Liquid flow sensors are designed to indicate the flow of a liquid substance, determine the speed and measure the level of product flow.
Modern flow switches are highly sensitive and able to respond even to a weak flow of liquid in the pipeline. A variety of models allows the use of flow sensors to work with various types of liquid products, including aggressive and hazardous substances. Some manufacturers offer explosion-proof options that are safe for use in hazardous industries.
Scope of liquid flow sensors
Liquid flow switches are used to solve various problems in many industries:
- in water supply and sanitation systems to control water supply, maintain the operation of pumping equipment, organize wastewater disposal systems, sewer facilities, protect pumping equipment and engines from "dry running",
- in heating, cooling, ventilation and air conditioning systems to control the supply of water, refrigerant, special liquids, removal of waste liquids from the system,
- in the oil and gas sector to control the flow of gas, oil, oil products during transportation and storage,
- in metallurgy, steel industry in systems for supplying and discharging water and other liquids,
- in the chemical industry to work with aggressive and dangerous types of liquid products, water supply and discharge systems,
- in agriculture when automating feeding processes, in drinking bowls, in watering and irrigation systems, when working with liquid fertilizers,
- in the food industry to control the supply of various types of liquid food products, including mineral water, dairy and sour-milk products, alcoholic beverages, beer, etc.
Some types of liquid flow sensors are also suitable for working with gases, which greatly expands the possibilities of using devices in industry and everyday life.
Types of liquid flow switches and their purpose
Modern types of fluid flow switches have a common main purpose - to control the presence or absence of the flow of the working fluid in the pipeline. The differences lie in the principles of operation and the possibilities of using the sensors.
- Mechanical paddle flow switch is a device built into the pipe, equipped with a special blade. If there is flow in the pipeline, the vane deflects, causing the contacts to close and trigger the sensor. The paddle relay has practically no restrictions in use, is little subject to wear and does not require maintenance.
- Thermal flow switch monitors the presence of flow by measuring the level of dissipation of thermal energy from the built-in heating element. Depending on the rate of change in the temperature of the heating element, the flow is recorded, as well as its speed if this function is available. The hot-wire principle of flow measurement is not suitable for some hazardous liquids. To maintain the reliability of registration, it is necessary to maintain the cleanliness of the sensitive elements of the sensor. Some types of devices are not suitable for operation in conditions of constantly changing flow rates.
The water level sensor in the conditions of modern technology performs the function of one of the human senses. The correct operation of the entire mechanism depends on how correctly it is possible to manage and control the state of the water flow. It is difficult to overestimate the importance of the reliability of the sensor device, if only because the device that controls water, as a rule, becomes the very "narrow" link in modern technology.
Design and principle of operation
Regardless of what principle of operation the device is based on, whether it works only in the signaling mode or simultaneously performs the functions of a watchman, automatic machine or control mechanism, the design of the device always consists of three main components:
- A sensing element capable of responding to the characteristics of the water flow. For example, the actual presence of water, the height of the column or the level in the tank, the fact of the movement of water flow in a pipe or line;
- A ballast element that balances the sensor part of the sensor. Without the ballast, the sensitive sensor would be triggered by the slightest jolt or the occasional drop of water;
- Transmitting or actuating part that converts the signal of the sensor mounted in the water sensor into a specific signal or action.
Approximately 90% of all water technology, one way or another, is connected with electric actuators - pumps, valves, heaters and electronic control machines. It is clear that such a device operating with water flows must be safe in the first place.
Of all the alarm systems, a sensor that monitors the state of water is considered the simplest and most affordable to set up and repair. Unlike sensors and devices that work with temperature, pressure or flow measurements, the water sensor is very easy to control using the simplest devices, or, in extreme cases, see the level or pumped flow with your own eyes.
Types of level sensors
One of the conditions for the successful operation of the sensor is the high sensitivity of the sensor, the higher the better, the more accurately it is possible to read the controlled water parameter. Therefore, as the value measured by the sensor, they try to choose the one that changes the most during the measurement.
Today, there are about two dozen different methods and methods for measuring the mechanical characteristics of water, but all of them are used to obtain information:
- The height of the water column in the container or tank;
- The speed of the flow or flow of water;
- The fact of the presence or absence of water in a closed container, tank, pipe or heat exchanger.
Of course, industrial sensors can be quite complex structurally, but the principles of operation used in them are the same as in household, garden or automotive equipment.
Float type overflow sensor
The simplest way to measure the water level is with a simple mechanical design, consisting of a sealed float, a rocker or link, and a check valve. In this case, the float is the sensor, the spring and float weighting are considered the ballast, and the valve itself acts as the actuator.
In all float systems, the sensor or float is adjusted to a specific response height. The water that has risen in the tank to the control level raises the float and opens the valve.
The float system can be equipped with an electric actuator. For example, a magnet insert is installed inside the float sensor, when the water rises to the working level, the magnetic field causes the vacuum reed switch to close the contacts, and thereby turns on or off the electrical circuit.
The float sensor can also be implemented in a free circuit, as, for example, in submersible pumps. In this case, the reed switch closes not under the influence of the magnetic field of the liner, but only due to the pressure difference inside the pump housing and at the level of the float. Today, a magnetic float sensor with an electric actuator is considered one of the safest and most reliable options for monitoring the liquid level.
Ultrasonic sensor
The design of the water sensor provides for the presence of two devices - an ultrasound source and a signal receiver. The sound wave is directed to the surface of the water, reflected and returned to the receiver.
At first glance, the idea of using ultrasound to make a sensor for controlling the level or speed of water movement does not look very successful. The ultrasonic wave can be reflected from the walls of the tank, refracted and interfere with the operation of the receiving sensor, and in addition, sophisticated electronic equipment is required.
In fact, an ultrasonic sensor for measuring the level of water or any other liquid is placed in a box a little more than a pack of cigarettes, while using ultrasound as a sensor provides certain advantages:
- The ability to measure the level, and even the speed of water at any temperature, in conditions of vibration or movement;
- The ultrasonic sensor can measure the distance from the sensor to the water surface even in heavily polluted conditions with variable liquid levels.
In addition, the sensor can measure the level of water located at a considerable depth, while the measurement accuracy is 1-2 cm for every 10 m of height.
Electrode water control principle
The fact that water is electrically conductive has been successfully used to make liquid level contact sensors. Structurally, the system consists of several electrodes installed in a container at different heights and connected into one electrical circuit.
As the container is filled with water, the liquid closes a pair of contacts in series, which turns on the pump control relay circuit. As a rule, the water sensor has two or three electrodes, so the measurement of the water flow is too differentiated. The sensor signals only when the minimum level is reached and starts the pump motor, or when the tank is full and turns it off, so such systems are used to control reserve or irrigation water tanks.
Capacitive type water sensor
Capacitive or capacitive type of sensor is used to measure the water level in narrow and deep tanks, it can be a well or a well. Using a capacitive sensor, you can determine the height of the water column in the well with an accuracy of tens of centimeters.
The sensor design consists of two coaxial electrodes, in fact a pipe and an internal metal electrode, immersed in the wellbore. Water fills part of the internal space of the system, thereby changing its capacity. Using the connected electronic circuit and the quartz oscillation coil, the capacitance of the sensor and the amount of water in the well can be accurately determined.
radar meter
A wave or radar sensor is used to work in the most difficult conditions, for example, if you need to measure the level or volume of liquid in a tank, an open reservoir, a well of asymmetric and irregular shape.
The principle of operation does not differ from the ultrasonic device, and the use of an electrical pulse allows you to perform a measurement with great accuracy.
Hydrostatic sensor option
One of the variants of the hydrostatic sensor is shown in the diagram.
Note! A similar sensor is used in washing machines and boilers, where it is very important to control the height of the water column inside the tank.
The hydrostatic sensor is a box with an elastic spring-loaded membrane that divides the sensor body into two compartments. One of the sections is connected with a strong polyethylene tube with a fitting soldered into the bottom of the tank.
The pressure of the water column is transmitted through the tube to the membrane and causes the contacts of the starting relay to close, most often a pair is used to start the actuator - a magnetic insert and a reed switch.
Water pressure sensor
Hydrostatic pressure is determined when a flow or a certain volume of water is at rest. Most often, a hydrostatic sensor is used in heating and heating devices - boilers, heating boilers.
Water pressure sensor device
Such devices most often operate in trigger mode:
- At high pressure water sensor closes the relay contacts and allows the pump or heater to work;
- At low pressure even the physical possibility of turning on the actuator is blocked in the sensor, that is, no shocks or temporary surges in pressure will make the device work.
With a good water pressure sensor, the sensor will give a signal to start the motor only if the load on the bellows is maintained for more than three seconds.
A typical device of a "smart" sensor is shown in the diagram.
The sensitive element of the system is a diaphragm connected to a bellows, the central rod can rise and fall depending on the pressure, and thereby change the capacitance of the built-in capacitor.
Connecting the water pressure sensor
A simplified sensor model is used in home accumulator-well pump systems. Inside the instrument is a box with a membrane connected to a rocker arm and two balancing springs.
The design is screwed onto the outlet fitting of the accumulator. With an increase in internal pressure, the membrane rises and opens the main pair of contacts so that the system responds properly to water pressure;
Water leakage sensor
Already from the name it becomes clear that we are talking about a device that detects the presence of water leakage from plumbing communications. The principle of operation of the device resembles an electrode system. Inside the plastic box, one or more pairs of electrodes are installed in a special pocket. In the event of an accident, water accumulating on the floor flows into the pocket and closes the contacts. The electronic circuit is triggered, and at the signal of the sensor, ball valves with an electric drive come into operation.
It is clear that the sensor, by itself, is a useless thing if used without a control system and automatic water cut-offs installed at the entrance to the house or on one of the branches of the water supply.
An example is one of the most popular protection systems - the Neptune water leakage sensor. The system includes three main blocks:
- The Neptune leak sensor itself is in wired or wireless modification, usually three separate sensors are included in the kit;
- Ball valve with electric drive, manufactured by the Italian company Bugatti, in the amount of two pieces;
- Control unit «Neptun Base».
The most valuable part of the kit is automatic taps, they are produced for installation on half-inch and inch pipe threads. The design withstands pressure up to 40 Atm., and the Italian quality of the drive guarantees at least 100 thousand opening and closing cycles.
The sensor itself looks like two brass plates in a box, to which a low-voltage voltage with a very high input resistance is connected, when the sensor is closed, the current is limited to 50 mA. The design itself is made according to the IP67 protocol, therefore it is absolutely safe for humans.
Installation of wireless water leakage sensors
In the Neptune system, the sensor can be removed from the control unit at a distance of more than 50 m. In more advanced NEPTUN PROW + wireless systems, water leakage sensors equipped with the WF module are used instead of a wire system.
The control unit is equipped with a channel protected from interference and moisture, a system for turning on and off ball valves. It is believed that no interference or accidental drops of moisture, condensate affect the operation of the sensors.
Boxes with a leakage sensor are installed at a distance of no more than 2 m from pipes; sensors cannot be shielded with metal plumbing or furniture.
Wireless water sensor
The design of a wireless meter is more complex than a conventional two-electrode wired version. A controller is installed inside, which continuously compares the current flowing between the electrodes with the reference value stored in the memory. In this case, the dry floor reference value can be set according to your own choice.
A very convenient solution, given that the humidity level in the bathroom can be very high, and regular condensation can lead to false alarms.
As soon as the controller determines the level corresponding to flooding, the water control device sends an alarm signal to the base unit. The most advanced models are able to duplicate the command with an SMS message over the GSM channel.
Water flow sensor
In many cases, for stable and trouble-free operation of equipment, a water presence sensor is not enough; information is required on whether the flow is moving through the pipeline, what is its speed and pressure. For these purposes, water flow sensors are used.
Types of water flow sensors
In household and the simplest industrial equipment, four main types of flow sensors are used:
- Pressure gauge;
- Petal sensor type;
- Blade measurement scheme;
- Ultrasonic system.
The older pitot tube design is sometimes used, but requires at least a clean and laminar flow of water to function reliably. The first three sensors are mechanical, so they are often subject to clogging or water erosion of the sensing element. The last type of sensor, ultrasonic, is able to work in almost any conditions.
The principle of operation of an ultrasonic meter can be understood from the diagram. Inside the tube is a wave emitter and a receiver. Depending on the flow velocity, the sound wave may deviate from its original direction, which is the basis for measuring the flow characteristics.
Device and principle of operation
The simplest petal flow sensors work on the principle of a rowing oar. A petal suspended on a hinge is immersed in the stream. The higher the flow velocity, the more the sensor lobe deviates.
More accurate paddle sensors use an impeller or impeller made of polyamide or aluminum alloy. In this case, it is possible to measure the flow velocity from the frequency of rotation of the moving element. The only drawback is the increased resistance created by the petals and blades in the water flow.
The pressure sensor works using dynamic flow pressure. Under the pressure of water, the movable element with a magnetic insert is squeezed upwards, thereby freeing up space for the movement of fluid. The reed switch installed in the head instantly reacts to the magnetic field of the insert and closes the circuit.
Application area
Water flow sensors are used exclusively in heating systems and automation systems of single-circuit heat exchangers. Most often, the failure of the flow sensor leads to burnout and severe damage to hot radiators and heaters.
DIY water level sensor
The simplest version of a device capable of signaling the filling of a tank or any other container with water is shown in the diagram below.
Structurally, the level detector consists of three metal electrodes mounted on a textolite plate. The circuit, assembled on a conventional low-power transistor, allows you to determine the maximum permissible upper and lower water levels in the tank.
The design is absolutely safe to use and does not require any expensive parts or control devices.
Conclusion
Water level sensors are widely used in household appliances, therefore, most often for the auxiliary needs of garage or garden equipment, ready-made designs from old equipment are used, redesigned and adapted to new conditions. With proper connection, such a device will last much longer than a home-made circuit.
In order to prolong the life of liquid flow devices, timely inspection, renewal and overhaul is recommended. But sometimes this is not enough for the pumps to work smoothly. A water flow sensor will come in handy. The protection relay prevents damage to the engine of surface, deep pumping equipment. Consider the types of equipment, the conditions for the correct selection and the technology of installation, do-it-yourself adjustment.
In domestic water supply systems, there is a problem of lack of water, which leads to a “dry run”. The incoming liquid cools the elements of the system, serves as a lubricant and ensures normal operation. If there is no water, the system runs dry, causing deformation and breakage of parts, equipment failure. The problem occurs in pump models of any configuration.
Causes of dry run:
- wrong choice of performance of pumping equipment;
- violation of installation technology;
- deformation, pipe rupture;
- reduced water flow pressure;
- lack of control over the liquid level;
- debris in the suction pipe.
An automatic or mechanical water flow sensor for the pump is needed to eliminate the threat of dry running. The device in a given mode measures, monitors and maintains a constant level of water flow. If a failure occurs in the station system, the sensor is triggered, the pump turns off in an independent mode, and when the flow level resumes, it turns on.
Types of water flow switch
The most common configuration of a water flow switch for a pump is the petal type. The classical scheme of the device consists of the following elements:
- inlet pass pipe;
- a valve (petal) located on the wall of the inner chamber;
- isolated switch;
- springs of a certain diameter.
The reed switch closes and opens the power circuits that actuate the compression spring. The principle of operation of the sensor in the water flow: when the chamber is filled with liquid, the flow displaces the valve from the axis by force, acting on the magnet, which actuates the switch. The contacts close, the pump turns on.
There are several types of sensors with their own features of operation and the possibility of application.
Mechanical vane
The device is a device equipped with a blade, which is built into the pipeline. The principle of operation is standard: when the flow enters, the blade deviates, acts on the magnet. The contacts close, the switch sensor is triggered. The simplicity of the unit explains the wide range of applications. In addition, such sensors are practically not subject to wear and tear and do not require maintenance - there is nothing to break in them.
Mechanical piston
The device works on the basis of a magnetic piston system. The principle of operation: when the flow enters, the piston with the magnet rises, closing the contacts - the relay is triggered to start. Without flow, the piston drops to its original position, preventing dry running. The main advantage of the device is a variety of designs that allow you to mount the device in any position. Mechanical piston switches are used in high pressure systems.
Thermal
The device is equipped with a level meter for dissipating thermal energy from the built-in heating element. Depending on the change in the rate of heating of the liquid, the flow itself and the speed of its flow are recorded. The thermal sensor is used only for safe types of liquid. Due to the hot-wire principle, it is forbidden to use the relay to measure flammable substances, as well as liquids that change composition when heated.
Advice! When choosing a device, it should be remembered that not all units operate with constant changes in flow. Thermal sensors require cleaning of sensitive elements.
Ultrasonic
The universal pulse water flow sensor works on the principle of the acoustic effect. The instrument transmits an ultrasonic pulse through the flow, detecting the level of the liquid. The most common are products whose functionality uses the movement of vibrations of a moving fluid. The devices are suitable for any substances, including combustible ones, they are easy to install and maintain.
How to choose a water flow switch
Before buying a unit, you must carefully read the technical characteristics, scope, and capabilities of the device.
What to look for:
- breadth of the operating temperature range;
- amplitude of pressure level indicators;
- diameter of thread and mounting holes;
- protection class;
- application features;
- manufacturing material.
The easiest way to handle a metal water flow switch, the price of units starts from $ 25-30, but it all depends on the type of device. The body and working elements made of metal are characterized by high strength, which means that the device will withstand long-term pressure loads from the fluid flow.
Important! The pressure indicator is selected according to the power of the pumping system - the characteristic affects the parameters of the fluid flow passing through the pipeline system.
Devices with two springs are considered especially practical, one of which controls the operation of the station according to the upper, the second - according to the lower pressure level. The climatic conditions of operation and the recommended level of humidity are taken into account. The limit of maximum permissible loads is indicated in the characteristics of the protection class.
The size of the diameter of the thread sections and mounting holes is checked for subsequent mounting of the device. With perfect compliance with the elements of the pipeline, docking will not cause difficulties, there will be no leaks during operation of the equipment.
Overview of well-known manufacturers and prices
The most famous and reliable are several models in the price range of $ 30-40:
- Genyo Lowara Genyo 8A. Manufacturer - Poland. The main direction of the company is the production of electronic equipment for control systems. The relay is designed to work in domestic water supply systems and is characterized by high quality, long service life. By monitoring the flow pressure in the pipes, the sensor starts the pumping system at a water flow rate of 1.6 l / minute. The unit requires connection to electricity, consumes 2.4 kWh. Operating temperature +5..+60 С.
- Grundfos UPA 120. The manufacturer's factories are located in Romania, China. The device has small dimensions, is conveniently mounted and is indicated for individual water supply systems. That is, it can be used both in private buildings and apartments. The device starts up at a fluid flow rate of 1.5 l / minute, completely preventing the functionality of the system at idle. Extreme operating temperature +60 C.
The models have been tested and adapted to domestic working conditions. Numerous reviews characterize metering sensors as durable and practical units at an affordable price.
Mounting the relay on a pump or station
If installation of the device is required, the work can be done independently, especially if you have to leave and there is no way to constantly monitor the operation of pumping equipment.
When not to install a relay:
- if water is pumped from a well with a large volume, that is, fluid reserves are not limited, and the pump power is minimal;
- it is possible to turn off the unit when the water level drops.
Equipment installation rules:
- It is important to monitor the membrane - the part must take a vertical position.
- Installation is carried out to the section of the drain pipeline with threaded couplings. There is a special socket for this.
- Before starting work, the thread is sealed with linen or other plumbing thread. Winding the thread to the end clockwise will increase the reliability of fastening and fixation.
- Factory sensors are equipped with an arrow drawn on the body - this is the direction of flow, which must match when installed.
- When arranging a relay in pipelines for supplying water with dirt particles, cleaning filters are first installed. It is better to mount them next to the sensor in order to extend the life of the device.
Testing of the installed device is carried out with the connection to the power supply:
- the free ends of the contacts are connected to the core wire;
- grounding is mounted to the screw;
- the device is connected by connecting the device with a wire (watch the color of the corresponding wires);
- system performance is checked.
Worth knowing! If the device is connected correctly, then the pressure mark will begin to grow on the pressure gauge, and then the pump will turn off automatically as soon as the pressure gauge arrow goes beyond the boundary value.
Self-adjustment of the water movement sensor
The factory device is supplemented with bolts, tightening or loosening which can increase / decrease the compression of the spring. Bolts will be required if you need to set the sensor to a certain pressure level at which the mechanism is triggered.
Action algorithm:
- drain fluid from the system;
- wait for the pressure mark to take a zero value;
- start the operation of the pumping unit;
- run water back in the slowest mode;
- memorize the flow pressure indicator when the pump relay is turned off;
- drain the liquid again, fixing the indicators of the start of the system.
Now you need to open the relay, adjust the compression level of the larger spring with a bolt - this will trigger the device when the pump starts. Adjustment is made taking into account the fact that strong compression will increase the degree of pressure, and weak compression will reduce it. Then the compression force of the smaller spring is adjusted - here the limit of the maximum pressure level is set, upon reaching which the relay will automatically turn off the pump.
As soon as the adjustment is completed, start the system, evaluate the result of the work when filling the pipeline and draining the flow. If adjustments are needed, repeat the procedure. Checking the functionality and adjusting the operating parameters is an annual procedure that extends the life of the device.
flow sensor- a device that generates an output signal in the presence of a liquid or gas flow. They are installed in pipelines and air ducts, where the presence of the flow of the working fluid is a critical parameter.
This sensor is also called flow switch, because its principle of operation is similar to the one with the only difference that its operation is caused not by the appearance of a control voltage on the coil, but by the presence of a liquid or gas flow. But the result of the operation of the flow sensor, as well as a conventional relay, is a change in the state of the output contacts to the opposite ones.
As a rule, the sensor has a normally closed (NC) and normally open (NO) contact. When a flow of the working medium appears, the NC contact opens, and the NO contact closes.
There are several types of flow sensors:
Petal flow switch
The figure shows a diagram of the petal-type duct sensor.
As the name implies, the main working element of this type of flow sensor is a flexible petal that contacts the working medium and deviates from the vertical position in case of flow. The petal is mechanically connected to the output contacts and changes their state when it bends itself.
Leaf switches Caleffi (left) and Danfoss (right)
Turbine flow sensor
The figure shows a diagram of a turbine-type flow sensor.
Such sensors are a small turbine, the rotor of which is equipped with a magnet. When the flow of the working substance passes through the device, the turbine begins to rotate, resulting in a magnetic field that is converted into electrical impulses that enter the electronic circuit of the sensor. The electronics cause the output contacts to change state when flow is present, just as in a lobe sensor.
Thus, such flow sensors have two types of outputs: output contacts (NO and NC) and a pulse output. The latter is used to determine the flow rate: the higher the pulse repetition rate, the greater the flow rate.
Flow sensor (turbine) for Ariston boiler
An example of this type of sensor is the Ariston gas boiler flow switch. When a flow appears (when the user opens a hot water tap), the sensor generates an output signal and switches the boiler to the DHW heating mode.
Using flow sensors
Flow sensors most often perform protective, informational or control functions.
The protective function is associated with the detection of the presence of flow in systems where its absence can lead to emergencies or equipment breakdowns. So, for example, they protect pumps, because when working in the absence of water flow, they overheat and fail. You can also determine the lack of air flow in ventilation systems when the filter is clogged, the damper is closed, or the fan breaks down. With the help of a flow switch, you can detect leaks in water supply systems, determine the lack of water in the storage tank, etc.
The information function of the flow switch is spoken of when the presence or absence of a flow is not associated with an emergency, but is a significant event in the system that the user needs to know about. In such cases, the sensor operation is used to turn on a light or sound indication, or to generate a message on the operator panel.
The flow switch performs the control function when other equipment is turned on or off at its signal. For example, in DHW systems, when the user opens a hot water tap, the gas boiler must turn on the pump and switch to DHW heating mode. This happens just when the flow sensor is triggered after the tap is opened.
Flow switch connection diagram
The following figure shows a typical connection diagram for a flow sensor for a pump.
In the absence of flow, the NO contact 1-2 is open, and the NC contact 1-3 is closed, the power circuit is open, the pump is stopped. When water flows through the relay, its contacts change their state, the pump power circuit closes and it turns on.
flow sensor- a device that generates an output signal in the presence of a liquid or gas flow. They are installed in pipelines and air ducts, where the presence of the flow of the working fluid is a critical parameter.
This sensor is also called flow switch, because its principle of operation is similar to the principle of operation of a conventional electromagnetic relay with the only difference being that it is triggered not by the appearance of a control voltage on the coil, but by the presence of a liquid or gas flow. But the result of the operation of the flow sensor, as well as a conventional relay, is a change in the state of the output contacts to the opposite ones.
As a rule, the sensor has a normally closed (NC) and normally open (NO) contact. When a flow of the working medium appears, the NC contact opens, and the NO contact closes.
There are several types of flow sensors:
Petal flow switch
The figure shows a diagram of the petal-type duct sensor.
As the name implies, the main working element of this type of flow sensor is a flexible petal that contacts the working medium and deviates from the vertical position in case of flow. The petal is mechanically connected to the output contacts and changes their state when it bends itself.
Leaf switches Caleffi (left) and Danfoss (right)
Turbine flow sensor
The figure shows a diagram of a turbine-type flow sensor.
Such sensors are a small turbine, the rotor of which is equipped with a magnet. When the flow of the working substance passes through the device, the turbine begins to rotate, resulting in a magnetic field that is converted into electrical impulses that enter the electronic circuit of the sensor. The electronics cause the output contacts to change state when flow is present, just as in a lobe sensor.
Thus, such flow sensors have two types of outputs: output contacts (NO and NC) and a pulse output. The latter is used to determine the flow rate: the higher the pulse repetition rate, the greater the flow rate.
Flow sensor (turbine) for Ariston boiler
An example of this type of sensor is the Ariston gas boiler flow switch. When a flow appears (when the user opens a hot water tap), the sensor generates an output signal and switches the boiler to the DHW heating mode.
Using flow sensors
Flow sensors most often perform protective, informational or control functions.
The protective function is associated with the detection of the presence of flow in systems where its absence can lead to emergencies or equipment breakdowns. So, for example, they protect pumps, because when working in the absence of water flow, they overheat and fail. You can also determine the lack of air flow in ventilation systems when the filter is clogged, the damper is closed, or the fan breaks down. With the help of a flow switch, you can detect leaks in water supply systems, determine the lack of water in the storage tank, etc.
The information function of the flow switch is spoken of when the presence or absence of a flow is not associated with an emergency, but is a significant event in the system that the user needs to know about. In such cases, the sensor operation is used to turn on a light or sound indication, or to generate a message on the operator panel.
The flow switch performs the control function when other equipment is turned on or off at its signal. For example, in DHW systems, when the user opens a hot water tap, the gas boiler must turn on the pump and switch to DHW heating mode. This happens just when the flow sensor is triggered after the tap is opened.
Flow switch connection diagram
The following figure shows a typical connection diagram for a flow sensor for a pump.
In the absence of flow, the NO contact 1-2 is open, and the NC contact 1-3 is closed, the power circuit is open, the pump is stopped. When water flows through the relay, its contacts change their state, the pump power circuit closes and it turns on.
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Purpose and benefits
When operating domestic water pipes, it is not uncommon for the pump to turn on when there is no liquid in the pipes. Such situations, if they occur frequently and continue for a long time, cause the pump motor to overheat and deform its parts, which ultimately leads to the failure of the entire device. The water pumped by pumping equipment simultaneously performs lubricating and cooling functions, therefore, “dry running”, as it is also called, negatively affects the technical condition of both circulation and submersible pumps.
In order to prevent the occurrence of the described situations, they just use a water flow sensor for the pump, which operates in automatic mode. Sensors that control the flow of water are successfully used to control the operation of pumping stations serving hot and cold water supply systems, as well as heating systems.
The considered automatic device controls the parameters of the flow of water that passes through it, and in cases where they differ from the normative ones, it automatically turns on or off the pumping equipment. Working according to this principle, the sensor not only protects the pumping equipment from “dry running”, but also ensures the constancy of the water flow parameters.
Among the advantages of operating pumping equipment on which a fluid flow sensor is installed, one can name:
- reduction in electricity consumption and, accordingly, reduction in the cost of its payment;
- minimizing the risk of failure of pumping equipment;
- increase the service life of pumping equipment.
Design features
The main tasks that water flow control sensors installed in domestic pipelines solve are to turn off pumping equipment at the moment when there is no liquid in the system or its flow pressure exceeds the standard value, and turn it on again when the pressure drops. The effective solution of these important tasks is ensured by the design of the sensor, which is formed by the following elements:
- a branch pipe through which water enters the sensor;
- a membrane constituting one of the walls of the inner chamber of the sensor;
- reed switch providing closing and opening of the pump power supply circuit;
- two springs of different diameters (the degree of their compression regulates the pressure of the fluid flow at which the water flow switch for the pump will operate).
The device of the above design works as follows:
- Entering the inner chamber of the sensor, the water flow exerts pressure on the membrane, displacing it.
- The magnetic element fixed on the reverse side of the membrane, when it is displaced, approaches the reed switch, which leads to the closure of its contacts and turning on the pump.
- If the pressure of the water flow passing through the sensor drops, then the membrane returns to its original position, the magnet moves away from the switch, its contacts open, respectively, the pumping unit is turned off.
In pipeline systems for various purposes, sensors that control the flow of water are installed quite simply. The main thing is to choose the right device, paying attention to its operating parameters and characteristics of pumping equipment.
Main characteristics
When choosing water flow sensors to equip the pipeline system, the following parameters should be taken into account:
- material for the manufacture of the body and internal elements;
- operating pressure for which the sensor is designed;
- the temperature range of the liquid for which the device will be used to control the flow;
- protection class and requirements for operating conditions;
- diameter of mounting holes and thread parameters in them.
Each of the above parameters affects the performance of water flow sensors, so it is worth considering them in more detail.
From what material the sensor body and its internal parts are made, the reliability of such a device, its ability to endure the loads that arise during operation, as well as its durability depend.
when choosing a fluid flow sensor, it is better to give preference to models for the manufacture of which various metals were used - stainless steel, brass or aluminum. During operation, both the body of the flow sensor and its internal elements experience significant pressure from the fluid passing through it. Only durable materials can withstand such a load for a long time. In addition, phenomena such as water hammer are not uncommon in pipelines, the consequences of which can quickly disable the sensor if inappropriate materials were used for its manufacture.
The value of the operating pressure at which the fluid flow sensor can operate correlates with the power of the pump used, so special attention should be paid to this parameter. In addition, this parameter also determines what characteristics the flow of liquid transported through the pipeline will have. Those models of water flow sensors, in the design of which two springs are provided, can control the operation of the pump according to the lower and upper pressure levels. It is better to give preference to devices of this particular type.
The temperature of the liquid for which the sensor is designed has a direct impact on the application in which applications it can be used. Naturally, when choosing such a sensor for equipping a heating or hot water supply system, one should pay attention only to those models that can work with water heated to a high temperature. For pipelines through which cold water is transported, flow sensors are used, designed to work with liquids having a temperature of 60–80 °.
The level of humidity and temperature conditions of the environment, under which the fluid flow sensor can be operated, are also important parameters. The protection class of such a device indicates what loads it is able to withstand when paired with pumping equipment.
Sensors that control the flow of water, as a rule, are chosen for ready-made pipeline systems or for those whose design has already been developed. That is why you should pay attention to the dimensions of the mounting holes: they must fully correspond to the dimensions of the pipeline elements on which the sensor is planned to be installed.
Connecting and adjusting the sensor
The efficiency of the sensor that controls the flow of water and controls the operation of pumping equipment largely depends on the correct installation of this device. It should be borne in mind that such a sensor, regardless of the type and purpose of the pipeline, can only be mounted on horizontal sections. In this case, it is necessary to control that the sensor membrane is located strictly in a vertical position.
When installing a liquid flow sensor, it is connected to the drain part of the pipeline using a threaded coupling. At the same time, the distance at which such a device should be located from the pipe itself cannot be less than 55 mm.
On the body of factory water flow sensors there is always an arrow that indicates in which direction the liquid should move through them. When installing the sensor on the pipeline, it is necessary to ensure that this arrow coincides with the direction of water movement. In the event that the sensor is installed in a system through which a heavily contaminated liquid is transported, filters must be placed in front of it for the correct operation of such a device.
Despite the fact that fluid flow sensors are supplied from manufacturing plants with already adjusted parameters, self-adjustment has to be performed periodically. For this, special bolts are provided in the design of the sensors. With the help of the latter, the degree of compression of the springs is increased or decreased, setting the level of pressure at which this device will operate.
So, to adjust the water flow sensor with your own hands, you must perform the following steps:
- drain the water from the pipeline system and make sure that the pressure has taken a zero value;
- turning on the pump, start filling the system with water;
- when the pump is turned off, which will occur on the signal of the sensor, fix the value of the liquid pressure;
- again draining the liquid from the system, fix the value of the pressure of its flow, at which the pump will turn on;
- after removing the sensor cover and using a special bolt, adjust the compression ratio of the large-diameter spring (this way you set the minimum pressure level at which the device will operate and the pump will turn on; it should be borne in mind that compression of such a spring increases the pressure level, and weakening reduces it);
- refilling the system with water and starting to drain it, check if the sensor is adjusted correctly and if it turns off the pump at the required pressure level (if the device is not adjusted correctly, the entire procedure described above should be repeated);
- by changing the compression ratio of a spring of small diameter, set the level of maximum pressure at which the pump will turn off (the difference between the sensor thresholds increases when such a spring is compressed and decreases when it is weakened);
- after adjusting the compression ratio of the small diameter spring, check the correctness of this procedure by starting to fill the system with water and fixing the pressure value at which the pump will turn off (if such an adjustment is not made correctly, it should also be repeated until the desired result is achieved).
In order for the pipeline system to function normally, experts recommend at least once a year to check the water flow sensors and, if necessary, adjust their operating parameters.
met-all.org
The main task of any water supply system is not only to provide water to the consumer, but also to implement its uninterrupted operation in automatic mode without breakdowns. For this purpose, the commonly used pressure switches and dry running, float devices for monitoring the liquid level are intended. These devices, in addition to automating the operation of the system, protect the pump from dry running and, as a result, from overheating and failure. The water flow switch for the pump is less known and common, but is also designed to automate the operation of the plumbing system and protect its main equipment from failure.
The flow switch is designed to monitor the flow of liquid in systems of cold and hot water supply, heating, cleaning and cooling installations.
Its main purpose is to protect electric pumps, motors and other devices from operation in the absence or small amount of water in the system, leading to overheating and equipment failure.
Fig.1 Appearance of the flow switch
The relays are designed for installation in a pipeline and allows you to automate the process of controlling the supply of liquids in domestic and industrial systems.
The water flow sensor for the pump is used in the following cases.
- If there is no hydraulic accumulator in the system. This does not allow you to install a pressure sensor designed to work in tandem with an expansion tank, it is better to use a flow sensor to protect the electric pump.
- In low pressure systems. The minimum threshold for triggering typical models of pressure sensors is 1 bar, that is, at a lower pressure in the system, the pump will always be turned off. Flow devices have a wider range of action, which can be expanded with adjustments. This allows the use of equipment protection devices in underpressure systems.
To adjust to work with a wide range of pressures, some petal models are equipped with petals of different sizes, providing different resistance to water flow. Sometimes notches are applied to the blade indicating the length. When installed, it is cut to obtain the required set pressure according to the table with various combinations of the length of the petal and the internal diameter of the pipeline.
Figure 2. Flow switch with adjustable blade length
- The vast majority of flow relays are designed to work in heating systems, so the temperature of their working fluid can be 100 C or more.
The principle of operation of the flow switch is based on the mechanical action of the water flow in the pipeline on the sensor that controls the electronic circuit for turning on and off the electric pump. Relays have a different principle of operation and, depending on the design of the sensor, are divided into several types.
One of the most common types, the main elements are a petal sensor with a magnet, located in the water flow and a reed switch, placed in the device body and reliably isolated.
Fig.3 Petal mechanical relay
When the water flow passes through the pipeline, the vertically located petal sensor rotates along its axis and deviates from the vertical position, bringing the built-in magnet closer to the reed switch. Its contacts inside the cylinder close and through the triac (double symmetrical thyristor) the pump is connected to the power source.
In the absence of water in the pipeline, the petal returns to its original position, moving the magnet away from the reed switch and thereby opening its contacts.
This leads to the termination of the supply voltage to the pump through the hemistor, as a result of which it turns off.
Fig. 4 External view of the relay with a reed switch and a sevenistor
Rotary sensors are mainly used to measure and control fluid flow. Structurally, they are made in the form of a paddle wheel rotating in a fluid flow, its rotation speed is recorded by sensor sensors. The electronic circuit allows analog, frequency or discrete control of equipment operation.
Fig.5 Rotary sensors
The piston is placed in the valve seat and, under the influence of water pressure, moves in a vertical direction to a height proportional to the flow force. The permanent magnet mounted on the piston approaches the reed switch and contacts are closed in it. Piston units can be installed in horizontal and vertical pipelines due to the built-in return spring that returns the piston to its original position in the absence of flow.
Rice. 6 Principle of operation and appearance of piston relays
Water flow switches, unlike pressure switches and dry running, float switches, are not so widely used for automatic control of electric water pumps in domestic water supply systems. This is due to the fact that they cannot work independently in the water intake system - to turn them on, it is necessary to create a flow of water and turn on the pump by other devices. Relays are designed to turn off electric pumps and are often built into electronic water supply control units in conjunction with other automation.
vizada.ru
1 Purpose and benefits
In everyday life, an emergency switching on of the pump without water occurs periodically, which is considered extremely dangerous, because this can cause equipment breakdown. Popularly referred to as "dry running" leads to overheating of the engine and deformation of parts.
Such negative changes occur because the water in the system performs a lubricating and cooling function. Operation in the "dry running" mode, even for a short time, adversely affects the equipment, whether it be a circulation pump or a submersible pump. To avoid such problems, the pumping station is equipped with automation - a water flow sensor. It will prevent negative changes in the system and avoid the cost of repairing the pump.
The water flow sensor is a device for controlling a pumping station in hot and cold water supply systems. In addition, this automatic device serves to increase the pressure and protect the pump, which is used in heating systems.
The principle of operation of the sensor is that it controls the power of the fluid flow and independently turns on or off the pumping station when the flow of water appears and passes through it. In this way, it is possible to prevent a possible "dry run", because a submersible or circulation pump drives the system and raises the pressure inside it only when required.
The installation of a water flow sensor entails a number of positive aspects in the operation of the pumping station:
- saving energy costs;
- reducing the risk of equipment failure;
- increase pump life.
1.1 Design and principle of operation
As it has already become clear, the built-in water flow sensor is used in the circulation systems of heating and water supply of private houses. His job is to stop the pumping station in the absence of a liquid flow, and prevent a “dry run”, and when water appears, put the equipment into action. The sensor received such working properties due to its design.
The device consists of a valve ("petal"), which is located in the flow part, and a reed switch. When water pressure occurs, the petal valve begins to move, squeezing the spring. At the same time, the magnet on the "petal" and the reed relay enter into interaction.
As a result, the contacts close, which drives the submersible or circulation pump. When there is no water and corresponding pressure in the system, the valve spring is released, moving the magnet to its original position - this causes the contacts to open and the equipment to stop.
The water flow sensor for a circulation or submersible pump is easy to install in an existing system, you just need to choose the right device, paying due attention to key parameters.
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1.2 Key Features
The purchase of a water flow sensor for a circulation pump should be approached in detail. We recommend that you focus on the following characteristics of the device:
- case material and working components;
- operating pressure;
- coolant temperature range;
- operating conditions and protection class;
- thread diameter.
To understand what effect each of these factors has on the operational features of the device, we will consider them in stages. The material of the housing and working components affect the reliability and durability of the sensor that is installed on the pump. It is desirable that the device is based on metals: stainless steel, aluminum or brass.
These materials are able to protect the working elements from a powerful flow of water and water hammer. Be sure to study the level of operating pressure at which the sensor is capable of functioning. For each circulation pump, this value will be individual, so you need to calculate the appropriate parameter in advance.
There are devices that provide two levels of pump control: by the lower pressure limit of the system to turn it on and by the upper pressure limit in the event of a cessation or an unacceptably low level of water flow to turn off the pumping station.
A sensor with the possibility of such programming is considered optimal. When choosing equipment for controlling the flow of water, it is impossible to neglect such a parameter as the temperature range of the coolant.
Conditions of use of devices may vary significantly. It is one thing if you have to mount the sensor in a heating system, where temperatures can reach 110 ° C, and quite another when the pump is used to turn on and supply cold water.
In the latter case, you can choose a device designed for a temperature range of 60-80 ° C. In order for the pump and the purchased sensor to remain operational for as long as possible, pay attention to the conditions under which the equipment should operate.
The instructions for the device must indicate the level of ambient temperature and the protection class. The last criterion determines the loads that the sensor installed in the pump can withstand.
To perform correct and accurate installation, you will have to pay attention not only to the permissible operating temperatures of the device, but also to the diameter of the connecting thread. Only with the correct and high-quality docking of the elements, it is possible to achieve the effective functioning of the sensor after its preliminary installation and switching on.
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1.3 About the device and characteristics (video)
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2 Adjustment and connection of the sensor
The flow sensor, which is used to monitor the water level and pressure in the system, should be adjusted immediately after purchase. The process is as follows: the device is shipped with the contacts open and the calibration screw tightened.
After the pump is turned on and the optimum water level is reached, the lamella moves in the direction of the liquid flow, which leads to the closing of the contacts. If the lamella does not start to move, this means that this level of water flow is not enough. In the case when the device does not respond, you need to set another value and do the operation again.
There are a number of rules that will facilitate the installation of the flow sensor, the main one being that the device must be installed on a horizontal pipeline, regardless of the temperature of the water moving inside. In this case, you need to ensure that the lamella is located vertically.
The distance between the pipe and the device should be carefully measured - the minimum allowable value is 55 mm. Using a threaded coupling, the sensor is connected to the drain pipeline, regardless of the water level inside.
The device must be oriented so that the arrows on its body correspond to the direction of water flow in the system. In the case of a high level of contamination of the coolant, a cleaning filter is mounted in front of the sensor.
byreniepro.ru
Features and Benefits of the Water Flow Sensor
Often there are situations in which the pump starts at the moment of complete absence of liquid in the pipeline. This provokes heating of the motor of the unit and its further breakdown. To avoid such situations, a fluid flow sensor should be used. This device works automatically and controls the flow of water inside the pipeline. If the amount of liquid passing through the sensor is less than the norm, the device automatically turns off the pump. Thus, the water flow switch not only prevents the pump from running dry, but also maintains normal operating conditions for the unit.
The benefits of using a sensor include:
- Reducing the electricity consumed by the pump and saving money;
- Protection of equipment from breakdowns;
- Extending the life of the pump.
Among other things, the water flow switch for the pump is distinguished by its modest dimensions, low cost and ease of installation.
Water flow switch - principle of operation and design
The main function of the sensor is to turn off the pumping equipment in the event of a drop in water level or an increase in pressure in the pipeline. If the amount of water increases or the pressure drops, the liquid flow indicator restarts the equipment. Its structural elements are responsible for the stable performance of the tasks assigned to the relay.
The device device consists of the following parts:
- A pipe through which liquid enters the device;
- A membrane that plays the role of one of the walls of the inner chamber of the device;
- Reed switch, which is responsible for opening and closing the circuit in the electrical circuit of the pump;
- Two springs of different diameters - by compressing them, the water pressure is controlled, at which the fluid flow sensor will be triggered.
The principle of operation of the relay is as follows:
- When it enters the internal chamber of the device, water exerts pressure on the membrane, thereby shifting it to the side;
- The magnet located on the back of the membrane gets closer to the reed switch, due to which its contacts close and the pump turns on;
- If the water level drops, then the membrane with the magnet moves away from the switch, which leads to the opening of its contacts and turning off the pump.
Installing a liquid flow detector in a pipeline is quite simple. To do this, you need to study the features of connecting the device and its correct configuration.
sadovij-pomoshnik.ru
Areas of use
In domestic conditions, water flow sensors have found their application mainly in devices that require constant monitoring of home life support systems and compliance with a certain mode of their operation. By controlling the water supply, motion sensors can significantly reduce the cost of maintaining a home, make life much more comfortable and safer.
For gas boiler
The main place of application of the water flow sensor in modern homes has become gas boilers. Equipped with such sensors, modern gas boilers combine the functions of a hot water heater and a heating boiler.
The water flow sensor installed on the tap water supply pipeline reacts to the beginning of the movement of water when the hot water tap is opened.
The sensor sends a signal to the boiler control board, and the electronics turns off the heating circulation pump, turns off the heating gas nozzles, and closes the water circulation valve in the heating system. And then the board turns on the nozzles for heating running water and the process of heating water begins in the heat exchanger. When the tap is closed, the sensor detects the stoppage of water movement, which is signaled to the control board.
for pump
Many modern households are equipped with autonomous water supply systems. Such systems allow you to have a level of comfort comparable to apartments in a private house, but at the same time not depend on a centralized water supply.
The system, consisting of a pump, a water tank and a control system, allows you to service all the systems necessary for a comfortable stay - automatic washing machines, dishwashers, use hot water and a toilet.
The role of the water flow sensor is that when any of the devices connected to the water supply system is turned on or water is taken, the sensor turns on the pump and the water supply automatically starts. It doesn't matter if the laundry starts, the tap in the kitchen opens or the toilet bowl goes down.
Another option for using water flow sensors is automatic irrigation systems. Here, in addition to the opening function, the flow sensor controls the amount of water used for irrigation. This function is necessary to control metered watering and avoid waterlogging of the soil. The sensor installed on the central pipeline provides information to the system control panel.
Kinds
Today, two types of water flow sensors have found the greatest application - a Hall sensor and a reed relay.
The flow water sensor, based on the principle of operation of the Hall sensor (it is also called a flow meter), is a small turbine on which a magnet is mounted. When the turbine rotates, the magnet creates a magnetic field and, like a turbine in a hydroelectric power plant, it generates small electrical impulses that go to the boiler control board. The speed of rotation of the turbine depends on the speed of the water supply, the greater the flow, the clearer the pulses. Thus, thanks to the Hall sensor, it is possible not only to signal the flow of water, but also the speed of the water supply.
The reed water flow sensor is a sensor based on the principles of a magnet. Basically, this sensor looks like this - inside the chamber made of composite material there is a magnetic float, with an increase in water pressure, the float moves around the chamber and acts on the reed switch.
The reed switch, and this is nothing more than two magnetic plates in a chamber without air, opens under the influence of the magnetic field of the float, and the control board switches the boiler to hot water mode.
Installation
Considering that most water flow sensors are structurally part of the devices, their installation is required only in case of replacement in case of failure. However, there are situations when the water flow sensor must be installed separately, for example, when it becomes necessary to increase the pressure of the water supply.
Indeed, situations often occur when there is insufficient pressure in the central water supply system, and in order to turn on the gas boiler in the hot water supply mode, it is necessary to create a good pressure. In this case, an additional circulation pump is installed, equipped with a water flow sensor.
In this case, the sensor is installed after the pump, so when the water begins to move, the sensor turns on the pump and the water pressure rises.
Overview of models and prices
Water flow sensor for pump Grundfos UPA 120
The main application is the automatic control of the pump of the water supply system. The sensor is designed to provide water supply to an individual house, apartment, equipped with an individual water supply system. Switching on the automatic sensor occurs with a steady flow of liquid in the range of 90-120 liters per hour.
The main purpose is to protect the pump from idling. The sensor is used with GRUNDFOS booster pumps of the UPA series. These units have small linear dimensions, which allows installation directly into the water supply line.
The use of a sensor allows the pump to operate in several operating modes, allowing both automatic switching on and switching on when necessary. The sensor automation turns off the pump in the event of an increase in pressure in the water supply to a normal value.
Characteristics:
- power consumption - up to 2.2 kW;
- degree of protection - IP 65;
- manufacturer - GRUNDFOS;
- country of origin - Romania, China;
The price is 30 dollars.
Water flow sensor of the GENYO series - LOWARA GENYO 8A
Products of a company specializing in the production of various electronic devices for control systems. The model is designed to control the domestic water supply system pump based on the actual water consumption. The main feature of the sensor is to control the pressure in the water supply during operation. The LOWARA GENYO 8A sensor is designed to start the pump when the water flow reaches 1.5-1.6 liters per minute.
Characteristics:
- the pump is started at a water flow rate of 1.5 liters per minute;
- operating voltage of the sensor - 220-240 V;
- current consumption frequency - 50-60 Hz;
- maximum current consumption - 8A;
- power consumption - up to 2.4 kW;
- operating temperature range - 5-60 degrees Celsius;
- degree of protection - IP 65;
- manufacturer - LOWARA ;
- country of origin - Poland;
The price is 32 dollars.
It is intended for installation in gas double-circuit coppers of the Immergas trademark. Compatible with models: Mini 24 3 E, Victrix 26, Major Eolo 24 4E | 284E. The flow sensor for hot water supply is designed for installation in gas boilers of the Immergas brand of chimney and turbocharged versions. The flow sensor is made in a plastic housing with a threaded connection. Hall sensor 1.028570 allows you to get water at the outlet of the hot water circuit with a stable temperature,
Price $41.