JPH0565016B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] "Field of Industrial Application" The present invention relates to mechanical seals. More specifically, the present invention relates to a method and apparatus for determining the condition of a sliding surface of a mechanical seal.

"Problems to be solved by conventional techniques and inventions" In rotating machines for the purpose of transporting fluids,
Mechanical seals are often used in shaft sealing devices, and although mechanical seals have an extremely high probability of failure compared to other mechanical elements, it is not possible to detect abnormalities until they actually cause a leak. However, it was difficult to predict failures in advance.

Conventionally, a method has been proposed in which a high-frequency vibration sensor is attached to the sliding member (fixed side) of a rotating machine, and the high-frequency vibration generated by sliding is detected to detect abnormalities in the sliding member (Japanese Patent Application Laid-Open No. 1983-1999). Publication No. 98353)
However, this method determines the presence or absence of an abnormality by simply comparing the amplitudes of the detected waveforms, and is effective in determining, for example, the presence or absence of contact between a balance disk and a balance sheet, a labyrinth seal and a shaft, etc. Unlike mechanical seals, it is not possible to constantly monitor and evaluate the sliding state of the seals. In addition, attempts have been made to monitor the sliding condition of mechanical seals by measuring vibrations of mechanical seals with vibration sensors that have sensitivity characteristics in a relatively low frequency band, but this method does not allow for bearings other than mechanical seals and fluid noise. It is not possible to fully evaluate the sliding condition of a mechanical seal because it is easily affected by noise caused by such factors.

An object of the present invention is to provide a device that can easily and reliably evaluate the sliding condition of a mechanical seal during operation and predict failures of the mechanical seal.

[Structure of the invention]

"Means to solve the problem" Noises caused by bearings other than mechanical seals, fluid sounds, etc. are in the low frequency band below 100KHz, while vibrations generated by mechanical seals are from 100KHz to
This is a high frequency band of 2MHz. The present invention operates from 100KHz to
Because we decided to use a high-frequency vibration sensor with a wide-band frequency sensitivity characteristic of 2MHz or a high-frequency vibration sensor with a narrow-band frequency sensitivity characteristic with a resonance point within the range of 100KHz to 2MHz, we ignored the effects of noise other than the mechanical seal. It can be made as small as possible. Furthermore, the high frequency vibration generated by the mechanical seal can be reliably detected by an extremely simple method of attaching the high frequency vibration sensor to the casing of a mechanical device.

The sliding surface of a mechanical seal performs two contradictory functions: sealing the liquid and preventing wear of the sliding material through the lubricating effect of the liquid.The formation state of the lubricant film and its stability are This greatly affects the life of the seal and the occurrence of failures. The high-frequency vibrations generated by mechanical seals are caused by solid contact between sliding materials and are closely related to the state of lubricant film formation. The frequency also becomes higher. Further, the sliding state of the mechanical seal is not necessarily constant, and if the lubricating film formation state is unstable, the high frequency vibrations generated by the mechanical seal will vary depending on the stability.

The present invention measures extremely high-frequency vibrations generated by mechanical seals externally, and calculates the effective value, energy value, and number of times the output amplitude of the high-frequency vibration sensor output exceeds a certain threshold per unit time. or some of them are measured continuously, and the level of the value and the fluctuation range in unit time, or the number of times the amplitude of the high frequency vibration sensor output exceeds a certain threshold in unit time, is determined as a threshold. Since we decided to use the amplitude distribution etc. obtained by counting while changing the magnitude of the values, it became possible to clearly evaluate the formation state of the above-mentioned lubricant film and its stability.

With the above method, it is possible to compare the magnitude of the sensor output level and the damage state of the sliding surface of a mechanical seal by accumulating data on both the sensor output and the damage state of the sliding surface for a specific mechanical seal. , the sensor output data is unique to each mechanical seal and has no general meaning. For this reason, for mechanical seals for which no data has been accumulated, it is not possible to immediately evaluate the sliding condition from sensor output data.

The present invention provides that high-frequency vibrations generated by mechanical seals are caused by solid contact between sliding materials, and that the degree of damage to the sliding surface of a mechanical seal is determined by the ratio of the solid contact area to the total sliding area. Focusing on the effective value of the high frequency vibration sensor output,
By introducing an evaluation coefficient consisting of the ratio of the energy value, etc. and the mechanical seal sliding area, and using this evaluation coefficient, it is now possible to evaluate the condition of the sliding surface even for mechanical seals with different shapes for which no data has been accumulated. This is what I did.

"Example" Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram including a longitudinal sectional view of the pump.

A pump shaft 3 directly connected to the motor shaft of the motor 1 by a shaft coupling 2 is supported by a bearing 5 housed in a pump casing 4, and is sealed by a shaft sealing device 6 such as a mechanical seal and an oil seal (not shown), and is connected to a pump chamber. An impeller 8 is provided in the pump chamber 7 so as to protrude from the pump chamber 7 .

The mechanical seal includes a driven ring 11 that is sealed in the pump casing 4 by a sealing shaft 9 and is movable in the axial direction, a rotating ring 12 fixed to the pump shaft 3 that slides on the driven ring 11, and a rotary ring 12 between the driven ring 11 and the pump casing 4. A spring 13 biases the driven ring 11 toward the rotating ring 12 in the axial direction.
Most of these are immersed in a liquid that serves both as cooling and lubricating. Note that a rotation stopper may be separately provided to prevent the driven ring 11 from rotating. The area A of the sliding surface of the mechanical seal is π/4 (D ₀ ² −D ₁ ² ), where the outer diameter of the sliding surfaces of the driven ring ₁₁ and the rotating ring 12 is D ₀ and the inner diameter is D 1 .

A high frequency vibration sensor 1 is installed in the pump casing 4.
4 is installed.

The vibration wave type of the mechanical seal detected by the high frequency vibration sensor 14 attached to the pump casing 4 is amplified by the amplifier 15 and then sent to the signal converter 1.
6, the effective value or the energy value or the amplitude of the output is converted into a number exceeding a certain threshold per unit time, and the converted value is input to the arithmetic unit 17.
Then, the ratio between the input value and the area A of the sliding surface of the mechanical seal stored in advance is calculated, and the result is output to the output display device 18 and displayed.

What is input to the arithmetic unit 17 is not limited to the number of times in which the effective value, energy value, or output amplitude obtained from the vibration waveform of the mechanical seal exceeds a certain threshold per unit time; It may be another statistical value corresponding to the condition of the sliding surface of the mechanical seal. By dividing such statistical value by the area A of the sliding surface of the mechanical seal, an evaluation value of the sliding surface of the mechanical seal in general can be obtained.

In order to reduce the influence of noise caused by bearings other than mechanical seals, fluid sounds, etc., the high frequency vibration sensor 14 focuses on the fact that these noises are in a relatively low frequency band of 100 KHz or less.
Wideband high frequency vibration sensor 14 with wideband frequency sensitivity characteristics from Hz to 2MHz or 100KHz to 2M
A resonant high-frequency vibration sensor 14 having narrow-band frequency sensitivity characteristics with a resonance point within the Hz range is used. FIG. 2 shows an example of the frequency sensitivity characteristics of the broadband high frequency vibration sensor 14, and FIG. 3 shows an example of the frequency sensitivity characteristics of the resonance type high frequency vibration sensor 14. The calculation device 17, such as a measurement electronic computer,
High-frequency vibration sensor 14 with high-speed A/D converter
Read the output and perform various calculations and evaluations.
Note that the calculation of the effective value etc. does not necessarily need to be performed by the electronic measuring computer, and a method may be used in which the output of the high frequency vibration sensor 14 is led to an effective value voltmeter or the like and the output is read by the electronic measuring computer.

An example of the operation of the present invention will be explained using the flowchart shown in FIG.

When the motor 1 is energized, the pump shaft 3 rotates via the shaft joint 2, and the impeller 8 sucks in liquid, increases the pressure and speed, and discharges the liquid. Rotating ring 12 and driven ring 1
1 is to rub. Rotating ring 12 and driven ring 11
Vibration based on the solid sliding component is transmitted through the casing 4 with almost no attenuation, and is detected by the high frequency vibration sensor 14.

When the system is activated, in step 101, the high frequency vibration sensor 14 measures high frequency vibrations generated from the sliding surfaces of the rotating ring 12 and the driven ring 11, and the amplifier 15 amplifies the high frequency vibrations. Step 101
In step 102, the signal is input to the signal converter 16 and converted into an effective value, an energy value, or an A/D
The number of converted outputs whose amplitude exceeds a certain threshold per unit time is determined and sequentially stored. In step 103, it is determined whether the above calculation has elapsed for a certain period of time (sampling time) necessary for the statistical value, and is repeated until the certain period of time has elapsed. The obtained data group is statistically analyzed in step 104, and the result is divided by the pre-stored area A of the sliding surface of the mechanical seal.In step 105, this data and the sliding state of the mechanical seal are analyzed. The evaluation results are output to a display device 18 such as a display, printer, plotter, etc. The above is repeated.

FIG. 5 shows an example of high frequency vibration data analysis and an example of a method for evaluating mechanical seal sliding surfaces using the data. Figure 5 shows the frequency distribution of a data group continuously measured at a given time. Any number exceeding the threshold may be used, and the vertical axis is the frequency of data. In the figure, the broken line indicates a case where a good lubricant film is formed on the sliding surface, the solid line indicates a case where the lubricant film is unstable, and the dashed line indicates a case where the lubricant film is unstable. This is a case where the formation is insufficient and close to dry friction. Further, the average values and deviations in each case are indicated by symbols a1 to a3 and s1 to s3 in the figure. These values allow the condition of the above-mentioned sliding surface to be quantitatively evaluated.

FIG. 6 shows another evaluation method. Figure 6 shows the amplitude distribution obtained by counting the number of times the amplitude of the high-frequency vibration sensor output exceeds a certain threshold per unit time by varying the size of the threshold. , △ indicates when a good lubricating film is formed on the sliding surface, ○ indicates when the lubricating film is unstable, and ● indicates when the lubricating film is unstable. This is a case where the formation is insufficient and close to dry friction. This evaluation method also makes it possible to clearly distinguish the condition of the sliding surface.

The evaluation value thus obtained is unique to that mechanical seal. The inventors (and others) of the present invention found that by dividing the above evaluation value by the area A of the sliding surface of the mechanical seal, it shows a nearly constant value corresponding to the condition of the sliding surface of the mechanical seal. Ta. Therefore, by using the evaluation coefficient obtained by dividing the above evaluation value by the area A of the sliding surface of the mechanical seal, the condition of the sliding surface can be immediately known even for mechanical seals for which no data has been accumulated.

〔Effect of the invention〕

The present invention includes a high-frequency vibration sensor that measures high-frequency vibrations generated by the mechanical seal during operation, which is attached to the outside of the mechanical seal of a rotating machine equipped with a mechanical seal, and inputs the output of the high-frequency vibration sensor. The computer includes a calculation device that analyzes and outputs high-frequency vibrations generated by the mechanical seal in each state of the sliding surface of the mechanical seal, and the calculation device analyzes the effective value, energy value, and amplitude of the output of the high-frequency vibration sensor per unit time. Continuously calculate one of the statistical values corresponding to the condition of the sliding surface unique to the mechanical seal, such as the number of times exceeding a certain threshold, and calculate from the ratio of that value to the area of the mechanical seal sliding surface. Since the mechanical seal sliding condition monitoring device is characterized in that it calculates an evaluation coefficient that The area where the condition of the sliding surface becomes unstable becomes clear. That is, the condition of the sliding surface can be grasped successively from the beginning of use until it wears out and becomes unusable.

According to the present invention, it has become possible to evaluate the sliding condition of a mechanical seal during operation, and it has become possible to predict failures of the mechanical seal.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram including a vertical cross-sectional view of a pump according to an embodiment of the present invention, Figs. 2 and 3 are diagrams showing sensitivity characteristics of a high frequency vibration sensor, Fig. 4 is a flowchart, and Fig. 5 , FIG. 6 is an evaluation diagram of the sliding state of the mechanical seal. 1...Motor, 2...Shaft coupling, 3...Pump shaft, 4...
Pump casing, 5... bearing, 6... shaft sealing device, 7
... Pump chamber, 8 ... Impeller, 9 ... Sealing ring, 11 ... Driven ring, 12 ... Rotating ring, 13 ... Spring, 14
...High frequency vibration sensor, 15...Amplifier, 16...Signal converter, 17...Arithmetic device, 18...Output display device, 101-105...Step.

Claims (1)

[Claims] 1 A high-frequency vibration sensor that measures high-frequency vibrations generated by the mechanical seal during operation is attached to the outside of the mechanical seal of a rotating machine equipped with a mechanical seal, and the output of the high-frequency vibration sensor is input to comprises a calculation device that analyzes and outputs high-frequency vibrations generated by the mechanical seal in each state of the sliding surface, and the calculation device analyzes the effective value of the output of the high-frequency vibration sensor;
Continuously calculate any of the statistical values corresponding to the sliding surface condition specific to that mechanical seal, such as the energy value or the number of times the output amplitude exceeds a certain threshold per unit time, and compare that value with the mechanical A mechanical seal sliding condition monitoring device, characterized in that it calculates an evaluation coefficient consisting of a ratio to the area of a seal sliding surface.