RU2783631C1 - Limit level alarm with possibility of control of circuit integrity - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to provision of safe operation of reservoirs on storage depots and other objects, allowing for elimination of filling or emptying of a reservoir above/below a set value of a liquid level. An alarm consists of a flange with a pipe attached to it, at an upper end of which a floater with an annular magnet is located. A range of floater movement is determined using limiting rings. Inside the pipe, at a level of maximum floater lift, an upper reed switch board is placed. In a lower part of the pipe of non-magnetic material, a movable holder with a magnet is placed, combined with a spring mechanism, to which a buoy is suspended using a cable. In the pipe, at a level of a compressed spring, a lower reed switch board is placed, a level of reed switch trigger is adjusted by changing a length of the cable. The structure is made with the possibility of additional adjustment of the trigger level, using a node for adjustment of the trigger level, without dismounting the limit level alarm.

EFFECT: creation of an alarm controlling upper and lower level of a product, providing signaling on a normal value of a liquid level in a reservoir or an emergency situation, controlling the integrity of signal circuits, and providing disconnection of a pump.

1 cl, 5 dwg, 7 tbl

Description

The invention relates to ensuring the safe operation of tanks at oil depots and other facilities, which makes it possible to exclude filling the tank above a predetermined liquid level and emptying the tank below a predetermined liquid level.

Overflow control is important from the point of view of fire and environmental safety.

Control of the minimum level is necessary to exclude the “dry running” of the pump (the pump may fail) and to exclude the intake from the reservoir of “dead residue” - an oil product with bottom sediments and produced water.

These tasks are solved by devices of two groups:

- systems for commercial metering of liquid in the tank, built on measuring the level, temperature, volume and density of the liquid and configured, among other things, for level control;

- signaling devices of level of various principles of action.

Recently, in accordance with the requirements of Federal norms and rules, in order to ensure safe operation for emergency protection (ESD) of tanks, it is required to use control devices (sensors or level indicators, as well as control devices designed to turn on light / sound alarms and turn off the filling / draining pump liquids when critical levels of liquid in the tank are reached), operating independently of commercial accounting systems and with the function of self-diagnostics of operability to improve the reliability of the ESD, therefore, the development of a class of level detectors, increasing their capabilities and reliability, becomes relevant.

The most simple, cheap and reliable are float level switches using reed switches.

A liquid level sensor with a free float is known (K. I. Kharazov. Automation devices with magnetically controlled contacts. M.: Energoatomizdat, 1990, p. 215-216). A vertical non-magnetic pipe is installed in the liquid tank, along which a float with an annular magnet moves freely. A reed switch or a group of reed switches is placed inside the pipe. When the float with the magnet moves, the reed switch is triggered. This sensor is easy to implement, but has a significant drawback. When the float with the magnet leaves the interaction with the reed switch, the information obtained about the liquid level is ambiguous, that is, it does not allow one to definitely judge the position of the liquid level in the gap between the reed switches. The same drawback has a liquid level sensor with a flexible rod made of non-magnetic material, fixed inside a non-magnetic pipe, and on which a number of reed switches are installed (RF patent for utility model No. 26847, class G01F 23/62). Sensors of such a device cannot be used for automatic level control and are difficult to operate.

These disadvantages are partially eliminated in the oil level sensor, in which the magnet is mounted on a polyamide rod connected to a float (RF patent for utility model No. 24557, class G01F 23/46), as well as in threshold float liquid level transducers translational movement of the float (collection EI (VINITI) "Control and measuring equipment", 1989, No. 15, p. 7-9, ref. 77), by limiting the maximum movements of the float, due to which, after issuing a signal and further moving the liquid level, issuing this The signal is preserved, which ensures the unambiguity of the output information and the fundamental possibility of using the sensor for automatic control of the liquid level. However, the functionality of the probe with a stem is limited to issuing a single signal, and only in filling mode; in addition, these sensors do not provide the ability to control the limits of liquid level regulation during operation.

Known liquid level sensor according to RF patent No. 2135961, class. G01F 23/74, in which these disadvantages are eliminated by the fact that the magnets with reed switches are fixed in the opposite direction relative to each other on a bar installed inside a non-magnetic guide tube, and the reed switches are located in the field of action of magnets interacting with the inner ferromagnetic wall of the float when it moves, and the guide pipe is equipped with a limiter for the upward travel of the float and, in order to expand the technological capabilities, is installed on the lid of the vessel with the possibility of changing its position in height. However, such an installation of a guide pipe with the possibility of moving for the adjustment process does not provide tightness, which is required for equipment operating at elevated temperatures, pressures, with flammable and aggressive media, and the tolerance for level control fixed by the design narrows the scope of the sensor. In addition, when the liquid level exceeds the upper limit, all reed switches of this device give a signal of the “off” nature, which does not allow objective control of this control limit, since the most possible failures such as “open” in the line and the lack of contact in its electrical connectors can be perceived by the control device as an alarm signal indicating an overflow of the tank.

Known liquid level indicator (aut.mon. RF No. 1742628, class G01F 23/56), in which the float with a magnet installed on it moves along a vertical non-magnetic pipe and the reed switch is turned on, which is recorded as a change in the liquid level. Known signaling device has a significant drawback - the ambiguity of the information received about the liquid level. So, when the magnet leaves the interaction with the reed switch, it is impossible to unambiguously determine whether the liquid level has risen or fallen, which leads to bias in its control, reduces efficiency and does not allow automation of control processes, since the liquid level can go beyond the maximum permissible critical values, which is especially dangerous in equipment operating at elevated temperatures, pressures and with flammable and aggressive liquids. In addition, said sensor arrangement does not provide control over the actual limits of liquid level control.

Known liquid level sensor according to the patent for the invention RU 2284482 dated 13.05.2005, class. G01F 23/74. The liquid level sensor allows you to control the upper and lower levels of the product in the tank, contains a float with a magnet, float limiters and a vertical guide non-magnetic pipe, inside which reed switches are located. The disadvantage of this level sensor is that the reed switches are installed continuously along the length of the sensor with a step less than the length of the float. For vertical tank farms up to 20 m high, a complex and expensive design is obtained - the sensor must be made sectional with sealing of joints (for ease of installation and transportation), the number of reed switches is very large: with a float length (typical) of about 100 mm, the number of reed switches N = 20 m / 0.1 m=200 pcs. Therefore, this sensor is only suitable for small tanks or fuel tanks of locomotives or cars.

Known level indicator according to the utility model of China CN202956168 U 2012-11-30, class. G01F 23/30. The liquid level switch contains two liquid level switches, a bracket and two spring contact control mechanisms, which are fixed on the bracket, and the spring contact control mechanisms are connected to the liquid level buoy. This signaling device allows you to control two levels of liquid in the tank, but it has several disadvantages:

1) two buoys hang on two cables, which can get tangled when filling the tank due to the turbulence of the liquid;

2) mechanical contacts have low reliability (due to water vapor, the contact surface oxidizes over time and contamination from dust penetration) compared to reed switches (sealed glass or plastic capsule);

3) there is no self-diagnosis of circuit integrity, which is necessary for emergency protection devices;

4) Requires a lot of space on the roof of the tank for installation (two seats).

A level switch is known according to the utility model of China CN209706909 U 2019-04-08, G01F 23/30, which can be used to control the level of two liquid levels in small tanks (horizontal) at gas stations, consisting of a protective casing with many through holes, inside which there are two floats moving along the pipe located inside the casing, located one above the other and having movement limiters at the top and bottom. The liquid level indicator and the protective sleeve are fixedly connected to the top of the tank. The working principle of the high level alarm and high level alarm is that when the magnet built into the float aligns with the normally open reed switch in the float guide rod when the liquid level rises, the normally open reed switch closes under the action of the magnetic field and the alarm is automatically turned on. . This signaling device allows you to control two levels of liquid in the tank, but it has several disadvantages:

1) for a vertical tank up to 20 m high, a complex and expensive design - it is necessary to make a long sectional pipe with sealed joints (for ease of installation and transportation);

2) there is no self-diagnosis of circuit integrity, which is necessary for emergency protection devices.

A device for controlling the upper position of a floating roof (pontoon) in a tank is known according to patent RU 2677412 dated 09/13/2018, B65D 90/26.

The device consists of a flange with a pipe made of non-magnetic material attached to it, on which a movable magnetic system is placed, combined with a spring mechanism, to which a buoy is suspended by means of a cable, contacting the floating roof (pontoon) when it rises to a controlled level, in a pipe made of non-magnetic material, two reed switches are located, the upper reed switch is located in such a way that it operates at the level of the unclenched spring, and the lower reed switch is located in such a way that it operates at the level of the compressed spring, the level of operation of the reed switches is adjusted by changing the length of the cable or using a collet clamp, for exact alignment of the position of the lower reed switch with the magnetic system with a compressed spring, a glass is installed, an umbrella is installed to protect against condensate, located above the spring mechanism, constant monitoring of the integrity of the circuits and reliable information about the position of the floating roof (pontoon) in the tank is provided by generating signals at three levels yum - Normal, Level 1 (warning), Level 2 (pump emergency shutdown), the weight of the buoy exceeds the compression force of the spring, and the volume of the buoy is designed so that when the floating roof (pontoon) is warped, jammed or sinks and the buoy is immersed in the product, the buoyancy force , acting on the buoy, allows the spring mechanism to straighten and ensure the operation of the upper reed switch, while the device is designed to simultaneously control both the position of the floating roof (pontoon) when it is raised to the upper position, and control the increase in the liquid level in the tank in case of skew, jamming or sinking of a floating roof (pontoon) with constant monitoring of the integrity of the circuits and the ability to quickly adjust the level of operation without dismantling the device. This device can also be used in vertical tanks without a pontoon, but it only controls the overflow of the product in the tank.

A level sensor is known according to Japanese patent No. 1-176918 G01F 23/00 (published on 07/01/1988), which is the closest in technical essence to the claimed level limit switch with the ability to monitor the integrity of the circuits. The specified sensor is used to control the oil level in the warehouses of fuels and lubricants. It includes a float (buoy) suspended on a filamentous element to a signaling device, with the help of a spring and located above the liquid (oil) level, the signaling device contains a reed switch surrounded by an annular magnet. The weight of the float exceeds the compressive force of the spring, and is made of a material whose specific gravity exceeds the weight of the liquid. The actuation level is adjusted by changing the length of the threadlike element. While the load is above the liquid, the magnet lowers under the weight of the load, the spring is in a compressed state, when the liquid level rises due to the buoyancy force acting on the buoy, the spring straightens and the magnet moves to the upper position, and the reed switch is triggered, signaling the achievement of level. This sensor has the following drawbacks - there is no information about the health of the sensor and supply circuits, it controls only the upper liquid level in the tank, the adjustment of the response level is carried out with the sensor dismantled.

The purpose of the invention is to create a signaling device for limiting liquid levels for tanks of oil depots and other objects with the ability to control the upper and lower liquid levels in the tank with the function of diagnosing the integrity of the circuits, the ability to quickly adjust the response level without dismantling.

The essence of the invention is that the proposed signaling device for the liquid level in the tank with the possibility of monitoring the integrity of the circuits not only controls the upper liquid level in the tank (liquid overflow above the permissible level) and the lower liquid level (level decrease to an unacceptably low value), but also provides a normal signaling the value of the liquid level in the tank or an emergency situation, provides control of the integrity of the signal circuits, ensures that the pump is turned off when filling in case the tank is overfilled above the set value, the pump is turned off when draining in case of an unacceptably low liquid level in the tank, the pump is turned off when filling / draining in case of violation of the integrity of the signal circuits and provides the ability to quickly control the level of operation without dismantling the limit level detector with the possibility of monitoring the integrity of the circuits.

The subject of the invention is a signaling device for limiting liquid levels in a tank with the possibility of monitoring the integrity of circuits, consisting of a flange with a pipe made of non-magnetic material attached to it, at the upper end of which there is a float with an annular magnet, freely moving along the pipe made of non-magnetic material, the range of movement of the float is determined by using restrictive rings, inside the pipe at the level of the maximum lift of the float, the upper board of the reed switches is placed in such a way that when the float with the magnet moves to the upper position, the reed switches are triggered; to which a buoy is suspended with a cable, the weight of the buoy exceeds the compression force of the spring, and the volume of the buoy is designed so that when the buoy is in the liquid, the buoyant force acting on the buoy allows the spring mechanism to straighten out, in a pipe made of non-magnetic material on the bottom plate of the reed switches is located on the level of the compressed spring, the level of operation of the reed switches is regulated by changing the length of the cable, for the exact alignment of the position of the lower reed switches with the magnetic system, when the spring is compressed, a cup is installed, the design is made with the possibility of additional regulation of the level of operation using the unit for adjusting the level of operation without dismantling the limit signaling device levels, to protect against condensate, an umbrella is installed, located above the float, while the first and second reed switches are installed on the upper board of the reed switches, located at the same level, triggered simultaneously when the float magnet approaches them at the maximum level, the third and fourth are installed on the lower board of the reed switches reed switches that operate simultaneously when a clip with magnets approaches them at a minimum level, the first output of the first reed switch in the terminal compartment is connected to the “Upper” contact, the second output of the first reed switch is connected to the “Common” contact, the first output of the second of the reed switch is connected to the "Normal" contact, the second output of the second reed switch is connected to the first output of the fourth reed switch, the second output of which is connected to the "Common" contact, the first output of the third reed switch is connected to the "Lower" contact, the second output of the third reed switch is connected to the "Common" contact , at the same time, constant monitoring of the integrity of the circuits is ensured by analyzing the state of all reed switches and reliable information about the level of the product in the tank by generating signals at three levels - "Normal", namely, the normal level of the liquid, "Upper", namely, the overflow of the tank, " Lower”, namely, an unacceptably low level of liquid in the tank.

The technical result is the creation of a signaling device for limiting liquid levels in a tank with the ability to control the integrity of the circuits, which controls the upper level of the liquid in the tank (liquid overflow is above the permissible level) and the lower level of the product (the level drops to an unacceptably low value), which provides signaling the normal value of the liquid level in the tank or an emergency situation that monitors the integrity of the signal circuits, which ensures that the pump is turned off when filling in case the tank is overfilled above a predetermined value, the pump is turned off when draining in case of an unacceptably low liquid level in the tank, and the pump is turned off when filling / draining in case of violation of the integrity of the signal circuits and ensuring the ability to quickly control the level of operation without dismantling the signaling device.

The figure 1 shows the design of the liquid level limit switch with the ability to monitor the integrity of the circuits, the figure 2 shows the operation of the limit level switch when the tank is normally filled, the figure 3 shows the operation of the limit level switch when the tank is overfilled above the set value, the figure 4 shows the option operation of the level limit switch at an unacceptably low liquid level in the tank, figure 5 shows the connection diagram of the reed switches with the contacts of the terminal compartment.

The numbers in the figures indicate:

1 - Terminal compartment

2 - Flange

3 - Upper restrictive ring

4 - Pipe made of non-magnetic material

5 - float

6 - Lower restrictive ring

7 - clip

8 - Thrust

9 - Rope

10 - Buoy

11 - Operation level adjustment unit

12 - Umbrella

13 - Spring

14 - Glass

15 - Clamp

16 - Reed switch G ₁

17- Reed switch G₂

18 - Upper plate of reed switches

19 - Float magnet

20 - Clip magnet

21 - Reed switch G ₃

22 - Reed switch G ₄

23 - Bottom plate of reed switches

24 - Reservoir

The liquid level alarm in the tank with the possibility of monitoring the integrity of the circuits consists of a flange 2 fixed on the roof of the tank 24, a terminal compartment 1 that is connected to an alarm device (not shown in the figures), a pipe made of non-magnetic material 4, a spring mechanism consisting of holder 7 with a magnet located in it of the holder 20, rod 8, spring 13, cup 14, actuation level adjustment unit 11 attached to flange 2. A buoy 10 is suspended from the rod 8 with the help of clamps 15 of the cable 9. A buoy 10 is suspended above the spring mechanism using the upper restrictive an umbrella 12 is fixed to the ring 3, an upper plate of reed switches 18 is placed inside the upper part of the pipe made of non-magnetic material 4, on which reed switches G ₁ 16 and G ₂ 17 are located, and outside the float 5 with a magnet 19 that controls the upper level of operation, the movement of the float 5 is carried out in within the lower 6 and upper 3 restrictive rings fixed on the pipe 4, inside the lower part of the pipe 4 p the bottom plate of the reed switches 23 is placed, on which the reed switches G ₃ 21 and G ₄ 22 are located, and outside there is a movable clip 7 with a magnet 20, combined with a spring mechanism consisting of a spring 13, a clip 7, a rod 8 and a cup 14, to which using a cable 9 suspended buoy 10, which controls the lower level of operation.

The upper board of the reed switches 18 is located in such a way that the reed switches G ₁ 16 and G ₂ 17 are triggered when the float 5 with the magnet 19 installed in it reaches the predetermined upper emergency level of liquid in the tank.

The bottom plate of the reed switches 23 is located in such a way that the reed switches G ₃ 21 and G ₄ 22 are triggered when the lower emergency level of the liquid in the tank 24 is reached at the level of the compressed spring 13, the lower level of operation of the reed switches is adjusted by changing the length of the cable 9. To accurately align the position of the lower board reed switches 23 with a clip magnet 20 with a compressed spring, a glass 14 is installed.

The design is made with the possibility of additional adjustment of the response levels using the response level adjustment unit 11, made in the form of a collet clamp, which provides additional fine tuning of the limit level indicator without dismantling by moving the pipe 4 relative to the flange 2.

The signals from the limit level detector with the possibility of monitoring the integrity of the circuits through the terminal compartment 1 enter the control device (not shown conventionally). The liquid filling/draining pump and light/sound alarm are connected to the output contacts of the control unit.

Limit level detector with the ability to monitor the integrity of the circuits works as follows.

The signaling device shown in figure 1 is placed in the tank 24. When the tank is normally filled (figure 2), the float 5 with the magnet 19 located inside it is either on the lower restrictive ring or below the level of operation of the reed switches G ₁ 16 and G ₂ 17, which are located in closed state, the buoy 10 is in the liquid and the buoyant force of the float provides a straightened position of the spring 13, resulting in the reed switches G ₃ 21 and G ₄ 22 are in the closed state. Terminal compartment 1 receives a "Normal" signal (normally closed).

When the tank 24 (figure 3) is overfilled above the set value, the float 5 with the magnet 19 located inside it rises to the location of the reed switches G ₁ 16 and G ₂ 17, as a result of this, the reed switches open and the signal “Normal” is sent to the terminal compartment 1 instead of the “Norm” signal. Upper level” and an alarm is generated in the control device and the pump is turned off when liquid is poured into the tank.

When the liquid level in the tank 24 drops below the allowable set value (figure 4), the buoy 10 is above the liquid level in the tank, as a result of which, under the action of the own weight of the buoy 10, the spring 13 is compressed and the cage with the magnets of the cage 20 located in it is in the area of the reed switches Г ₃ 21 and Г ₄ 22, as a result of this, the reed switches open and instead of the “Normal” signal, the “Lower level” signal enters the terminal compartment and an alarm is generated in the control device and the pump is turned off when the liquid is drained from the tank.

If the integrity of any circuit of the signaling device in the control device is violated, an alarm is generated and the tank filling/draining pump 24 is turned off.

During operation at temperatures close to zero values, condensate of the liquid in the tank forms on the roof of the tank 24 and on the pipe made of non-magnetic material 4 and falls down in the form of drops, while the normal operation of the signaling device is disrupted when the temperature drops (condensate freezing disrupts mobility of the magnetic system). To protect the limit level indicator, an umbrella 12 is installed in the tank, covering the float 5 and the spring mechanism from the ingress of condensate drops.

The design of the level switch is made with the possibility of additional regulation of the levels of operation using the unit for adjusting the level of operation 11 without dismantling the level switch with the possibility of monitoring the integrity of the circuits.

Control of the integrity of the signal circuits and levels of operation consists in the analysis of the states of the reed switches G ₁ ... G ₄ and is carried out as follows.

In normal mode (h _min <h<h _max ) all reed switches are closed. This allows you to detect breaks in the wires from the signaling device to the control device, since the break is perceived by the control device as the occurrence of emergencies: overflow of the tank or emptying below the set level value.

For example:

1) a break in the “Upper” wire will be perceived as an excess of the liquid level in the tank above the allowable level;

2) a break in the “Lower” wire will be perceived as a drop in the liquid level in the tank below the permissible level;

3) wire break "Normal" will be perceived as one of the events 1) or 2).

Thus, the most dangerous situation is eliminated, when the wires are broken and the signal from the level detectors (sensors) at a critical level in the tank is not sent to the control device.

An example of diagnosing wire breaks in normal mode (h _min <h<h _max ):

1 A break in the “Upper” wire will result in the formation of the “Upper” signal (opening). Since in this case the "Normal" signal remains in the active (closed) state, which is a logical contradiction, an error is registered, and the tank filling pump is blocked.

2 A break in the “Lower” wire will lead to the formation of the “Lower” signal (opening). Since in this case the "Normal" signal remains in the active (closed) state, which is a logical contradiction, an error is registered, and the pump for emptying the tank is blocked.

3 A break in the "Normal" wire will turn off the "Normal" signal (opening). Since in this case the signals "Upper" and "Lower" remain in a passive (closed) state, which is a logical contradiction, an error is recorded, while the emergency protection system blocks the operation of the pump for loading / draining the liquid.

4 Breakage of all wires will turn off the signals "Upper", "Lower", "Normal" (opening of all circuits), which is a logical contradiction, therefore an error is registered and the control device blocks the operation of the liquid loading / draining pump.

The essence of logical analysis is described in more detail below. The normal operating mode of the limit level detector with the possibility of monitoring the integrity of the circuits is summarized in table 1.

If you enter the designations: 0 - closed, 1 - open, then we get a logical truth table (Table 2) in the normal operation mode of the signaling device (there are no open circuits).

When the circuits between the level detector and the control device are broken, truth violations occur in the output state (Table 2), which are easily diagnosed by the control device, since when any circuit is broken, instead of state 0 (closed), state 1 (open) occurs.

The diagnostic method can be illustrated as follows. The state of the signaling device outputs will be presented in the form of binary and decimal numbers (Table 3).

Tables 4-7 present the various alarm open circuits and corresponding truth violations with respect to Table 3 (shown in bold).

Table 4 shows that the truth violation occurs at all levels, except for (h≥h _max ), but this is safe, since in this case the control device turns off the liquid loading pump.

If the level drops when draining, the controller will also block the pump due to errors "4" and "7".

From table 5 it can be seen that the violation of truth occurs at all levels except (h≤h _min ) but this is safe, since in this case the control device turns off the pump when draining.

If the filling level rises, the controller will also block the pump due to errors "2" and "7".

Table 6 shows that the truth violation occurs at all levels except (h≤h _min ) and (h≥h _max ), but this is safe, since in this case the control device turns off the filling/draining pump.

At the level (h _min <h<h _max ) the controller will also block the drain/fill pump due to error "1".

From table 7 it can be seen that the violation of truth occurs at all levels, but this is safe, since in this case the control device turns off the fill/drain pump due to error 7.

Thus, under any situation, overflow or emptying of the tank below the set value is excluded.

At the enterprise, prototypes of the limit level indicator with the possibility of monitoring the integrity of the circuits were manufactured and the operation of the indicator was tested, and during the tests, not only normal operation was checked, but also the situation was simulated with imitation of open circuits of the limit level indicator.

Tests have confirmed the increase in the reliability of monitoring the levels of the product in the tank due to the constant monitoring of the integrity of the device circuits, the possibility of additional regulation of the level of operation using a collet without dismantling the device, monitoring the presence of a signal of a normal or emergency level of the liquid in the tank, protection against condensate.

Claims (1)

Liquid level limit switch in the tank with the ability to control the integrity of the circuits, consisting of a flange with a pipe made of non-magnetic material attached to it, at the upper end of which there is a float with an annular magnet, freely moving along the pipe made of non-magnetic material, the range of movement of the float is determined using restrictive rings , inside the pipe at the level of the maximum lift of the float, the upper board of the reed switches is placed in such a way that when the float with the magnet moves to the upper position, the reed switches are triggered; the buoy is suspended from the cable, the weight of the buoy exceeds the compression force of the spring, and the volume of the buoy is made in such a way that when the buoy is in the liquid, the buoyant force acting on the buoy allows the spring mechanism to straighten out, in a pipe made of non-magnetic material at the level of the compressed spring on the bottom board of the reed switches, the level of operation of the reed switches is adjusted by changing the length of the cable, for precise alignment of the position of the lower reed switches with the magnetic system with a compressed spring, a cup is installed, the design is made with the possibility of additional regulation of the level of operation using the unit for adjusting the level of operation without dismantling the limit level detector, for protection against condensate, an umbrella is installed located above the float, characterized in that the first and second reed switches are installed on the upper board of the reed switches, located at the same level, triggered simultaneously when the float magnet approaches them at the maximum level, the third and fourth reed switches are installed on the lower board of the reed switches , triggered simultaneously when clips with magnets approach them at a minimum level, the first output of the first reed switch in the terminal compartment is connected to the “Upper” contact, the second output of the first reed switch is connected to the “Common” contact, the first output of the second reed switch is connected with the "Normal" contact, the second output of the second reed switch is connected to the first output of the fourth reed switch, the second output of which is connected to the "Common" contact, the first output of the third reed switch is connected to the "Lower" contact, the second output of the third reed switch is connected to the "Common" contact, with this ensures constant monitoring of the integrity of the circuits by analyzing the state of all reed switches and reliable information about the liquid level in the tank by generating signals at three levels - "Normal", namely the normal liquid level, "Upper", namely the overflow of the tank, "Lower", and the liquid level in the tank is unacceptably low.

Images