JPS6120722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an actuator having an electropneumatic positioner for operating a diaphragm valve, and particularly to an actuator that is explosion-proof and safe.

[Conventional technology]

In the past, most of the mainstream actuators were those operated by pneumatic signals, that is, air signals. However, this type of actuator has drawbacks such as a delay in the transmission time of control signals, so it is hardly used at present.

As an alternative to this actuator, actuators currently used in general industrial plants are mainly operated by electrical signals. Power methods include pneumatic, hydraulic, and electric motors. Among these, in chemical plants where explosion-proof safety measures are most required, 90%
More than % are pneumatic types operated by electrical signals.

Here, a general example of a pneumatic actuator operated by an electric signal is shown in FIG. 1st
In the figure, the excitation coil 2 of the force motor 1 is supplied with an electric signal as an operation signal (for example, DC 4 to 20
[mA] A is given. The lever 3 moves in response to this electric signal A, and the amount of air discharged from the nozzle 5 is adjusted by a flapper 4 attached to the lever 3.

On the other hand, the pilot valve 6 is supplied with compressed air (for example,
A pressure of 1.4 [Kg/cm ² ]) B is supplied. This supplied compressed air B is adjusted by the flapper 4 and the nozzle 5 to the operating pressure corresponding to the electrical signal A (for example, 0.2~
1 [Kg/cm ² ]) of compressed air C is added to the diaphragm 8 of the diaphragm valve 7. This operating pressure opens and closes the valve 10 via the main shaft 9. A feedback link mechanism 11 for adjusting the stroke of the valve 10 is connected to the main shaft 9, and includes a stroke adjustment pin 12, a restoring lever 13,
Feedback is provided via the restoring spring 14. The valve opening degree is determined by the balance between the stroke amount and the command amount from the force motor 1.

For the above actuators, force motor 1
The plant contains electrical systems such as the electrical system, and exposing this to the plant atmosphere must be avoided for explosion-proof measures. For this reason, conventional measures have been taken to ensure safety, such as housing the entire diaphragm valve and actuator shown in Figure 1 inside a casing and purifying it with clean air, or burying it underground with only the exhaust pipe exposed to the surface. retained their sexuality.

[Problem that the invention seeks to solve]

However, such actuators and valves are used at many locations in a plant, and are usually attached to high-output electrical equipment. In other words, the actuator is placed in an environment where electromagnetic noise is likely to occur, and there is a risk of malfunction due to electromagnetic noise. In order to eliminate the influence of such disturbances, the above-mentioned pneumatic signal system may be used, but as mentioned above, there are problems with controllability such as delays in signal transmission time.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an actuator that is essentially safe from an explosion-proof perspective and is less susceptible to external disturbances.

[Means for solving problems]

The present invention provides an actuator that includes a pilot valve that controls the pressure of compressed air and a force motor that drives the pilot valve. It is characterized in that it includes an electric power system that supplies electric power, and the drive circuit and the electric power system are housed in a storage container and isolated from the outside atmosphere.

[Effect]

The present invention ensures fire prevention safety by enclosing the electrical system in compressed air.

〔Example〕

The present invention will be described in detail below based on illustrated embodiments. In addition, in the figures shown in each example below, the first
The same reference numerals are given to parts that overlap with those in the figures, and explanations thereof will be omitted.

First Embodiment In FIG. 2, the actuator uses the optical signal D as a control signal, uses electric power as an auxiliary power, and uses air pressure as the operating power source for the diaphragm valve 7.

The coil 2 of the force motor 1 is driven by power supplied through a power line 15, a drive circuit 16, and a power line 17. Power line 15 connects to pilot valve 6
The drive circuit 16 is housed in a pressure vessel 19 that communicates with the supply piping 18, and the power line 17 is similarly connected to the piping 2.
0, and the coil 2 is similarly placed in the pressure vessel 2.
It is contained within 1. In other words, all electrical systems are housed in piping that communicates with the supply piping 18 or in a pressure vessel, and are isolated from the outside air.

The drive circuit 16 controls the movement of the lever 3 by applying power supplied from the power line 15 to the coil 2 in response to the light control signal D. The optical control signal D is transmitted through the optical fiber 22 from the outside.

The pressure vessel 21 is constructed using a non-magnetic material (for example, austenitic stainless steel, titanium, etc.). Alternatively, the entire coil 2 may be integrally molded with epoxy resin to isolate it from the outside air.

As described above, by enclosing the entire power system within the pipe or pressure vessel that communicates with the supply pipe 10, the electrical system is not exposed and safety is ensured. Further, the energy of the optical control signal transmitted by the optical fiber 22 is extremely small, so even if the optical fiber 22 is damaged, no explosion-proof problem will occur. Furthermore, since control is performed using optical signals, there is no influence from external magnetism, so malfunctions due to electromagnetic noise can be prevented.

The other configurations and operations are the same as those in FIG. 2, so their explanations will be omitted.

Second Embodiment See Figure 3. This embodiment does not use electric power supplied from outside as a drive source for the force motor 1,
A feature is that a generator 24 housed in a pressure vessel 23 communicating with the supply pipe 18 is used. That is, the pressure vessel 23 is provided in an air flow path branched from the supply pipe 18, and the air flow rate is controlled by the valve 2.
5, it can be adjusted. As the generator 24, for example, a turbine type generator or a spring winding type generator using an air cylinder is used. The amount of power generation can be adjusted by adjusting the opening degree of the valve 25.

By doing so, there is no need to draw the power line 15 through the supply pipe 18. Also,
The point that the power system is cut off from the outside air is similar to the above.

Other Embodiments In the actuator shown in FIG. 4, the force motor 1 is replaced with an electric piston 26 in the actuator shown in FIG.
It is used to adjust and operate.

In the actuator shown in FIG. 5, the force motor 1 in the actuator shown in FIG. 3 is replaced with an electric piston 26, and the flapper 4 is adjusted by the movable shaft 26.

〔Effect of the invention〕

As described above, according to the present invention, in a pneumatic actuator operated by an electrical signal with excellent controllability, the entire power system is housed in the compressed air supply piping to the pilot valve or in the pressure vessel leading thereto, and is connected to the outside air. Since it is designed to be shut off, explosion-proof safety can be ensured. Furthermore, since control is performed using optical signals, it is possible to prevent disturbances caused by electromagnetic noise.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram showing an example of a conventional electro-pneumatic actuator, FIG. 2 is a cross-sectional explanatory diagram showing a first embodiment of the present invention, and FIG. 3 is a cross-sectional explanatory diagram showing a second embodiment. , FIG. 4, and FIG. 5 are explanatory diagrams showing other embodiments. 1...Force motor, 6...Pilot valve,
15... Power line, 16... Drive circuit, 18... Supply piping, 19... Pressure vessel, 20... Piping, 21
... Pressure vessel, 22 ... Optical fiber, 24 ... Generator, C ... Supply compressed air, D ... Light control signal.

Claims (1)

[Claims] 1. A pilot valve that controls the pressure of compressed air;
The actuator is equipped with a force motor that drives the pilot valve, and includes a drive circuit that is a drive circuit for the force motor and is controlled by an optical signal, and a power system that supplies power to the drive circuit. An actuator characterized in that it is housed in a storage container and is isolated from the external atmosphere. 2. The actuator according to claim 1, wherein the storage container is a supply path for supplying compressed air to the pilot valve or a pressure vessel communicating with the supply path. 3. The actuator according to claim 1 or 2, wherein the power system is a power line that transmits power from an external power source. 4. The actuator according to claim 1 or 2, wherein the electric power system is a generator powered by compressed air supplied to the pilot valve.