JPH0521481B2 - - 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 means for detecting the amount of wear of a mechanical seal.

"Problems to be solved by the prior art and the invention" In rotating machines that use mechanical seals to seal their shafts, not only do mechanical seals leak, which degrades the performance of the rotating machines or processes, but also flammable In cases such as pumps that handle pumped liquid, there is a risk of a major accident. Therefore, maintenance and inspection of conventional mechanical seals is performed with great concern.

In evaluating the lifespan and operational soundness of a mechanical seal, the amount of wear and wear rate of the sliding material of the mechanical seal are extremely important parameters.
Conventionally, there are two methods to determine the amount of wear on the sliding material of a mechanical seal: one is to stop the machinery, disassemble the machinery and mechanical seal, and measure it directly, and the other is to measure the displacement of the driven ring using a non-contact displacement meter, etc. There are two ways. The former method requires stopping and disassembling the mechanical equipment, which requires a lot of maintenance cost and time, and therefore, although it may be carried out during periodic inspections, it cannot be used as a monitoring method during normal operation. The latter requires space to install the sensor. There are disadvantages such as being subject to many restrictions such as the atmosphere, and when measuring for a long time, the characteristics of the sensor change and it is not possible to measure displacement with high precision.
In reality, it is almost never done. Japanese Unexamined Patent Publication 1977-
The invention disclosed in Publication No. 98353, for example, is one in which a high frequency vibration sensor is attached to a fixed sliding member of a balance sheet, but this earlier invention uses fluid lubrication to detect whether or not the sliding state of the balance disk and balance sheet is abnormal. Although it is possible to determine whether the device is sliding underneath or in contact with a solid object, it is not possible to determine the amount of wear, and the original purpose was to detect abnormal contact conditions. Another problem is that in order to attach the detection means to the fixed sliding member, the fixed sliding member or its casing must be processed and the lead wires must be passed through the inside and outside of the machine.

An object of the present invention is to provide an apparatus that can easily evaluate the amount of wear of a mechanical seal during operation.

[Structure of the invention]

``Means for Solving the Problems'' The present invention provides a shaft sealing means and an impeller driven by a driving means, which is housed in a pump casing, and the driving means is a motor with little unevenness in rotation, and the pump casing and the impeller are driven by a shaft sealing means and a driving means. The pump casing of a pump that has a large mass and whose vibrations are low frequency, and has a mechanical seal in the shaft sealing means, and the mechanical seal has a small mass and whose vibrations are 100 KHz or more due to wear. to the outside
This is a mechanical seal wear amount evaluation device equipped with a high frequency sensor with sensitivity characteristics of 100KHz or higher and a calculation device that determines the wear of the mechanical seal based on the amplitude of vibration output by this high frequency sensor.

"Operation" Since the vibration generated by the mechanical seal is high frequency, there is only a slight attenuation and it is detected by a high frequency vibration sensor outside the casing where the mechanical seal is installed. When operating continuously or at regular intervals with a certain sampling time, the variables related to the vibration wear of the mechanical seal obtained and processed by the high-frequency vibration sensor, such as amplitude, effective value or energy value, are integrated by a calculation unit. The amount of wear of the mechanical seal is evaluated by comparing this integral value with a previously known relationship between the amount of wear of the mechanical seal.

"Example" Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is a flow sheet including a longitudinal cross-sectional view of the pump. First, a pump will be explained as an example of a rotating machine equipped with a mechanical seal. A pump shaft 3 connected to the motor shaft of a motor 1 with little uneven rotation by a shaft coupling 2 is supported by a bearing 5 housed in a pump casing 4 having a large mass, and is supported by a mechanical seal having a small mass, an oil seal (not shown), etc. An impeller 8 whose shaft is sealed by the shaft sealing device 6 and which protrudes into the pump chamber 7 and has a large mass in the pump chamber 7.
Equipped with.

The mechanical seal includes a driven ring 11 that is sealed in the pump casing 4 by a sealing ring 9 and is movable in the axial direction, a rotating ring 12 that is 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 1 biases the driven ring 11 in the axial direction toward the rotating ring 12.
3, most of which are immersed in a liquid that serves both as cooling and lubricating. Note that a rotation stopper may be separately provided to prevent the stationary ring 11 from rotating. The mechanical seal described above has vibrations of 100 KHz or more due to wear.

In the pump casing 4, the oscillation frequency during operation of the bearing 5, the oil seal sliding surface (not shown), the impeller 8, etc. is at most several tens of kilohertz or less, and is higher than this.
A high frequency vibration sensor 14 having a sensitivity characteristic of 100 KHz or more is attached. In this example
A high frequency vibration sensor 14 with a measurement range of 100KHz to 2MHz was used. 15 is an amplifier that voltage-amplifies the output signal of the high-frequency vibration sensor 14; 16 is a signal converter such as an effective value voltmeter that inputs the output of the amplifier 15; and 17 is an arithmetic unit that integrates the effective value obtained by the signal converter 16. , 18 is a display device such as a printer that displays the output of the arithmetic device 17.

When the motor 1 is energized, the pump shaft 3 rotates via the shaft joint 2, and the impeller 8 sucks in liquid, accelerates the pressure, 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 fixed sliding portion is transmitted through the casing 4 with almost no attenuation, and is detected by the high frequency vibration sensor 14. The solid contact portion between the rotating ring 12 and the driven ring 11 oscillates high-frequency vibrations, but the amplitude and frequency of this vibration are different from that of the rotating ring 1.
2 and the driven ring 11 become compatible, and when the rotary ring 12 and the driven ring 11 are worn out. In the pump shown in Fig. 1, vibrations are transmitted to the pump casing 4 due to fluid force applied unbalancedly to the bearing of the motor 1, the bearing 5 of the pump, the friction between the oil seal and the pump shaft, and the impeller 8. High frequency vibration sensor 1 lower than 100KHz
4, the size is not significantly detectable. Therefore, the high frequency vibration sensor 14 senses only vibrations caused by the fixed friction between the sliding surfaces of the driven ring 11 and the rotating ring 12.

FIG. 2 is a diagram showing the time period during which the coaxial motor 1 is operating and the pump shaft 3 is rotating, and the time period during which the driven ring 11 and rotating ring 12 of the mechanical seal are sliding on the horizontal axis. The signal obtained by the high frequency vibration sensor 14 is a vibration waveform shown in amplitude on the vertical axis in FIG. 2a. This signal is amplified by the amplifier 15 and processed by the signal converter 16, resulting in an effective value rms
is plotted on the vertical axis, the change in effective value is shown by curve 1 in Figure 2 b.
9. This effective value is determined by the arithmetic unit 17, and the vertical axis is expressed as the effective value rms.As shown in FIG.
1 is required. This integral value 21 is shown in Figure 3 for the driven ring 11 and rotating ring 12 of the mechanical seal.
The vertical axis shows the amount of wear on the sliding surface, and the horizontal axis shows the amount of wear on the sliding surface of
Wear curve 2 of a mechanical seal shown by calculating the integral value of the effective value rms obtained by the calculation device 17 as shown in FIG.
It is compared with the diagram showing 2. For example, when the integrated value 21 of the effective value is 21a in Fig. 3, the wear amount is determined to be 21a', and the effective value 21 is 21b in Fig. 3.
When the amount of wear is 21b', the amount of wear is determined to be 21b'. The above judgment can be made by displaying the integral value 21 of the effective value on the display device 18 and comparing it manually, but by storing FIG. 3 as a data table in the arithmetic device 17 in advance, 16 output signals to A/
The D-conversion is input to the arithmetic unit 17 and calculated to determine the amount of wear of the mechanical seal, for example, the amount of wear 21.
It is appropriate to output a', 21b', etc. to the display device 18. In the above, the processing unit 17 captures the processed effective value coming from the high frequency vibration sensor 14 continuously or at regular intervals of sampling time. The time variable in the integration using the time variable of the effective value of the vibration of the mechanical seal in the arithmetic unit 17 described above is obtained from the control device (not shown) for the motor 1, thereby obtaining the pump operating time.

In FIG. 3, reference numeral 23 indicates the point at which destructive wear begins, and it is preferable that the display device 18 issue a warning before the amount of wear approaches this point to notify the time for maintenance and inspection.

The wear curve 22 shown in FIG. 3, which represents the wear versus the integral value of the effective value rms, differs depending on the materials of the driven ring 11 and the rotating ring 12, the sealing fluid, the cooling lubricant, and the like. However, the progress of wear due to solid friction is large at the time of initial wear and before destructive wear occurs. Therefore, the arithmetic unit 17 calculates the change in the slope of the wear curve 22, and the display unit 18 calculates the change in the slope of the wear curve 22 before destructive wear occurs.
It may also be possible to output an alarm to the

In the embodiment, mechanical vibrations obtained by a high-frequency vibration sensor are captured as effective values, but this is equivalent to capturing them as vibration energy values, and a time-integrated value of vibration energy may also be used. Alternatively, the representative value of the amplitude of the mechanical seal vibration, for example, the average value,
It may be based on the mode value, maximum value, etc.

〔Effect of the invention〕

The present invention has an impeller driven by a shaft sealing means and a driving means, which is housed in a pump casing, and the driving means is a motor with little uneven rotation, and the pump casing and the impeller have a large mass, and vibrations originating from them. is a low frequency, and the shaft sealing means has a mechanical seal, and this mechanical seal has a small mass and vibrations of 100 KHz or more due to its wear are applied to the outside of the pump casing of the pump.
This is a mechanical seal wear amount evaluation device equipped with a high frequency sensor with a sensitivity characteristic of 100KHz or more and a calculation device that determines the wear of the mechanical seal based on the amplitude of the vibration output by this high frequency sensor. 1. Disassemble the mechanical device. The amount of wear can be evaluated during operation without having to

2. The sensor can be attached to the casing of a mechanical device, making it extremely easy to measure regardless of the space or atmosphere.

[Brief explanation of drawings]

Figure 1 is a flow sheet of an embodiment of the present invention;
Figure a is a diagram showing the vibration of a mechanical seal.
Fig. 2b is a diagram showing the effective value of vibration of the mechanical seal, Fig. 2c is a diagram showing the integral value of Fig. 2b, and Fig. 3 is a diagram showing the wear characteristics 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, 1
7... Arithmetic device, 18... Display device, 19... Curve, 21, 21a, 21b... Integral value, 21a',
21b'...Wear amount, 22...Wear curve, 23...
point.

Claims (1)

[Claims] 1. An impeller driven by a shaft sealing means and a driving means is housed in a pump casing, the driving means is a motor with little uneven rotation, and the pump casing and impeller have a large mass and vibrations originating from them are low. The shaft sealing means has a mechanical seal, and the mechanical seal has a small mass and the vibration resulting from wear of the mechanical seal is 100KHz or more on the outside of the pump casing.
Equipped with a high frequency sensor with sensitivity characteristics of Hz or higher,
A mechanical seal wear amount evaluation device equipped with a calculation device that determines mechanical seal wear based on the amplitude of vibration output by this high-frequency sensor.