JP6867972B2 - Wear detection method for electric valve drive device - Google Patents

Description

The present invention relates to a method for detecting wear of a stem nut of an electric valve drive device installed in various plants such as a thermal power plant.

There are various types of valves installed in various plants, but the present invention is a technique relating to a method for detecting wear of a stem nut of an electric valve drive device that drives a valve such as a sluice valve in which the stem reciprocates.

The general drive mechanism of the electric valve drive device has a structure in which the rotation of the motor is decelerated by a reduction gear train such as a worm gear and transmitted to the drive sleeve, and the stem nut fitted in the drive sleeve is rotated. There is. Then, in the case of a sluice valve, the stem screwed with the stem nut is reciprocated to open and close the valve. Steel-based materials such as stainless steel and special steel are used as the material of the stem, and male threads are formed on the outer peripheral surface of the stem. On the other hand, a brass-based material is often used for the stem nut screwed with the male screw in order to prevent galling of the sliding surface. This enables smooth sliding between the male screw of the stem and the female screw of the stem nut.

However, when the electric valve drive device is operated for a long period of time, the sliding surface of the male screw of the stem made of steel material does not wear, but the sliding surface of the female screw of the stem nut made of relatively soft brass material is often. More or less wear is inevitable. The degree of wear varies depending on the environmental conditions in which the electric valve drive device is installed and the maintenance conditions, but if the sliding surface of the female screw of the stem nut progresses, in the worst case, the thread of the female screw will fall off. It is possible that the function as a stem nut will be lost.

Therefore, for the electric valve drive device that drives an important valve, it is necessary to take measures such as detecting the wear of the female screw of the stem nut and replacing it before the function as the stem nut is lost. ~ 3 discloses a technique relating to a method for detecting wear of a stem nut.

Patent Document 1 focuses on the fact that when the sliding surface of the stem nut is worn, the delay time from the start of the stem nut to the start of the stem becomes long, and a method of detecting the amount of wear of the stem nut. Is disclosed. Specifically, the valve lift sensor, the vibration acceleration sensor, and the time sensor are used to calculate the time from the impact sound of the start of rotation of the worm wheel to the start of movement of the stem to detect wear.

Similar to Patent Document 1, Patent Document 2 discloses a method of detecting the amount of wear of a stem nut, focusing on a hammer blow mechanism provided as standard in an electric valve drive device. Specifically, a displacement detection sensor, a vibration detection sensor, and a time sensor are used to calculate the time from the occurrence of a hammer blow due to the collision between the worm wheel and the drive sleeve to the start of movement of the stem to detect wear. is there.

Similar to Patent Document 2, Patent Document 3 discloses a method of detecting the amount of wear of the stem nut by focusing on the hammer blow mechanism of the electric valve drive device. Specifically, a torque detection sensor and a time sensor are used to calculate the time from the generation of impact torque by a hammer blow to the increase in torque at the start of movement of the stem to detect wear.

Japanese Unexamined Patent Publication No. H02-307033 Japanese Unexamined Patent Publication No. H09-005064 Japanese Unexamined Patent Publication No. 2002-130531

However, in the invention of Patent Document 1, a valve lift sensor and a vibration acceleration sensor are indispensable, but since these sensors are not standard equipment in the electric valve drive device, they need to be separately arranged and installed. Therefore, there is a problem that time and money must be spent.

Further, the invention of Patent Document 2 also requires a displacement detection sensor and a vibration detection sensor, and has the same problems as the invention of Patent Document 1.

Further, in the invention of Patent Document 3, a torque detection sensor is indispensable, and although a standard electric valve drive device is provided with a mechanical torque limiting mechanism, a torque detection sensor capable of outputting a torque signal is provided. Absent. Therefore, in a standard electric valve drive device, it is necessary to separately arrange and install a torque detection sensor, and there is a problem that time and cost must be spent.

Under these circumstances, there is a strong demand for detecting and managing the wear state of the stem nut of the electric valve drive device without requiring a displacement detection sensor, a vibration detection sensor, or a torque detection sensor. Therefore, the present invention provides a wear detection method for calculating the amount of wear of the stem nut of the electric valve drive device without requiring these sensors and only by using a current sensor that detects the current supplied to the motor. The purpose is.

According to the first aspect of the present invention, the rotation of the motor is decelerated by the reduction gear train and transmitted to the drive sleeve, and the rotation of the stem nut fitted in the drive sleeve causes the stem screwed with the stem nut to reciprocate. The valve drive device includes a current sensor that detects the current supplied to the motor and a wear detector that calculates and records the amount of wear of the stem nut, and when the operation of the stem is started in the opposite direction, The first set value for the motor current at the start of rotation of the drive sleeve (A) is registered in the storage unit, and the second set value for the motor current at the start of operation of the stem (B) is registered in the storage unit. , The first set value is a value predetermined from the measured current at the time of hammer blow occurrence with respect to the average value of no-load current, and the second set value is increased by a predetermined amount from the average value of the current after hammer blow occurrence. As a value, the delay time (ΔT) from the start of operation (B) of the stem to the time (C) when the second set value is reached is grasped for each model and size of the electric valve drive device, and the motor. When the current reaches the second set value (C), the delay time (ΔT) is subtracted to make the stem operation start (B), and from the drive sleeve rotation start (A) to the stem operation start (B). ) Is a method for detecting wear of an electric valve drive device, which is characterized in that the amount of wear of the stem nut is calculated based on the time until.

The invention of claim 2 is the invention of claim 1 , wherein the wear detector includes a calculation unit, a timer, and a storage unit, calculates the wear rate of the stem nut, and records it in the storage unit together with a time stamp. However, it is characterized in that the time when the allowable wear limit value is reached is predicted by performing regression analysis from the cumulative operating time and the wear rate of the electric valve drive device.

According to the present invention, it is not necessary to attach a torque sensor or a vibration sensor to the electric valve drive device, and simply by attaching a non-contact current sensor to the power supply line that supplies current to the motor, the stem nut of the electric valve drive device The amount of wear can be calculated. Therefore, the work safety is higher than that of the conventional technique, and the work time and cost can be significantly reduced, which is an excellent effect.

It is a block diagram which shows the structure of this invention. It is a waveform figure which shows the relationship of a motor torque value, a motor current value, and a stem displacement.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a wear detection method for the electric valve drive device 1 according to the present invention. The structure is such that the rotation of the motor 2 is decelerated by a reduction gear train 3 such as a worm gear and transmitted to the drive sleeve 4, and the stem nut 5 fitted in the drive sleeve 4 is rotated. Then, in the case of a sluice valve, the stem 6 screwed with the stem nut 5 is reciprocated to open and close the valve 7.

Further, between the worm wheel, which is the final gear of the reduction gear train 3, and the drive sleeve 4, a hammer blow in the circumferential direction acts on the drive sleeve 4 when the worm wheel reversely starts. There is. This configuration is the same as that of the prior art, and is not shown because it is a well-known technique.

A three-phase induction motor is often used for the motor 2. This is because it is robust, hard to break down, and has the advantages of low maintenance costs. A current transformer (CT) as a current sensor 8 that can detect current in a non-contact manner is attached to one of the power lines that supply power from an AC power supply to a three-phase induction motor, and the output signal of the current sensor 8 is a signal cable. Is transmitted to the wear detector 9. In this embodiment, a current transformer is used as the current sensor 8, but even a commercially available clamp type ammeter can be used as long as it has an output.

The wear detector 9 calculates an A / D converter 10 that converts analog data into digital data, a timer 11 having a timing function, a storage unit 12 that records digital data, current data, time data, and the like. A calculation unit 13 is provided. Current data is input to the A / D converter 10 from the current sensor 8.

FIG. 2 is a waveform diagram showing the relationship between the motor torque value, the motor current value, and the stem displacement of the embodiment in which the sluice valve is inverted by the electric valve drive device. The horizontal axis in FIG. 2 is the time axis, the time changes from the left side to the right side, and the time axes of the three data are shown on the same scale in synchronization. The cursor line (A) shown by the broken line is when the hammer blow occurs, that is, when the drive sleeve starts rotating, and also when it corresponds to the first set value described later. The cursor line (B) indicates the start of operation of the stem. The cursor line (C) is a time point corresponding to the second set value described later.

On the other hand, the vertical axis shows the state quantities of the torque value, the current value, and the stem displacement, and the scale range of each data is adjusted in advance in order to make it easy to see the state change of these data. That is, the absolute value of each data does not have a big meaning, and the transition of the state change with respect to the horizontal axis of each data has a meaning.

The section I shown on the horizontal axis is a section after the stem is raised by the electric valve drive device, stopped once, and then the motor is reversely started to start the lowering operation. In this section, although the rotation of the motor is transmitted to the reduction gear train, it is in a state of almost no load for the motor because it is before the hammer blow occurs. Therefore, the torque value and the current value are extremely small, and can be treated as no load in practice. Further, since the drive sleeve and the stem nut do not rotate, the stem displacement does not change in the section I as a matter of course.

The section II shown on the horizontal axis is a section from the occurrence of the hammer blow to the start of operation of the stem. In other words, it is the time from the start of rotation of the drive sleeve to the start of operation of the stem. The time of this section II will depend on the amount of wear of the stem nut. That is, the drive sleeve starts to rotate due to the occurrence of the hammer blow, but even if the female threaded surface of the stem nut that was in contact at that stage is separated from the male threaded surface of the stem, the female threaded surface and the male threaded surface of the stem are still in contact with each other. Because there is a backlash (gap) between them, the operation of the stem is delayed, and the stem does not operate immediately at that stage.

The operation delay time of the stem is proportional to the amount of backlash. In other words, if the time from the start of rotation of the drive sleeve due to the occurrence of the hammer blow to the start of operation of the stem can be detected, the amount of backlash can be known. Although this finding has been carried out as a prior art, a characteristic feature of the present invention is that the time can be detected from the current data supplied to the motor.

Here, since the female thread pitch of the stem nut is equal to the male thread pitch of the stem to be screwed, even in the existing electric valve drive device, the pitch of the stem nut to be wear-detected can be easily known from the male thread pitch of the stem. be able to. If the amount of backlash obtained by the wear detection method according to the present invention can be calculated, the residual thickness of the female thread of the stem nut can be grasped. Therefore, it is possible to easily determine whether or not the stem nut needs to be replaced without disassembling and inspecting the electric valve drive device.

The section III shown on the horizontal axis is the time during which the stem is in the descending operation, and the stem descends at a constant speed. However, even if the stem is descending at a constant speed, if there are fluctuations in the pressure, flow rate, etc. of the fluid flowing through the piping line where the valve is installed, as shown in the torque data and current data in FIG. In addition, a primary peak may occur.

(First Embodiment)
In the first embodiment, the start of rotation of the drive sleeve (A) is detected as when the current of the motor reaches the first set value, and the current of the motor is the second when the operation of the stem starts (B). It is detected when the set value of is reached.

As is clear from the current data of the motor shown in FIG. 2, the drive sleeve starts to rotate due to the occurrence of the hammer blow, so that the current of the motor increases sharply. From this, it is possible to easily detect the start of rotation (A) of the drive sleeve from the change in the current of the motor. When the model, size, usage conditions, etc. of the electric valve drive device are determined, the specifications of the motor are also determined, and the average value of the no-load current in the section I shown on the horizontal axis of FIG. 2 is specific except for individual differences of the motor. It is decided. Therefore, the current at the time of hammer blow generation with respect to the average value of the no-load current is measured in advance, and the current is registered in the storage unit as the first set value. For example, a current that is 10% higher than the average value of the no-load current is registered in the storage unit as the first set value. In this way, when the current of the motor reaches the first set value, a hammer blow is generated (A), and the rotation of the drive sleeve is started.

On the other hand, detecting the start of operation of the stem from the change in the current of the motor is more difficult than detecting the start of rotation of the drive sleeve. As is clear from the current data of the motor shown in FIG. 2, the rate of increase of the current at the start of operation (B) of the stem is gradual. Moreover, the time when the current of the motor increases (C) is delayed as compared with the time when the operation of the stem is started. However, it is known that this delay time becomes a substantially constant value when the model and size of the electric valve drive device are determined. Therefore, it is possible to determine the start of operation (B) of the stem from the current change of the motor after incorporating this delay time. For example, a current increased by 10% from the average value of the current in the section II after the occurrence of the hammer blow is registered in the storage unit as the second set value.

As described above, when the first set value and the second set value are registered in the storage unit for the motor current and compared with the actual current detected by the current sensor, when the drive sleeve starts rotating ( A) is detected when the motor current reaches the first set value, and the stem operation start (B) is detected as when the motor current reaches the second set value (C). be able to. The comparison between each set value and the actual current is performed by the calculation unit.

(Second Embodiment)
In the second embodiment, the start of rotation of the drive sleeve (A) is detected by the current increase rate of the motor, and the start of operation of the stem (B) is detected by the current increase rate of the motor (C). It is calculated as when the predetermined time is subtracted.

The time from the occurrence of the hammer blow (A) to the start of operation (B) of the stem nut shown in FIG. 2 is short if the amount of wear of the stem nut is small, and long if the amount of wear is large. The detection of the occurrence of the hammer blow (A) is possible from the change in the current of the motor in the same manner as described in the first embodiment. When the hammer blow occurs (A), for example, it is registered in the storage unit as a time when the motor current increases by 10% from the average value of the no-load current in the section I based on the data actually measured in advance. In section II, due to the occurrence of hammer blow, the current momentarily has a large peak, but immediately becomes a calm value, and remains a constant value until the stem starts the descending operation.

FIG. 2B shows the start of operation of the stem, and the stem displacement does not change until the start of operation of the stem. The detection at the start of operation (B) of the stem can be detected according to the torque waveform. That is, it can be detected by defining it as when the torque waveform increases by approximately 10% from a constant value after the occurrence of the hammer blow. However, (B) cannot be accurately detected from the current waveform. This is because there is no change in the current value at the start of operation (B) of the stem.

As is clear from the current waveform and the stem displacement waveform shown in FIG. 2, there is a delay in the change of the current waveform as compared with the stem displacement waveform. Here, if (C) is defined when the current waveform is increased by 10% from the average value of the current after the hammer blow occurs, the delay time from (B) to (C) is ΔT. The value of ΔT does not become the same value if the model and size of the electric valve drive device are different, but if the model and size are the same, it becomes substantially the same value. This is because the main component of the electric valve drive device is made of a metal material, and if the dimensions and mass of the component are the same, the delay time ΔT required for the function is substantially the same.

Therefore, by grasping ΔT in advance for each model and size of the electric valve drive device, (B) can be detected only by grasping the current data even if there is no torque data or stem displacement data. It will be possible. That is, in the current data detected by the current sensor, for example, if the time point (C) in which the current is increased by 10% from the average value after the occurrence of the hammer blow is defined and detected, and the delay time ΔT is subtracted from this detection time, The start of stem operation (B) can be calculated.

As described above, by grasping the delay time ΔT for each model and size of the electric valve drive device in advance, the motor current detected by the current sensor without the need for a torque sensor or vibration sensor. From the data, it is possible to accurately grasp the wear status of the stem nut.

The calculation unit calculates the amount of wear of the stem nut from the time difference between the start of rotation of the drive sleeve and the start of operation of the stem detected by the change in the current of the motor. Further, the amount of wear of the stem nut with respect to the half pitch is calculated as the wear rate, and is recorded in the storage unit together with the time stamp indicating the time at that time. Further, the allowable wear limit value of the stem nut is registered in the storage unit, and the time when the allowable wear limit value is reached is predicted by performing regression analysis from the cumulative operating time and the wear rate of the electric valve drive device. In this way, according to the present invention, it is possible to diagnose the wear state of the stem nut and appropriately manage it.

Although the present invention has been described above based on the examples, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, the sluice valve has been described, but the valve is not limited to the sluice valve, and any valve having a reciprocating valve stem can be applied. Further, the applicable valve may be an existing valve as well as a newly installed valve.

Further, although the process of starting the stem downward has been described as an example, the process of starting the stem ascending can be similarly applied.

The method for detecting wear of an electric valve drive device according to the present invention can be applied to detect wear of a stem nut of an electric valve drive device provided in piping or the like of various plants.

1 Electric valve drive device 2 Motor 3 Reduction gear train 4 Drive sleeve 5 Stem nut 6 Stem 8 Current sensor 9 Wear detector

Claims (2)

In an electric valve drive device in which the rotation of the motor is decelerated by the reduction gear train and transmitted to the drive sleeve, and the stem screwed with the stem nut is reciprocated by the rotation of the stem nut fitted in the drive sleeve.
A current sensor that detects the current supplied to the motor and a wear detector that calculates and records the amount of wear of the stem nut are provided.
When starting the operation of the stem in the opposite direction , the first set value for the motor current at the start of rotation (A) of the drive sleeve is registered in the storage unit, and the motor current at the start of operation (B) of the stem is registered. Register the second set value in the storage unit,
The first set value is a value predetermined from the measured current when the hammer blow occurs with respect to the average value of the no-load current, and the second set value is a value increased by a predetermined amount from the average value of the current after the hammer blow occurs. age,
The delay time (ΔT) from the start of operation (B) of the stem to the time (C) when the second set value is reached is grasped for each model and size of the electric valve drive device.
When the motor current reaches the second set value (C), the delay time (ΔT) is subtracted to set it as the start of stem operation (B).
A method for detecting wear of an electric valve drive device, which comprises calculating the amount of wear of a stem nut from the time from the start of rotation (A) of the drive sleeve to the start of operation (B) of the stem. The wear detector includes a calculation unit, a timer, and a storage unit, calculates the wear rate of the stem nut, records it in the storage unit together with a time stamp, and performs regression analysis from the cumulative operating time and wear rate of the electric valve drive device. The wear detection method for an electric valve drive device according to claim 1 , wherein the time when the allowable wear limit value is reached is predicted.

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