JPH0525512U - Pneumatic drive abnormality detection device - Google Patents

Abstract

(57) [Summary] [Purpose] A pneumatic system that can easily and easily detect leakage of control air due to deterioration of parts at the initial stage and prevent serious accidents such as plant shutdown. An abnormality detection device for a drive unit is provided. In a pneumatic drive unit 1 provided with a first chamber 5 into which air pressure is introduced, a second chamber 6 communicating with the outside, and a displaceable partition wall 4 separating these chambers 5 and 6,
A valve device 15 that opens and closes the communication between the chamber 6 and the outside so that it can be opened and closed, and a predetermined signal is generated when the internal pressure of the second chamber 6 rises above a set value while the valve device 15 is in the closed state. It is characterized in that it comprises means 16 and 17. When the partition wall that separates the first chamber and the second chamber leaks, the air pressure in the first chamber leaks to the second chamber, so that the internal pressure of the second chamber rises when shut off from the outside. By detecting this pressure, a signal is generated and the leakage of the partition wall is detected.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an abnormality detection device for a pneumatic drive unit that detects an abnormality such as air leakage due to deterioration of components in a pneumatic drive unit that drives a control valve or the like used in the field of process control, for example.

[0002]

[Prior Art]

 The pneumatic drive unit provided in the control valve, etc. has sufficient performance for general process control, for example, it is easy to use because it can perform proportional position control, and even if it is cut off from the power source for some reason, it automatically The valve can be fully open or fully closed, or locked in place. Moreover, it is most widely used in the process field because it has many advantages such as simple structure, easy maintenance and handling, high reliability and low cost.

By the way, as will be described later with reference to FIG. 3, a general pneumatic drive unit 1 includes two chambers 5 and 6 partitioned by a diaphragm 4, and is introduced into the first chamber 5 through a ventilation hole 7. The diaphragm 4 is displaced to a position where the controlled control air pressure and the restoring force of the spring 13 provided in the second chamber 6 communicating with the outside through the ventilation hole 8 are balanced, and the drive shaft that interlocks with the diaphragm 4. The opening of a control valve or the like (not shown) is controlled via 11. Therefore, when the diaphragm 4 deteriorates during use and air leaks, the valve adjusting function 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 easily deteriorated in a relatively short period of time than other shared parts. Therefore, in the past, the product was regularly replaced with a new one in consideration of deterioration over time. However, since reliability has improved remarkably these days, considering the environment of the equipment site, the actual results of use, experience, etc., the optimum inspection period is set individually mainly from an economical point of view, and replacement is performed according to the inspection result. The necessity is judged.

[0005]

[Problems to be solved by the device]

 At the time of the conventional inspection as described above, the surface deterioration of the diaphragm 4 was judged by visual inspection, touch, or a simple airtight test. Therefore, the deterioration of the rubber material and the reinforcing cloth embedded in the rubber material was deteriorated. It is difficult to accurately grasp Therefore, even if it is determined that it can be used, it is not guaranteed that it will be fault-free until the next inspection, and it is unavoidable if there is a slight anxiety in operation. .

As a result of various researches for solving the above-mentioned problems, the inventors of the present invention focused on detecting leakage before the allowable limit of leakage due to deterioration of the diaphragm, and blocked it from the outside. It was examined how much the internal pressure of the second chamber 6 fluctuates due to the leakage in the operated state. FIG. 4 is an example showing the result, and when a pin hole with a diameter of 1.5 mm is opened in the diaphragm of the standard drive unit, the internal pressure P of the first chamber 5 is_aThe internal pressure P of the second chamber 6 when the valve is disconnected from the outside for only 10 seconds for various values of_bRise P of_d  Is indicated by a solid line. That is, the internal pressure P of the second chamber 6 in the state of being shut off from the outside_bIt was confirmed that the occurrence of the leak can be detected well before the leakage exceeds the allowable limit by detecting. The broken line in the figure is P_aThe moving amount H of the drive shaft 11 with respect to is shown.

The present invention has been made based on the above-mentioned circumstances, and it is possible to easily and easily detect a leak of control air due to deterioration of parts at the initial stage of occurrence, and to prevent a plant from shutting down. It is an object of the present invention to provide a pneumatic drive abnormality detecting device capable of preventing a serious accident.

[0008]

[Means for Solving the Problems]

 According to the present invention, in 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 separating the two chambers, the second chamber communicates with the outside. 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 open and closed. Is.

[0009]

[Action]

 In the above configuration, if the partition wall that separates 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 chamber rises and exceeds the set value, a predetermined signal is generated to detect the partition wall leak.

[0010]

【Example】

 Hereinafter, the present invention will be described with reference to an embodiment shown in FIGS. 1 and 2. First, a general pneumatic drive unit to which the present invention is applied will be described as a sequence.

As illustrated in FIG. 3, the pneumatic drive unit 1 includes a leg portion 3 protruding from the lower portion of a main body 2, and is used by being connected to a control valve or the like (not shown) via the leg portion 3. . The main body 2 is provided with a first chamber 5 and a second chamber 6 which are airtightly partitioned from each other by a diaphragm 4, and a ventilation hole 7 for introducing control air pressure into the first chamber 5 and a first chamber 5 Vents 8 are provided to connect the two chambers 6 to the outside. The diaphragm 4 is made of a hard elastic material (for example, hard rubber) having a reinforcing cloth embedded therein, and is connected to the upper end of the drive shaft 11 via a support plate 9 and a holding plate 10. A compression coil spring 13 is interposed between a spring seat 12 provided on the inner bottom portion of the main body 2 and the support plate 9. The lower end portion of the drive shaft 11 penetrating the bottom portion of the main body 2 in a reciprocating manner and airtightly extending to the outside is connected to the valve shaft of the control valve or the like.

In the embodiment of the present invention applied to the pneumatic drive unit 1, one end of the second chamber 6 is opened and closed as shown in FIG. Is connected to a solenoid valve 15 via a ventilation pipe 14 connected to the ventilation hole 8. A pressure detector 16 is connected to the communication pipe 14, and an output signal of the pressure detector 16 is guided to the controller 17.

The control unit 17 (see FIG. 1) controls the solenoid valve 15 to be closed (open) according to a start (release) signal input to the start / stop control unit 18, and at the same time, the first timer 19 is started. (Stopped). The first memory 20 receives the signal from the pressure detection unit 16 and the first timer 19 immediately after the electromagnetic valve 15 is closed and after a predetermined time t.₁After each pressure P₁And P₂Memorize each. The calculation unit 21 determines the increase width P of these pressures._d  Is calculated (P₂-P₁) Do. The comparison unit 22 uses this pressure increase width P_dAnd the reference pressure P preset in the pressure setting unit 23.₀Compare with.

When P _d <P ₀ , it is recognized that the diaphragm 4 has not leaked, and therefore the control unit 17 is in the initial state by the release signal input from the comparison unit 22 to the start / stop control unit 18. Then, 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 leakage has occurred in the diaphragm 4, but in order to confirm this, the second memory 24 causes the second memory 24 to output the signal from the comparison unit 22 for the first time (n = 1). When is input, it is stored and the second timer 25 is started. As a result, the release signal is sent from the second timer 25 to the start / stop control unit 18, and the control unit 17 is once returned to the initial state, but is sent when the 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, if the result is P _d <P ₀ , it is recognized that no leakage has occurred, and the control unit 17 is returned to the initial state. If P _d ≧ P ₀ also at the second time, the second memory 24 stores that the second signal (n = 2) is input, and it is confirmed that the leakage of the diaphragm 4 is confirmed. The alarm 26 is activated. 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. Although it is desirable that the detection of the pressures P ₁ and P ₂ be performed in a stable state of the control air pressure, a predetermined time t ₁ for holding the solenoid valve 15 in the closed state according to the performance of the drive unit ₁ and By appropriately setting the reference pressure P _{0 and the} like set in the pressure setting unit 23, the influence of fluctuation can be minimized. Further, the operation method, the installation place, the number, etc. of the alarm 26 can be set appropriately.

It should be noted that the present invention is not limited to the above embodiment, and for example, the partition wall for partitioning the first chamber 5 and the second chamber 6 is an appropriate bellows or a piston instead of the diaphragm 4. May be. The detection target is also the above pressure increase width P_dPressure rise rate (P_d/ T₁) Or the internal pressure P of the second chamber after an appropriate time has passed since the solenoid valve 15 was closed._bIt is also possible to In addition, the internal pressure P of the first chamber 5_aAccording to the reference pressure P₀  It is also possible to set variably. Further, the repetitive operation by the second timer 25 whose main purpose is to remove the influence of the control air pressure may be omitted or the number of repetitions thereof may be set to 3 or more._d<P₀In this case as well, the repetitive operation may be performed a suitable number of times. Other various modifications and applications are possible within the scope of the gist of the present invention.

[0017]

[Effect of the device]

 As described above, according to the present invention, it is possible to easily and easily detect the leakage of the control air due to the deterioration of parts at the initial stage of occurrence, and prevent serious accidents such as plant shutdown. An abnormality detection device for a pneumatic drive unit can be provided.

[Brief description of drawings]

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

FIG. 2 is a flow chart 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 an example of a leakage test result by the drive unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pneumatic drive part, 4 ... Diaphragm, 5 ... 1st chamber, 6
... second chamber, 7, 8 ... vent hole, 14 ... communication pipe, 15 ... solenoid valve, 16 ... pressure detection unit, 17 ... control unit.

Front page continued (72) Inventor Katsuro Takahashi 1-12-1, Tsutsumi-cho, Aoba-ku, Sendai-shi, Miyagi Motoyama Manufacturing Co., Ltd. No. Motoyama Works Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. 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 wall separating these chambers from each other. It is characterized by comprising a valve device for opening and closing the communication freely 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 the closed state. Pneumatic drive unit abnormality detection device.