JPH0371652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for diagnosing the occurrence of an abnormality caused by leakage of a sealed liquid in a pressure transmitter such as a differential pressure transmitter.

[Conventional technology]

A pressure transmitter that measures pressure, differential pressure, etc. is equipped with a high pressure chamber and a low pressure chamber via a center diaphragm, each chamber is sealed by a barrier diaphragm, and a liquid such as silicone liquid is filled into each chamber. This is manufactured to prevent leakage from each room, but after installation at the measurement site, leakage to the outside or between each room may occur for some reason, and in this case, Since the detection force of the pressure transmitter is inaccurate, conventionally, the presence or absence of an abnormality was determined empirically according to the detection force value, or the pressure transmitter was checked during periodic inspection, and the amount of sealed liquid was checked. Diagnosing the presence or absence of abnormalities based on leaks, etc.

[Problem that the invention seeks to solve]

However, judgment based on experience can only provide inaccurate results, and periodic inspections require various measuring instruments, and even if an abnormality is detected, it is difficult to determine where the leakage of the sealed liquid is occurring. The only way to determine this is to carry out a disassembly inspection, and in any case, the problem arises that diagnosis is troublesome and requires a large amount of man-hours.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

In other words, the initial constants required to calculate the volume change of each chamber of a pressure transmitter that is equipped with a high pressure chamber and a low pressure chamber filled with liquid and a center diaphragm between the chambers are stored in memory. A static pressure sensor that detects the static pressure in at least one of the chambers and a temperature sensor that detects the temperature of the pressure transmitter are provided, and a known pressure is applied to the pressure transmitter, and the pressure is transmitted at this time. The amount of change in volume of each chamber is calculated using the detected force of the chamber, the detected force of the static pressure sensor, the detected force of the temperature sensor, and the initial constant of the memory, and the amount of change in volume of each chamber is calculated. It is designed to determine whether there is any leakage of the sealed liquid.

[Effect]

Therefore, it is possible to determine whether or not the sealed liquid has leaked based on the amount of change in volume of the high-pressure chamber and the low-pressure chamber.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing examples.

FIG. 2 is a cross-sectional view of the differential pressure transmitter, in which covers 2a and 2b having through holes 1a and 1b to which the pressure to be measured is applied are connected to gaskets 3a and 3b from both sides.
The bodies 4a and 4b are sealed in a sealed manner.
, barrier diaphragms 5a, 5b are provided in close contact with the bodies 4a, 4b around the periphery, facing the through holes 1a, 1b, and gaps 6a, 6 are provided inside each of the barrier diaphragms 5a, 5b.
b are formed, and these central parts and communication holes 7a, 7
A center diaphragm 9 is provided between the inner chambers 8a and 8b, which communicate with each other through b, for sealingly separating the inner chambers 8a and 8b.

In addition, there is a gap 6 between the bodies 4a and 4b and below.
communicates with a, 6b and inner chambers 8a, 8b, and
Communication holes 12a, 12b are provided which communicate with the injection ports 11a, 11b for the filled liquids 10a, 10b, and inner chambers 8a, 8 are provided above the bodies 4a, 4b.
The covers 2a, 2b and the bodies 4a, 4b are tightly secured to each other by bolts 14 and nuts 15, respectively.

On the other hand, an annular gap 2 is provided between the outer cylinder 21 fixed to the upper surface of the bodies 4a and 4b by welding.
A cylindrical member 23 is provided which forms a cylindrical member 2 and is fixed in the same manner.
A support cylinder 25 made of glass is fixed to the lower surface of the sensor base 24 that fits into the interior of the sensor base 24 in close contact with the periphery of the upper end, and the sensor base 24 and the support cylinder 25
A communication hole 26 connecting the gap 22 and the lower surface of the support tube 25 is bored in the support tube 2.
A diaphragm-shaped composite sensor 27 is fixed to the lower surface of the sensor 5 to seal the communication hole 26 from the surroundings.

Further, a sleeve 28 is fixed to the lower surface of the sensor base 24, forming a gap with the support cylinder 25 and the cylindrical member 23, and protruding downward from the composite sensor 27. A shield plate 29 for noise prevention having a through hole is attached.

Note that the lead wire of the composite sensor 27 passes through the sleeve 28 and the sensor base 24, is led out to the pins 20a and 20b on the upper surface, and is connected to a circuit in the pressure transmitter 30 that is locked upward.

FIG. 1 is an enlarged plan view of the composite sensor 27, in which a substrate 31 made of silicon or the like is used, and a diaphragm 32 is formed in the center of the substrate 31.
Differential pressure sensors 33a to 33d are formed near the boundary between the diaphragm 32 and the substrate 31 on four diagonal sides using integrated circuit technology on these insulating film surfaces, and static pressure sensors are formed near these and on the substrate 31. 34a to 34d are formed, while a temperature sensor 35 is formed on the substrate 31 and approximately between the differential pressure sensors 33a and 33b, and the temperature sensor 35 is formed on the substrate 31, and the differential pressure sensors 33a to 33d and the static pressure sensors 34a to 34d.
For the temperature sensor 35, a semiconductor element that functions as a strain gauge is used, and as the temperature sensor 35, a semiconductor element that functions as a thermistor is used.

Further, the differential pressure sensors 33a to 33d and the static pressure sensors 34a to 34d are connected in a bridge shape by a conductor 36, and each connection point is connected to a lead wire by a land 37, so that the strain on the diaphragm 32 is reduced. The differential pressure between the two surfaces of the diaphragm 32 is detected by the resistance value change of the differential pressure sensors 33a to 33d in response to the change in the resistance value of the substrate 31 and the static pressure sensor 34a in response to the static pressure applied to the surfaces on which the static pressure sensors 34a to 34d are formed. Since the resistance values of the static pressure sensors 34a to 34d change due to the difference in compression ratio between the static pressure sensors 34a to 34d, the static pressure is detected based on this.

Note that the temperature sensor 35 has a resistance value that changes depending on the ambient temperature, which causes the differential pressure sensor 33a to
It is designed to detect the temperature of the entire differential pressure transmitter including 33d to 33d.

Therefore, if high pressure P _H is applied to the through hole 1a side in FIG. 2 and low pressure P _L is applied to the through hole 1b side, the barrier diaphragms 5a, 5
b is displaced, this displacement is applied to the center diaphragm 9 via the filled liquids 10a and 10b, and P _H and
According to the differential pressure with P _L , the center diaphragm 9
is displaced, thereby absorbing most of the differential pressure, while a portion of the differential pressure is applied to the diaphragm 32 of the composite sensor 27 via the communication holes 13a, 13b, the gap 22, and the communication hole 26, and this The differential pressure between P _H and P _L is detected by the differential pressure sensors 33a to 33d according to the strain _of
Or the static pressure of P _L is detected, and these detection conditions are shown by the broken line in Figure 2 of the pressure transmitter 3.
0 as an electrical signal.

FIG. 3 is a schematic diagram showing the differential pressure transmitter described above, and in order to explain the principle of diagnosing the leakage situation of the sealed liquids 10a and 10b, the signals are determined as follows.

V _H : Total volume of the high pressure chamber 41 including the inner chamber 8a and parts communicating with it V _L : Total volume of the low pressure chamber 42 including the inner chamber 8b and parts communicating with it P _H : Applied high pressure P _L : Applied low pressure P _h : Static pressure in the high pressure chamber 41 P _l : In the low pressure chamber 42 〃 ΔV _H : Amount of displacement of the barrier diaphragm 5a ΔV _C : Amount of displacement of the center diaphragm 9 ΔV _L : Amount of displacement of the barrier diaphragm 5b φ _H : Amount of displacement of the barrier diaphragm 5b Compliance of 5a φ _C : Center diaphragm 9 〃 φ _L : Barrier diaphragm 5b 〃 Δv ₁ : Volume change of high pressure chamber 41 Δv ₂ : Low pressure chamber 42 〃 α: Temperature expansion coefficient ΔT of sealed liquids 10a, 10b: Temperature difference from the initial temperature at the time of shipment from the factory Furthermore, using the above-mentioned symbols, the following formula generally holds true in the configuration of FIG. 3.

P _H −P _h =1/φ _H ΔV _H …(1) P _l −P _L =1/φ _L ΔV _L …(2) P _h −P _l =1/φ _C ΔV _C …(3 ) Δv ₁ = ΔV _C −ΔV _H +α・V _H・ΔT ……(4) Δv ₂ = ΔV _L −ΔV _C +α・V _L・ΔT ……(5) Here, the pressure transmitter 30 is installed at the factory. to the internal memory, V _H based on the design value or measured value,
V _L , φ _H , φ _C , φ _L , α, and the actual measured temperature T ₀ at this time are each stored as initial constants, and the pressures P _H and P _L applied to the differential pressure transmitter are passed through these. By opening and closing the pipes, a known pressure of, for example, Kgf/cm ³ is established, and the differential pressure sensors 33a to 3 at this time are
3b, the detected force P _h or P _l by the static pressure sensors _34a to _34b , and the detected force T by the temperature sensor 35. For example, based on the above formula, each chamber 41,
The volume change amounts Δv ₁ and Δv ₂ of 42 are calculated. be able to.

That is, the following equation is obtained from equations (1) to (3).

ΔV _H =φ _H (P _H −P _h )……(6) ΔV _L =φ _L (P _l −P _L )……(7) ΔV _C =φ _C (P _h −P _l )……(8 ) Furthermore, if you find either P _h or P _l , then
When the detection force (P _h - _{P l} ) of the differential pressure transmitter is known and (P _h - _{P l} ) = K, P _h = K + P _l P _l = P _h - K ……(9) The other can be found by

Therefore, from equations (4), (5) and equations (6) to (8), the volume changes Δv ₁ and Δv ₂ of each chamber 41, 42 are given by the following equations.

Δv ₁ =φ _C (P _h −P _l )−φ _H (P _H −P _l ) +α・V _H・ΔT ……(10) Δv ₂ =φ _L (P _l −P _L )−φ _C (P _h − P _l ) +α・V _L・ΔT ……(11) Therefore, ΔT=T−T ₀ Therefore, each initial setting V _H , V _L ,
Read and use φ _H , φ _C , φ _L , α, and T ₀ , and
Δv ₁ and Δv ₂ can be calculated by calculation using the detection force (P _h −P _l ) of each sensor, P _h or P _l , and .

These Δv ₁ and Δv ₂ indicate the amount of change in volume of the sealed liquids 10a and 10b in each chamber 41 and 42, and each decrease means leakage to the outside or to the other chamber side, and these decreases mean leakage to the outside or to the other chamber side. The following judgment can be made based on the changing situation.

(A) Δv ₁ <0, Δv ₂ =0 Occurrence of leakage to the outside of the high pressure chamber 41 (B) Δv ₁ =0, Δv ₂ <0 Occurrence of leakage to the outside of the low pressure chamber 42 (C) Δv ₁ <0, Δv ₂ <0 Occurrence of leakage to the outside of each chamber 41, 42 (D) Δv ₁ + Δv ₂ = 0 Occurrence of leakage between each chamber 41, 42 In other words, as shown in (A) to (C), the volume of at least one of them decreases As shown in (D), it can be determined that a leak has occurred to the outside.
If the sum of the two volume changes is found and this value is approximately zero, it can be determined that leakage has occurred between the chambers 41 and 42.

In addition, it can be determined that leakage has occurred in one of the parts simply by the fact that a change in volume has occurred.

FIG. 4 is a block diagram of an example of a circuit configuration based on the above principle, and shows the differential pressure transmitter (hereinafter referred to as
DPT) 51 and a pressure transmitter (hereinafter referred to as
PTR) 30, the differential pressure sensor (hereinafter referred to as DPS) 33 and the static pressure sensor (hereinafter referred to as SPS) in Fig. 1 are used.
34, and a detection circuit (hereinafter referred to as TS) that detects each resistance value change of temperature sensor (hereinafter referred to as TS) 35 (hereinafter referred to as DET).
Each detection power from 52 is sequentially and repeatedly selected by a multiplexer (hereinafter referred to as MPX) 53, and then connected to an analog-to-digital converter (hereinafter referred to as ADC).
54 converts the signal into a digital signal and supplies it to a processor (hereinafter referred to as CPU) 55 such as a microprocessor, which normally converts the detected force of the DPS 33 into a differential pressure measurement value by a predetermined calculation and converts it into a digital-to-analog converter. (hereinafter referred to as DAC) 56 and drive circuit (hereinafter referred to as DR) 57, a forward bias corresponding to the measured value is applied to transistor (hereinafter referred to as TR) Q ₁ , and the collector-emitter resistance value of TR Q ₁ is determined. Based on the power supply E applied to the two-wire transmission line consisting of lines L ₁ and L ₂ via the resistor R, a current is passed through a unified signal of, for example, 4 to 20 mA, and the measured value is determined based on the current value. This current value is detected as the terminal voltage of the resistor R, and this is given to the control device etc. as a measurement signal S _n .

Further, the voltage change between the lines L ₁ and L ₂ is detected by a comparator (hereinafter referred to as CP) 58 after comparing it with the reference voltage E _S1 , and is given to the CPU 55 via the ADC 59, and this is used as a received signal to the CPU 55. is to be deciphered and to respond to the contents.

Note that the CPU 55 has fixed memory (hereinafter referred to as
It executes the instructions in the non-volatile memory (hereinafter referred to as NVM) 61 while accessing the necessary data to variable memory (hereinafter referred to as RAM) 60.
Each of the above-mentioned initial constants is stored in the initial constants at the time of shipment from the factory.

On the other hand, the portable tester (hereinafter referred to as PST) 70 is bridge-connected to the lines L ₁ and L ₂ by lead wires l ₁ and l ₂ .
It is possible to freely transmit and receive signals based on voltage changes between lines L ₁ and L ₂ , and keyboard (hereinafter referred to as KB) 7
The CPU 72, which is similar to the CPU 55, responds to the operation of 1, and transmits TR/TR via the DAC 73 and DR 74.
By controlling Q ₂ and passing a current other than the current flowing through TR/Q ₁ from the power source E as a coded pulse, the line voltage is changed in a pulse, and the transmission to PTR 30 is changed. At the same time, the line voltage corresponding to the current value change controlled by TR Q ₁ is detected by comparison with the reference voltage E _S2 in the CP75, decoded by the CPU 72 via the ADC 76, and displayed by the display (hereinafter referred to as DP) 77. It is designed to display information.

Note that the CPU 72 also performs calculations and control by executing instructions in the ROM 78 and accessing necessary data from the RAM 79.

Therefore, the PST 70 can check the measured values of the PTR 30, send various commands to the PTR 30, and receive response transmissions in response to these commands, and the KB 71 can issue leak check commands. If so, this is the PTR
received by CPU 55 of 30, and in response
The CPU 55 transmits each initial constant in the NVM 61 by changing the current of the pulse code, and the DPS 3
3. DET52 each detection force of SPS34 and TS35
and MPX53, and each detected value based on these is transmitted in the same way, so these are received by the CPU 72, and the CPU 72 uses them to perform calculations according to equations (10) and (11) above. and, depending on this result, the above
The judgments shown in (A) to (D) are made, and the diagnostic status based on the judgment is displayed on the DP 77.

Figure 5 shows the external shape of PTS70, (A) is a front view,
(B) is a side view, in which all the circuits and power supply are housed in a hand-held outer case 81, and a plurality of pushbutton keys 8 are provided on the front.
A KB71 consisting of 2 parts is provided, and a DP77 such as a liquid crystal display element is attached above this, and lead wires connected to tip helicips 83a and 83b are provided.
A code 84 consisting of l ₁ and l ₂ is derived, and from this,
The lines L ₁ and L ₂ can be freely connected to terminal boards, etc.

Therefore, after making the above connection using the clips 83a and 83b, "LEAK CHECK"
When the key 82 is pressed, the above-mentioned judgment is made through transmission/reception and calculation by the internal CPU 72.
For example, "LP LEAK" is displayed on the DP 77, which immediately indicates that there is a leak to the outside of the low pressure chamber 42. Therefore, the DPT 51 can be easily and accurately detected without preparing a special measuring device or disassembling the DPT 51. It is possible to diagnose abnormalities in

However, the NVW 61 only needs to be attached to the DPT 51, and it is also possible to use other memory elements that can retain the contents for a long time.The above-mentioned calculations and judgments are performed in the CPU 55 of the PTR 30,
Alternatively, it may be performed by a CPU such as a control device, and the diagnosis results may be displayed on a separate display.
In addition to what is shown in the figure, you can select according to the conditions, etc.
Various modifications are possible.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, it is possible to easily and accurately diagnose the leakage situation of the sealed liquid in differential pressure transmitters, etc., and therefore it has a remarkable effect in diagnosing abnormalities in various pressure transmitters having the same configuration. can get.

[Brief explanation of drawings]

The figures show embodiments of the present invention, in which Figure 1 is a plan view of a composite sensor, Figure 2 is a sectional view of a differential pressure transmitter, and Figure 3 is a cross-sectional view of a differential pressure transmitter.
The figure is a schematic diagram of the differential pressure transmitter, FIG. 4 is a block diagram of the circuit configuration, and FIG. 5 is an outline diagram of the portable tester. 5a, 5b... Barrier diaphragm, 7a, 7
b, 13a, 13b, 26...Communication hole, 8a, 8
b...Inner chamber, 9...Center diaphragm, 10
a, 10b...Filled liquid, 27...Composite sensor, 3
0... Pressure transmitter, 31... Board, 32... Diaphragm, 33, 33a to 33d... DPS (differential pressure sensor), 34, 34a to 34d... SPS (static pressure sensor), 35... TS ( temperature sensor), 41...high pressure chamber, 42...low pressure chamber, 51...DPT (differential pressure transmitter), 55, 72...CPU (processor), 59,
78...ROM (fixed memory), 60, 79...
RAM (variable memory), 61...NVM (non-volatile memory), 58, 75...CP (comparator), 71...
KB (keyboard), 77...DP (display), Q ₁ ,
Q ₂ ...TR (transistor), L ₁ , L ₂ ... line,
l ₁ , l ₂ ... Lead wire, E ... Power supply.

Claims (1)

[Claims] 1 Store in memory the initial constants required to calculate the volume change for each chamber of a pressure transmitter that is equipped with a high-pressure chamber and a low-pressure chamber filled with liquid and a center diaphragm between the chambers. a static pressure sensor for detecting the static pressure in at least one of the chambers and a temperature sensor for detecting the temperature of the pressure transmitter; applying a known pressure to the pressure transmitter; The amount of change in volume of each chamber is calculated using the detection force of the pressure transmitter, the detection force of the static pressure sensor, the detection force of the temperature sensor, and the initial constant of the memory, and the volume of each chamber is calculated. A method for diagnosing an abnormality in a pressure transmitter, comprising determining whether or not the sealed liquid has leaked according to the amount of change.