JPH06137982A - Pressure transfer equipment - Google Patents

Abstract

PURPOSE:To detect abnormality in an equipment and change with time the lapse of by providing a sensor for detecting the physical property of a sealed liquid at a part where the sealing flow of a differential pressure transfer equipment is housed for monitoring the output of the sensor. CONSTITUTION:When a small crack or a void occurs in liquid-contact diaphragms 114a and 114b of a differential pressure transfer equipment due to damage caused by corrosion etc., a process fluid penetrates or is diffused into a sealed flow 120 inside pressure-reception chambers 126a and 126b. Therefore, change in physical property occurs in the liquid 120 so that its specific dielectric constant also begins to change. At this time, the between parallel flat-plate capacitors of the physical property change detection sensors 150a and 150b provided inside the pressure reception chambers 126a and 126b simultaneously changes. The capacitance change is sent to a signal processing circuit 122 via insulation terminals 132 and 131 and is converted to electrical signal, thus allowing the differential pressure transfer equipment itself to detect that the diaphragms 114a and 114b are damaged or failed rapidly and also an upper- level instrumentation equipment controlling the differential pressure transfer equipment to detect it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a function of identifying damage, abnormality, or stability of equipment itself in a differential pressure and pressure transmitter for detecting flow rate, pressure, liquid level, density, etc. in various plants. The present invention relates to a differential pressure and pressure transmitter equipped with.

[0002]

2. Description of the Related Art Differential pressure and pressure transmitters are field sensors widely used in various plants to measure various process variables. The differential pressure / pressure transmitter generally receives the pressure of the fluid to be measured in the process by the seal diaphragm, and the pressure which is the pressure-electricity conversion element through the incompressible liquid filled inside. The pressure is transmitted to a sensor or the like and converted into an electric signal. Various improvements have been made to these pressure transmitters so that the static characteristics and quality of the pressure transmitters are improved, and a structure having excellent stability can be achieved. On the other hand, JP-A-55-95373
As disclosed in No. 1, even if an abnormality occurs in the pressure sensor, by providing a means for detecting the abnormality,
Improvements have also been proposed that reliably and quickly notify the abnormality of the pressure sensor and further improve the reliability of the device.

By the way, the seal diaphragm, which is one of the components of the differential pressure and pressure transmitter, and the interface with the process fluid, is the most important factor in the configuration of the equipment and the most easily damaged component. Is.
For this reason, if any abnormality or deterioration occurs in the seal diaphragm, the static characteristics of the device will change and the measurement accuracy cannot be maintained.In addition, if the seal diaphragm should be damaged, the process fluid will not flow to the device. Since it will enter the inside of the plant, the equipment will malfunction and it will be impossible to control the plant. Further, if a device is damaged or abnormal, maintenance work such as investigation of the cause or replacement is required, and the plant cannot be operated efficiently. Conventionally, damage or abnormality of equipment due to damage or abnormality of this seal diaphragm, or change over time of equipment is an important management item of equipment, but experience and perception of plant maintenance personnel However, it was difficult to detect these damages, abnormalities, changes over time, etc. early.
Therefore, various problems have occurred in the operation of the plant. Furthermore, based on the experience of plant operation, measures such as separately preparing equipment for maintenance in advance were implemented to prevent trouble in plant operation. For this reason, management of maintenance equipment and maintenance costs are also required, and an efficient and labor-saving plant could not be constructed.

[0004]

In the structure of the conventional pressure transmitter, there is no means for detecting damage or abnormality of the constituent elements of the device itself, and a system for notifying the signal to the host control device. We cannot guarantee the long-term quality and stability of the device itself.

2) Since it is not possible to inform the upper control device of damage or abnormality of the equipment itself, labor saving of equipment maintenance cannot be achieved, and improvement and maintenance of plant operation quality and labor saving cannot be achieved either.

There is a problem.

Further, in the conventional differential pressure and pressure transmitter configuration, there is no means for detecting the time-dependent change of the equipment itself and a system for notifying the signal to the host control device. I cannot measure improvement.

2) It is not possible to save labor for maintenance of equipment during plant operation, and also labor saving for plant operation.

There was a problem.

A first object of the present invention is to provide a configuration method capable of guaranteeing long-term quality and stability of the device itself by providing a means for detecting damage or abnormality of a component of the device itself. It is intended to provide a system capable of improving the quality of plant operation and maintaining it, and also saving labor by constructing a system which provides the above-mentioned signal to the host control device.

Another object of the present invention is to construct a system for improving the quality of plant operation by providing a means for detecting the change with time of the equipment itself, and for notifying the signal to the host control device. The purpose of the present invention is to provide a system that saves labor for equipment maintenance and plant operation during plant operation.

[0012]

In order to achieve the above object, the pressure transmitter according to the present invention has a high insulating property in the space formed between the opposite surface of the diaphragm in contact with the process fluid and the body member of the pressure transmitter. Incompressible fluid (filled liquid)
In addition to filling, at least one or more sensing means capable of detecting a change in physical properties of the incompressible filled liquid is provided in this region, and a signal from this sensing means is detected at a predetermined timing, The detection signal processing means for determining the damage or abnormality of the differential pressure or the pressure transmitter is provided.

In order to achieve the above-mentioned other objects, at least one sensing means capable of detecting the operation of the diaphragm is provided, and a signal from the sensing means is used as a reference data of the differential pressure and pressure transmitter. And a signal processing means for comparing with.

[0014]

It is assumed that the diaphragm in contact with the process fluid of the differential pressure / pressure transmitter is damaged due to some factor and a minute crack or void is generated in the diaphragm. At this time, the process fluid invades or diffuses into the enclosed liquid via the minute cracks or voids, so that the physical properties of the enclosed liquid change. As the physical property change, for example, the dielectric constant of the filled liquid, the ion concentration, the pH concentration, or the humidity rate and the water content of the filled liquid change. By detecting at least one of these physical property changes by the sensing means, it is possible to quickly and accurately determine that the device is in an abnormal state.

Further, the seal diaphragm, which is in contact with the process fluid of the pressure transmitter, has a constant equilibrium position (zero point position of the device) during its normal operation, and its operating position (span) during the pressure measurement. The position) is also constant. Therefore, the operation of the seal diaphragm is detected by the sensing means, those signals are periodically stored in the storage element provided in the signal processing means, and the difference from the predetermined reference data is calculated in the signal processing means. It is calculated by a device (microprocessor). As a result, if some cause, such as an abnormality in the flow path of the filled liquid or deterioration of the seal diaphragm, an abnormality occurs in the operation of the seal diaphragm, which causes a difference from the reference data. Therefore, it is possible to quickly and accurately determine that the pressure transmitter has changed over time even during normal operation.

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

The pressure transmitter used for process control includes a pressure transmitter for detecting the pressure of the process fluid, a pressure transmitter for detecting the absolute pressure, and a differential pressure transmitter for detecting the differential pressure between the process fluids. However, in the following description of the embodiments, the differential pressure transmitter most used for process control will be mainly described.

FIG. 1 is a sectional view showing the structure of a differential pressure transmitter according to the present invention. Inside the differential pressure transmitter, a single-chip composite sensor 110 composed of a differential pressure sensor, a static pressure sensor, and a temperature sensor is separated from the high pressure side and the low pressure side, and the composite sensor 110 is protected from excessive differential pressure. A center diaphragm 112 and a high-pressure side and low-pressure side wetted diaphragms 114a and 114b that are in contact with the process fluid and receive pressure are housed in a main body member 118 of the differential pressure transmitter. The pressure applied to each of the liquid contact diaphragms 114a and 114b is transmitted to the composite sensor 110 through the enclosed liquid 120 such as silicone oil which is a non-compressible fluid having high insulation property inside, and the pressure is an electric signal. Is converted to. Further, in this differential pressure transmitter, the physical property change detection sensors 150a, 15 which detect the physical property changes of the high pressure side pressure receiving chamber 126a and the low pressure side pressure receiving chamber 126b respectively of the low pressure side and the high pressure side.
0b is provided, and these physical property change detection sensors 1
The physical property values detected by 50a and 150b are also converted into electric signals.

The signals detected by the composite sensor 110, the physical property change detection sensor 150a on the high pressure side, and the physical property change detection sensor 150b on the low voltage side are transmitted to the signal processing circuit 122 via the hermetic seal pins 130, 131, 132. . An amplifier that amplifies a signal, a microprocessor 130 that performs a correction calculation of a signal, a storage element that stores a calculation result, a detection setting value of a differential pressure transmitter, and the like can be changed in the signal processing circuit 122 through a communication path. It has a communication signal processing circuit for performing bidirectional communication with a host instrument.

FIG. 2 is a main enlarged cross-sectional view of FIG. 1 showing a portion characterizing the constitution of the present invention. When a physical property change of the encapsulating liquid 120 occurs, this physical property change is enclosed. An example of sensing by a change in the dielectric constant of a liquid is shown.
0a and 150b are capacitors with the filled liquid as a dielectric to serve as sensing means.

A conductive electrode 330 is formed on the side of the liquid contact diaphragms 114a, 114b that contacts the enclosed liquid 120, with an insulating film 320 interposed therebetween. On the other hand, the pressure receiving member 1
18 has another electrode 3 facing the electrode 330.
32 is formed. These electrodes are respectively arranged in the high pressure side pressure receiving chamber 126a and the low pressure side pressure receiving chamber 126b of the pressure receiving section, and can sense the high pressure side chamber and the low pressure side chamber, respectively.

A parallel plate capacitor is formed by these electrodes, and its dielectric constant is equal to the relative dielectric constant of the enclosed liquid 120. In addition, these electrodes are connected to the signal processing circuit 122 via airtight insulating terminals 131 and 132 provided on the pressure receiving member 118. Further, in this embodiment, each of the parallel plate capacitors is provided close to the fixed portion of the liquid contact diaphragm.
The reason for this is that there is almost no shape displacement in the vicinity of the fixed part of the liquid contact diaphragm, so that the capacitance change occurs only when the relative permittivity of the enclosed liquid changes. If the liquid contact diaphragms 114a and 114b in contact with the process fluid of the differential pressure transmitter are damaged by some factor (for example, due to corrosion or the like) and minute cracks or voids are generated in the liquid contact diaphragm, these minute cracks or The process fluid enters or diffuses into the sealed liquid 120 in the pressure receiving chamber through the void. For this reason,
Since the physical properties of the enclosed liquid change, the relative permittivity also starts to change. At this time, the capacitance between the parallel plate capacitors also begins to change at the same time.

This change in capacitance is caused by the insulation terminals 131, 13
2 is sent to the signal processing circuit 122 and converted into an electric signal. Therefore, according to this configuration, it is discovered that the liquid contact diaphragm, which is one of the constituent elements of the differential pressure transmitter, is damaged or abnormal, and the signal is transmitted to the differential pressure transmitter itself. It is possible to detect the damage or abnormality accurately and quickly, and also to detect it from the higher-level instrumentation device that controls the differential pressure transmitter via the communication means.

In the above embodiments, the physical property detecting sensor is provided in the pressure receiving chamber of the differential pressure transmitter, but in the following embodiments, the physical property detecting sensor is provided in a place other than the pressure receiving chamber.

The differential pressure transmitter of FIG. 3 has a physical property detecting sensor 150.
This is an example in which a and 150b are provided in the high pressure side measurement chamber 386a and the low pressure side isolation chamber 376b, respectively, and the state of the seal diaphragm can be detected even when placed in such a place. Because the seal diaphragm 114a,
When 114b is damaged, the process fluid enters from the damaged portion and mixes with the filled liquids 320 and 321 to change the physical properties of the filled liquids, but the effect is not limited to the pressure receiving chamber and the filled liquid is filled. This is because the influence propagates in the space. Therefore, it is possible to detect the state of the seal diaphragm even if the physical property detecting sensor is arranged in the isolation chamber or the measuring chamber which is a place away from the pressure receiving chamber as in the embodiment of this figure. It is possible to detect even if a physical property detection sensor is mounted on 110.

In the arrangement example of the physical property detection sensors shown in FIGS. 3 and 4, an example in which the capacitance detection sensor shown in FIG. 2 is provided is shown.

FIG. 4 is an enlarged view of the main portion of FIG. 3, and in FIG. 4, the low-voltage side isolation chamber 376b has a conductor electrode 43.
2b and 430b form a capacitance detection sensor, and the high voltage side measurement chamber 386a includes a capacitance detection sensor formed of conductor electrodes 432a and 430a. As a result, even if the seal diaphragms 114a and 114b on the low pressure side and the high pressure side are damaged, the state can be detected. In the present embodiment, the composite sensor 110 and the airtight terminal 33 are further detected.
Since 0 and 331 can be shared, there is an effect that the wiring structure can be simplified.

FIG. 5 shows an example in which the physical property detection sensor is mounted on a composite sensor.

In the figure, the physical property detection sensor 150 is mounted on the composite sensor 110 via the insulating film 520, and the output thereof passes from the bonding wire 580 through the wiring on the composite sensor and further to the bonding wire 581.
Via the airtight terminal 531 to the outside.
In this embodiment, when the composite sensor is incorporated into the pressure receiving member, by mounting the physical property detection sensor, its output can be taken out from the airtight terminal common to the composite sensor, so that the processing of the body member of the differential pressure transmitter can be reduced. I have to. Further, in the present embodiment, an example in which the physical property detection sensor 150 is mounted on the composite sensor 110 is shown, but the composite sensor 11
It is possible to form the physical property detection sensor on the same substrate in the process of making 0, and further to take out the output of the composite sensor from the airtight terminal 531 when taking out the output thereof. In this embodiment, the physical property detection sensor is arranged only in the high pressure side measurement chamber 386a.
By providing the physical property detection sensor in the portion of the composite sensor facing the low pressure side measurement chamber 386b, the state of the low pressure side seal diaphragm can also be detected.

In the above embodiments, when a physical property change of the enclosed liquid occurs, a method of sensing the change by the capacitance change between the flat plate capacitors is illustrated.
In addition to this method, there are methods for sensing this physical change in physical properties, such as ion concentration, pH concentration, or humidity rate and moisture rate of the filled liquid. Here is an example:

FIG. 6 shows the configuration of the sensors of the hygrometer and the moisture meter.

The humidity / moisture meter has a lead wire 6 on the substrate 618.
80,681 is made, and moisture or water sensitive film 6 is formed on it.
10 is provided, and a protective film 620 is further formed thereon. When the seal diaphragm is damaged, the process fluid mixes with the filled liquid, and the humidity and moisture content of the filled liquid change. The humidity or moisture sensitive film of the moisture sensor or the water sensitive film can take this change to change the electric resistance, and the change is detected by the lead wires 680 and 681. By using the sensors of such a hygrometer and a moisture meter in place of the flat plate capacitors shown in FIGS. 2 and 4, as shown in the graph of FIG. 7, the output value when the first seal diaphragm is not damaged ( It is possible to detect the state of the seal diaphragm by capturing the change from R ₁ , α ₁ ) to the output value (R ₂ , α ₂ ) when the breakage occurs.

FIG. 8 shows the configurations of the ion concentration sensor and the pH sensor. An element in which impurities are diffused is formed on a semiconductor substrate 818, and SiO ₂ insulation is formed on the surface of the element. In addition, on top of it certain ions such as K
A thin film 810 that reacts with (monovalent cation), Na (monovalent cation), H (monovalent cation), Ca (divalent cation), Cl ^−, etc. is placed, and Ag is further formed thereon. / A
An electrode such as gCl is formed to be a sensor. When the seal diaphragm is damaged by providing such a sensor at a position in contact with the sealed liquid of the differential pressure transmitter, the ions in the measured fluid enter, so that the ion concentration of the sealed liquid changes. Therefore, it is possible to detect the state of the seal diaphragm by catching this change.

As described above, one or more sensors capable of detecting the physical properties of the filled liquid are provided in the portion of the differential pressure transmitter where the filled liquid is contained, and the output of this sensor is monitored to prevent damage to the seal diaphragm. Anomalies can be detected.

FIG. 9 shows a sensor for detecting the change with time of the differential pressure transmitter.

The electrode 33 is provided between the seal diaphragms 114a and 114b and the main body member 118 with an insulating film 320 interposed therebetween.
0 and 332 are fixed to form a parallel capacitor, and the detection signal from this capacitor is taken out from the insulating terminals 131 and 132 to the outside. The capacitance C _x of the parallel capacitor is expressed by the following equation using the enclosed liquid 120 as a dielectric.

[0037]

[Equation 1]

Therefore, when the seal diaphragm is operated by receiving the pressure P, the change in the capacitance C _x of the parallel capacitor does not cause the change in the relative permittivity of the filled liquid unless the wetted diaphragm is damaged. The change in the capacity changes only by the operation of the liquid contact diaphragm.

At this time, the sealing diaphragm 1 against the pressure
Since the movement of 14a has a linear relationship, the change in the capacitance C _x of the capacitor is a change in capacitance inversely proportional to the pressure P.
Therefore, the change in pressure P and the change in capacity C _x are related.

On the other hand, provided in the other pressure receiving chamber,
The capacitor changes as well, but in the case of a differential pressure transmitter it works in reverse. Thus, it is possible to relate the change in capacitance of each capacitor individually or in the form of their sum, difference to pressure and differential pressure. Also, when the temperature changes, it is related in the same manner.

FIG. 10 shows the voltage ΔP when pressures P _H and P _L are applied to the high-pressure and low-pressure receiving chambers of the differential pressure transmitter which operates normally, and the high-pressure side and low-pressure side receiving chambers. It is a graph showing the relationship of the capacity of the parallel capacitors provided, from this graph the pressure applied to each pressure receiving chamber and the output relationship of each capacitor, and the pressure difference between the pressure applied to each pressure receiving chamber. It can be seen that a linear relationship holds for the output relationship of the capacitors. From this, the liquid contact diaphragm in contact with the process fluid of the differential pressure transmitter has a constant equilibrium position (zero point position of the differential pressure transmitter) during normal operation, and also during measurement of the differential pressure. It can be seen that the operating position (span position of the differential pressure transmitter) is also related by a predetermined value.

Therefore, these data are collected at the same time when the data is created to determine the characteristics of the differential pressure transmitter at the time of manufacture, and the data are collected by the differential pressure sensor, the static pressure sensor,
By adding pressure and temperature to the temperature sensor etc. as parameters,
It is stored in the storage unit of the differential pressure transmitter as a characteristic formula of capacitance change or contact data.

By providing the differential pressure transmitter with these reference data, the position of the seal diaphragm is detected by the parallel plate capacitors provided in the pressure receiving chambers, and these signals are processed by the signal processing means of the differential pressure transmitter. The signal is periodically stored in a storage unit provided therein, and a calculation performed by the microprocessor provided in the signal processing means to obtain the pressure applied to each differential pressure chamber and the differential pressure based on this signal value. At this time, if the position of the seal diaphragm changes when a predetermined pressure is applied for some reason, the position signal and the comparison calculation result differ from the predetermined reference data and the calculation result data. Therefore, even during normal operation, some factor of the differential pressure transmitter, for example, deterioration due to aging of the seal diaphragm, or drift when an abnormality occurs in the flow path of the filled liquid is caused by one component. It can be detected by a change in the capacitance of a certain seal diaphragm, and the signal can be transmitted. Therefore,
The change with time of the differential pressure transmitter itself can be quickly and accurately determined.

Although the above description has been focused on the differential pressure transmitter as an embodiment of the present invention, it is obvious that these configurations can be applied to a pressure transmitter for detecting absolute pressure.

That is, in the pressure transmitter for detecting the absolute pressure, unlike the differential pressure transmitter, there is only one pressure receiving chamber containing the filled liquid, the isolation chamber, the measuring chamber, and the sealing diaphragm in contact with the process fluid. This can be dealt with by providing a physical property detection sensor and a seal diaphragm operation detection sensor in the portion filled with the filled liquid and the seal diaphragm, respectively, and providing a signal processing means for processing an output signal from the sensor.

FIG. 11 shows the signal processing circuit 122 of the differential pressure transmitter.
The block diagram of is shown. The composite sensor 110 outputs changes in gauge resistance due to differential pressure, static pressure, and temperature as electrical signals,
It is selectively taken into the multiplexer (MPX) 231. At the same time, the multiplexer 231 also outputs electric signals from at least one of the above-mentioned sensing means 150 provided in the pressure receiving chamber or a portion in contact with the enclosed liquid.
Is taken into. In the example of the sensing means described above,
Since a method for detecting changes in the dielectric constant, water content and other physical properties of the enclosed liquid is illustrated, a circuit for converting the output from this detecting means into a frequency may be provided so that the circuit configuration facilitates digital processing. .

Various signals taken in by the multiplexer 231 are sent to the programmable gain amplifier (PGA) 23.
3 and then converted into a digital signal by the A / D converter 234, and the microprocessor (MPU) 130
Sent to. The memory 239 (EPROM) has a differential pressure,
Each characteristic of the static pressure and the temperature sensor (in the case of the pressure transmitter, each characteristic of the pressure and the temperature sensor) is stored in advance, and the microprocessor 130 corrects and calculates by using these data, thereby achieving high accuracy. Differential pressure signal value and static pressure,
Calculate the temperature signal value. This operation result is converted into a normal analog signal via the D / A converter 237 and the V / I converter 238, and is converted into a signal of DC 4 to 20 mA and sent to the computer 740 which is a higher-level control device. Has become.

On the other hand, a signal from at least one sensing means provided in the pressure receiving chamber is stored in a memory (EEPROM) 239 which is another storage element regularly or at any time according to a command from the microprocessor 130. And in some cases updated. The microprocessor 130 periodically or at any time performs a comparison operation with reference data held by the differential pressure transmitters based on the data stored in the memory (EEPROM) 239. When these reference data and the comparison calculation result are not different from the previous results, the normal task as the differential pressure transmitter (differential pressure signal value, static pressure, temperature signal value is calculated, and the calculation result is D / The signal is converted into a normal analog signal through the A converter 237 and the V / I converter 238, becomes a signal of DC 4 to 20 mA, and transmits the signal to the computer 740 which is a higher-level control device.). .

FIG. 12 shows an example of a flow rate / pressure measuring system using the differential pressure and pressure transmitter of the present invention. The differential pressure generated at both ends of the orifice 710 for determining the flow rate provided in the pipeline 700 of a chemical plant or the like is measured by the differential pressure transmitter 720, while the pressure of the pipeline is measured by the pressure transmitter 730, The flow rate and the pressure in the pipeline are transmitted to the upper control computer 740 as a differential pressure (flow rate) and a pressure signal. The control computer 740 controls an actuator such as a pump that supplies fluid into the pipeline according to the measured flow rate and pressure signal, and adjusts so that an appropriate flow rate and pressure can be supplied. In addition, the communicator 750 includes the differential pressure / pressure transmitters 720 and 730.
And two-wire transmission lines connecting the high-order control computer 740 with each other, digital bidirectional communication is performed at an arbitrary position between the transmission lines to operate the differential pressure / pressure transmitter and control the pressure transmitter. It is a portable input / output device for instructing change, setting, update, etc. for quantity change and setting or maintenance management.

In this system, the differential pressure, the differential pressure in contact with the non-measuring fluid flowing in the pipeline of the pressure transmitter, and the damage or abnormality of the diaphragm which is a constituent element of the pressure transmitter can be sensed. , It is possible to judge that the pressure transmitter itself is in an abnormal state. Also, during normal operation, the diaphragm is not damaged, its equilibrium position (device zero point position) is constant, and its operating position (span position) is also set to a specified value during pressure measurement. ing. Therefore, if these positions can be sensed, it is possible to determine that the differential pressure and the pressure transmitter itself have changed with time by processing and calculating data of these signals by a microprocessor.

In the conventional system, even if an error occurs in the measured values of the differential pressure, the pressure transmitter, etc. due to some factors, or even if a part of the equipment is damaged, it can operate. Even so, the situation depends on preventive maintenance by periodic inspection of the plant and the experience and intuition of daily maintenance personnel or operation personnel. I couldn't. Therefore, even if abnormal conditions or changes over time occur in measuring equipment such as differential pressure and pressure transmitters, defects can be identified only after almost all plant malfunctions occur or after a predetermined response period. The improvement of the operating rate, improvement and maintenance of quality, and labor saving were not achieved as expected.

FIG. 13 shows an example of the storage state of the data stored in the memory (EEPROM) 239. In FIG. 13, a polygonal line A shows a change state of a signal from a pressure / differential pressure transmitter having a parallel plate capacitor as a characteristic detection sensor. Since the value is almost constant until time t3, it can be determined that the transmitter is operating normally. However, the value suddenly changes at time t4. This is because the relative permittivity of the filled liquid inside has changed due to the hardware configuration, so that the liquid contact diaphragm in contact with the process fluid of the differential pressure transmitter is damaged due to some factor (for example, due to corrosion etc.) It can be judged that minute cracks or voids have occurred in the liquid diaphragm.

At this time, the microprocessor 130
Executes the abnormal task, superimposes the content of the calculation result on the analog signal via the D / A converter 237 and the V / I converter 278, and sends it to the computer 740, which is a higher-level control device. Informs of request for transmitter replacement or repair. FIG. 14 shows an example of the transmitted signal. The signal value is normal until time t3, but the abnormal signal 76 is superimposed on the analog signal at time t4. The abnormal signal has a predetermined recognition code, and has a code system that can identify at least the damage to the device due to an external factor and the factor due to the change over time of the device. Further, as the signal to be sent, the output signal is transmitted with a value obtained by holding the output signal in association with the recognition code, or a value obtained by swinging the output signal to the plus side or the minus side. This abnormality information is stored again in the memory (EEPROM) 239 and is retained until the device is disposed.

As a result, the abnormal state of the differential pressure transmitter itself can be notified to the maintenance person and the operation person of the plant promptly and with high accuracy, if necessary, and it is very necessary to deal with it. It is easy and labor-saving can be achieved, and its quality can be maintained without impairing the plant operation rate.

The signal processing circuit 122 further includes a digital I / O having a bidirectional communication signal processing function that enables bidirectional communication with the input / output device 750.
An O circuit 240 is provided. Therefore, the abnormal state can be confirmed not only by the computer 740, which is a higher-level control device, but also at the time of site patrol in the daily inspection of the plant, so that the plant operation can be operated more efficiently.

Although a parallel plate capacitor is shown as an example of a sensor for detecting an abnormality, a pressure / differential pressure transmitter having a sensor for measuring ion concentration, pH concentration, humidity and moisture content may be used. The signal processing as described above can be applied.

As a sensor for detecting the change over time, a parallel plate capacitor is provided near the center of the seal diaphragm, and the equilibrium position (zero point position of the differential pressure transmitter) and operating position (differential pressure transmitter) are based on the capacitance change. Span position) is set as a predetermined value, and the data is stored in the memory (EEPROM).
The operation of processing the differential signal stored in 239 as reference data and the abnormal signal of the pressure transmitter will be described below.

In these differential pressure and pressure transmitters, the position of the seal diaphragm is detected by the parallel plate capacitors provided in the pressure receiving chambers, and the signal data thereof and the reference data are compared and calculated by the microprocessor 130. . FIG. 15 shows an example of the storage state of the data stored in the memory (EEPROM) 239. In FIG. 15, the broken line Ba
Shows the changed state of the stored state of the zero point position of the differential pressure transmitter, and the broken line Bb shows the changed state of the stored state of the span position of the differential pressure transmitter of the differential pressure transmitter. Since the value is almost constant until time t3, it can be determined that the transmitter is operating normally. However, at time t
Between 3 and time t4, the value has a slight gradient (θz,
θs), and tends to increase and decrease after time t4. It can be determined that, due to a hardware configuration, the differential pressure transmitter causes a drift due to a change with time in the device due to some factor, and the amount thereof exceeds an allowable value.

At this time, the microprocessor 130
16 executes an abnormal task (this task is an example) as shown in FIG.
An abnormal signal is superimposed on the analog signal through the V. 37 and the V / I converter 238 and sent to the computer 740, which is a higher-level control device, to notify the need for transmitter replacement or maintenance. FIG. 17 shows an example of the transmitted signal. The signal value is normal until time t3, but the abnormal signal 762 is superimposed on the analog signal at time t4. This abnormal signal has a code capable of recognizing a change with time, and the signal to be sent is output with a value obtained by holding the output signal associated with the recognition code or with a value that is swung to the plus or minus side. Sending a signal. This abnormality information is stored again in the memory (EEPROM) 239 and is retained until the device is disposed.

As a result, it is possible to notify the time-dependent change of the differential pressure transmitter itself to the maintenance person and the operation person in charge of the plant promptly and with high accuracy, if necessary. It is easy and labor-saving can be achieved, and its quality can be maintained without impairing the operation rate of the plant. Further, similarly to the above, since the input / output device 750 can be checked at any time during the site patrol of the daily inspection of the plant, the plant operation can be more efficiently operated.

As described above, in the detection method according to the present embodiment, the parallel plate capacitor is installed near the center of the seal diaphragm, and the capacitance change causes the differential pressure, the zero point position of the pressure transmitter and the span of the pressure transmitter. The position is set by a given seed,
Although the master data and the measured data are compared or calculated to determine the change with time of the device, the effect is not changed even by the method described below. That is, as the master data, the signal of the differential pressure or static pressure sensor of the composite sensor and the signal from the parallel plate capacitor are related to the zero point position and the span position, respectively, and the sensor relationship, the difference or the correlation such as the sum. This is a method of obtaining or setting an allowable value and using the value as reference data for comparison or calculation. (In FIG. 11, this master data is mapped and stored in the EPROM 236.) In this case, since the data of the differential pressure or static pressure sensor has already been created, it is a more efficient method. I can say. Further, as a method other than detecting their positions by the capacitance change, a minute rod is provided in the liquid contact diaphragm, and an insertion hole portion having an inductance is provided in the pressure receiving chamber of the pressure receiving portion corresponding to the rod. . Since the inductance changes according to the operation of the seal diaphragm, it serves as a sensor for detecting the position.

In the above-described embodiment of the present invention, the microcomputer 130, which houses the memory device in which the signal from the physical property detection sensor is housed in the differential pressure and pressure transmitter, is further housed in the signal processing means. Although the abnormality determination is made, it is also possible to make this abnormality determination centrally by the control computer.

FIG. 18 shows a system in which the control computer 740 centrally determines an abnormality. Output signals from the differential pressure transmitter 720 and the physical property detection sensor of the pressure transmitter 730 are transmitted to the control computer 740 via the transmission line 741 at any time or at a predetermined timing.
Control computer 7 of detection data from the sensor at this time
As a transmission method to the 40, the detection data is 4 to 20 mA.
The DC current signal can be transmitted by superimposing a digital signal on a DC current of 4 to 20 mA or by converting it into a digital signal only. By collecting these sensor detection data, the control computer 740 can monitor the sensor output itself of each differential pressure and pressure transmitter. Thus, for example, the control computer can automatically issue the warning 771 to the plant supervisor even if the differential pressure and pressure transmitters do not generate an abnormal signal.

Also, in this way, the control computer 740
By centrally managing the state of the sensor at the plant monitor, the plant supervisor can control the computer 7 as shown in FIG.
It becomes possible to directly read the sensor information of the differential pressure and pressure transmitter on the information display screen of 40.

Although the differential pressure transmitter has been mainly described as the embodiment of the present invention, it is needless to say that the present invention can be applied to the pressure transmitter. That is, by providing a physical property change detection sensor at the portion in contact with the enclosed liquid that transmits the process fluid pressure to the pressure sensor means, it becomes possible to detect the damage of the seal diaphragm, and the position and operation of the seal diaphragm of the pressure transmitter can be detected. By providing a sensor for detecting, it becomes possible to detect a change with time.

[0066]

As described in detail above, according to the pressure transmitter of the present invention, it becomes possible to detect an abnormality in the pressure transmitter itself and a change with time. Therefore, 1) it is possible to guarantee the long-term quality and stability of the device itself.

2) It is possible to save labor in maintenance of equipment, improve and maintain the quality of plant operation, and save labor.

3) It is possible to improve the quality of plant operation.

4) Since a preventive maintenance system for plant equipment can be established, a highly reliable instrumentation system can be constructed.

The effect is as follows.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a differential pressure transmitter according to an embodiment of the present invention.

FIG. 2 is an example in which a dielectric constant sensor is provided in the embodiment of FIG.

FIG. 3 is an overall configuration diagram of another embodiment of the differential pressure transmitter of the present invention.

FIG. 4 is an example including a dielectric constant sensor in the embodiment of FIG.

FIG. 5 is another embodiment of the differential pressure transmitter of the present invention.

FIG. 6 is another type of sensor used in the transmitter of the present invention.

FIG. 7 is an operation explanatory view of the sensor of FIG.

FIG. 8 is another type of sensor used in the transmitter of the present invention.

FIG. 9 shows another embodiment of the transmitter according to the present invention.

10 is an explanatory diagram of the operation of the transmitter of FIG.

FIG. 11 shows an example of the overall configuration of signal processing of the transmitter of the present invention.

FIG. 12 is an overall configuration diagram of a plant system using the transmitter of the present invention.

FIG. 13 is an operation explanatory diagram of the transmitter of the present invention.

FIG. 14 is an explanatory diagram of an output signal of the transmitter of the present invention.

FIG. 15 is a diagram for explaining another operation of the transmitter of the present invention.

16 is a flowchart of the processing means of FIG.

17 is an explanatory diagram of output signals of the transmitter of FIG.

FIG. 18 is an overall configuration diagram of a plant system using the transmitter of the present invention.

19 is an example of information display of the plant system of FIG.

[Explanation of symbols]

110 ... Compound sensor, 112 ... Center diaphragm, 1
14a, 114b ... Seal diaphragm, 118 ... Main body member, 120 ... Fill liquid, 122 ... Signal processing circuit, 126
a, 126b ... Pressure receiving chamber, 130 ... MPU, 131, 13
2 ... Terminal, 150 ... Physical property change detection sensor, 231 ... MP
X, 233 ... PGA, 234 ... A / D converter, 236 ...
EPROM, 237 ... D / A converter, 238 ... V / I converter, 239 ... EEPROM, 240 ... Digital I / O, 32
0 ... Insulating film, 330, 332 ... Electrode, 700 ... Pipeline, 710 ... Orifice, 720 ... Differential pressure transmitter, 73
0 ... Pressure transmitter, 740 ... Control computer, 741 ...
Transmission line, 750 ... I / O device, 761, 762 ... Signal waveform.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruo Kobayashi 882, Mao, Katsuta-shi, Ibaraki Hitachi Ltd. Measuring Instruments Division

Claims (15)

[Claims] 1. A pressure transmitter, comprising: a seal diaphragm for receiving a fluid pressure from a process fluid; and a sealed fluid for transmitting a pressure received by the seal diaphragm to a pressure detecting means, to detect a state of the seal diaphragm. A pressure transmitter, comprising: a seal diaphragm state detecting unit for comparing the output value from the seal diaphragm state detecting unit with a predetermined reference value. 2. The pressure transmitter according to claim 1, wherein a physical property detection sensor for detecting a physical property of the enclosed fluid is provided as the seal diaphragm state detecting means, and a breakage of the seal diaphragm is detected. Pressure transmitter. 3. The pressure transmitter according to claim 2, wherein a dielectric constant sensor for measuring the dielectric constant of the enclosed liquid is formed as the physical property detecting sensor. 4. The pressure transmitter according to claim 2, further comprising a moisture content sensor for detecting the moisture content of the filled liquid as the physical property detection sensor. 5. The pressure transmitter according to claim 2, further comprising a PH sensor that detects the PH of the enclosed liquid as the physical property detection sensor. 6. The pressure transmitter according to claim 2, further comprising an ion concentration sensor for measuring a specific ion concentration of the enclosed liquid as the physical property detection sensor. 7. The pressure transmitter according to claim 1, wherein a seal diaphragm operation detecting sensor for detecting an operation of the seal diaphragm is provided as the seal diaphragm state detecting means, and a change with time of the pressure transmitter is detected. A pressure transmitter characterized in that. 8. The pressure transmitter according to claim 7, further comprising a capacitive sensor having electrodes on the seal diaphragm as the seal diaphragm operation detection sensor. 9. A seal diaphragm for transmitting a fluid pressure from a process fluid to an enclosed fluid, and a pressure detection means for receiving the pressure of the enclosed fluid and detecting the pressure of the process fluid, the pressure detection means detecting. A process state display device for displaying the pressure of the process fluid includes a seal diaphragm state detecting means for detecting the state of the seal diaphragm, and displays a difference between a detected value of the seal diaphragm state detecting means and a predetermined reference value. A process status display device characterized by the above. 10. A pressure sensor, which is in contact with a fluid and detects the pressure of the fluid under the influence of the pressure of the fluid, comprising a sensor for detecting the physical properties of the fluid. 11. The pressure sensor according to claim 10, wherein the physical property detection sensor detects a dielectric constant of the fluid. 12. The pressure sensor according to claim 10, wherein the physical property detection sensor detects the moisture content of the fluid. 13. The pressure sensor according to claim 10, wherein the physical property detection sensor detects the humidity of the fluid. 14. The pressure sensor according to claim 10, wherein the physical property detection sensor detects PH of the fluid. 15. The pressure sensor according to claim 10, wherein the physical property detection sensor detects an ion concentration of the fluid.