereafter.

According to this embodiment, the large capacity machine for 3600 rpm is DSS
Shrink-fit thrust collars can be used even when in operation.

In addition, in the 5661b turbine, both the high-pressure and intermediate-pressure rotors are made of 12Cr steel, so the thrust collar is shrink-fitted, and measures to extend the life of the shrink-fit thrust collar are required.

〔Effect of the invention〕

According to the present invention, it is possible to prevent the shrink-fit thrust collar from loosening in the axial direction during operation and to reduce the shrink-fit allowance, thereby extending the life of the thrust collar.

[Brief explanation of drawings]

Fig. 1 is a sectional view of one embodiment of the present invention, Fig. 2 is a detailed view of Tabe in Fig. 1, Fig. 3 is a sectional view taken along the line mm in Fig. 1, and Fig. 4
The figure is a cross-sectional view of the conventional structure, Figure 5 is a detailed view of the V section in Figure 4, and Figure 6 is a detailed view of the V section in Figure 4.
The figure is a sectional view taken along the line VI-vi in FIG. 4. Figure 1 Figure 20 Figure 3

Claims (1)

[Claims] 1. Hold the thrust collar in the axial direction, apply an axial cold spring to the sleeve positioned by the shaft nut during assembly, and the moment the rotor rotates up for the first time and the tightening force on the inner diameter part is relaxed, By using the cold spring force to move the thrust collar in the axial direction toward the fillet of the rotor and bringing it into close contact with the fillet, the thrust collar can be easily moved during subsequent increases in rotor rotation and turbine operation. A shrink-fit thrust collar that is characterized by having a pressing force that prevents it from loosening in the axial direction.