JPS5859302A - Monitor for steam turbine - Google Patents

Abstract

PURPOSE:To detect the abnormal vibration of a turbine shaft and to enable an alarm to be produced for informing of cracks by a method wherein a rotary synchronizing vibration and a rotary synchronizing double vibraion component are extracted from the vibration of the turbine shaft and compared to each other, and the compared value is further compared with a total amplitude. CONSTITUTION:A vibration sensor 11 transduces the sensed vibration of a turbine shaft 8 to an electrical signal. A full amplitude calculater 13 calculates a full amplitude value of vibration. A synchronized vibration calculater 14 separates the vibration value of a rotating synchronizing vibration component as VOMEGA. The synchronizing double vibration calculater 15 separates a vibration value of the rotating synchronizing double vibration component as Z2OMEGA. A comparater calculater 17 compares all the amplitudes from the full amplitude calculater 13 with a value of V2OMEGA/VOMEGA from the divider 16, and when both values exceed the prescribed relation, an alarm signal is produced. In this way, some cracks in the turbine shaft 8 can properly be detected.

Description

[Detailed description of the invention]

The present invention relates to a monitoring device for steam turns used in thermal power generation, nuclear power generation, etc., and in particular, it is capable of detecting vibrations peculiar to the occurrence of cracks in the turn shaft, thereby preventing subsequent major accidents. The present invention relates to a steam turbine monitoring device that can prevent steam turbines from occurring. Generally, in large capacity steam turbines, for example,
As shown in FIG. 1, a high pressure turbine 1, an intermediate pressure turbine 2
, the low pressure turbine 3 and the generator 4 each have a plurality of radial shafts 5. ......, supported by 5. Further, each of the shafts is integrally connected by a plurality of shaft joints (for example, couplings) 6, 6.6, and is held in the thrust bearing by one thrust bearing 7. The reason why only one thrust bearing 7 is provided in this model is because each shaft is heated to a high temperature.

[This is to prevent the shaft from being restrained when it is extended in the axial direction.] Further, as shown in FIG. 2, the shaft couplings 6, 6 are normally shrink-fitted onto the turbine shaft 8. Since the turbine shaft 8 is loaded with a bending moment M due to the weight of the disk, cylinder, etc. and its own weight, a bending moment M is also loaded on the shrink-fit portions of the shaft couplings 6, 6.6. . Therefore, as shown in Fig. 3 and Fig. 4, the contact points A and B (Fig. 3) with the sixth end face of the shaft coupling on the turbine shaft 8 when no moment) M is applied are the moment).
When M is loaded, each moves to 4VC (Fig. 4). This movement is repeated as the turbine shaft 8 rotates, whereby the outer peripheral surface of the turbine shaft 8 and the inner peripheral surface of the shaft coupling 6 rub against each other (fretting phenomenon). When this phenomenon occurs, the turbine shaft 8 becomes extremely disadvantageous in terms of strength and becomes susceptible to cracking.・In other words, cracks occur even when a very small bending stress is applied compared to the case of normal bending fatigue. Finally, the turbine shaft 8 breaks. In this case, as described above, each two-bin shaft 8 and the generator shaft are connected to a plurality of shaft couplings 6.
It is integrally connected by ゜6.6, and its integral axis is
Since they are supported in the axial direction by a single thrust bearing 7, if a shaft fracture like the one described above occurs at any location, axial support of all the turbine shafts 8 and the generator shaft will become impossible, and the fracture will occur. Not only will the turbine be damaged, but
In all turbines, it is conceivable that the turbine blades may come into contact with the casing or nozzle, causing severe secondary damage. Therefore, the present invention provides a steam turbine monitoring device that is capable of preventing serious secondary damage by simultaneously detecting the occurrence of cracks in the turbine shaft due to the 7 retting phenomenon and issuing an alarm. is intended to provide. The present invention includes a vibration detector that detects rotational vibration of a turbine shaft of a steam turbine and converts the detected vibration into an electrical signal;
an amplifier that amplifies the electrical signal from the vibration detector; a total amplitude calculator that integrates the electrical signal to obtain a total amplitude value of vibrations possessed by the turbine shaft; A synchronous vibration calculator and a synchronous double vibration calculator that respectively calculate the amplitude value of a vibration component having the same frequency as the rotation speed and the amplitude value of a vibration component having a frequency twice the rotation speed, and the synchronous double vibration calculator Dividing the obtained amplitude value by the amplitude value obtained by the synchronous vibration calculator. a comparator; and a comparator that determines the magnitude of the divisor - determined by the divider with respect to the total amplitude value determined by the total amplitude arithmetic unit, and outputs an alarm signal if the magnitude exceeds a predetermined amount. It is characterized by consisting of. Hereinafter, the details of the vibration detector 11 will be explained based on the drawings of the embodiments of the present invention. A conical detector lie is formed at the tip of the detection portion 11m, and the detector lie is pressed against the outer circumferential surface of the turbine shaft 8 via the detection rod lid, thereby suppressing vibrations of the turbine shaft 8. It is designed to reciprocate according to the This reciprocating motion of the detector 11o is transmitted to the converter 11b through the detection rod lid, and converted into an electric signal corresponding to the speed or amplitude of vibration of the turbine shaft. The electrical signal is amplified by an amplifier 12 and then output to a full amplitude calculator 13, a synchronous vibration calculator 14, and a synchronous double vibration calculator 15. First, the total amplitude calculator 13 is
It has an integration function, and its total amplitude calculator 13 integrates all frequency components included in the electrical signal from the vibration detector 11. the result,
The total amplitude value of the vibrations of the turbine shaft 8 is determined, and the value is output to the comparator 17. Next, in the synchronous vibration calculator 14, among all the frequency components of the vibration of the turbine shaft 8 detected by the vibration detector 11, a vibration component having the same frequency as the turbine shaft 80 rotation speed (a rotation synchronous vibration component ) is separated as VΩ. Similarly, in the synchronous double vibration calculator 15, a vibration component having a frequency twice the rotational speed of the turbine shaft 8 (rotation synchronous double vibration component ) is separated as V2O. These VΩ and v20 signals are then sent to the divider 16. In the divider 16, v2
The calculation ΩΔΩ is performed, and the signals of v2Ω and /VΩ are output to the comparator 17. Now, the comparison calculator 17 compares the total loss width value from the total amplitude calculator 13 with the value of v2Ω7haW from the divider 16, and when both values exceed a predetermined relationship, an alarm signal is issued. It is designed to emit. This alarm signal is output to an alarm device (not shown), and if there is no crack in the alarm device-bin shaft 8, the vibration of the turbine shaft 8 is mostly a rotational synchronous vibration component, and other frequencies are detected. The vibration component of is very small. Note that the amplitude value of this vibration changes from moment to moment due to temperature changes of the turbine shaft 8 and other conditions. When cracks occur due to the fretting phenomenon,
Since the bending rigidity of the turbine shaft 8 is asymmetric with respect to the central axis, vibrations having a frequency that is an integral multiple of the rotation speed of the turbine shaft 8 occur (for example,
n B@havior of A Turbln@Ro
torComtalning A Transurse
Crack, B., Grabowiki. 140/Vol 102, January 198
0 Transaatlon of The ABME
2), the amplitude value v2Ω of the rotationally synchronized double vibration component becomes large. However, the occurrence of cracks can be determined by the value of 2Ω. However, like VΩ, the value of v2Ω varies depending on the conditions of the turbine shaft 8, so to determine the occurrence of cracks, simply
(2) Instead of looking at the magnitude of 20, it is necessary to make a judgment based on the magnitude of the value of V20/VΩ. Furthermore, since the shaft of the generator connected to the turbine shaft 8 is structurally non-axisymmetric, it is originally rotated with a constant amplitude.
It has a double vibration component. Since the double vibration component is transmitted to the turbine shaft 8 via the shaft coupling 6, the excessive vibration detected from the turbine shaft 8 has a constant value regardless of cracks or fluctuations in the total loss width value. Contains v2Ω. Therefore, even when no cracks occur in the turbine shaft 8, if the value of ■ changes to the smaller side. The value of v2Ω/VΩ becomes thick. That is, v2ΩAΩ
It is difficult to judge the occurrence of cracks using only the value of (m
When VΩ is small, cracks have not occurred unless the value of V2Ω/V^ is larger, and a total loss~゛ If the width value or the value of ■Ω is large, sometimes the value of v2Ω/■) Cracks may occur even if they are small. Therefore, in order to correlate the occurrence of cracks with the value of v2ΩAΩ, it is necessary to
There is a chikuwa that evaluates and cuts the value of 2Ω/VΩ. In the end □,
The curve shown in FIG. 6 represents the boundary where cracks occur, and cracks occur in region A above this curve, and no cracks occur in region B below. Therefore, in the comparator 17, v2Ω/■Ω
When the value exceeds a predetermined value and is in the A@ range, an alarm signal is issued. As described above, the present invention detects vibrations occurring in the turbine shaft, and detects rotation-synchronous vibration components and rotation-synchronous double vibration components from the detected and captured images. By extracting the amplitude values and comparing the two amplitude values, and by comparing the compared values with the total amplitude value of the shaft vibration, a warning signal is issued. When a crack occurs in the turbine shaft due to the fretting phenomenon in which the turbine shaft and shaft joint rub against each other, K accurately detects an abnormality in the turbine shaft at the same time as the crack occurs. This has a great effect in that it can issue a warning and prevent secondary damage that could cause a chain reaction of accidents to other turbines. ]

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the arrangement of a plurality of steam turbines and a generator, Fig. 2 is a schematic diagram showing a shaft joint of a turbine shaft, and Fig. 5 is a monitoring device in an embodiment of the present invention. Fig. 6 is a system diagram showing the structure of the system, and is a line diagram showing the occurrence of cracks i-. 1.2.3... Steam turbine, 4... Generator, 6...
...Axis 4 (main hand, 8...turbine shaft, 11...shaft @
Detector, 12... Amplifier, 13... Total amplitude calculator,
14... Synchronous photographing and dipping device, 15... Synchronous double vibration calculator, 16... Divider, 17... Comparison operator II.・ ・Deputy of dispatcher Inomata Figure 6 Figure JIfJz Figure 6

Claims (1)

[Claims] A vibration detector for detecting the rotational vibration of the turbine shaft of a steam turbine and converting the detected vibration into an electric signal; an amplifier for amplifying the electric signal from the MiJ vibration detector; and an amplifier for integrating the electric signal. A total amplitude calculator that calculates the total amplitude value of 1 to 1 of the turbine shaft, and the amplitude value of the vibration component of the vibration detection electric signal having the same frequency as the rotation speed of the turbine shaft and the rotation speed of the turbine shaft. A synchronous vibration calculator and synchronous 2 that calculate the amplitude values of vibration components with twice the frequency.
Double vibration calculation 4, ■1■ A divider that divides the amplitude value obtained by the Ho-synchronous double vibration calculation unit by the amplitude value calculated by the four-period vibration 1 calculation unit, and a Moe d Pi total amplitude calculation unit. A steam turbine characterized in that it comprises a ratio soft calculator which judges the magnitude of the divisor value obtained by the above-mentioned division 'l+i with respect to the total amplitude value and outputs an alarm signal when the magnitude exceeds a predetermined value. monitoring equipment.