JPH0353140A - Differential pressure transmitter - Google Patents

Abstract

PURPOSE:To easily adjust the zero point in a remote place by opening/closing a three- way valve consisting of an equalizing valve and stop valves with a valve driving mechanism of low power. CONSTITUTION:A differential pressure detecting element 23 is attached to a medium passage 21 in a differential pressure transmitter main body 20, and the passage 21 is filled up with a pressure transmission medium 20 and is provided with partition diaphragms 24a and 24b. Extension pipes 26a and 26b are connected to pressure receiving flanges 25a and 25b and are filled up with the pressure transmission medium, and remote seal diaphragms 27a and 27b are provided in end parts of pipes 26a and 26b to isolate the medium from process fluids A and B. Pipes 26a and 26b are provided with stop valves 29a and 29b, and a by-pass pipe 28 is provided with an equalizing valve 29c. A driving signal generating means 33 drives valve driving mechanisms 30a to 30c, and the equalizing valve 29c and stop valves 29a and 29b are normally closed and opened respectively to detect the differential pressure between fluids A and B by the element 23; and at the time of zero point adjustment, the equalizing valve 29c is opened to set the differential pressure to zero after stop valves 29a and 29b are closed, and the output of the element 23 is used to perform the zero point adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement in a pressure transmitter that automatically performs zero point adjustment by remote control.

(Prior Art) In general, this type of differential pressure transmitter is a differential pressure transmitter that is installed so as to block a pressure transmission medium passage 2 communicating across both sides of a block 1, as shown in FIG. an element 3, and partition diaphragms 5a, 5b that are fluid-tightly attached to concave portions on both sides of the block 1 in order to fill the long holes 2, etc. with pressure transmission media 4a, 4b such as silicone oil, ethylene glycol, etc. , a pressure transmitter main body 8 consisting of pressure receiving flanges 7a and 7b fixed to both sides of the block 1 with bolts and nuts 6 so as to sandwich the partition diaphragms 5a and 5b.
and each pressure receiving flange 7a of this pressure transmitter main body 8,
Process piping 1 is connected to the fluid inlet ports 9a and 9b of 7b, respectively.
0a, 10b are connected, and this process piping 10a. 1
The pressures P, P2 of process fluid A and process fluid B introduced from the other end side of 0b are applied to the differential pressure detection element 3 via partition wall diaphragms 5a, 5b and pressure transmission media 4a, 4b. There is. In addition, 11... is a packing that liquid-tightly seals the block 1 and the pressure receiving flanges 7a, 7b, 12 is a hole for a signal line, and 13 is a signal line that transmits the differential pressure detection signal detected by the differential pressure detection element 3. , 14 are hermetic seals. Moreover, the partition diaphragms 5a, 5
For example, two elongated holes 2 extending from both sides of the block 1 are guided to the upper part of the block through the inside of the block, and the elongated holes 2 are placed in the upper part of the block. There are various configurations using the same measurement principle, such as a configuration in which the differential pressure detection element 3 is arranged so as to divide a room established so as to communicate with the room into two parts.

However, in the case of the differential pressure transmitter as described above, permanent distortion occurs due to aging, excessive pressure, etc., and this may cause zero point drift.

Therefore, in the above-mentioned differential pressure transmitter, a bypass pipe 15 is installed between both process pipes 10a and 10b in advance during installation.
These pipes 10a, 10b, 15. Attach a three-way valve consisting of stop valves 16a, 16b and pressure equalizing valve 16c to the
After closing, the equalizing valve 16c is opened to equalize the pressures of both fluids A and B, and the output of the differential pressure detection element 3 obtained at this time is used to perform zero point adjustment in a signal converter (not shown). After the adjustment, the pressure equalizing valve 16c is closed and the stop valves 16a and 16b are subsequently opened to set the original differential pressure measurement state.

In addition, FIG. 9A is a diagram schematically representing the configuration of FIG. 8, and FIG. 9B is a schematic diagram of a conventional general differential pressure transmitter provided with overpressure prevention valves 17a and 17b that respond to overpressure. It is.

(Problems to be Solved by the Invention) In recent years, in order to save labor and improve the efficiency of zero point adjustment work, it has become possible to send necessary signals from a remote location and operate a three-way valve using a valve drive mechanism such as an electric motor or compressed air. It is requested to operate.

However, this three-way valve directly receives the pressure of process fluids A and B, and when the pressures P and P2 of these fluids A and B are large, the pressure between the atmospheric pressure and P1 or the atmospheric pressure The valve drive mechanism must be driven with a large amount of electric power to sufficiently cope with the pressure difference between P2 and P2. By the way, for example, P r - 101 kg / cm 2P
2-100 kg/cm”, 101 kg/cm against the atmosphere despite P, -P2-1
The driving part of the airtightly sealed three-way valve is moved with a driving force of 100 kg/cm2, which requires a considerable amount of driving power.

In addition, process fluids A and B often contain dust, sand, rust, etc., and these unnecessary substances can get caught in the seal part of the three-pronged valve, causing leakage in the valve itself, which can cause errors. You may end up making a zero point adjustment. In particular, in the case of remote control, it is very difficult to detect any abnormality because it is unmanned, and therefore highly reliable zero point adjustment is desired.

The present invention has been made in view of the above circumstances, and allows zero point adjustment to be easily performed from a remote location with low power drive, while also preventing dust from entering the process fluid. It is an object of the present invention to provide a differential pressure transmitter that does not affect zero point adjustment even if it contains sand or the like.

[Structure of the Invention] (Means for Solving the Problems) First, in order to solve the above problems, the invention as claimed in claim 1 is characterized in that the pipes extending from the outside of each bulkhead diaphragm of a differential pressure transmitter are filled with a remote seal diaphragm that isolates a pressure transmission medium from the process fluid; a three-way valve consisting of a pressure equalization valve and a stop valve provided in the plurality of extension pipes and bypass pipes interposed between the extension pipes; A low-power valve drive mechanism is used to drive the three-way valve, and upon receiving a zero point adjustment command from the outside, the stop valve is closed via the valve drive mechanism, and the pressure equalization valve is opened and closed. This configuration is provided with a zero point adjusting means for zero point adjusting the output of the differential pressure detection element obtained.

Next, the invention according to claim 2 provides that the pressure extending from both sides of the differential pressure detecting element inside the differential pressure transmitter main body is different from the one provided outside the differential pressure transmitter main body as in the invention according to claim 1. A pressure equalization valve is provided in the bypass passage spanning the transmission medium passage, or a three-way valve consisting of a stop valve and a pressure equalization valve is provided in the pressure transmission medium passage and the bypass passage, and a low power drive for driving these valves is provided. The valve drive mechanism is attached to the differential pressure transmitter body, and the structure is compact as a whole and allows zero point adjustment.

(Function) Therefore, by taking the above-described measures, the invention according to claims 1 and 2 allows the pressure equalizing valve to be set to the closed state and the stop valve to be open at all times, that is, when measuring the differential pressure of the process fluid. Since the pressure of each process fluid is transmitted through the remote seal diaphragm and the second pressure transmission medium, it is further applied to the differential pressure sensing element via the bulkhead diaphragm and the first pressure transmission medium within the differential pressure transmitter body. Therefore, the differential pressure between the two process fluids can be measured by this differential pressure detection element.

When a zero point adjustment command is sent during zero point adjustment, the valve driving mechanism closes the stop valve in response to the command, and then opens and closes the pressure equalizing valve to reduce the pressure in both extension pipes or both pressure transmission medium passages. become equal, resulting in a so-called zero differential pressure state. Therefore, zero point adjustment is performed by setting the output of the signal conversion portion to zero using the output of the differential pressure detection element at this time.

(Example) Hereinafter, an example of the present invention according to claim 1 will be described with reference to FIG. In the figure, 20 is a differential pressure transmitter main body schematically shown, and inside this differential pressure transmitter main body 20, a pressure transmitting medium 2 is filled in a pressure transmitting medium passage 21.
A differential pressure detection element 23 is installed so as to block 2, and
In order to isolate the pressure transmission medium 22.22 filled in the pressure transmission medium passage 21 extending from both sides of the differential pressure detection element 23, a partition wall diaphragm 24a. 24b is attached. 25a and 25b are pressure receiving flanges.

Extended piping 26a, 26b of a predetermined length is connected to the outside of the partition diaphragms 24a, 24b, that is, the pressure receiving flanges 25a, 25b.
6a and 26b are similarly filled with a pressure transmission medium. Corrosion-resistant remote seal diaphragms 27a and 27b are attached to the ends of the extension pipes 26a and 26b to liquid-tightly seal the pressure transmission medium inside the pipes and isolate them from the process fluids A and B. There is.

A bypass pipe 28 spans the extension pipes 26a, 26b, and these pipes 26a, 26b, 28 are provided with three-way valves. This three-way valve has extension pipes 26a, 2
6b, and a pressure equalizing valve 29c provided in the bypass pipe 28. These valves 29a to 29c are driven to open and close by, for example, actuators 30a to 30c as valve drive mechanisms. In addition, 31a, 3lb, 32a, 32b are diaphragms 24a. This is a diaphragm position detector for detecting deviation of 24b, 27a, and 27b.

33 is a drive signal generating means, which receives a zero point adjustment command from the outside and operates the actuators 30a to 30a in a predetermined order.
30c, and position detectors 31a, 31b,
32a, 32b and outputs a necessary signal, such as an alarm signal to the outside, or all valves 29 based on information when the fluid in the process piping is empty.
A to 29C are commanded to open, and due to natural balance, the diaphragms 24a, 24b. 27a and 27b, or when it is detected from the output of the differential pressure detection element 23 that a differential pressure in the direction opposite to the one-sided direction has occurred, two of the three valves are opened and the remaining valves are closed. You may return the deviated diaphragm to the ideal position by repeating closing, opening, closing, opening, etc. at high speed.

34 is the process fluid A, B based on the output of the differential pressure detection signal 23.
A signal conversion section 35 that converts the signal into a signal proportional to the pressure difference is a zero adjustment section and has a function of setting the output of the signal conversion section 34 to zero based on a command from the drive signal generation means 33.

Next, the operation of the differential pressure transmitter will be explained.

Normally, the stop valves 29a and 29b are set to open based on a command from the drive signal generating means 33, and the pressure equalizing valve 29c is set to a closed state. As a result, the pressure P of process fluid A
1 is applied to one surface of the differential pressure detection element 23 via the remote seal diaphragm 27a1, the stop valve 29a1 in the open state, the pressure transmission medium of the pressure transmission medium passage 26H, and the pressure transmission medium 22 of the partition wall diaphragm 24a1, the pressure transmission medium passage 21. . On the other hand, the pressure P2 of the process fluid B is the same as that of the two stop valves b in the open state of the remote seal diaphragm 27b1.
1 Pressure transmission medium in pressure transmission medium passage 26b, partition diaphragm 24b1 Pressure transmission medium 2 in pressure transmission medium passage 21
2 to the other surface of the differential pressure detection element 23. Here, the differential pressure detection element 2.3 outputs a signal proportional to the pressure difference (PI F2) between both process fluids A and B, and sends it to the signal conversion section 34. The signal converter 34 converts the signal from the differential pressure detection element 23 into an appropriate signal, and then sends the signal to a remote center or the like.

By the way, when the drive signal generating means 33 receives an external command and determines that zero point adjustment is to be performed, the drive signal generating means 33 first activates the actuator 3.
A drive signal of a predetermined power is applied to the stop valves 29a, 30b to operate the stop valves 29a. After closing the pressure equalizing valve 29b, the pressure equalizing valve 29c is subsequently opened via the actuator 30c. As a result, both pressure transmission medium pipes 26a and 26b are communicated with each other, and the pressures in both pipes 26a and 26b become equal, so the output of the differential pressure detection element 23 at this time is measured by the measurement circuit part of the signal converter 34. . Thereafter, after a predetermined period of time, the drive signal generating means 33 generates a command to close the pressure equalizing valve 29C via the actuator 30c. Similarly, the output of the differential pressure detection element 23 is measured by the signal conversion sections 3 and 4, but at this time, the zero point adjustment section 35 performs processing to make the output of the signal conversion section 34 zero.

Note that if the signal converter section 34 is a digital circuit, zero point adjustment may be performed in the form of initialization.

After this zero point adjustment, the drive signal generating means 33
It outputs a signal to open 9a and 29b and enters the original differential pressure measurement state.

Next, an embodiment of the invention according to claim 2 will be described with reference to FIGS. 2 to 4. Figure 2 is a diagram schematically representing the entire body, Figure 3 is a diagram schematically representing the main body of the differential pressure transmitter, and Figure 4 shows the specific configuration of the main body of the differential pressure transmitter shown in Figure 3. FIG. That is, this differential pressure transmitter has a zero point adjustment function built into the differential pressure transmitter main body 20, and specifically, as shown in FIG. A bypass passage 41 is formed in the pressure transmission medium passage 21, and a stop valve 2 is provided on the pressure transmission medium passage 21 side.
9a, 29b1 A pressure equalizing valve 29c is provided on the bypass passage 41 side, a so-called three-way valve is built inside the pressure transmitter main body 20, and actuators 30a to 30c corresponding to each valve 29a to 29c are installed in the differential pressure transmitter main body 20. It is configured by attaching it. 42a and 42b are overpressure prevention valves.

FIG. 4 is a diagram showing the internal structure of the differential pressure transmitter main body 20, in which a pressure transmission medium passage 21 is formed from the left end of the block 43 in a predetermined length in the right direction.
A presser pusher 44 to which a differential pressure detection element 23 is attached is fitted so as to block the pressure difference detecting element 23. 45 is a hermetic seal, and 46 is a signal line led out from the differential pressure detection element 23.

Further, medium passages 47a and 47b are formed at a predetermined interval from the upper part of the block 43 and extend directly downward to cross at least the pressure transmission medium passage 21, and from the lower end of the medium passages 47a and 47b, both sides of the block 43 are formed. Narrow media passages 48a, 48b are formed to communicate with the media. Further, both medium passages 47a and 47b
A bypass passage 41 is formed so as to communicate with the
A medium passage 47c, which is wider than the bypass passage 41, is formed so as to be located between the two medium passages 47a, 47b and directly downward from the top of the block, but against the bypass passage 41. These medium passages 47a, 47b are provided with stop valves 29a. Norman open type actuators 30a and 30b equipped with pressure equalizing valve 29b are mounted in a fluid-tight manner, and similarly, a Norman closed-type actuator 30c equipped with a pressure equalizing valve 29c is fluid-tightly mounted in the medium passage 47c. These actuators 30a to 30
- In C, a is a solenoid coil, b is a coil excitation wire, C is a ferromagnetic material, d is a fixture, e is a spring, and f is a plunger.

49 is a ball seal, and 50 is a sealing body.

Note that the operation of this embodiment is the same as that shown in FIG. 1, so a description thereof will be omitted.

Therefore, according to the embodiment of the invention described in claims 1 and 2, the stop valves 29a, 29b1 and the pressure equalizing valve 29 are provided in the pressure transmission medium passages 26a, 26b, 21 and the bypass passages 28, 41.
Since a three-way valve consisting of c is provided, these valves 29a to 29
The actuators 30a to 30c that control the opening and closing of the valves 30a to 30c can be sufficiently driven with low electric power because a differential pressure is applied to both sides of the valve, unlike the conventional actuators. Furthermore, even if the process fluids A and B contain dust, sand, etc., the remote seal diaphragms 27a and 27b and the partition wall diaphragm 24a. 24b, and the valves 29a-2
No more getting caught in 9c. Furthermore, when adjusting the zero point, the stop valves 29a and 29c are closed via the actuators 30a and 30b, and the zero point adjustment is performed with the pressure equalizing valve 29c opened via the actuator 30c, according to a command from the drive signal generating means 33, Thereafter, when the valve is closed again after a predetermined period of time, even if the zero point moves a little due to the operating conditions of the valve, it is still physically the zero point. The configuration may be such that this point is regarded as the zero point and recognized on the circuit. Alternatively, when the pressure equalizing valve 29c is opened via the actuator 30c and closed again after a predetermined time without performing zero adjustment, the differential pressure detection element 23 Since the output of the signal converter 34 is set to zero with the output obtained from the pressure equalizing valve 29c, zero point adjustment can be performed reliably even if the output of the differential pressure detection element 23 differs when the pressure equalizing valve 29c is opened and closed. It goes without saying that zero point recognition operations such as initialization may be performed by a host computer system. Furthermore, diaphragms 27a, 27b. Position detectors 31a, 3lb, 32a, and 32b are provided to detect the deviation of 24a and 24b, and when the deviation is detected, the drive signal generating means 33 issues an alarm signal or operates the valves in a predetermined order as necessary. By doing so, the deviation of the diaphragm can be quickly corrected.

Note that the present invention is not limited to the above embodiments.

That is, in the above embodiment, two stop valves 29g, 2
9b was used, but one side, for example 29a, was used as shown in FIG.
It is also possible to have only one.

Alternatively, as shown in FIG. 6, the stop valves 29a and 29b may be removed and only the pressure equalizing valve 29c provided. Furthermore, the differential pressure detection element 23 generally uses a silicon diaphragm, but instead of the silicon diaphragm, a capacitance detection element or other various detection elements commonly used in the past may be used. Further, the valve drive mechanism is not limited to an actuator, and the types of valves are not limited. For example, instead of a solenoid type, a sliding flat plate valve,
A similar configuration can be made using a rotary valve, a ball valve, or the like. Furthermore, as a means for externally giving a zero point adjustment command to the drive signal generating means 33, an orifice plate 52 is provided in the process piping 51 as shown in FIG. A differential pressure gauge 53 is provided between the process piping 51 and the downstream side to detect a state where there is no differential pressure in the process piping 51, or a liquid detector 54 is installed between the process piping 51 and the downstream side.
This may be done by providing a controller to detect the absence of process fluid in the process piping 51 and supplying this detection signal to a remote center or drive signal generating means 33.

Note that a differential pressure detection element 2 is installed at an intermediate position of the differential pressure transmitter main body 20.
3, the pressure transmission medium 22 is guided as appropriate, for example, to the upper or lower part of the differential pressure transmitter main body 20, a chamber is provided in the upper or lower part, and the differential pressure detection element 23 is inserted so as to divide this chamber into two.
A configuration with .

In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, the zero point can be easily adjusted from a remote location with low power drive, and the process fluid is free from dust and dust.
It is possible to provide a differential pressure transmitter that does not affect zero point adjustment even if it contains sand or the like.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a differential pressure transmitter according to the invention as claimed in claim 1, and FIGS. 2 to 4 are as claimed in claim 2.
FIG. 2 is a schematic configuration diagram, FIG. 3 is a diagram equivalently representing the main body of the differential pressure transmitter, and FIG. The figure is a sectional view of the specific configuration inside the main body of the differential pressure transmitter, and FIGS. 5 and 6 are schematic configuration diagrams illustrating other embodiments of the invention as claimed in claim 2.
FIG. 7 is a diagram explaining an embodiment of the invention as claimed in claim 3, FIG. 8 is a schematic configuration diagram of a conventional differential pressure transmitter, and FIG.
FIG. 9B is an equivalent configuration diagram in which an overpressure prevention valve is provided. 20... Differential pressure transmitter main body, 21... Pressure transmission medium passage, 22... Pressure transmission medium, 23... Differential pressure detection element, 24a, 24b-... Partition diaphragm, 26a, 2
6b...Extension piping, 27a, 27b...Remote seal diaphragm, 28...Bypass piping% 29a
．． 29b...Stop valve, 29c...Pressure equalization valve, 30
a~30c-...actuator, 31a, 31b
, 32a, 32b... diaphragm position detector, 33
... Drive signal generation means, 34 ... Signal converter, 35
... Zero adjustment section, 41 ... Bypass passage, 42a, 4
2b...Overpressure prevention valve, 43...Block, 51...
・Process piping, 5 2... Orifice plate, 5 3... Differential pressure gauge, 54... Liquid detector.

Claims (3)

[Claims] (1) A differential pressure detection element is installed so as to block the pressure transmission medium passage formed inside the differential pressure transmitter main body, and
The first pressure transmission medium filled in the pressure transmission medium passage extending from both sides of the differential pressure detection element is liquid-tightly sealed by a partition diaphragm, and the differential pressure of the process fluid is transferred between the partition diaphragm and the first pressure transmission medium. In the differential pressure transmitter that detects the differential pressure with the differential pressure detection element via a pressure transmission medium, a remote that isolates the process fluid from a second pressure transmission medium filled in piping extending from the outside of each of the partition diaphragms; A three-way valve consisting of a seal diaphragm, a stop valve and a pressure equalization valve provided in the plurality of extension pipes and a bypass pipe extending between these extension pipes, and a low-power drive for driving the three-way valve. zero point using a valve drive mechanism and an output of the differential pressure detection element obtained by closing the stop valve via the valve drive mechanism and opening and closing the pressure equalization valve in response to a zero point adjustment command from the outside. A differential pressure transmitter comprising: zero point adjustment means for performing adjustment. (2) A differential pressure detection element is installed so as to block the pressure transmission medium passage formed inside the differential pressure transmitter main body, and
The pressure transmission medium filled in the pressure transmission medium passage extending from both sides of the differential pressure detection element is liquid-tightly sealed by a partition diaphragm, and the differential pressure of the process fluid is transmitted through the partition diaphragm and the pressure transmission medium. In the differential pressure transmitter that detects the differential pressure with the differential pressure detecting element, a pressure equalizing valve provided in a bypass passage spanning the pressure transmission medium passage extending from both sides of the differential pressure detecting element inside the differential pressure transmitter main body; a three-way valve consisting of a pressure equalization valve and a stop valve provided in the pressure transmission medium passage and the bypass passage; a low-power valve driving mechanism attached to the differential pressure transmitter body for driving these valves; The zero point is adjusted using the output of the differential pressure detection element obtained by opening and closing the pressure equalizing valve via a valve drive mechanism in response to a zero point adjustment command from the outside, or by closing the stop valve and opening and closing the pressure equalizing valve. A differential pressure transmitter characterized by comprising: zero point adjustment means for adjusting. (3) The means for outputting the zero point adjustment command from the outside is provided with a sensor that detects the presence or absence of fluid in the process piping or the pressure, and outputs the zero point adjustment command from the sensor when there is no fluid or under a predetermined pressure condition. Or the differential pressure transmitter described in 2.