JP2539707Y2 - Abnormality detection device for pneumatic drive - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pneumatic drive unit for driving a control valve or the like used in, for example, a process control field, which detects an abnormality such as air leakage due to deterioration of parts. It relates to a detection device.

[0002]

2. Description of the Related Art A pneumatic drive unit provided in a control valve or the like has sufficient performance for general process control. For example, it is easy to use because it can perform proportional position control, and is cut off from a power source for some reason. Even in this case, the valve can be automatically fully opened or fully closed, or locked in the current state. Moreover, the structure is simple, maintenance and handling are easy,
It is the most widely used in the process field because of its many advantages, such as high reliability and low cost.

As will be described later with reference to FIG. 3, a general pneumatic drive unit 1 has two chambers 5 and 6 separated by a diaphragm 4 and is introduced into the first chamber 5 through a vent hole 7. The diaphragm 4 is displaced to a position where the control air pressure and the restoring force of the spring 13 provided in the second chamber 6 communicating with the outside via the vent hole 8 are balanced, and the drive shaft 11 interlocked with the diaphragm 4 is moved. It is configured to control the degree of opening of a control valve or the like (not shown) via the control unit. Therefore, if the diaphragm 4 deteriorates during use and air leaks, the function of adjusting the valve is inevitably impaired.

The diaphragm 4 is usually formed of a rubber-based material reinforced with cloth, and is frequently deformed, so that it is more likely to deteriorate in a relatively short time than other common parts. Therefore, in the past, it has been regularly replaced with a new one in consideration of aging. However, recently reliability has improved significantly, so the optimum inspection period is set individually from the economical point of view, taking into account the environment of the equipment location, actual use and experience, etc., and replacement according to the inspection result. The necessity is determined.

[0005]

At the time of the conventional inspection as described above, the state of deterioration of the surface of the diaphragm 4 is determined by visual inspection, tactile sensation or a simple airtight test. It is difficult to accurately grasp the state of deterioration of the reinforcing cloth and the like. Therefore, even if it is determined that it can be used for the time being, it is not guaranteed that there is no failure until the next inspection.
It is considered unavoidable even if there is some uneasiness in operation.

As a result of various studies to solve the above problems, the inventors of the present invention focused on detecting leakage due to diaphragm deterioration before exceeding a permissible limit, and were isolated from the outside. It was examined how much the internal pressure of the second chamber 6 in the state fluctuates due to leakage. FIG. 4 is an example showing the result. In the case where a pinhole with a diameter of 1.5 mm is opened in the diaphragm of the standard driving unit, the first case is shown.
For various values of the internal pressure P _a of the chamber 5, there is shown a rise P _d of the internal pressure P _b in the second chamber 6 when the blocking only the external and 10 seconds by a solid line. That is, by detecting the internal pressure P _b in the second chamber 6 in a state of being cut off from the outside, it was confirmed that leakage may sense sufficient before its occurrence than exceed the allowable limits. The broken line in the figure shows the movement quantity H of the drive shaft 11 with respect to P _a.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to easily and easily detect the leakage of control air due to the deterioration of parts at an early stage of occurrence, and to prevent the operation of the plant from being stopped. An object of the present invention is to provide an abnormality detection device for a pneumatic drive unit that can prevent a serious accident from occurring.

[0008]

According to the present invention, there is provided a pneumatic drive unit provided with a first chamber into which air pressure is introduced, a second chamber communicating with the outside, and a displaceable partition partitioning the two chambers. A valve device for opening and closing the communication between the second chamber and the outside, and means for generating a predetermined signal when the internal pressure of the second chamber rises above a set value while the valve device is in a shut off state It is characterized by having.

[0009]

In the above arrangement, if the partition separating the first chamber and the second chamber leaks due to deterioration or the like, the air pressure in the first chamber leaks to the second chamber. When the internal pressure of the second chamber rises and becomes equal to or higher than a set value, a predetermined signal is generated, thereby detecting leakage of the partition wall.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to one embodiment shown in FIGS. 1 and 2. First, a general pneumatic driving section to which the present invention is applied will be described in order.

As shown in FIG. 3, the pneumatic drive unit 1 includes a leg 3 projecting from a lower portion of a main body 2 and is connected to a control valve or the like (not shown) through the leg 3 for use. . The main body 2 is provided with a first chamber 5 and a second chamber 6 which are separated from each other by a diaphragm 4 in an airtight manner, and a ventilation hole 7 for introducing control air pressure into the first chamber 5 and a second chamber 5. Room 6
The air holes 8 for communicating the outside with the outside are respectively opened. The diaphragm 4 is formed of a hard elastic material (for example, hard rubber or the like) in which a reinforcing cloth or the like is embedded, and is connected to the upper end of the drive shaft 11 via a support plate 9 and a holding plate 10. Spring seat 12 provided on the inner bottom of main body 2
A compression coil spring 13 is interposed between the support plate 9 and the support plate 9. The lower end of the drive shaft 11 extending reciprocally and airtightly through the bottom of the main body 2 and extending to the outside is connected to the valve shaft of the control valve.

In the embodiment of the present invention applied to the pneumatic drive unit 1, one end of the second chamber 6 is connected to the outside as shown in FIG. A solenoid valve 15 is connected via a ventilation pipe 14 connected to the ventilation hole 8.
It is connected to the. Further, the pressure detecting unit 1 is provided in the communication pipe 14.
6 is connected, and its output signal is guided to the control unit 17.

The control unit 17 (see FIG. 1) controls the solenoid valve 1 in response to a start (release) signal input to a start / stop control unit 18.
5 is closed (opened), and at the same time, the first timer 19 is started (stopped). The first memory 20 stores the respective pressures P ₁ and P ₂ immediately after the solenoid valve 15 is closed and after a lapse of a predetermined time t ₁ therefrom in response to signals from the pressure detection unit 16 and the first timer 19. Calculating section 21 calculates the rise P _d of the pressure (P ₂ -P ₁₎ to. The comparison unit 22 compares the pressure increase width _Pd with a reference pressure P ₀ set in the pressure setting unit 23 in advance.

If P _d <P ₀ , it is recognized that no leakage has occurred in the diaphragm 4, and the control unit 17 receives a release signal input from the comparison unit 22 to the start / stop control unit 18.
Is returned to the initial state, the solenoid valve 15 is opened, and the drive unit 1 continues the normal control operation.

When P _d ≧ P ₀ , it is recognized that the diaphragm 4 has leaked. To confirm this, the second memory 24 sends the first signal (n =
When 1) is input, it is stored and the second timer 25 is started. Thus release signal from the second timer 25 to the start-stop control unit 18 is sent, the control unit 17 but is once returned to the initial state, it is transmitted when a predetermined time t ₂ set in the second timer 25 has elapsed The same operation as described above is repeated according to the start signal. Therefore, the result is P _d
<Accepted leakage if P ₀ has not occurred, the control unit 17 is returned to the initial state. Also, the second time P _d ≧ P
_{When the value} becomes ₀ , the second memory 24 stores that the second signal (n = 2) has been input, whereby the alarm 26 is activated as a confirmation that the leakage of the diaphragm 4 has been confirmed. Then, the control unit 17 is returned to the initial state in response to the release signal sent from the second timer 25 to the start / stop control unit 18. The detection of the pressures P ₁ and P ₂ is desirably performed in a stable state of the control air pressure. However, according to the performance of the driving unit 1, a predetermined time t ₁ for keeping the solenoid valve 15 closed and
By appropriately setting the reference pressure P _{0 and the} like set in the pressure setting unit 23, the influence of the fluctuation can be minimized. Further, the operation method, the installation place, the number, and the like of the alarm 26 can be appropriately set.

The present invention is not limited to the above embodiment. For example, a partition for separating the first chamber 5 and the second chamber 6 is a suitable bellows or piston instead of the diaphragm 4. Is also good. It detected even pressure rise rate in place of the pressure rise _{P d (P d / t 1} ) or,
May be such as a second chamber of the pressure P _b after appropriate time has elapsed since the closing of the solenoid valve 15. Further, the first chamber 5 pressure P _a
It is also possible to variably set the reference pressure P ₀ according to. Further, the repeated operation by the second timer 25 mainly for removing the influence of the control air pressure may be omitted,
Alternatively, the number of repetitions may be set to 3 or more, and if necessary, the repetition operation may be performed an appropriate number of times even when P _d <P ₀ . In addition, various modifications and applications are possible within the scope of the gist of the present invention.

[0017]

As described above, according to the present invention, it is possible to easily and easily detect the leakage of control air due to the deterioration of parts in the early stage of occurrence, and to prevent a serious accident such as a stoppage of plant operation. It is possible to provide a pneumatic drive unit abnormality detection device that can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the present invention.

FIG. 3 is a half-sectional view illustrating a general pneumatic drive unit.

FIG. 4 is a diagram illustrating a result of a leakage test performed by the driving unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pneumatic drive part, 4 ... Diaphragm, 5 ... 1st chamber, 6
... Second chamber, 7, 8 ... vent, 14 ... communication pipe, 15 ... solenoid valve, 16 ... pressure detector, 17 ... controller.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuro Takahashi 1-12-1, Tsutsumicho, Aoba-ku, Sendai, Miyagi Prefecture Inside Motoyama Works (72) Katsuaki Sato 1-chome, Tsutsumicho, Aoba-ku, Sendai, Miyagi Prefecture No. 12 No. 1 in Motoyama Works Co., Ltd. (56) References Jiko 61-46241 (JP, Y2)

Claims (1)

(57) [Scope of request for utility model registration] In a pneumatic drive unit provided with a first chamber into which air pressure is introduced, a second chamber communicated with the outside, and a displaceable partition for partitioning the two chambers, the second chamber is connected to the outside. A valve device for opening and closing the communication, and a means for generating a predetermined signal when the internal pressure of the second chamber rises above a set value while the valve device is in a shut-off state. Abnormality detector for pneumatic drive.