FI116421B - Level switch - Google Patents

Description

116; /: i

Level switch

The invention relates to a level switch according to the preamble of claim 1.

In order to measure the level of the liquid surface of tanks containing explosive liquids, the sensors used for measuring must be so constructed that they do not present an explosion hazard. In the past, the level of such explosive liquids has been measured using either mechanical or electrical devices.

When using mechanical devices, it is difficult for the user to transmit the height information and alarm information to the user, and often the user has to visit the tank 10 to check the level. In addition, in mechanical level sensors, moving parts come into contact with the liquid and tend to malfunction due to contamination. Such a mechanical level sensor may be, for example, a float attached to a wire, whereby information about the movement of the float with the surface of the liquid and at the same time information about the level of the fluid is transmitted via the wire 15 to the outside of the container.

The level may also be measured by supplying compressed air to a tube in the tank, the end of which is below the surface of the liquid. When the liquid level in the tube falls: I: I. the pressure is reduced and a warning of lowering the level can be given. Such-!;:; ' however, implementing a system like this is expensive.

* · · /·.*. 20 Electrical level sensors include, for example, reed-relay sensors and surface-mounted switches. The reed relay sensor around the shaft has: a fixed float that floats on the surface of the liquid. As the fluid level rises or falls! ···, the shaft transmits the movement of the float to the pivot point of the shaft where the switch closes and transmits the electrical signal forward. In another type of reed relay type, 25, the shaft remains stationary and the float around the shaft moves with the surface of the fluid; As the surface of the liquid rises, the magnet on the float closes the reed relay inside the accumulator. The level switch hangs on its cord; i; · Within the float at the end of the float is a switch which, when the float position changes, as the surface of the liquid rises or lowers, closes and transmits an electrical signal.

However, when using electronic liquid level sensors, they must be ·· 'manufactured to Exi protection requirements to avoid the risk of explosion. This is not always possible, requiring the use of a separate Exi- 2 1 1 6 4 / i relay, through which a non-hazardous circuit is connected to the measuring system. This increases the cost of the sensor and makes the connections required to connect the sensor more complicated. Electronic sensors also generally do not have self-diagnostics. No damage to the sensor or its cable is known until the potential damage occurs.

Additionally, sensors using a fiber optic cable for transmitting height information are known. However, these known fiber level sensors using fiber optic cables are sensitive to soiling. In addition, they are structured so that they either do not provide information on cable breakage or require continuous monitoring to maintain a constant level of 10.

In addition, conventional liquid level sensors are large in size. Generally, the sensors can only be installed in the tank from a small hole that does not accommodate conventional level sensors. Sensors mounted through the tank wall, on the other hand, should provide sufficient sealing and pressure resistance between the sensor and the tank wall, which makes installation difficult.

In addition, it is often necessary to continuously monitor the level of the liquid in the tank. Conventional electrical level sensors generally do not provide continuous monitoring. They only report exceeding certain thresholds, such as tank emptying or overfilling.

It is an object of the present invention to provide a new level switch which does not have the disadvantages mentioned above.

To achieve this, the level switch according to the invention is characterized by 7 *; i is as set forth in claim 1.

'I I I «

Preferred embodiments of the invention are characterized in what is stated in the unclaimed claims.

* * * ·: 'The level switch according to the invention is smaller in size than the prior art level switches and can therefore be used in containers with smaller holes. Furthermore, the level switch according to the invention does not contain any electrical parts, so it can be safely used in potentially explosive atmospheres. It is also cheaper to manufacture 30 than an Exi-shielded conventional electrical switch.

Further, the level switch of the invention is not in contact with a liquid; '· 1 moving parts, so there will be no malfunctions due to contamination 1 1 6 4 Z i 3 nights. A malfunction of the switch or its cable can easily be detected.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which Figs. and Figure 3 illustrates the use of a level switch 10 for monitoring the level of a liquid in accordance with a preferred embodiment of the invention.

1a, Ib and le, the surface switch according to the preferred embodiment of the invention comprises a float 1, air space 2, plug 3, optical fiber 4, mounting bracket 5, glass ball 6, rest plane 7 and mirror 8.

The level switch 15 according to another preferred embodiment of the invention shown in Figures 2a and 2b comprises a float 1, air space 2, plug 3, optical fiber 4, mounting bracket 5, glass ball 6 and resting platform 7.

«

The use of a level switch 4 'according to a preferred embodiment of the invention for monitoring the level of the liquid shown in Figure 3 comprises a sensor 10, a fiber optic cable 11,' 'control unit 12, a transmitter 13, a receiver 14 and a container 15.

, * 6 * 7.7,: 20 When using the level switch of the invention to monitor the level of the liquid in the container 15 to be monitored, the light cable 11 of the level switch is inserted into the container 15; ”*) through a hole in the upper surface of the container. By adjusting the length of the optical cable 11, the sensor 10 hanging at the end of the optical cable 11 is set to the desired height. If desired: warning of overfilling of tank 15, sensor 10 is lowered to a height such that sensor. · · '25 turns upside down when the liquid level reaches the alarm level. If you want a warning | · F · ;. * from the emptying of the tank 15, the sensor 10 is lowered to float on the surface of the liquid at such a height that the sensor turns upright as the surface of the liquid drops to the alarm level.

The fiber optic cable 11 is inserted into the sensor 10 through the sealed plug 3 at the end of the sensor 10. The optical fiber 4 is attached to the mounting bracket 5 and the end of the optical fiber 4 is directed toward a reflective surface, such as a mirror 8, or at one end of the optical fiber. The fiber optic cable 11 is supplied with a beam of light from the transmitter 13 of the control unit 12, the return of which along the optical cable 11 is detected by the receiver 14 of the control unit 12.

The level switch according to the preferred embodiment of the invention shown in Fig. 1 provides information on the surface height of the container 15. The level switch is mounted on the hanging-ground level switch fiber optic cable 11 at the desired height at the top of the tank 15. In this case, the float 1 of the level switch is not in contact with the liquid and the sensor 10 is in an upright position as shown in Figure 1a. The glass ball 6 inside the float is then located in the middle of the rest plane 7. The glass ball 6 acts as a lens, and the light beam reflected from the mirror 8 to the optical fiber 4 is of medium intensity.

10 As the level of the liquid in the reservoir 15 increases and the level of the liquid reaches the level switch sensor 10, the level switch begins to float due to the buoyancy caused by the float 1 on the surface of the liquid. As the level of the liquid increases, the position of the level switch changes to that of Figure le, and the glass ball 6 changes its position between the mounting bracket 5 and the rest plane 7. In this case, the intensity of the light beam reflected from the mirror 8 becomes weak. When the level switch sensor 10 has completely turned upside down as shown in Figure Ib, the glass ball changes its position in the middle of the mounting bracket 5. Thus, when the glass ball 6 acts as a lens, the intensity of the light beam reflected from the mirror 8 is strong.

The control unit 12 deduces the intensity of the light beam returning along the fiber optic cable 10 from the current position of the sensor 10 and the level of the liquid in the container 10; Y; den. In the embodiment of Fig. 1, the strong intensity corresponds to the upper limit of the surface height, the moderate intensity to the lower limit of the surface height and the weak intensity,. : Intensity half-height of the alert thresholds.

By means of the level switch, '25 25 of another preferred embodiment of the invention shown in Fig. 2, a warning can be obtained to reach the upper or lower limit of the liquid level of the container 15. If information on reaching the upper limit is desired, the sensor 10 should be lowered in the i: tank 15 such that the sensor will rotate horizontally when the liquid level reaches the upper limit. Similarly, if desired, information about reaching the lower limit should be lowered by sensor 10 so that the sensor rotates vertically ;; · 30 ton liquid level when reaching the lower limit.

: When the sensor 10 floats on the surface of the liquid in the tank 15, the float 1 is in a horizontal position. 2b. In this case, the glass ball 6 is located on the mounting bracket 5 and the rest plane *, /. 7 in between. The light beam returning to the fiber-optic fiber 4 through the glass bead 6 acting as a lens is then weakened in intensity.

5 1164/1

As the level of the liquid decreases, the sensor 10 rotates to an upright position as shown in Figure 2a and the glass ball 6 changes its position to the center of the rest plane 7. Then, the light beam returning to the optical fiber 4 passes through the center of the glass ball 6 and the intensity of the returning light beam is strong.

The liquid level is inferred in the case of Fig. 2 as in the case of Fig. 1. In the embodiment of Fig. 2, the high intensity corresponds to the lower limit of the surface height and the low intensity corresponds to the upper limit of the height of the surface.

It will be apparent to one skilled in the art that the invention is not limited to the foregoing description, but may vary within the scope of the following claims. For example, the surface switches of the invention may also be used to measure the surface height of a granular explosive material, for example, grain stored in a grain silo. All of the above sensors can be used in addition to providing upper and lower limit alarms to control solenoid valves or pumps.

* «» * »· * · • i» • · · •> · I · • * r * • # 44 * * t * »* i ·.

, I

i I «* * * f» t <.

sr1 t »*» *? i i «· • '" /

Claims (3)

1164/1 A level switch, for example, for measuring the level of an explosive liquid stored in a container (15) comprising a float (1), an air space (2), a plug (3), an optical fiber (4), a mounting bracket (5), a ball (6, 9) 7), characterized in that: - the level information is transmitted from the sensor (10) to the receiver (14) of the control unit (12) along the optical cable (11), - the level information corresponds to the intensity of the incident light beam, . A level switch according to claim 1, characterized in that the light beam is reflected back from the mirror (8). A level switch according to any one of the preceding claims, characterized in that an alarm is given to the user when the light beam returns to the control unit (12). 15 Patentkrav, - 1. Nivävakt exempelvis för att rtnivän hos en i en behällare (15) lagrad ex-! plosionsfarlig vätska, innefattande et flöte (1), luftrum (2), en propp (3), en liber fiber (4), monteringsstöd (5), en kula (6, 9) och et viloplan (7), kännetecknad: av att 20. ythöjdsinformation förmedlas frän en detektor (10) account styrenhetens (12) motagare (14) längs en ljuskabel (11), - intensiteten av en atervändande ljussträle motsvarar ythöjdsinformationen,; ; och - intensively hos den atervändande ljussträlen styrs med en glaskula (6, 9). 2. Nivävakt enligt patentkrav 1, kännetecknad av att ljussträlen äterspeglas frän; / en spegel (8). , | 3. Nivävakt enligt nägot av föregäende patentkrav, kännetecknad av att dä ljus strälen som ätervänder account styrenheten (12) bryts ges et larm account användaren.