JP7621212B2 - Wear measuring device and wear measuring method for stem bush of valve drive system - Google Patents

Description

The present invention relates to a wear measuring device and a wear measuring method for a stem bush equipped in a valve drive system.

In a valve drive device in which a valve element such as a gate valve or globe valve advances and retreats together with a stem, a stem bush meshed with the stem is given the rotational force of a motor and rotates, moving the stem and the valve element forward and backward. Since the stem is made of a hard metal such as stainless steel, while the stem bush is made of a soft metal such as brass, wear actually occurs in the stem bush rather than the stem. As wear in the stem bush progresses, problems such as the stem falling off the stem bush can occur, so the amount of wear in the stem bush is measured periodically.

One method for measuring the wear of stem bushes is to use a screw gauge. The screw gauge must be designed to match the stem bush, and a screw gauge that matches each model (standard) of stem bush must be prepared.
As a method that does not use a screw gauge, Patent Document 1 discloses a method for detecting the amount of wear in the stem bush by detecting the rotational angle of the drive sleeve that rotates together with the stem bush (stem nut), the axial play component of the drive sleeve, and the start of stem movement.

JP 2010-261587 A

However, the method disclosed in Patent Document 1 requires a special spiral jig to detect the axial backlash component of the drive sleeve, and further has the problem that the jig must be designed for each model of valve drive system.
The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a wear measurement device and a wear measurement method that are capable of measuring the amount of wear of a stem bush without using special tools for each model of valve drive device.

The wear measuring device according to the first invention, which is in line with the above-mentioned object, measures the wear of a stem bush of a valve drive device in which a stem bush threaded onto a stem is rotated by the operation of a motor to move a valve body together with the stem in the axial direction of the stem, and is equipped with a motor operation detection means for detecting the operation of the motor, a forward/backward detection means for detecting the axial movement of the stem of a forward/backward member having the stem and the valve body, and a wear amount calculation means for obtaining detection data from the motor operation detection means and the forward/backward detection means, respectively, and determining the wear amount of the stem bush based on the pre-movement time from when the motor starts operating until when the forward/backward member starts moving.

A wear measurement method according to a second invention that meets the above objective measures the wear of a stem bush of a valve drive device in which a stem bush threaded onto a stem is rotated by the operation of a motor to move a valve body together with the stem in the axial direction of the stem, and includes the steps of detecting the operation of the motor and detecting the axial movement of the stem of a reciprocating member that includes the stem and the valve body, deriving a pre-movement time from the start of operation of the motor until the reciprocating member begins to move, and determining the wear of the stem bush based on the pre-movement time.

The wear measuring device according to the first invention and the wear measuring method according to the second invention detect the operation of the motor and the axial movement of the stem of the reciprocating member having the stem and the valve body, and calculate the amount of wear of the stem bush based on the pre-movement time from when the motor starts to operate until the reciprocating member starts to move, so it is possible to measure the amount of wear of the stem bush without detecting the axial backlash component of the drive sleeve, i.e., without detecting using a special jig designed for each model of valve drive device.

1 is an explanatory diagram of a valve drive system in which a wear measuring device according to an embodiment of the present invention is used; FIG. FIG. FIG. 13 is an explanatory diagram showing the relationship between motor current, pre-movement time, and wear of the stem bush. FIG. 4 is an explanatory diagram of a linear function for deriving the amount of wear.

Next, with reference to the attached drawings, an embodiment of the present invention will be described for understanding the present invention.
1, 2 and 3, a wear measuring device 10 according to an embodiment of the present invention is a device for measuring the amount of wear of a stem bush 12 of a valve drive device 15 that moves a valve body 14 together with the stem 11 in the axial direction (axial center direction) of the stem 11 by rotating a stem bush 12 screwed onto the stem 11 by operation of a motor 13. The device will be described in detail below.

The valve drive device 15, in which the wear amount of the stem bush 12 is measured by the wear measuring device 10, has a casing 16 as shown in FIG. 1, which houses a worm 17, a worm wheel 18 meshed with the worm 17, a cylindrical sleeve 19 to which the worm wheel 18 is attached, and the stem bush 12 fixed within the sleeve 19.

The stem bush 12 is a cylindrical member with a female screw structure formed on the inside and rotates around its axis. The rod-shaped stem 11 has a male screw region, and is arranged vertically with the male screw region meshing with the female screw structure of the stem bush 12 when the axis of the stem 11 coincides with the axis of the stem bush 12. The casing 16 has a through hole 20 formed at the bottom (one side) through which the stem 11 is inserted, and a through hole 22 closed by a spindle cover 21 formed at the top (other side). The upper end of the stem 11 is located lower than the through hole 22, and the through hole 22 is provided on an extension of the stem 11.

The spindle cover 21 is fixed to the upper part of the casing 16 by a plurality of screw members 24 whose tips are screwed into a plurality of screw holes 23 formed around the through hole 22 of the casing 16 while penetrating the spindle cover 21.
In this embodiment, as shown in Figures 1 and 3, the through hole 22 is circular, and the casing 16 has screw holes 23 formed at the 0° position, 90° position, 180° position, and 270° position outside the through hole 22, and there are four screw members 24.

2, the valve drive device 15 further includes a power transmission mechanism (not shown) which is made up of the motor 13 operated by electricity supplied from an external power source 25, and gears and the like and transmits the rotational force of the motor 13 to the worm 17. When the rotational force of the motor 13 is transmitted to the worm 17, the worm wheel 18, sleeve 19 and stem bush 12 rotate integrally, and the valve body 14 connected to the lower end (one end) of the stem 11 and the stem 11 move up and down (moving in the axial direction of the stem 11).
In this embodiment, the stem bush 12 is formed from brass, the stem 11 is formed from stainless steel, and a reciprocating member 26 that moves back and forth in the axial direction of the stem 11 as the stem bush 12 rotates is configured to include the stem 11, the valve body 14, etc.

As shown in Figures 2 and 3, the wear measuring device 10 includes a motor operation detection means 27 that detects the operation of the motor 13, a forward/backward detection means 28 that detects the elevation of the forward/backward member 26 (in this embodiment, the stem 11), a sensor support mechanism 29 that supports the forward/backward detection means 28, and a wear amount calculation means 30 that obtains detection data from the motor operation detection means 27 and the forward/backward detection means 28 and calculates the amount of wear of the stem bush 12.

In this embodiment, the motor operation detection means 27 is a clamp meter that measures the value of the current flowing through the power supply circuit 31 that connects the external power source 25 and the motor 13, as shown in FIG. 2. As shown in FIG. 4, the motor 13 starts operating when current begins to flow through the motor 13 (when the current through the motor 13 rises). The motor operation detection means 27 measures the current flowing through the motor 13 to detect the operation of the motor 13. Note that when a motor that starts operating when the current value flowing through it reaches a predetermined value is used instead of the motor 13, the motor operation detection means 27 is set to detect the time when the current value reaches the predetermined value as the start of operation of the motor 13.

As shown in FIGS. 2 and 3, the advancement/retraction detection means 28 is a non-contact sensor that measures the distance to the measurement object. For example, a laser displacement sensor can be used as the advancement/retraction detection means 28.
As shown in Figure 3, when the wear measurement device 10 is used to measure the amount of wear of the stem bush 12, the sensor support mechanism 29 is attached (fixed) to the casing 16 of the target valve drive device 15, and the advance/retract detection means 28 is positioned at a position where it can detect the axial movement of the stem 11.

The sensor support mechanism 29 has a base member 32 fixed to the casing 16 and an arm member 34 fixed to the base member 32 by a butterfly bolt 33. The base member 32 is formed by bending one end of a long metal plate at a right angle, with a long hole 35 provided in the bent one end, and a long hole 36 that is long in the longitudinal direction provided in the long region excluding the one end.

The arm member 34 is formed by bending one end of an L-shaped metal plate at a right angle, and the bent end functions as a retaining portion 37 that supports the advance/retract detection means 28, and a long hole 38 that is long in the longitudinal direction is formed in the long region excluding the one end. The arm member 34 is attached to the base member 32 by a wing bolt 33 that passes through the long holes 36, 38 and a nut (not shown) is attached to the base member 32. The arm member 34 attached to the base member 32 is arranged so that the long region is perpendicular to the long region of the base member 32.

When fixing the base member 32 with the arm member 34 attached to the casing 16, first the spindle cover 21 is removed from the casing 16. The base member 32 is fixed to the casing 16 in an upright position by screwing the tip of the butterfly bolt 39 that passes through the long hole 35 into the screw hole 23 formed at the 0° position of the casing 16 from which the spindle cover 21 has been removed. The arm member 34 becomes horizontal when the base member 32 is fixed to the casing 16.

The height position of the arm member 34 is adjusted by changing the position of the wing bolt 33 relative to the long hole 36 of the base member 32, and the advance/retract detection means 28 is positioned at a predetermined height. The horizontal position of the arm member 34 relative to the base member 32 is adjusted by changing the position of the wing bolt 33 relative to the long hole 38 of the arm member 34, and the advance/retract detection means 28 is positioned directly above the center of the through hole 22 (which is also directly above the stem 11).

As shown in Figures 2 and 3, the wear measuring device 10 further comprises a base table 43 having long holes 40, 41 formed at both ends of a long metal plate and a through hole 42 formed in the center, an inverted U-shaped guide member 44 fixed to the base table 43, and a rod 46 that is attached to the base table 43 and the guide member 44 so as to be freely movable forward and backward while passing through the through hole 42 and a through hole 45 formed in the guide member 44.

The base stand 43 is fixed to the casing 16 in a state in which it is arranged radially of the through hole 22 by screwing the tip of the wing bolt 47 that passes through the long hole 40 into the screw hole 23 formed at the 90° position of the casing 16, and screwing the tip of the wing bolt 48 that passes through the long hole 41 into the screw hole 23 formed at the 270° position of the casing 16. The base stand 43 is designed so that the long holes 40 and 41 are long in the longitudinal direction of the base stand 43, and the distance between the screw hole formed at the 90° position and the screw hole formed at the 270° position is different from that of the casing 16, allowing it to be fixed to a casing.

The through position of the long hole 40 of the wing bolt 47 and the through position of the long hole 41 of the wing bolt 48 are adjusted so that the through holes 42, 45 are positioned directly above the center of the through hole 22, whereby the rod 46 attached to the base stand 43 and the guide member 44 is positioned so that its lower end (one end) contacts the upper end (other end) of the stem 11 and rises and falls together with the stem 11 (moves forward and backward in the axial direction of the stem 11).

Also, a disk-shaped receiving base 49 is connected to the upper end (other end) of the rod 46, and is disposed directly below the advance/retract detection means 28. The advance/retract detection means 28 directly measures the receiving base 49, irradiates the receiving base 49 with a laser to measure the displacement of the receiving base 49, and detects the movement of the advance/retract member 26 from the measured displacement of the receiving base 49. Note that instead of the advance/retract detection means 28, a contact-type linear sensor that comes into contact with the receiving base 49 to measure the displacement of the receiving base 49 may be used as the advance/retract detection means.

The base stand 43, guide member 44, rod 46 and receiving stand 49 are not necessarily required. For example, for a valve drive device in which the upper end of the stem protrudes upward from a through hole formed in the upper part of the casing, the base stand 43, guide member 44, rod 46 and receiving stand 49 are not used, and the direct measurement target of the advance/retract detection means 28 may be the upper end of the stem.

The wear amount calculation means 30 can be configured to include a CPU and a memory, and is connected to the motor operation detection means 27 and the advance/retract detection means 28 as shown in FIG.
Here, because there is backlash in gears and other components provided on the path along which the rotational force of the motor 13 is transmitted from the motor 13 to the stem 11, there is a time lag between when the motor 13 starts operating and when the stem 11 (the advancing and retracting member 26) starts moving, as shown in Fig. 4. Hereinafter, the time (length of time) from when the motor 13 starts operating to when the advancing and retracting member 26 starts moving will be referred to as the "pre-movement time."

The pre-movement time becomes longer as the wear of the threads of the female screw structure of the stem bush 12 due to use of the valve drive device 15 (hereinafter also simply referred to as "wear of the stem bush 12") progresses. In other words, the pre-movement time is a length that corresponds to the amount of wear of the stem bush 12. Therefore, the difference between the pre-movement time of an unused (brand new) valve drive device 15 and the pre-movement time that has been lengthened due to use of the valve drive device 15 (hereinafter this difference is also referred to as "extended time due to use") becomes longer as the amount of wear of the stem bush 12 increases. Therefore, the amount of wear of the stem bush 12 can be derived based on the extended time due to use.

In this embodiment, a linear function (one example of a relational expression between the pre-movement time and the wear amount of the stem bush 12) that can calculate the wear amount of the stem bush 12 based on the measured value of the extended time due to use is derived in advance from the pre-movement time of an unused (brand new) valve drive device 15, the pitch of the threads of the male screw region of the stem 11, and the number of rotations (rotational speed) of the stem bush 12 when the motor 13 is operating, as shown in FIG. 5, and this linear function is stored in the wear amount calculation means 30. Hereinafter, this linear function is also referred to as the "linear function for deriving the wear amount".

There is a unique linear function for deriving the amount of wear for each model of valve drive system. The wear amount calculation means 30 stores multiple linear functions for deriving the amount of wear that correspond to multiple models of valve drive systems. When setting up the wear measurement device 10, the user selects the linear function for deriving the amount of wear that corresponds to the valve drive system for which the wear of the stem bush is to be measured by operating an input device (not shown) connected to the wear amount calculation means 30.

The wear amount calculation means 30 obtains detection data from the motor operation detection means 27 and the advance/retract detection means 28, and uses the selected linear function for deriving the wear amount to calculate the wear amount of the stem bush 12 based on the pre-movement time. Therefore, the wear amount calculation means 30 calculates the wear amount of the stem bush 12 using the relational equation between the pre-movement time and the wear amount of the stem bush 12, which is derived in advance from the design values of each component of the valve drive device 15. The relational equation between the pre-movement time and the wear amount of the stem bush 12 can also be derived by actually measuring the wear amount of the stem bush 12 and the pre-movement time for a wear measuring device 10 that has been used for a certain period of time.

Next, a wear amount measuring method for measuring the amount of wear of the stem bush 12 of the valve drive device 15 in use using the wear measuring device 10 will be described.
First, the process begins with a step of removing the spindle cover 21 from the casing 16, and then fixing the sensor support mechanism 29 and the base table 43 to the location of the casing 16 from which the spindle cover 21 was removed.

Then, a rod 46 to which a receiving base 49 is connected is attached to the base stand 43 and a guide member 44 fixed to the base stand 43 so that its lower end contacts the upper end of the stem 11, and the sensor support mechanism 29 is adjusted so that the advance/retract detection means 28 is positioned directly above the receiving base 49.
Next, the motor 13 is rotated forward to confirm the movement of the receiving base 49 (advance/retract member 26) (in this embodiment, the movement of the receiving base 49 in the direction away from the advance/retract detection means 28), and then the supply of electricity to the motor 13 is temporarily stopped. Thereafter, electricity is started to be supplied to the motor 13 to rotate it in the reverse direction, and this is the step in which the operation of the motor 13 is detected by the motor operation detection means 27, and the rise and fall of the advance/retract member 26 (ascension in this embodiment) is detected. Note that the enlarged view of Figure 1 shows the state of the stem 11 and stem bush 12 when the advance/retract member 26 rises (the state in which the lower side of the screw thread of the stem 11 is in contact with the upper side of the screw thread of the stem bush 12).

In the present embodiment, the operation of the motor 13 is detected by measuring the current flowing through the motor 13, but this is not limiting. For example, the operation of the motor 13 may be detected by measuring the voltage applied to the motor 13.
This is followed in sequence by a step in which the wear amount calculation means 30 derives the pre-movement time from when the motor 13 starts to rotate in the reverse direction until the advancing/retreating member 26 starts to move, and a step in which the wear amount calculation means 30 derives the amount of wear of the stem bush 12 based on the pre-movement time.

Here, the derivation of the wear amount of the stem bush 12 in this embodiment is premised on the assumption that there is no wear on the components other than the stem bush 12. In this regard, an experiment was conducted to compare the wear amount of the worn stem bush 12 with the wear amount derived by the wear amount measurement method of this embodiment, and it was confirmed that both wear amounts are equal. This is thought to be because the wear amount of the components other than the stem bush 12 is extremely small compared to the wear amount of the stem bush 12, and the reduction ratio from the motor 13 to the stem bush 12 is large (e.g., 100 times), so that the wear amount of the components other than the stem bush 12 has little effect on the measurement of the wear amount of the stem bush 12.

In addition, in this embodiment, the wear amount of a stem bush 12 with no wear is 0%, the wear amount of a stem bush 12 with the threads completely worn away is 100%, and a wear amount of 50% of the stem bush 12 is the value at which the stem bush 12 in use is replaced with a new stem bush 12. By measuring the wear amount of the stem bush 12 in this way and replacing the stem bush 12, it is possible to implement CBM (Condition Based Maintenance), which performs maintenance based on the equipment condition, rather than TBM (Time Based Maintenance), which performs maintenance at predetermined intervals.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and all changes in conditions that do not depart from the gist of the present invention are within the scope of application of the present invention.
For example, instead of using a sensor support mechanism that is fixed to the casing of the valve drive device, it is possible to use a sensor support mechanism that is fixed to a member other than the casing of the valve drive device.
Further, the movement of the valve body in the axial direction may be detected by the advancement/retraction detection means.

10: wear measuring device, 11: stem, 12: stem bush, 13: motor, 14: valve body, 15: valve drive device, 16: casing, 17: worm, 18: worm wheel, 19: sleeve, 20: through hole, 21: spindle cover, 22: through hole, 23: screw hole, 24: screw member, 25: external power source, 26: forward/backward member, 27: motor operation detection means, 28 : Advance/retract detection means, 29: Sensor support mechanism, 30: Wear amount calculation means, 31: Power supply circuit, 32: Base member, 33: Wing bolt, 34: Arm member, 35, 36: Long hole, 37: Holding part, 38: Long hole, 39: Wing bolt, 40, 41: Long hole, 42: Through hole, 43: Base stand, 44: Guide member, 45: Through hole, 46: Rod, 47, 48: Wing bolt, 49: Receiving stand

Claims (5)

A wear measuring device for measuring the wear of a stem bush of a valve drive device in which a stem bush screwed onto a stem is rotated by the operation of a motor to move a valve body together with the stem in the axial direction of the stem, the device comprising:
a motor operation detection means for detecting the operation of the motor;
a movement detection means for detecting the axial movement of the stem of a movement member having the stem and the valve body;
a wear amount calculation means for obtaining detection data from the motor operation detection means and the advance/retract detection means, and determining the amount of wear of the stem bush based on a pre-movement time from when the motor starts to operate until when the advance/retract member starts to move;
a sensor support mechanism to which the advancement/retraction detection means is attached and which is fixed to a casing of the valve drive device that houses the stem bush, and which disposes the advancement/retraction detection means at a position where the advancement/retraction detection means can detect movement of the stem;
a bolt for fixing the sensor support mechanism to the casing;
the bolt is screwed into a screw hole formed in the casing for fixing the spindle cover to the casing with a screw member, thereby fixing the sensor support mechanism to the casing from which the spindle cover has been removed ;
The wear amount calculation means calculates the wear amount of the stem bush using a relational equation between the pre-movement time and the wear amount of the stem bush, the relational equation being derived in advance from design values of each component of the valve drive system and the pre-movement time of an unused valve drive system . The wear measuring device according to claim 1, characterized in that the sensor support mechanism is capable of adjusting the position of the advancement/retraction detection means relative to the casing. 3. The wear measuring device according to claim 1 , wherein said motor operation detecting means detects the operation of said motor by measuring a current flowing through said motor. A method for measuring wear of a stem bush of a valve drive device in which a stem bush screwed onto a stem is rotated by the operation of a motor to move a valve body together with the stem in an axial direction of the stem, comprising:
removing a spindle cover from a casing of the valve drive device that accommodates the stem bush, and fixing a sensor support mechanism having a movement detection means attached thereto to a portion of the casing from which the spindle cover was removed;
a step of detecting the operation of the motor and detecting the axial movement of a reciprocating member including the stem and the valve body by the reciprocating detection means;
A step of deriving a pre-movement time from a start of operation of the motor to a start of movement of the advancing and retreating member;
and determining an amount of wear of the stem bush based on the pre-movement time,
a screw member for fixing the spindle cover to the casing by screwing a bolt into a screw hole formed in the casing, thereby fixing the sensor support mechanism to the casing ;
a wear measurement method for determining the amount of wear of the stem bush using a relational equation between the pre-movement time and the amount of wear of the stem bush, the relational equation being derived in advance from design values of each component of the valve drive system and the pre-movement time of an unused valve drive system. 5. A method for measuring wear according to claim 4 , wherein the operation of said motor is detected by measuring a current flowing through said motor.

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