JPH0454406Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention is an explosion-proof electromagnetic flowmeter that can be installed in hazardous locations where explosive gas or vapor exists, which is particularly easy to install, has little measurement error, and This article relates to a structure that can ensure explosion-proof properties.

[Prior art and its problems]

When electrical equipment is installed in a hazardous location such as the one described above, it is necessary to form and install the electrical equipment in accordance with explosion-proof guidelines established by the Ministry of Labor's Safety Research Institute. Figure 3 is a configuration diagram of a conventional explosion-proof electromagnetic flowmeter installed based on these guidelines. An excitation winding that generates a magnetic flux passing through the once-through tube 1 in a direction perpendicular to the tube axis of the tube;
These two electrodes 4, 4 are opposite electrodes provided on the tube wall.
can be in contact with the measuring fluid 2 and the through-flow tube 1
It is electrically isolated from the The inner surface of the flow-through tube 1 is coated with an electrical insulator. Reference numeral 5 denotes an outer sheath provided to surround the flow tube 1, and 6 represents a detection container which is hermetically constructed of the outer sheath 5 and the flow tube 1. The excitation winding 3 is housed in a detection container 6. Reference numeral 7 denotes a measuring tube consisting of the above-mentioned parts, and this measuring tube 7 is installed in a dangerous place 23 where explosive gas 22 is present. Since the measurement tube 7 is configured in this way, when an excitation current is passed through the excitation winding 3, a magnetic flux is generated that crosses the once-through tube 1.If the measuring fluid 2 is made to flow through the once-through tube 1 in this state, Faraday's law is satisfied. Therefore, a voltage corresponding to the flow rate of the fluid 2 is generated between the electrodes 4, 4. 8a and 8b are the counter electrodes 4,
A terminal that leads the voltage generated between 4 to the outside of the measuring tube 7.
Both terminals 8a and 8b are installed in a terminal box 8 provided in the detection unit container 6. The through-flow tube 1 and the jacket 5 are electrically connected by a connecting member 9, and the measuring fluid 2 inside the through-flow tube 1 is also electrically connected to the jacket 5 by means not shown. , 8c are terminals provided in the terminal box 8 in order to guide the potential of the detection unit container 6, which is made up of the through-flow tube 1 and the jacket 5 connected by the connection member 9, to the outside of the measurement tube 7. The detection unit container 6 is grounded via a ground terminal 6a provided on the container. 8d and 8e are terminals provided in the terminal box 8 for supplying exciting current to the exciting winding 3.

Reference numeral 10 indicates an excitation current supply unit which is supplied with power by a power source 11 and sends an excitation current to the terminals 8d and 8e via an excitation cable 12, and 13 indicates a flow of the measuring fluid 2 output from the electrodes 4 and 4. A signal processing section that processes a voltage signal as a detection signal corresponding to the flux and outputs a flow rate signal 14 corresponding to the flow rate of the measurement fluid 2 flowing through the once-through tube 1; A conversion unit container 16 that houses the processing unit 13 is a conversion unit that includes the container 15, the supply unit 10, and the processing unit 13. 17 is flow rate signal 1
This is a receiver that receives 4 and performs operations such as display and recording. Reference numeral 18 denotes a signal cable that guides a voltage signal as a flow velocity detection signal outputted from terminals 8a and 8b to the signal processing unit 13. The potential of terminal 8c is also controlled via this cable 18 in order to perform stable flow rate measurement. It is configured to be guided to the signal processing section 13. Reference numeral 19 denotes a safety retainer interposed in the middle of the signal cable 18 that constitutes the electric path for guiding the flow velocity detection signal to the signal processing section 13 as described above.
a, 19b, 19c are terminals 8a, 8 of the measuring tube 7
b, 8c, respectively.
Signal input terminals provided at 9, 19e, 19f, 19
g is a signal output terminal provided on the holder 19 corresponding to the terminals 19a, 19b, and 19c, respectively, and 19d is a ground terminal of the holder 19. The safety holder 19 is grounded via a terminal 19d. 20 is a wall forming the control room 21, the cable 18 is laid so as to pass through the wall 20 in an airtight manner, and the safety retainer 19 is installed.
, the converter 16 , the receiver 17 , and the power source 11 are installed in the control room 21 . Reference numeral 24 denotes a conduit into which the cable 12 is inserted, and this conduit is constructed so as to satisfy the pressure-resistant and explosion-proof regulations of the above-mentioned explosion-proof guideline, and is attached to the measuring tube 7. A conduit 24 is also laid through the wall 20, and this penetration also carries the gas 22.
It is configured to be airtight so that it does not enter into the control room 21. Reference numeral 25 denotes the above-mentioned electromagnetic flowmeter consisting of various parts except for the instrument chamber 21. Therefore, in this flowmeter 25, the flow rate of the measurement fluid 2 can be measured by the receiver 17.

In FIG. 3, the safety keeper 19 is constructed as shown in FIG.
9 in the middle of the signal cable 18, the flow rate measurement system of the electromagnetic flowmeter 25, which is related to the signals output from the terminals 8a, 8b, and 8c of the measuring tube 7, can meet the intrinsic safety requirements of the above-mentioned explosion-proof guidelines. Constructed to meet explosion-proof regulations. That is, in FIG. 4, 26 is a current limiting element such as a fuse inserted in series in the electrical path 27 connecting the terminals 19a and 19e, and 28 is a current limiting element such as a fuse inserted in series in the electrical path 29 connecting the terminals 19b and 19f. In the element, an electric path 30 connecting terminals 19c and 19g is connected to a ground terminal 19d. Current limiting element 2
6 and 28 may be composed of resistors. 32
is a voltage limiting element in which two Zener diodes 31 are connected in series with opposite directions,
Two elements 32 are each connected between the terminal 19a side of the electric line 27 and the electric line 30 and between the terminal 19b side of the electric line 29 and the electric line 30. The safety keeper 19 is constructed as described above, and the electrical characteristics of each part are set in accordance with the above-mentioned intrinsically safe explosion-proof regulations. Therefore, in the electromagnetic flowmeter 25 shown in FIG. 3 that uses such a safety barrier 19, even if an excessive current attempts to flow for some reason in each electric circuit connected to the electrodes 4, 4, this current is limited. is limited to a predetermined value or less by elements 26 and 28,
Furthermore, even if an excessive voltage is generated for some reason between each electrical circuit that leads the voltage signal generated in the electrodes 4, 4 to the signal processing section 13 and the ground, this voltage is controlled to a predetermined value by the voltage limiting element 32. As a result of the following limitations, the above-described flow rate measurement system involving the signal cable 18 is ensured to be inherently safe and explosion-proof.
In other words, in this case, there is no risk of an explosion occurring, for example, even if the electrodes 4, 4 exposed within the flow-through tube 1 are in an atmosphere of explosive gas. In addition, in the electromagnetic flowmeter 25, the excitation winding 3 and the electric circuit for supplying excitation current to it are installed in a series of voids consisting of the detection part case 6 and the conduit 24, and are made to be flameproof and explosion-proof in accordance with the above-mentioned explosion-proof guidelines. Therefore, there is no possibility that an explosion will occur in the hazardous area 23 due to the electric circuit connected to the excitation winding 3.

[Purpose of invention]

An object of the present invention is to provide an explosion-proof electromagnetic flowmeter that is explosion-proof even against ground fault current that may flow through the container of the electromagnetic flowmeter due to an accident.

[Key points of the idea]

In order to achieve the above-mentioned object, the present invention constructs a pressure-resistant explosion-proof structure casing from a detection part container, a conversion part container, and a cylindrical combination body that communicates these two containers, and further includes a cylindrical combination body. An insulator is provided to cut off electrical conductivity between the detection part container and the conversion part container. According to the present invention, even if a ground fault current attempts to flow through the flameproof explosion-proof structure casing due to an electrical circuit accident, the ground fault current is easily cut off by the insulator. Explosion-proof properties are ensured.

[Example of idea]

FIG. 1 is a longitudinal side view of a major part of an embodiment 34 of the present invention, and this figure shows the through-flow tube 1 and excitation winding of the measuring tube 7 shown in FIG. 3 with the terminal box 8 removed. 3, an electrode 4, a detection unit container 6, and a ground ring 62, which will be described later, are shown attached to a circular pipe path 33 through which the measurement fluid 2 flows. However, here, the detection container 6 includes the through-flow tube 1 and the ring-shaped side plates 3 attached to each of its both ends.
5 and the cylindrical jacket 5 form a ring-shaped space 36, and the excitation winding 3 is inserted into this space 36.
It is stored in Each part constituting the detection unit container 6 is made of metal.

FIG. 2 is a partially vertical front view of the electromagnetic flowmeter 34 shown in FIG. 1. Next, the configuration of the flowmeter 34 will be explained using FIG. 1 and FIG. 2. 37 is an iron core around which the excitation winding 3 is wound; 38 is an insulating coating provided from the inner surface of the once-through tube 1 to the outer surface of the side plate 35; and a metal earth ring 62 formed in the shape of an annular plate;
It is electrically conductively fixed to the metal side plate 35 by a fastening means (not shown) so that one surface thereof comes into contact with an insulating coating 38 provided on the outer surface of the side plate 35. Reference numeral 100 denotes a resin filled in a space 36 that accommodates the excitation winding 3 and the iron core 37. 39,39
is a flange cut in the middle of the circular pipe 33 and provided at each opening end of the pipe, and the measuring pipe 61 is flanged with a fastening member 40 consisting of a bolt and a nut so that the measuring fluid 2 flows through the through-flow pipe 1. The gaskets 63, 63 are sandwiched and fixed between the gaskets 39, 39. A grounding terminal 6a of the detection container 6 is provided on the outer surface of the jacket 5 in this case, and the container 6 is grounded via this terminal 6a. Since the container 6 and the ground ring 62 are electrically connected as described above, the measured fluid 2 is grounded via the terminal 6a. Reference numeral 41 denotes a circular tubular connector whose one end is welded to the jacket 5 so as to protrude laterally from the measurement tube 61. The connector 41 includes a metal base 41a welded to the jacket 5 and a metal base 41a that forms the protruding end. an engaging part 41c made of ceramic; an insulator 41b made of ceramic to which the base 41a and the engaging part 41c are brazed at both ends;
The engaging portion 41c is provided with a flange-shaped portion 42 projecting outward in the middle thereof. Connector 41
Inside, there is an electric wire 43 that connects to the excitation winding 3 from inside the detection unit container 6 through a through hole provided in the outer sheath 5, and corresponds to the excitation cable 12 shown in FIG. An electric wire 44 corresponding to the signal cable 18 is pulled out, and a safety holder 19 is connected to the end of the pulled out electric wire 44, and this safety holder 19 is installed in the engaging part 41c. . Although not shown, the electric wire corresponding to the electric wire in the signal cable 18 connected to the connection member 9 shown in FIG. 6 into the connecting body 41, and its other end is connected to the safety holder 19 as in the case of FIG.

In FIGS. 1 and 2, the converter container 1
5 is a cylindrical main body part 45 provided with a flange-like part 46 projecting inward in a ring shape near the right end in FIG. 1, and the right and left open ends of the main body part 45 in FIG. The main body 45 is further provided with a cylindrical body 49 that protrudes downward, and a cylindrical body 49 that protrudes laterally. Two cylindrical cable entry ports 50 and 51 are provided in the cylindrical cable inlet. Flange-shaped portion 46
A terminal block 52 is attached to the terminal block 52 via an O-ring 53 so as to airtightly close the opening from the cover 47 side.
The power supply 11 shown in FIG.
A terminal 54 to which a cable corresponding to the electric wire connecting the converter 16 and the converter 16 is connected, and a cable inlet 51
The receiver 17 shown in FIG.
Terminals 55 to which cables corresponding to the electric wires connecting the converting section 16 and the converting section 16 are connected are hermetically installed. Each of the cable entry ports 50, 5 is arranged so that the aforementioned cables drawn into the cable entry ports 50, 51 are drawn through the conduit conduits connected to each cable entry port.
1 is constructed, and in this case, each cable entry port 50, 51 is constructed so that the conduit connection satisfies the pressure-proof and explosion-proof performance in the above-mentioned explosion-proof regulations. Both the excitation current supply section 10 and the signal processing section 13 are connected to the main body section 45 between the collar section 46 and the cover 48.
It is stored inside.

The main body part 45 of the converter container 15 is assembled by inserting the engaging part 41c of the connecting body 41 into the cylindrical body 49 until the inner surface level difference part of the cylindrical body 49 comes into contact with the collar part 42, and then tightening the cylindrical body with the screw 56. 49 and the engaging portion 41c are fixedly connected to the measuring tube 61. Reference numeral 57 denotes an O-ring designed to ensure airtightness between the cylindrical inner surface of the cylindrical body 49 and the cylindrical outer surface of the engaging portion 41c in contact therewith. The main body part 45 is provided with a through hole 58 that communicates the inside thereof with the inside of the cylindrical body 49, and the electric wire 43 connected to the excitation winding 3 disposed in the connecting body 41 passes through the side of the safety retainer 19. The electric wire 44 is connected to the excitation current supply unit 10 through the through hole 58 after passing through the safety holder 1
9 into the through hole 58.
It is connected to the signal processing section 13 through. 64
Reference numeral 59 denotes a combined body made up of the above-mentioned connecting body 41, cylindrical body 49, screw 56, and O-ring 57, and 59 is a housing made of this combined body 64, the detection part container 6, and the conversion part container 15. Covers 47, 48 and screws 5
Each of the portions 6 is provided with a locking structure, and the casing 59 as a whole is constructed to satisfy the above-described pressure-resistant explosion-proof structure according to the explosion-proof regulations.

Electromagnetic flowmeter 34 illustrated in FIGS. 1 and 2
Since the electromagnetic flowmeter 3 is configured as described above, it can be installed in a hazardous location where explosive gas or steam exists to measure the flow rate.
4 does not require the signal cable 18 or excitation cable 12 shown in FIG. Measurement errors are less likely to occur because there is less attenuation or disturbance due to intrusion of noise from the outside before reaching the signal processing section 13. Further, such a flowmeter 34 includes a converter container 15, an excitation current supply section 10, and a signal processing section 1.
3 and the terminal block 52, and the measuring tube 61 are integrated via the connecting body 41, and the safety retainer 19 is placed inside the casing 59 of the electromagnetic flowmeter 34 integrated in this way. Since the converter and the safety retainer do not need to be installed in the control room as shown in FIG. 3, there is an advantage that the control room can be used widely. Furthermore, operating energy is supplied to the electromagnetic flowmeter 34 from the AC power supply 11 shown in FIG.
Even if a ground fault current attempts to flow sequentially through the detection unit container 6 and the ground terminal 6a, this ground fault current will flow through the insulator 41.
It is cut off by b. If the insulator 41b is not provided, the above-mentioned ground fault current flows due to the grounding resistance of the grounding point connected to the grounding terminal 6a, and the potential of the terminal 6a rises. The electromagnetic flow rate propagates from the flow through the flow pipe 1, the electric line 30 shown in FIG. Since the insulator 41b is provided in the total 34, such a situation does not occur. That is, such a flowmeter 34 is an explosion-proof electromagnetic flowmeter that is explosion-proof even against ground fault current as described above.

In the above embodiment, the insulator 41b is provided on the connecting body 41, but the present invention is not limited to such arrangement of the insulator 41b, and the insulator is provided on the cylindrical body 49, or The insulator is provided between the connecting body 41 and the cylindrical body 49, or the insulator is provided at the base of the connecting body 41 or the cylindrical body 49 to prevent ground fault current that may flow through the housing 59. It is also possible to cut it off.

[Effect of idea]

As described above, in the present invention, a pressure-resistant and explosion-proof structure is constructed of a detection part container, a conversion part container, and a cylindrical assembly that communicates these two containers, and the cylindrical combination further includes a detection part container and a cylindrical combination body. Since an insulator is provided to break the electrical conductivity between the converter and the converter container, this configuration prevents ground fault current from flowing into the flameproof explosion-proof structure case due to an accident in the electrical circuit. Even if an attempt is made to do so, the ground fault current is cut off by the insulator, thereby providing an explosion-proof structure electromagnetic flowmeter in which explosion-proof properties are ensured.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional side view of the main part of an embodiment of the present invention.
Figure 2 is a partially longitudinal front view of the electromagnetic flowmeter shown in Figure 1.
FIG. 3 is a block diagram of a conventional explosion-proof electromagnetic flowmeter, and FIG. 4 is a block diagram of a safety barrier in FIGS. 1 to 3. 1... Through-flow tube, 2... Measuring fluid, 3... Excitation winding, 4... Counter electrode, 6... Detection unit container, 7, 6
1...Measuring tube, 10...Exciting current supply section, 13...
... Signal processing section, 14 ... Flow rate signal, 15 ... Conversion section container, 16, 60 ... Conversion section, 19 ... Safety holder, 23 ... Hazardous area, 25, 34 ... Electromagnetic flow meter, 27, 29, 30... Electric circuit, 41b... Insulator, 59... Housing, 64... Combined body.

Claims (1)

[Scope of utility model registration request] a detection unit housing a through-flow tube through which the measurement fluid flows; a detection unit container housing an excitation winding that generates a magnetic flux that crosses the measurement fluid flowing through the through-flow tube; A converter container that houses a signal processing section that outputs a flow rate signal corresponding to the flow rate, and a cylindrical combination that communicates the detection section container and the converter container, and the cylindrical combination includes the detection section. 1. An explosion-proof electromagnetic flowmeter characterized in that an insulator is provided to cut off conductivity between the converter container and the converter container.