JP2005292911A - Electropneumatic converter or valve positioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost and easy-to-maintain electropneumatic converter or valve positioner. <P>SOLUTION: The electropneumatic converter or valve positioner comprises differential pressure measuring means for measuring a correct gauge pressure by differencing a device output pressure and an atmospheric pressure, and has an air pressure in a storage box including pressure sensors different from the atmospheric pressure. The differential pressure measuring means have a first pressure sensor for measuring the output pressure with reference to the air pressure in the storage box, a second pressure sensor for measuring the atmospheric pressure with reference to the air pressure in the storage box, and an arithmetic part for differencing the measured signals of the first pressure sensor and second pressure sensor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electropneumatic converter or a valve positioner that is inexpensive and easy to maintain.
An electropneumatic converter is a device that controls air pressure and outputs air pressure in response to an input signal.
A valve positioner is a device that controls the position of a valve by adjusting the air pressure in response to an input signal.

  Prior art documents related to electropneumatic converters or valve positioners include the following.

Published by Yokogawa Electric Corporation, Instruction Manual, Number: IM21B3D1-01 “PK200 Electropneumatic Converter [Style: S2]”, February 1996, P7-1

FIG. 3 is an explanatory diagram of a main part configuration of a conventional example that is generally used conventionally, and shows an example of an electropneumatic converter.
FIG. 4 is an explanatory diagram of a main part configuration of the specific example of FIG.
In FIG.
A current input signal 1 of 4 to 20 mA or 10 to 50 mA is input to the electropneumatic converter as an operation input signal from an electronic controller or the like.

This signal is input to the torque motor 2 via an electric circuit, and torque proportional to the current signal is generated.
When the input signal increases, the flapper at the tip of the movable piece of the torque motor 2 constituting the nozzle flapper mechanism 3 operates in a direction to block the nozzle.

When the nozzle is blocked, the back pressure increases and the input diaphragm inside the control relay 4 is displaced.
For this reason, it operates in the direction in which the output air pressure 5 of the control relay 4 increases.
This operation input signal is output as an output pressure of the electropneumatic converter and also input to the pressure sensor 6 for feedback.

This is converted into an electric signal by the pressure sensor 6 and fed back to the electric circuit.
Here, the correction operation is performed until the output air pressure 5 is compared with the operation input signal and balanced with the operation input signal.
Thus, an output air pressure proportional to the input signal that is the operation signal can be obtained.

  Here, in order to obtain the gauge pressure, the pressure sensor 6 uses a differential pressure type pressure sensor to obtain the difference between the output air pressure 5 and the atmospheric pressure.

In FIG. 4, 11 is a storage box.
The storage box 11 is divided into a terminal box 12 for receiving an electric signal and a main body box 13 in which an electric circuit and the like exist, and both are partitioned by a die-cast partition wall.

In the main body box 13, in addition to the electric circuit 131, an I / P electropneumatic converter 132 (corresponding to the torque motor 2 in FIG. 3) that converts an electric signal into a pressure signal, and a pressure sensor 6 that measures pressure are provided. Built in.
The I / P electropneumatic converter receives an electric signal and outputs a pressure corresponding to the electric signal. However, since the I / P electropneumatic converter has the nozzle-flapper mechanism 3, a very small amount of air is always passed through the main body box 13.

Therefore, the main body box 13 has a slightly higher pressure than the atmospheric pressure.
On the other hand, the output pressure of the electropneumatic converter needs to output a pressure (gauge pressure) based on the atmospheric pressure. Therefore, in the prior art, in order to remove the influence of the pressure in the main body box 13, an expensive differential pressure sensor 6 is used to measure the atmospheric pressure and the output pressure.

The differential pressure type pressure sensor 6 is more expensive than a general-purpose (one-side input) pressure sensor.
Alternatively, the structural design of the sensor and its surroundings becomes complicated, which increases the cost.
Moreover, generally availability is also not good.
Since the pressure in the storage box cannot be grasped, it is difficult to detect when there is an abnormality in the nozzle flapper mechanism.

  An object of the present invention is to solve the above-described problems, and an object thereof is to provide an electropneumatic converter or a valve positioner that is inexpensive and easy to maintain.

In order to achieve such a problem, in the present invention, in the electropneumatic converter or valve positioner of claim 1,
In an electropneumatic converter or valve positioner comprising a differential pressure measuring means for measuring the difference between the output pressure of the apparatus and the atmospheric pressure, and the air pressure of the storage box including the pressure sensor is different from the atmospheric pressure,
A first pressure sensor for measuring an output pressure based on an air pressure of the containment box; a second pressure sensor for measuring an atmospheric pressure based on an air pressure of the containment box; and the first pressure sensor. And a differential pressure measuring means having a calculating means for calculating a difference between measurement signals of the second pressure sensor and the second pressure sensor.

In the electropneumatic converter or valve positioner according to claim 2 of the present invention, the electropneumatic converter or valve positioner according to claim 1,
It is characterized by comprising first detection means that is substantially connected to the second pressure sensor and detects air leakage of components in the storage box.

In Claim 3 of this invention, in the electropneumatic converter or valve positioner of Claim 1,
And a second detection means which is substantially connected to the second pressure sensor and detects an air leak of a component in the storage box with reference to an output signal of the first pressure sensor. .

According to claim 4 of the present invention, in the electropneumatic converter or valve positioner according to claim 2 or claim 3,
Alarm means for issuing a warning based on a signal from the detection means is provided.

According to claim 1 of the present invention, there are the following effects.
Since a general-purpose pressure sensor can be used, a low-cost electropneumatic converter or valve positioner can be obtained.
Even if the pressure sensor needs to be changed, a general general-purpose pressure sensor can be used. Therefore, an electropneumatic converter or a valve positioner that can be easily changed to an alternative sensor and can be easily maintained can be obtained.

According to claim 2 of the present invention, there are the following effects.
Connected to the second pressure sensor and provided with detection means to detect air leakage of parts in the containment box, air leakage of parts, I / P electropneumatic converter damage / abnormality, and other equipment damage -A diagnostic function that can easily detect abnormalities can be added, and a highly reliable electropneumatic converter or valve positioner can be obtained.

According to claim 3 of the present invention, there are the following effects.
Since the pressure in the storage box changes depending on the output of the equipment, it is not possible to correctly determine whether the equipment is abnormal simply by grasping the pressure in the storage box.
Therefore, an electropneumatic converter or valve that can detect an abnormal state in the device more accurately by referring to the measured output pressure by the output pressure measuring sensor and the pressure in the device by the atmospheric pressure measuring sensor. A positioner is obtained.

According to claim 4 of the present invention, there are the following effects.
Since alarm means for issuing an alarm based on a signal from the detection means is provided, an electropneumatic converter or a valve positioner can be obtained that can easily know the failure of the apparatus.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory view of the main part configuration of an embodiment of the present invention.
The differential pressure measuring means 31 includes a first pressure sensor 311 that measures the output pressure based on the air pressure in the main body box 13 and a second pressure sensor that measures the atmospheric pressure based on the air pressure in the main body box 13. 312 and calculation means 313 for calculating a difference between measurement signals of the first pressure sensor 311 and the second pressure sensor 312.

The detection means 32 is substantially connected to the second pressure sensor 312 and detects air leakage of components in the main body box 13.
The alarm means 33 issues an alarm based on the signal from the detection means 32.

  In addition, the 2nd detection means (not shown) which is substantially connected to the 2nd pressure sensor 312 and detects the air leak of the components in a storage box with reference to the output signal of the 1st pressure sensor 311 May be provided.

  In the above configuration, the measured pressures of the sensors 311 and 312 are input to the calculation means 313, and by calculating the pressure difference between the two, an accurate difference between the output pressure and the atmospheric pressure (gauge pressure) can be measured. .

As a result,
Since general general-purpose pressure sensors 311 and 312 can be used, a low-cost electropneumatic converter or valve positioner can be obtained.
Even if the pressure sensors 311 and 312 need to be changed, general general-purpose pressure sensors 311 and 312 can be used. Therefore, an electropneumatic converter or a valve positioner that can be easily changed to an alternative sensor and is easy to maintain. can get.

  Since the detecting means 32 connected to the second pressure sensor 312 and detecting the air leakage of the components in the main body box 13 is provided, air leakage of components, damage / abnormality of the I / P module 132, and other equipment A diagnostic function that can easily detect damage and abnormalities can be added, and a highly reliable electropneumatic converter or valve positioner can be obtained.

Since the pressure in the main body box 13 changes depending on the output of the device, it is not possible to correctly determine the abnormality of the device only by grasping the pressure in the main body box 13.
Therefore, if the measured output pressure by the output pressure measuring sensor 311 and the pressure in the device by the atmospheric pressure measuring sensor 312 are referred to, an abnormal state in the device can be detected more accurately. An empty converter or valve positioner is obtained.

  Since the alarm means 33 for issuing an alarm based on the signal from the detection means 32 is provided, an electropneumatic converter or a valve positioner that can easily know the failure of the apparatus is obtained.

FIG. 2 is an explanatory view showing the construction of the main part of another embodiment of the present invention.
In this embodiment, the present invention is applied to a valve positioner.
Reference numeral 41 denotes a displacement sensor attached to the valve A. The displacement of the valve A is fed back to the electric circuit 131 by the displacement sensor 41.
In the case of a valve positioner, the pressure sensors 311 and 312 are mostly not used for direct valve position control, but are used for diagnosis to measure the output pressure.
By using the present invention, a more accurate gauge pressure can be measured at a low cost.

The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention.
Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.

  In the above-described embodiment, the signals of the two pressure sensors 311 and 312 are respectively input to the calculation unit. However, the difference is obtained in advance by an analog circuit using an OP amplifier or the like and then input to the calculation unit. You may do it.

  In the above embodiment, a digital pressure control circuit using a microprocessor is assumed. However, the input signal may be an analog 4-20 mA signal or a digital signal such as a foundation field bus. Of course, the circuit 131 can also be realized by a digital pressure control circuit or an analog control circuit using an OP amplifier.

It is principal part structure explanatory drawing of one Example of this invention. It is principal part structure explanatory drawing of the other Example of this invention. It is structure explanatory drawing of the prior art example generally used conventionally. It is principal part structure explanatory drawing of the specific example of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current input signal 2 Torque motor 3 Nozzle flapper mechanism 4 Control relay 5 Output air pressure 6 Pressure sensor 11 Storage box 12 Terminal box 13 Main body box 131 Electric circuit 132 I / P electropneumatic converter 31 Differential pressure measuring means 311 1st pressure sensor 312 Second pressure sensor 313 Calculation unit 32 Detection means 33 Alarm means 41 Displacement sensor

Claims (4)

Comprises a differential pressure measuring means for measuring the difference between the output pressure of the apparatus and the atmospheric pressure,
In the electropneumatic converter or valve positioner where the air pressure of the containment box containing the pressure sensor is different from the atmospheric pressure,
A first pressure sensor for measuring an output pressure based on an air pressure of the storage box;
A second pressure sensor for measuring atmospheric pressure with reference to the air pressure of the containment box;
An electropneumatic converter or a valve positioner, comprising: a differential pressure measuring means comprising: a calculating means for calculating a difference between measurement signals of the first pressure sensor and the second pressure sensor. 2. The electropneumatic converter or valve positioner according to claim 1, further comprising: a first detection unit that is substantially connected to the second pressure sensor and detects an air leak of components in the storage box. And a second detection means which is substantially connected to the second pressure sensor and detects an air leak of a component in the storage box with reference to an output signal of the first pressure sensor. The electropneumatic converter or valve positioner according to claim 1. The electropneumatic converter or valve positioner according to claim 2 or 3, further comprising alarm means for issuing a warning based on a signal from the detection means.

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