JP2002277233A - Method and instrument for measuring screw abrasion wear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need to detach and disassemble an operating machine and further drive the operating machine and to stably measure a screw abrasion wear with high precision without requiring much labor. SOLUTION: The screw abrasion wear is computed from the measurement in movement of a round rod screw body which is obtained when the round rod screw body is axially loaded while threadably engaging a nut body. Further, the load placed on the round rod screw body and displacement data on the measurement in the movement of the round rod screw body are displayed on a display, and the measurement in the movement of he round rod screw body is found according to the difference of the displacement data from the beginning of the loading to the time when the displacement data on the measurement in the movement become constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the amount of screw wear at a screw joint between a bolt member and a nut member, which are round bar-shaped screw members. The present invention relates to a technique for measuring the amount of screw abrasion from the amount of movement by forcibly moving the member by applying a load.

[0002]

2. Description of the Related Art In a nuclear power plant or a thermal power plant, inspection and inspection of various valve devices are periodically performed to ensure safety. Especially in a nuclear power plant, it is a system isolation valve that operates valves periodically during plant operation and performs a function check periodically, a valve that periodically switches the system for plant operation, and a valve used in thermal power plants etc. Therefore, a valve for performing a load change operation is subjected to a relatively frequent test such as an opening / closing operation.

Such a valve is normally opened and closed by an operating device 51 using an electric motor 50, as shown in FIG. 1, and the torque of the electric motor 50 is transmitted to a worm gear 53 via a helical gear 52. Further, by transmitting the rotational force of the worm gear 53 to the stem nut 54, the valve stem 5 meshed with the stem nut 54 is transmitted.
Generally, a structure that converts the movement into a vertical movement of 5 is used. That is, the valve stem 55 and the stem nut 54 have a so-called screw connection structure using bolts and nuts.

By the way, the screw of the valve rod 55 slides on the female screw of the stem nut 54 at the time of opening / closing operation of the valve. Absent. In particular, the material of the stem nut 54 is generally a copper alloy-based metal having excellent lubricity and seizure resistance in consideration of compatibility with the valve rod 55. It is a combination of materials having a relatively low material strength in relation to the valve stem 55, and the abrasion of the screw surface proceeds relatively quickly. Then, the progress of screw wear lowers the screw strength of the stem nut 54, and the operating force required for valve operation acts on the worn screw surface and becomes unbearable. In the worst case, the screw is sheared and damaged,
It develops to a situation where opening and closing of the valve becomes impossible.

Therefore, conventionally, for valves that operate relatively frequently, aging management for measuring the amount of screw wear is carried out as condition monitoring and maintenance. Conventionally, the following methods have been adopted for measuring and investigating the amount of screw wear, but each method has advantages and disadvantages, and various improvements have been desired.

[0006]

In the first measuring method, the operating device 51 is removed from the valve, the stem nut 54 is taken out from the operating device, and the female screw of the stem nut 54 is molded to reduce the amount of screw wear. It is to measure. This first method can reliably measure the amount of screw abrasion with a certain degree of accuracy, but has a problem that it requires labor and time because the valve device is disassembled and further molded.

The second measuring method is advantageous to the first method in that it can be performed with the operating device 51 attached to a valve. The second measuring method is provided opposite to the electric motor 50 of the operating device 51. By operating the provided manual handle (not shown), the stem nut 54 is rotated in the opening direction or the closing direction, and the valve stem 55 is rotated.
Is to measure the idling angle of the stem nut 54 or the manual handle until the start of the vertical movement, and calculate the screw wear amount from the measured idling angle. However, according to the second method, the idling angle can be measured immediately after the stem nut 54 comes into contact with the screw of the valve stem 55, that is, immediately before the point at which the stem nut 54 or the valve stem 55 is actuated. Can not. However, it is difficult to accurately detect such points, and there is a problem that a certain degree of accuracy cannot be stably secured, particularly when a manual handle is operated by a person.

[0008] A third measuring method is a method in which a sensor is attached to the operating device 51 so that the screw of the valve stem 55, which is the rotation start point of the stem nut 54, is in contact with the screw surface of the stem nut 54, The starting point when the rod 55 is rotated in the reverse direction is detected, and the amount of screw wear is calculated from the delay time during this time. The following equation is used to calculate the amount of screw wear from the delay time.

(Equation 1)

[0009] However, in the third method, stable measurement can be performed with high accuracy by using a sensor, but the operating device must be driven for the measurement. The operating device is usually driven by remote control from a work monitoring room provided in a separate room.However, in the third method, personnel must be assigned to the work site and the work monitoring room, respectively, and the timing of operation and measurement start of both must be set. There was a problem that there was a certain difficulty in matching.

The present invention solves the above-mentioned problems, and
The object is to remove and disassemble the operating device, further eliminate the need to drive the operating device, eliminate the need for a large number of manual operations, and accurately and stably measure the amount of screw wear. It is to disclose.

[0011]

In order to achieve the above-mentioned object, according to the present invention, a screw of a stem nut for moving a valve stem of a motor-operated valve, which is used in, for example, a power plant and has an electric drive device frequently and has an electric driving device, up and down. This is used to measure the amount of wear. A compressive load or a tensile load is applied to the valve rod (round rod-shaped screw body) to forcibly move the valve rod, and the amount of screw wear is measured from the amount of movement. Is used.

As the device, a load generating device for applying a compressive load or a tensile load to the valve stem is mounted above the valve stem through hole of the operating device, and the spindle of the device and the end face of the valve stem are connected by a jig. A load is applied to the valve stem, the amount of movement of the valve stem moving through the screw wear gap is measured by a load meter or displacement meter, and the screw wear amount is calculated from the displacement data displayed on the computer or its display. A means of calculating is used.

[0013]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. First, in this embodiment, an example will be described in which the present invention is applied to measurement of a screw wear amount in a valve device and an operating device having the structure shown in FIG. Also,
In this embodiment, an example will be described in which a hydraulic cylinder is used as a load generating device for forcibly moving a valve stem up and down without driving an operating device.

In this embodiment, as shown in FIG. 2, a measuring device 3 including a hydraulic cylinder is provided above the operating device 1 as shown in FIG. The details are shown in FIG. In the figure, reference numeral 4 denotes a valve stem, and 5 denotes a stem nut, which measures the amount of screw wear at these screw joints. Reference numeral 6 denotes a hydraulic cylinder mounted on the upper part of the operating device 1 via a base 7, reference numeral 8 denotes a hydraulic pump for driving the hydraulic cylinder 6, reference numeral 9 denotes a displacement plate which moves up and down in conjunction with a cylinder piston 6a of the hydraulic cylinder 6, 10 Is a displacement meter for measuring the vertical displacement of the displacement plate 9, and 11 is the cylinder piston 6a.
Load meter for measuring the load applied to
This is an electronic computer that inputs measurement data of 0 and the load cell 11 and calculates a later-described graph display and screw wear amount by various calculations. As the electronic computer 12, a current general so-called notebook personal computer can be adopted.

The valve stem 4 corresponds to a round rod-shaped screw body referred to in the present invention, and the stem nut 5 corresponds to a nut body.

In this embodiment, the valve stem 4 is forcibly moved in the axial direction by a compressive load or a tensile load by the hydraulic cylinder 6, and the amount of screw wear is measured from the amount of movement. That is, if screw wear occurs between the valve stem 4 and the stem nut 5, a gap is formed in the meshing surface, and by forcibly pulling or pushing the valve stem 4, the valve stem 4 is moved by an amount corresponding to the gap. Moving.

Here, the cylinder piston 6a of the hydraulic cylinder 6 and the valve rod 4 are connected by the following configuration.
The valve rod 4 is moved in the axial direction by the hydraulic cylinder 6. That is, a lock nut 14 is connected to a first connecting rod 13 having a forward thread engraved on the upper end of the valve stem 4, and a reverse screw is engraved on a lower end of the cylinder piston 6 a. The second connecting rod 15 is connected,
Finally, the first connecting rod 13 and the second connecting rod 15 are connected by the turnbuckle 16 to connect the two connecting rods 13 and 15 together. With this connection structure, the interlock between the valve stem 4 and the cylinder piston 6a is secured. What is characteristic of this connection structure is that a turnbuckle 16 having a slit is used, and this slit is tightened with a set screw 17 so that the turnbuckle 16 and the first and second connection rods 13 and 15 are formed. This is to eliminate screw gaps. That is, with this structure, the screws of the first and second connecting rods 13 and 15 are in close contact with the female screw of the turnbuckle 16 and are meshed with no gap. Therefore, in this connection structure, careless measurement of the screw gap, that is, the amount of screw wear, can be eliminated, and only the amount of screw wear between the valve stem 4 and the stem nut 5 can be always measured.

The inside of the hydraulic cylinder 6 is partitioned by an upper chamber 6b and a lower chamber 6c.
By applying hydraulic pressure to each, the piston cylinder 6a can be moved up and down. In addition, since the springs 6d are attached to the respective chambers 6b and 6c in the hydraulic cylinder 6, the piston cylinder 6a is automatically returned to the center position if the hydraulic pressure in the respective chambers 6b and 6c is the same. Has functions. Therefore, according to the hydraulic cylinder 6, by setting the stroke position of the piston cylinder 6a at the center (neutral), either the compressive load or the tensile load can be applied to the valve rod 4.

However, the use of such a hydraulic cylinder 6 is an example in the present invention, and it is also possible to use a hydraulic cylinder 6 that can act only in one of the upper and lower directions, that is, only a compressive load or a tensile load. is there. This is because the valve stem 4 can be moved in any case, and in the present invention, the amount of screw wear can be measured as long as the amount of movement of the valve stem 4 can be measured. Also, the load generating device is preferably a hydraulic cylinder 6,
Other configurations may be used.

Next, the procedure for measuring the amount of screw wear according to this embodiment will be described. First, a displacement meter 10 and a load meter 11
Is connected to the computer 12, and the operator drives the hydraulic pump 8 to operate the hydraulic cylinder 6 while monitoring the display of the computer 12, and applies either the compression load or the tension load to the valve rod 4. Let it work.

FIG. 4 is a graph showing changes in data measured by the displacement meter 10 and the load meter 11 at this time. In other words, when a gap is formed on the meshing surface between the valve stem 4 and the stem nut 5 due to screw wear, a load is applied to the valve stem 4 so that the valve stem 4 moves in accordance with the gap. When the load is increased, a point where the screw of the valve stem 4 and the stem nut 5 come into close contact and mesh appears, and from this point, the valve stem 4 does not move even if a load is applied, and as a result, the displacement data is constant. Becomes At this point, the data acquisition is completed, and thereafter, the screw wear amount is calculated based on the acquired data by a method described later.

After the threaded surfaces of the stem 4 and the stem nut 5 are in close contact with each other, the load data increases sharply, and the stem 4 is overloaded. If this overload is overlooked, the valve device or the hydraulic cylinder may be destroyed. However, since the transition of the load data together with the displacement data can be confirmed on the display of the computer 12, the displacement data becomes constant by this confirmation work. If the drive of the hydraulic cylinder is stopped at this point, an inadvertent overload state can be avoided in advance.

The following equation is used to calculate the amount of wear of the screw based on the acquired displacement data. Where T
(Effective diameter) is defined as the allowable cutting width of the thread shown in FIG. The execution of this formula is programmed in the computer 12 in advance.

(Equation 2)

According to the above equation (2), by inputting the screw size for each valve to be detected, the screw thickness can be calculated even if the screw size is different, and the amount of wear of the screw and the allowable wear The quantity can be algebraically evaluated.

The calculation of the screw wear amount is performed by the electronic computer 12.
Is an example. If at least a configuration capable of displaying displacement data and load data on a display is used, the displacement of the valve stem 4 can be obtained from the displayed displacement value, and the wear of the screw is reduced. The amount can be measured.

[0026]

As described above, according to the present invention,
For example, when the present invention is applied to a power plant, it is not necessary to remove or disassemble the operating device, and it is possible to measure the amount of screw abrasion. The amount of movement of the round bar-shaped screw body is measured by a displacement meter, and the displacement data is displayed on the display of the computer. Therefore, the point from the start to the stop of the movement of the round bar-shaped screw body, ie, the movement of the round bar-shaped screw body The quantity can be measured with high accuracy and stability. In addition, all measurements can be performed on site, and there is no need to drive any operating devices, so that the operation is simple and the measurement time can be extremely reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a general valve device used in a power plant.

FIG. 2 is an overall view of an embodiment according to the present invention.

FIG. 3 is a detailed explanatory diagram of the same measuring device.

FIG. 4 is a display diagram showing a data transition of load and movement applied to the valve stem.

FIG. 5 is an explanatory view showing an effective diameter of a screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Operating device 3 Measuring device 4 Valve stem (round rod shaped screw body) 5 Stem nut (nut body) 6 Hydraulic cylinder 7 Mounting base for measuring device to operating device 8 Hydraulic pump 9 Displacement plate 10 Displacement meter 11 Load meter 12 Electronic computer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F062 AA02 AA15 BC62 BC63 CC22 CC27 EE01 EE62 FF13 FF25 FG08 HH05 HH22 2F069 AA06 AA24 BB40 CC03 CC05 DD15 DD25 GG02 GG18 GG62 HH02 JJ13 JJ21 MM21 MM02 MM13 MM02 MM04

Claims (4)

[Claims] 1. A method for measuring a screw wear amount of a round bar-shaped screw body having an external thread engraved on an outer periphery thereof and a nut body having a female screw meshed therewith. A screw wear amount is calculated from a movement amount of the round bar-shaped screw body obtained when an axial load is applied to the round bar-shaped screw body in a state where the screw is engaged. 2. A load applied to the round bar-shaped screw body and displacement data of the amount of movement of the round bar-shaped screw body are displayed on a display, and the data from when the load is started to when the displacement data of the amount of movement becomes constant are displayed. The method for measuring the amount of screw wear according to claim 1, wherein the amount of movement of the round bar-shaped screw body is obtained based on a difference between the displacement data. 3. An apparatus for measuring the amount of screw wear of a round bar-shaped screw having an external thread formed on the outer periphery thereof and a nut having a female screw engaged with the same, wherein one end of the round bar-shaped screw is provided. A load generator that is connected to apply a compressive or tensile load to the round bar-shaped screw body, a load meter that measures a load applied to the round bar-shaped screw body, a displacement meter that measures a displacement of the round bar-shaped screw body, A gauge and a displacement meter are connected, and comprise an electronic computer having a display for displaying the transition of these data.The displacement of the round bar-shaped screw body is calculated from the displacement data measured by the displacement gauge, and the displacement is calculated from the displacement. An apparatus for measuring the amount of screw wear characterized by calculating the amount of screw wear. 4. The screw wear amount measuring device according to claim 3, wherein the calculation of the screw wear amount from the movement amount of the round bar-shaped screw body is performed by an electronic computer.