JPH056782B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field] The present invention is a nuclear power plant, a thermal power plant, and various other plants that issue an alarm or operate an emergency shutoff valve when the liquid level in a tank or the like exceeds a certain level. This is related to the level switch for.

Prior Art Since Japan is a country prone to earthquakes, if a major earthquake were to occur and a malfunction of this type of level switch occurred, there is a risk that plant operations would be seriously disrupted. For this reason, when installing equipment such as level switches in important facilities such as nuclear power plants, it is necessary to select an appropriate mounting position so as not to amplify the shaking during an earthquake, and to use complex earthquake-resistant designs to support and fix equipment. This required a great deal of design work and construction costs. Under these circumstances, there has been a strong desire to develop a level switch with high seismic performance that is unlikely to malfunction even in the event of an earthquake, but conventional level switches have not been able to satisfy this demand as described below.

FIG. 11 shows a vertical cross-section of a conventional level switch for high temperature and high pressure applications. Reference numeral 1 indicates a fluid connection port 1a at the bottom and side for connecting to a tank or the like (not shown) to detect the liquid level. A main body provided with 1b,
2 is a lid with heat dissipation fins, which is fixed to the main body 1 by bolts and nuts, and has a center hole 2a;
3 is an upper guide held between the main body 1 and the lid 2; 4 is a lower guide press-fitted into the main body 1; 5 is a lower guide that is press-fitted into the main body 1;
6 is a float located inside the main body 1 and fitted into the float rod 5 and fixed to the float rod 5 by a pin 7; 8 is a float A large diameter spring is interposed between the flange portion of 6 and the stepped portion of the main body 1 to support the weight of the float 6;
A plurality of seal rings are inserted into the inside of the tube and are used to prevent high-temperature fluid from penetrating between the float rod 5 and the upper guide 3 to keep the detection cylinder at a low temperature, which will be described later. Coil spring type spacer for holding at appropriate intervals, 11 is the lid 2
A detection tube 12 fitted to the upper end is a suction tube rod made of a non-magnetic material, which passes vertically slidably through the center hole of the seal ring 9, and whose lower end is connected to the upper end of the float rod 5 by a pin. 13 is a magnetic suction tube fixed to the upper end of the suction tube rod 12 in the detection tube 11 using a non-magnetic double nut, 14 is a micro switch fixed to the side wall of the detection tube 11, and 15 is a It is pivotally attached to the side wall of the detection tube 11, and magnets 15a and 15b are fixed to the upper and lower ends, respectively, and their sliding causes the microswitch 14 to be activated.
16 is a base fixed to the base of the detection tube 11, and 17 is a switch cover fixed to the base 16.

In this level switch, the main body 1
The position of liquid level 31 within (hereinafter also referred to as liquid level 31)
As the suction tube 13 rises and reaches a predetermined position as the buoyancy of the float 6 increases, the magnet 15a is attracted to the suction tube 13 and the magnet 15b
is separated and the actuating piece 15 rotates to the left, the contact point of the micro switch 14 is switched, and the liquid level 3
1 and the resulting decrease in the buoyancy of the float 6 causes the adsorption tube 13 to descend and reach a predetermined position.
The magnet 15b is attracted to the suction tube 13 and the magnet 15
When a is separated and the actuating piece 15 is rotated to the right, the contact point of the micro switch 14 is switched in the opposite direction from the previous direction. A structure including such a magnet and a microswitch has been commonly used in the past. With such a mechanism, when the liquid level (corresponding to the liquid level 31 in the main body 1) in a tank or the like reaches an upper limit position at which it is dangerous to rise any further, a micro switch is activated to issue an upper limit alarm. Furthermore, when the liquid level in the tank or the like falls and reaches a safe level, the microswitch can be reset to its original state to cancel the upper limit alarm. Regarding the lower limit alarm, the operation is simply reversed from the above case.

However, when a vibration test is performed on such a level switch assuming an earthquake, large springs with a large center diameter, such as spring 8, have a vibration acceleration of approximately
When a horizontal vibration of more than 1G is applied, the spring's own inertial force (=mass x acceleration) causes extreme deformation similar to a buckling phenomenon, causing the end of the spring to collapse into the flange of the float 6 or the steps of the main body 1. At the same time, the spring 8 begins to rotate in one direction due to the shape of the rolled-up portion of the spring end, and the float 6 also rotates and oscillates accordingly. The complex deformation and rotation of the spring 8 due to the fact that the characteristics of the spring 8 are not uniform depending on the orientation of the spring 8, and the moment of inertia of the float 6 itself [mass x (radius of rotation) ² ] interact in a complex manner to reduce the liquid level. The float 6 begins to move abnormally up and down, regardless of the increase or decrease in the buoyancy of the float 6 due to the rise or fall of the float 31. In addition, the liquid level 31 that violently shakes while raising droplets further promotes the unstable vibration of the spring 8, and the spring 8 that swings laterally rubs against the side of the float 6 and the inner surface of the main body 1, and these combined effects As a result, the level switch began to malfunction at a liquid level 31 that was significantly deviated from the predetermined operating point, and this level switch had significantly poor earthquake resistance.

Purpose In view of the above-mentioned problems, the present invention aims to provide a level switch with excellent seismic performance that maintains operational stability even in the event of an earthquake.

Overview The level switch according to the present invention uses a small diameter spring that supports the weight of the float between an upper spring receiving part provided on a tubular float rod below the float and a lower spring part provided on the main body side below that. At the same time, the upper and lower ends of the spring are fitted into the upper and lower spring receivers, and the protruding ends of the upper and lower ends are respectively locked to the upper and lower spring receivers, and a spring retainer, etc. By holding and fixing the upper end of the spring, it is possible to prevent the spring from shifting laterally, rotating, and deforming, and in a balanced state where the liquid level is on the float, the spring is completely immersed in the liquid to lower the liquid level. This prevents wave motion from acting on the spring.
In addition to the above effects, the level switch according to the present invention has a structure in which the lever fixed to the float rod is guided by a vertical lever guide provided on the main body, so that a spring supporting the weight of the float can be used. It is also designed to prevent torsional vibrations. Furthermore, in addition to the above-mentioned effects, the level switch according to the present invention has a wave-preventing cylinder having a wave-stop plate inserted between the float and the main body, thereby minimizing the wave motion of the liquid surface caused by vibration and the inertial force of the fluid. It was designed to be smaller.

Embodiment Hereinafter, the present invention will be described in detail based on the first embodiment shown in FIGS. The fixed float rod 5 is constructed from a hollow, thick tube, thereby reducing the weight, reducing the moment of inertia, and increasing the rigidity, thereby preventing bending due to rolling as much as possible. Further, as shown in FIG. 2, a lower stopper 18 is provided below the float 6.
is firmly fixed to the float rod 5 by a pin 19. In addition, the lower stopper 18 has an upper spring receiver 2.
0 is screwed onto the lower guide 4, and a lower spring receiver 4a is formed in the lower guide 4, and a small diameter spring 8 ( 3) are elastically loaded, and by fitting the upper and lower ends of the spring 8 into the upper spring receiver 20 and the lower spring receiver 4a, respectively, a buckling phenomenon of the spring 8 can be achieved. This prevents extreme deformation and lateral displacement. In addition, 32 is a lock nut. The upper protruding end 8a of the upper end of the spring 8 and the lower protruding end 8b of the lower end of the spring 8 are connected to the groove 20a of the upper spring receiving part 20 and the through hole 4b of the lower guide 4 (about 4 to 6 locations are provided). By engaging them together (see FIG. 5), rotation of the spring 8 in one direction is completely prevented, although some torsional vibration remains. Further, a spring presser 21 is attached to the upper surface of the upper spring receiver 20, and the spring presser 21
The upper end of the spring 8 is held by three to six claws 21a provided in the spring 8. (See Figure 4) Therefore,
Deformation due to lateral displacement of the spring 8 is more reliably prevented. Incidentally, instead of the spring retainer 21, the upper spring receiving part 20 and the spring 8 may be fixed to each other by welding or the like.

FIGS. 6 to 8 show a second embodiment, which includes the structure of the other essential requirements of the present invention in the first embodiment. 22 is an upper stopper which is firmly fixed to the float rod 5 by a pin 23 above the float 6; 24 is a horizontal direction screwed to the float rod 5 through the upper stopper 22 and fastened and fixed by a nut 25; The lever 26 is a lever guide that is fixed to the lower surface of the upper guide 3 with a screw 27 and has a vertical groove 26a that fits and guides the tip of the lever 24 as shown in FIG. , lever 24 and lever guide 26
Although the float 6 is allowed to move up and down due to changes in the liquid level, rotation of the float 6 is prevented and torsional vibration of the spring 8 can be prevented.

9 and 10 show a third embodiment, in which the second embodiment includes the structure of other essential requirements of the present invention. 28 has an inner diameter slightly larger than the outer diameter of the float 6, has an appropriate number of through holes 28a in the side wall, and has about three to four corrugated positioning fittings on the upper and lower parts of the outer circumference. Reference numeral 29 denotes a wave prevention cylinder fixed radially by welding or the like, and this wave movement prevention cylinder 28 is attached to the main body 1.
Since the outer end of the positioning metal fitting 29 comes into elastic contact with the inner surface of the main body 1 when pushed into the inside of the main body 1, the anti-wave motion cylinder 28 can be securely fixed at approximately the center of the main body 1. In addition, about two to four ring-shaped wave-stop plates 30 are fixed to approximately the center of the outer periphery of the wave prevention cylinder 28 by welding or the like, and the size of the wave-stop plates 30 is equal to that of the main body 1. The wave stop plate 30 is set to be slightly smaller than the inner circumference of the wave, and the action of the wave stop plate 30 minimizes the wave motion of the liquid surface due to wave motion, and the wave stop plate 30 acts as a resistance to the fluid, reducing the risk of fluid earthquakes. The force exerted on the float 6 by inertial force is reduced.

Effects of the Invention As mentioned above, the level switch according to the present invention has the following effects:
The structure prevents the spring that supports the weight of the float from rotating, shifting laterally, and separating from the spring holder at the top end.
Irregular deformation of the spring due to these does not occur, and the vertical movement of the float movable part is stable. Furthermore, since the spring is located below the float, the entire spring is below the liquid level, so it is not adversely affected by waves in the liquid level. Furthermore, since the spring does not come into contact with the float or the main body, there is no adverse effect due to friction. Furthermore, since the spring is smaller and lighter than conventional products, even if severe horizontal shaking occurs, the buckling-like deformation caused by the spring's own inertial force is extremely small, supporting the weight of the float movable part. It is possible to stably maintain the original function of Therefore, according to the present invention, the float movable part can smoothly move up and down even under severe rolling motion,
The deviation from the operating performance when no vibration is applied is very small, and the performance can be demonstrated without any practical problems.
Furthermore, since the springs are less likely to deform, earthquake resistance against vertical shaking can be improved.

Furthermore, even with the structure that prevents the spring from rotating as described above, it is not possible to prevent the spring from generating fine torsional vibrations due to horizontal vibrations, which are transmitted to the float. If torsional movement is forcibly prevented by guiding the lever fixed to the lever with a lever guide fixed to the main body side, the deviation from the operating point (liquid level) when no vibration is applied is further reduced, improving earthquake resistance. In addition, the wave motion of the liquid surface due to the horizontal shaking increases and collides with the float, and the inertia of the fluid exerts an abnormal force on the float, increasing the variation in the operating point. If the influence of waves applied to the float is prevented by inserting a wave prevention tube with a shaped wave stop plate into the main body, even better earthquake resistance can be obtained. In particular, the ring-shaped break plate prevents vertical fluctuations in the liquid level in the space between the wave prevention cylinder and the main body, so it prevents vertical fluctuations in the liquid level inside the wave prevention cylinder that communicates with the space. As a result, more stable operation of the level switch can be maintained not only in horizontal vibrations but also in vertical vibrations.

Therefore, the level switch according to the present invention has extremely high seismic performance compared to conventional products, and can improve the safety of important facilities such as nuclear power plants. Furthermore, by improving the seismic performance of the level switch itself, there is no need for the complicated seismic design and construction of supports around the level switch, which has been done in the past, which is of great practical value.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a level switch according to the present invention, FIG. 2 is an enlarged sectional view of the main part of FIG. 1,
FIG. 3 is a longitudinal sectional view of the spring 8 of the above embodiment, FIGS. 4 and 5 are sectional views taken along lines - and -, respectively, in FIG. 2, and FIG. 6 is a longitudinal sectional view of the second embodiment. ,
Figure 7 is an enlarged sectional view of the main part of Figure 6, and Figure 8 is an enlarged sectional view of the main part of Figure 7.
9 is a longitudinal sectional view of the third embodiment, FIG. 10 is a perspective view of the wave prevention cylinder of the third embodiment, and FIG. 11 is a longitudinal sectional view of the conventional example. It is. 1...Body, 2...Lid, 3...Top guide, 4
...Lower guide, 4a...Lower spring receiver, 4b...
...Through hole, 5...Float rod, 6...Float, 7
...Pin, 8...Spring, 9...Seal ring, 1
0... Spacer, 11... Detection tube, 12... Adsorption tube rod, 13... Adsorption tube, 14... Micro switch, 15... Actuation piece, 16... Base, 17...
Switch cover, 18...Lower stopper, 19...
... Pin, 20 ... Upper spring receiver, 21 ... Spring holder, 22 ... Upper stopper, 23 ... Pin, 24
... Lever, 25 ... Nut, 26 ... Lever guide, 27 ... Screw, 28 ... Wave prevention tube, 29
...Positioning metal fitting, 30...Wave stop plate, 31...
Liquid level, 32... Locknut.

Claims (1)

[Claims] 1. In a level switch in which the weight of a float for detecting changes in liquid level is supported by a spring, an upper spring receiver fixed to the float rod below the float and a main body below the upper spring receiver. The spring is resiliently loaded between a lower spring receiver provided on the side, and both upper and lower ends of the spring are respectively locked to the upper spring receiver and the lower spring receiver, and the spring is protruded from the float rod. The level switch is characterized in that the lever is guided by a lever guide vertically installed on the main body side, and a wave prevention cylinder surrounded by a wave stop plate is inserted and arranged between the float and the main body.