JP6289195B2 - Diaphragm diagnosis method for swing check valve - Google Patents

Description

  The present invention relates to a valve shaft thinning diagnosis method for a swing check valve that can diagnose the degree of wall thinning of a valve rod of a swing type check valve.

  Conventionally, in a power plant or the like, a swing type check valve (swing check valve) is used in order to prevent an internal fluid such as gas or liquid from flowing backward in the pipe.

  FIG. 7 is a diagram schematically showing a cross-sectional structure of a general swing check valve, in which (A) is a valve open state and (B) is a valve closed state. FIG. 8 is a front view schematically showing a valve rod and an arm of the swing check valve.

  The swing check valve 1 includes a valve box 2, a valve rod 4 accommodated in the valve box 2, an arm 6 having a through hole 7 through which the valve rod 4 is inserted, a valve body bolt 9 and a nut 20. A valve body 8 attached to the arm 6 and a valve lid 10 attached to the upper opening surface of the valve box 2 are provided.

  In the swing check valve 1, when the internal fluid flows forward in the pipe, the valve body 8 is opened by the arc motion using the valve rod 4 as a support shaft until the arm 6 contacts the backstop 14. At the time of reverse flow, the valve body 8 is configured to close by performing an arcuate motion until the valve body 8 contacts the valve seat 12.

  The swing check valve 1 described above deteriorates as the plant continues to operate. Examples of the deterioration include wear thinning of the valve stem 4 due to opening and closing of the valve body 8, and thinning due to crevice corrosion near both ends of the arm of the valve stem 4.

  Specifically, in this swing check valve 1, when the arm 6 moves in an arcuate manner, the inner surface of the through hole 7 of the arm 6 and the valve stem 4 slide, and therefore, with the repeated opening and closing by the valve body 8. As the number of times of sliding increases, the sliding portion 4a of the valve stem 4 disposed in the through hole 7 of the arm 6 is worn and thinned, as shown in FIG.

  On the other hand, as shown in FIG. 7B, when the state in which the valve body 8 is closed continues, the internal fluid stagnates in the valve box 2, and depending on the material of the valve stem 4 and the type of the internal fluid, it is shown in FIG. As described above, the thickness reduction due to crevice corrosion occurs in the portions 4b and 4c in the vicinity of both ends of the arm of the valve stem 4.

  The above-described thinning due to wear (hereinafter referred to as “wear thinning”) and crevice corrosion progress as the plant operation period increases, and the valve stem breaks and the arm 6 and the valve body 8 fall off. This causes the swing check valve 1 to stop functioning.

  Therefore, conventionally, the swing check valve is periodically removed from the pipe and disassembled, and the thinning is detected by measuring the outer diameter of the valve stem. The valve stem was changed.

  However, since the decomposition of the swing check valve cannot be performed while the plant is in operation, it is necessary to stop the operation of the plant for inspection, which causes a reduction in operating efficiency.

  In addition, as a method for diagnosing an abnormality without disassembling a valve attached to a pipe, the methods described in Patent Document 1 and Patent Document 2 have been proposed, but the above-described method is described without disassembling the swing check valve. A diagnostic method capable of accurately diagnosing the degree of thinning due to wear thinning or crevice corrosion has not been developed yet.

JP 2010-54434 A JP 2011-80805 A

  The present invention provides a swing that can accurately diagnose the degree of thinning due to wear thinning or crevice corrosion of the valve stem of the swing check valve without disassembling the swing check valve even during plant operation. It is an object of the present invention to provide a check valve thinning diagnosis method for a check valve.

The invention described in claim 1
A valve shaft of a swing check valve for diagnosing the degree of thinning of the valve rod of a swing check valve having a valve rod housed in a valve box and an arm that performs arcuate motion with the valve rod as a support shaft A method for diagnosing thinning,
An ultrasonic sensor is installed above the arm at a predetermined angle position ,
By oscillating the ultrasonic wave from the ultrasonic sensor toward the arm and receiving the reflected ultrasonic wave, the distance between the ultrasonic sensor and the arm is measured,
The measured distance between the ultrasonic sensor and the arm, and the ultrasonic sensor in the case where there is no wear thinning in the preset valve rod and the arm at the same angular position as the predetermined angular position. By comparing the distance, the distance by which the arm descends due to wear thinning generated in the valve stem is calculated,
A valve shaft thinning diagnosis method for a swing check valve characterized in that the degree of wear thinning of the valve rod is diagnosed based on the calculated descending distance.

The invention described in claim 2
A valve shaft of a swing check valve for diagnosing the degree of thinning of the valve rod of a swing check valve having a valve rod housed in a valve box and an arm that performs arcuate motion with the valve rod as a support shaft A method for diagnosing thinning,
An ultrasonic sensor is installed on the side of the valve box to which the valve stem is fixed,
A peak of the reflected ultrasonic wave is generated by oscillating an ultrasonic wave from the ultrasonic sensor toward the arm at a predetermined angle while receiving the reflected ultrasonic wave while moving the ultrasonic sensor in the vertical direction. Measure the position where the value is maximum,
When the measured peak value is maximum, and when the ultrasonic wave is oscillated to the arm at the predetermined angle when the valve stem is set to have no wear thinning , the reflected ultrasonic wave is received. By comparing with the position where the peak value is maximum, the distance by which the arm descends due to wear thinning generated in the valve stem is calculated,
A valve shaft thinning diagnosis method for a swing check valve characterized in that the degree of wear thinning of the valve rod is diagnosed based on the calculated descending distance.

The invention according to claim 3
A valve shaft of a swing check valve for diagnosing the degree of thinning of the valve rod of a swing check valve having a valve rod housed in a valve box and an arm that performs arcuate motion with the valve rod as a support shaft A method for diagnosing thinning,
An ultrasonic sensor is installed above at least one of the both ends of the valve stem arm,
By oscillating ultrasonic waves downward from the ultrasonic sensor and receiving the reflected ultrasonic waves, the distance between the ultrasonic sensor and the vicinity of the arm end of the valve stem is measured,
The ultrasonic sensor and the valve stem when there is no crevice corrosion between the measured ultrasonic sensor and the vicinity of the arm end portion of the valve stem and the arm end portion of the valve stem of the valve stem set in advance By comparing the distance with the vicinity of the arm end of the valve rod, the amount of thinning of the valve stem that occurs near the arm end of the valve stem is calculated,
A valve shaft thinning diagnosis method for a swing check valve, characterized in that the degree of thinning due to crevice corrosion of the valve rod is diagnosed based on the calculated thinning amount.

  According to the present invention, it is possible to accurately diagnose the degree of thinning due to wear thinning or crevice corrosion of the valve stem of the swing check valve without disassembling the swing check valve even during plant operation. It is possible to provide a method for diagnosing valve rod thinning of a swing check valve.

It is a figure explaining the valve-rod thinning diagnosis method of the swing check valve which concerns on the 1st Embodiment of this invention. It is a figure explaining the valve-rod thinning diagnosis method of the swing check valve which concerns on the 2nd Embodiment of this invention. It is a figure explaining the valve-rod thinning diagnosis method of the swing check valve which concerns on the 3rd Embodiment of this invention. It is a figure which shows typically the valve stem used in the Example. It is a figure which shows the waveform signal of the ultrasonic wave (reflected wave) which the ultrasonic sensor in FIG. 1 received. It is a figure which shows the waveform signal of the ultrasonic wave (reflected wave) which the ultrasonic sensor in FIG. 3 received. It is a figure which shows typically the cross-section of a general swing check valve. It is a front view which shows typically the valve rod and arm of a swing check valve. It is a front view which shows typically the swing non-return valve in which wear thinning produced in the valve stem. It is a front view which shows typically the swing check valve which the crevice corrosion produced in the valve stem.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

1. First Embodiment FIG. 1 is a view for explaining a valve rod thinning diagnosis method (hereinafter also simply referred to as “valve rod thinning diagnosis method”) of a swing check valve according to a first embodiment. . The valve stem thinning diagnosis method according to the present embodiment is a method for diagnosing the degree of wear thinning (see FIG. 9) of the above-described valve stem 4.

  As shown in FIG. 1, in the valve rod thinning diagnosis method according to the present embodiment, the ultrasonic sensor 30 a is installed above the arm 6. Specifically, the ultrasonic sensor 30a is installed on the valve lid 10 that forms the upper surface of the valve box 2 (see FIG. 7) so that the arm 6 is disposed directly below.

  Then, an ultrasonic wave is oscillated from the ultrasonic sensor 30 a toward the upper surface of the arm 6. The oscillated ultrasonic wave passes through the internal fluid in the valve lid 10 and the valve box 2 and is reflected by the upper surface of the arm 6, and the reflected ultrasonic wave (reflected wave) is received by the ultrasonic sensor 30a.

  At this time, the time (TOF: Time of flight) from when the ultrasonic sensor 30a oscillates the ultrasonic wave until the reflected wave is received is measured, and based on the result, the ultrasonic sensor 30a and the upper surface of the arm 6 are measured. Measure distance.

  Specifically, since the above-described TOF corresponds to the time when the ultrasonic wave makes one reciprocation from the ultrasonic sensor 30a to the upper surface of the arm 6, the ultrasonic velocity in the internal fluid (in the case of water, about 1500 m / s) The distance between the ultrasonic sensor 30a and the upper surface of the arm 6 can be obtained based on the ultrasonic velocity in the valve lid 10 (about 3500 m / s in the case of bronze).

  Next, the distance between the obtained ultrasonic sensor 30a and the upper surface of the arm 6 is compared with the distance between the ultrasonic sensor 30a and the upper surface of the arm 6 when there is no wear thinning in the valve stem 4 set in advance. In addition, as a distance when there is no wear thinning in the valve stem 4 set in advance, for example, an actual measurement value immediately after replacement of the valve stem 4 may be used, or a value obtained as a result of a preliminary experiment may be used. Also good.

  As described above, when the arm 6 repeats the arcuate motion, the entire sliding portion 4a of the valve stem 4 becomes thin due to wear thinning (see FIG. 9). For this reason, a gap is generated between the through hole 7 of the arm 6 and the sliding portion 4a of the valve stem 4, and as shown by a dotted line 6 'in FIG. When the arm 6 is lowered, the distance between the ultrasonic sensor 30a and the upper surface of the arm 6 is increased.

  In the valve stem thinning diagnosis method according to the present embodiment, the distance between the ultrasonic sensor 30a and the upper surface of the arm 6 when the preset valve stem 4 has no wear thinning, and the measured ultrasonic sensor 30a and the arm 6 are measured. By comparing the distance with the upper surface, the distance by which the arm 6 is lowered due to the wear thinning of the valve stem 4 is calculated, and the degree of wear thinning of the valve stem 4 is diagnosed based on the calculated lowered distance. it can.

  As a result, it is possible to accurately diagnose the degree of wear thinning of the valve stem 4 of the swing check valve without disassembling the swing check valve, so the operation of the plant is stopped for diagnosis of wear thinning. There is no need to let them. As a result, it is possible to prevent a decrease in the operation efficiency of the plant. In addition, it is possible to prevent accidents due to operational mistakes or internal fluid leakage when the swing check valve is disassembled.

2. Second Embodiment FIG. 2 is a view for explaining a valve rod thinning diagnosis method for a swing check valve according to a second embodiment. The second embodiment is a method of diagnosing the degree of wear thinning of the valve stem 4 as in the first embodiment described above.

  In the present embodiment, as shown in FIG. 2A, the ultrasonic sensor 30 b is installed on the side surface 3 of the valve box 2 to which the valve stem 4 is fixed, and along the side surface 3 of the valve box 2. Ultrasound is oscillated while moving up and down.

  Then, the reflected wave from the side surface of the arm 6 is received by the ultrasonic sensor 30b, and the position where the peak value of the reflected wave is maximum is obtained. The TOF at this time does not change whether it is normal or wear thinning occurs, but when the arm 6 is lowered due to wear thinning, the peak value of the reflected wave is maximized accordingly. Also descends.

  For example, as shown in FIG. 2B, the peak value of the reflected wave is maximized at the position of the central portion of the side surface of the arm. At this time, when the central portion of the side surface of the arm descends as the entire arm 6 descends due to wear thinning, the position where the maximum peak value of the reflected wave is measured also descends.

  In other words, in the present embodiment, a position where the peak value is maximized when there is no wear thinning in the valve stem 4 is set in advance, and this set value is compared with the position where the measured peak value is maximized. By doing so, it is possible to calculate the distance by which the arm 6 descends due to wear thinning that has occurred in the valve stem 4, and to diagnose the degree of wear thinning of the valve stem 4 based on the calculated descending distance.

  According to the present embodiment, as in the first embodiment, it is possible to accurately diagnose the degree of wear thinning of the valve stem 4 of the swing check valve without disassembling the swing check valve. Therefore, it is not necessary to stop the operation of the plant for diagnosis of wear thinning.

3. Third Embodiment FIG. 3 is a view for explaining a valve rod thinning diagnosis method for a swing check valve according to a third embodiment. Unlike the first and second embodiments described above, the third embodiment can diagnose the degree of thinning of the valve stem 4 due to crevice corrosion.

  As shown in FIG. 3, the valve rod thinning diagnosis method according to the present embodiment has an ultrasonic sensor above at least one of the ends 6b and 4c of the arm 6 of the valve rod 4 (above 4b in FIG. 3). It differs from the first embodiment described above in that 30c is installed.

  In the valve stem 4 where the crevice corrosion has occurred, the arm ends 4b and 4c are locally thinned and become thinner. In the present embodiment, the ultrasonic sensor 30c is installed so that ultrasonic waves are oscillated toward the vicinity of the arm end 4b of the valve stem 4 where the occurrence of thinning due to crevice corrosion is assumed.

  Thereafter, an ultrasonic wave is oscillated downward from the ultrasonic sensor 30c, and a time until the ultrasonic wave sensor 30c receives the reflected wave reflected by the arm end vicinity 4b of the valve stem 4 is measured. Based on this, the distance between the ultrasonic sensor 30c and the arm end portion vicinity 4b of the valve stem 4 can be obtained.

  Then, the distance between the obtained ultrasonic sensor 30c and the arm end vicinity 4b is compared with the distance between the ultrasonic sensor 30c and the arm end vicinity 4b when there is no preset crevice corrosion. Thereby, it is possible to calculate the thinning amount generated in the vicinity of the arm end 4b of the valve stem 4 due to the crevice corrosion of the valve stem 4, and based on the calculated thinning amount, the vicinity of the arm end 4b of the valve stem 4 can be calculated. The degree of thinning due to crevice corrosion can be diagnosed.

  According to the present embodiment, it is possible to accurately diagnose the degree of thinning due to crevice corrosion of the valve stem 4 of the swing check valve without disassembling the swing check valve. Even in this case, it is not necessary to discontinue the operation of the plant and disassemble the swing check valve when diagnosing wear thinning, and it is possible to prevent a decrease in the operation efficiency of the plant and to prevent work errors and internal fluid leaks. Accidents can be prevented.

  In addition, the valve rod thinning diagnosis method according to the first to third embodiments described above can be implemented in combination. For example, by simultaneously carrying out the valve stem thinning diagnosis method according to the first and third embodiments, the degree of wear thinning and the degree of thinning due to crevice corrosion can be diagnosed simultaneously.

1. Example FIG. 4 is a diagram schematically showing a valve stem used in the example. As shown in FIG. 4, a new valve stem 4 with no thinning (no thinning) and a valve stem 4 (with small wear) in which the entire sliding portion 4a is thinned by 1.0 mm in radius by simulating wear. ), And the valve stem 4 (large wear) with the entire sliding portion 4a reduced by 2.5mm in radius, and the portions 4b and 4c near both ends of the arm reduced by 2.5mm in radius by simulating crevice corrosion. Four kinds of valve stems 4 (with crevice corrosion) were prepared, and each was attached to a swing check valve 1 as shown in FIG. The internal fluid is water, and the valve lid 10 of the swing check valve 1 is made of bronze. Note that “simulate wear thinning” in FIG. 4 represents both low wear and high wear.

  Then, the valve rod thinning diagnosis method according to the first embodiment described above was performed on the valve rods with no thinning, small wear, and large wear, and the degree of wear thinning of each valve rod was confirmed. Further, the valve rod thinning diagnosis method according to the third embodiment was performed on the valve rod with no thinning and with crevice corrosion to confirm the degree of thinning due to crevice corrosion.

2. Results FIG. 5 shows a waveform signal of the reflected wave received by the ultrasonic sensor in FIG. 1 when the valve rod thinning diagnosis method according to the first embodiment is performed. The solid line in FIG. 5 indicates the waveform signal of the reflected wave of each valve stem with no thinning, the one-dot chain line with small wear, and the dotted line with large wear.

  FIG. 6 shows a waveform signal of the reflected wave received by the ultrasonic sensor in FIG. 3 when the valve rod thinning diagnosis method according to the third embodiment is performed. FIG. 6A shows the transition of the reflected wave signal of each valve stem with crevice corrosion, and FIG. 6B without thinning.

  Next, based on the phase difference between the reflected waves in FIGS. 5 and 6, the ultrasonic velocity in water (about 1500 m / s), and the velocity inside the bronze valve lid 10 (about 3500 m / s). Thus, the amount of thinning of each valve stem was calculated. The results are shown in Table 1.

  From Table 1, the difference between the actual thinning amount and the measured thinning amount is 0.3 mm or less for any of the valve stem diagnosis results, and the valve stem thinning diagnosis method according to the present invention is applied. Thus, it was confirmed that a diagnosis result appropriately reflecting the actual degree of thinning due to wear thinning or crevice corrosion was obtained.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Swing check valve 2 Valve box 3 Side of valve box 4 Valve rod 4a Sliding part of valve rod 4b, 4c In the vicinity of arm end of valve rod 6 Arm 7 Through hole 8 Valve body 9 Valve body bolt 10 Valve lid 12 Valve Seat 14 Backstop 20 Nut 30a-30c Ultrasonic sensor

Claims (3)

A valve shaft of a swing check valve for diagnosing the degree of thinning of the valve rod of a swing check valve having a valve rod housed in a valve box and an arm that performs arcuate motion with the valve rod as a support shaft A method for diagnosing thinning,
An ultrasonic sensor is installed above the arm at a predetermined angle position ,
By oscillating the ultrasonic wave from the ultrasonic sensor toward the arm and receiving the reflected ultrasonic wave, the distance between the ultrasonic sensor and the arm is measured,
The measured distance between the ultrasonic sensor and the arm, and the ultrasonic sensor in the case where there is no wear thinning in the preset valve rod and the arm at the same angular position as the predetermined angular position. By comparing the distance, the distance by which the arm descends due to wear thinning generated in the valve stem is calculated,
A valve shaft thinning diagnosis method for a swing check valve, wherein the degree of wear thinning of the valve rod is diagnosed based on the calculated descending distance. A valve shaft of a swing check valve for diagnosing the degree of thinning of the valve rod of a swing check valve having a valve rod housed in a valve box and an arm that performs arcuate motion with the valve rod as a support shaft A method for diagnosing thinning,
An ultrasonic sensor is installed on the side of the valve box to which the valve stem is fixed,
A peak of the reflected ultrasonic wave is generated by oscillating an ultrasonic wave from the ultrasonic sensor toward the arm at a predetermined angle while receiving the reflected ultrasonic wave while moving the ultrasonic sensor in the vertical direction. Measure the position where the value is maximum,
When the measured peak value is maximum, and when the ultrasonic wave is oscillated to the arm at the predetermined angle when the valve stem is set to have no wear thinning , the reflected ultrasonic wave is received. By comparing with the position where the peak value is maximum, the distance by which the arm descends due to wear thinning generated in the valve stem is calculated,
A valve shaft thinning diagnosis method for a swing check valve, wherein the degree of wear thinning of the valve rod is diagnosed based on the calculated descending distance. A valve shaft of a swing check valve for diagnosing the degree of thinning of the valve rod of a swing check valve having a valve rod housed in a valve box and an arm that performs arcuate motion with the valve rod as a support shaft A method for diagnosing thinning,
An ultrasonic sensor is installed above at least one of the both ends of the valve stem arm,
By oscillating ultrasonic waves downward from the ultrasonic sensor and receiving the reflected ultrasonic waves, the distance between the ultrasonic sensor and the vicinity of the arm end of the valve stem is measured,
The ultrasonic sensor and the valve stem when there is no crevice corrosion between the measured ultrasonic sensor and the vicinity of the arm end portion of the valve stem and the arm end portion of the valve stem of the valve stem set in advance By comparing the distance with the vicinity of the arm end of the valve rod, the amount of thinning of the valve stem that occurs near the arm end of the valve stem is calculated,
A valve shaft thinning diagnosis method for a swing check valve, characterized in that the degree of thinning due to crevice corrosion of the valve rod is diagnosed based on the calculated thinning amount.

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