Dry-running sensor for pumping station connection. Protection against dry running of the pump: what are they, installation. How can you protect the pump from dry running?

The equipment installed in the water intake system is not cheap and requires professional installation skills. A prerequisite for smooth operation is well-organized protection borehole pump from dry running. The danger of working in dry mode lies in the complexity of diagnostics: the device will stop working only after failure. The cost of restoration is comparable to the price of a new device, and in the event of a malfunction due to improper operation, the equipment is not subject to warranty repair, the manufacturer must indicate the working environment in the instructions. For this reason, it is recommended to install special protective electrical devices on all types of borehole pumps.

Well protection should be comprehensive. It is necessary to take into account all the main factors that can make a device for pumping water unusable:

Water hammer: a sharp increase in inlet pressure. As a result of sharp fluctuations in pressure, mechanical damage to the elements of the housing and impeller occurs.
Suspended solid particles. Poor filtration is the reason for the ingress of small insoluble inclusions inside the device.
Dry running. The device works by pumping water. If, instead of water, air appears inside, the situation is fraught with overheating, deformation of parts, and a drop in power.

Consequences of dry running: damaged impeller

Causes of downhole pump breakdowns

Situations when the downhole equipment starts to operate in an abnormal mode can be caused by:

Incorrect calculation of power. The most common mistake is installing a powerful submersible device in a well with a low flow rate. The device quickly pumps out a large volume of liquid, and the water does not have time to fill the container.
Incorrect installation. If the pump is not installed at a sufficient depth, there is a risk of dry running at the slightest drop in level. If the device is too lowered, a situation may arise when the equipment sucks in sand together with the silted liquid, the opening at the inlet becomes clogged with dirt.
Seasonal change in production rate. Well pump protection will ensure correct operation in hot weather when the water level drops and it becomes necessary to adjust the power of the equipment.

Dry running: what is dangerous and how to cope with the problem

Why is dry running dangerous for equipment? The submersible pump models are designed to use water as a protection. Cold liquid cools inner surfaces mechanism, provides working pressure. In addition, for equipment used at depth, there is no way to organize a classical lubrication system for rubbing parts: this function is also performed by water. The result of even short-term dry operation is overheating, deformation of parts, engine combustion. To protect the equipment, it is necessary to install devices that instantly turn off the pump when the water supply stops.

How to choose the right mechanism for dry running protection

Dry-running protection of a borehole pump should be selected taking into account the type of equipment and the characteristics of the well. Manufacturers offer systems for wells, common centralized pipelines, wells of different depths. Also, experts recommend taking into account the performance of the source, the power of the pump. The choice can be significantly limited by the specifics of the well device: pipe diameter, location and type pumping equipment... It is definitely worth getting the advice of an experienced specialist before purchasing and installing.

Ready-made solutions with pressure sensors

Types of devices and features of their application

All electronic protection systems operate according to general principle: Switch off the pump if there is a risk of dry running or if there is a lack of water inside the device. After the water level has returned to normal, the equipment starts up as usual.

Types of devices:

Self-assembly or professional: is it possible to save

It is better if well protection is thought out and organized before the first start-up of the equipment. In this case, it is possible not only to prevent equipment malfunctions, but also to timely identify miscalculations during well construction and equipment installation.

The choice of a system that reliably protects an expensive device should be entrusted to a specialist. It is difficult to take into account all the criteria on your own. The wizard will help you determine the type of system that is optimal for your specific conditions.

It will not be possible to save on self-installation: the process requires preliminary calculations... Some systems provide for intervention in the design and power system of the device, so it is better if a qualified technician is engaged in the installation.

Video: how to protect the pump from dry running

Pump protection methods

In the "General" heading, we will consider ways to protect pumps from "dry running". "Dry running" is the operation of the pump without a flow of liquid, the most common reason failure centrifugal pumps... The problem, the operation of a pump without a fluid flow, is relevant to any type of centrifugal pump: surface, circulation, well borehole, fecal or drainage. During the operation of the pumping equipment, the pumped liquid performs the functions of "lubrication" of the working surfaces of the pump and their cooling. In the absence of a flow, even if the pump is filled with water, due to friction at revolutions asynchronous motor constituting 2850 - 2900 min -1 there is a rapid heating and boiling of the liquid. The working elements of the pump (diffusers, wheels) begin to heat up and deform. This primarily applies to pumps whose working elements are made of heat-resistant plastic - noril. The first signs that a pump has run dry is a decrease in head and flow performance. More severe consequences lead to seizure of the pump shaft and overheating of the stator windings (motor burned out). Plants manufacturers of pumping equipment in the instructions for installation and operation indicate an unacceptable mode of using pumps without a liquid flow. Which of the ways to protect the pumping equipment from operation in the "dry running" mode to choose, the buyer determines independently. To facilitate its choice, let us consider the most frequently used and used methods. And so, these include the following protection methods: float switch, pressure switch with dry-running protection function, pressure switch and dry-running protection relay, flow switch, level switch. Short review ways to protect centrifugal pumps.

Float switch

Protection of pumping equipment from "dry running" with help is one of the cheapest and most commonly used methods. The main advantage of this method of protecting and controlling pumps is that the float switches can simultaneously be used both as a water level sensor and as an actuator. They are installed in storage tanks, reservoirs, tanks, pits, wells and are used to control household and industrial pumps in water supply, sewerage and sewerage systems. The required actuation level of the float switch is determined by the length of the cable and the place of its installation. By changing the length of the arm, you can change the filling or emptying level of the tank. Several float switches can be installed in one tank, and they can perform various functions: control of the main or standby pump, control of an automatic pumping station, or be used as a level or overflow sensor. Some types of well, drainage and sewage pumps are available with built-in float switches. The pumps also have the ability to change the length of the float and thereby adjust the level of activation and deactivation of the pump. Float switches are of two types, light and heavy. Light ones are mainly used in water supply and sewerage systems, and heavy ones for drainage, fecal (sewage) drains. Float switches are sold with different cable lengths 2 - 5 - 10 meters depending on the model. The maximum switching current for reactive loads (pumps, fans, compressors, etc.) is 8A: For the float switch to function properly, the minimum diameter of the well must be at least 40 cm. For this reason, floats cannot be used as universal remedy to protect pumps from dry running.

Dry-running protection pressure switch

This is a conventional pressure switch with additional function protection against "dry running" when the pressure drops below the level set by the manufacturer. The pressure switch with dry running protection controls, according to the set pressure values, the switching on and off of the surface, borehole or well pumps when they are used in conjunction with or the operation of an automatic pumping station... The switch-off pressure of the relay in the "dry running" mode is usually 0.4 - 0.6 bar, this is factory setting and it cannot be changed. If the pressure in the water supply system changes within the settings set on the pressure switch, the pump works without interruptions. When the pressure at the outlet of the pump drops to a level of 0.4 - 0.6 bar, and this can happen when the pump starts to work in the absence of water. At this pressure, the relay switches off dry-running. To restart it in operation, you must first eliminate the cause of shutdown of the pump in the "dry running" mode. Then fill the pump with the pumped liquid. Then forcibly press the lever and turn on the pump.

Pressure switches PM - 5, PM - 12 and dry-running relay LP3

Pressure and dry running switches

Another one is joint applicationWith . The pressure switch controls, according to the set pressure values, the switching on and off of the surface, borehole or well pumps when they are used in conjunction with hydraulic accumulators or the operation of an automatic pumping station. The pressure switch is used to set autonomous system water supply at home or irrigation system under specific tasks... In this case, the LP 3 dry-running relay is used to protect a pump or an automatic pumping station from running in a dry-running mode. The dry running mode is controlled according to the preset pressure values on the relay. The LP3 relay switches off the pump when the pressure in the system is lower than the preset one. To start the device into operation, you must press and hold down the red button until the pressure in the water supply system rises higher than that set on the relay. The LP3 relay can also be used to protect pumping equipment from dry running when connected directly to the mains pipeline. The activation of the dry-running switch occurs when the pressure in the water supply system becomes higher than a preset value. When using a dry-running relay to control pumping equipment, the maximum switching current is 10A.

Pressure switch RM - 5, RM - 12 anddry-running relay Spin

Next method of protection of pumps from "dry running"- this is a combined application of the pressure switch RM-5 and RM-12 s. Turning on and off of surface, borehole, well pumps when they are used in conjunction with hydraulic accumulators, as well as automatic pumping stations occurs at the set pressure values. preset on the relay, When the maximum set pressure in the water supply system is reached, the relay is turned off, and when the pressure drops to the minimum set value, the relay is switched on. With the help of a pressure switch, an autonomous water supply system at home or an irrigation system is configured for specific tasks. Spin is used to protect pumping equipment from working without a liquid flow, or, more simply, from "dry running". The device turns off the pumping equipment in the event that water runs out in a tank, well or well, as well as after all taps are closed. When energized, the Spin relay starts the pump and keeps it running. When the water flow is completely stopped, the device starts a timer, which provides a delay in turning off the pump for a certain period of time, preset when setting up the device. After this time has elapsed, the pump is switched off. In the process of putting the equipment into operation, it is necessary to set the delay time for switching off the relay due to the absence of a liquid flow. The shutdown delay time depends on the volume of the accumulator and the type of pump used. The pump starts up when check valve with a magnet inside the device, it moves under the action of the water flow (when the water draw-off tap is opened), the magnet closes the reed switch contacts and the automation gives the command to turn on the pump. Electrical connection must be done in the following sequence: Socket → Pressure switch → Spin → Pump. The Spin relay has an automatic restart function (multiple attempts) that turns on the pump at regular intervals after going into dry running due to lack of fluid flow. After these attempts are made, the device finally goes into an accident. To put it into working mode, you must press the restart button. The maximum switching current is 12A.

Pressure and flow regulators

Unlike a pressure switch in its various combinations, where it is necessary in conjunction with pumping equipment in mandatory install a hydraulic accumulator, if you use pressure and flow regulators, the accumulator is not needed. When turned on, the regulator starts the pumping equipment in operation and maintains this state as long as there is water consumption. When water consumption is completely stopped, the pumping equipment is turned off due to the lack of fluid flow with a time delay. In the control circuit of the pressure and flow regulators there is: a magnetic relay (reed switch). Either a spring-loaded check valve or a float with permanent magnet, The flow of water displaces the check valve with a magnet, and the reed switch contacts are closed under the action of the magnet, thereby the electronics determines that the pump is pumping water to consumers. As soon as for some reason the pump stops supplying water, under the action of the spring, the check valve returns to its original state, and the float goes down, the reed switch contacts open, and after a delay, the pump turns off. The time delay is necessary to reduce the number of switching on and off the pump if the water consumption is very low. The pressure and flow controllers do not have an upper cut-off pressure limit. The pressure in the system is equal to the maximum pump head, and shutdown occurs only due to the lack of flow. When the pressure in the water supply system decreases to a value of 1.5 bar (in Brio and Flusstronic series 3 it is possible to change the lower switch-on value), the pumping equipment is switched on. The main advantage of the relay is its small size and weight. In the event of a temporary power outage, the devices start up the pumping equipment automatically after its supply. Due to the presence of a buffer tank, the possibility of water hammer is excluded when the pump is turned on and off.

Dry-running relay with level sensors

Dry-running relay

The "dry running" relay allows you to control the liquid level in the well and controls the power supply of the borehole pump to exclude its operation without liquid. Control required level liquid is carried out by an electric micro-current circuit "level sensor - pump body". On the front panel of the relay there are control and indication elements:

- LED “NETWORK” - signals the presence of supply voltage to the relay;

- LED "LEVEL" - signals the presence of water in the monitored pipeline (reservoir, well capacity);

- potentiometer for changing the value of the delay for switching off the relay in the absence of water (0.5 ... 12 sec.).

The principle of operation of the relay is as follows. When installing the pump in a well or in a tank, a level sensor is additionally mounted, which is connected to the relay using a single-core cable with a cross section of no more than 2.5 mm 2. The signal cable is attached to the cable or piping leading to the pump. The pump body is used as the second electrode. If the level sensor is immersed, then a microcurrent flows between it and the pump casing. In this case, the contacts for controlling the operation of the pump are closed, and the pump pumps water. In the case when the level sensor comes out of the water (the pump has pumped out the water), the microcurrent circuit is broken and the timer starts to count down the delay time set during the setting. The shutdown delay time is set using a potentiometer on the front panel of the dry-running relay. In the extreme left position - the delay will be minimal, in the extreme right - maximum. After this time has elapsed, the relay contacts that control the operation of the pump are disconnected. The pump turns on when the level sensor is again in the water. Dry-running relay can be used with single-phase borehole pumps low power(up to 1.5 kW, 11 A). If it is necessary to connect a more powerful single-phase pump, or a three-phase pump, it is necessary to use a magnetic starter or a contactor of the corresponding power.

There are a huge number of types of dry-running relays with level sensors. We have considered the simplest option, when one level sensor and pump body are used. There are circuits with two and three level sensors. The principle of their operation is similar to the one discussed above.

Is not complete list devices for protecting pumping equipment from the "dry running" mode, and we did not set ourselves the task of considering all existing ways and methods of protecting centrifugal pumps.

Thank you.

The workflow of water pumps is fraught with numerous structural threats. These include contamination, engine overheating, breakdowns due to faulty connections, etc. But even correct organization the operational process in accordance with the instructions does not guarantee the elimination of indirect threats. Lowering the level of the pumped water below the minimum value can lead to equally serious damage. To prevent this from happening, manufacturers recommend using a dry-running sensor for the pump, which detects the critical level of the working environment and decides to turn off the equipment.

General principle of operation of the device

Majority protective devices of this type are associated with control automation. The controller fixes the operating parameters for the subsequent correction of the supply volumes, switching on or off the unit. In this regard, dry or idle sensors act as only one of the signaling devices about the state of the working environment. Determination of water scarcity can be made different ways depending on the type of dry-running sensor used for the pump. The principle of operation of devices such as pressure gauges, for example, is based on fixing the pressure level. When the threshold level is reached, the detector sends a signal to the controller, which, in turn, automatically turns off the pumping equipment. Moreover, the sensor can continue to work as a pressure gauge. And when a sufficient pressure level is restored, it also resumes the pump function through the control controller. Again, the symptoms of water scarcity can vary.

Multifunctional relays are connected to several types of detectors, which increases the accuracy of determining the level of the served environment.

Dry running sensor classifications

The simplest systems of this kind provide protection based on the indications of mechanical alarms. These are models of float and flow-through type, which can be directly structurally related to the target equipment. For effective work even the introduction of automation is not necessary for such devices. Most often, mechanical protection is used for a borehole pump. In this case, the dry-running sensor should not even determine the critical level of lack of the pumped medium, but its approach to the place of intake. For instance, optimal height the water column for borehole pumps averages 150-200 cm, and a decrease to 100 cm will be a critical point. Automatic systems, as noted above, involve control by means of automation. The control relay stops supplying power and the equipment stops. But in both cases, the principles for determining the parameters of water supply may be different.

Float sensors

Such models are widely used in equipment that pumps water from wells, storage tanks or drainage systems. When the water level drops at the point of intake, a short circuit occurs and the sensor cuts off the power. This occurs in parallel with the lowering of the float detector connected to the contacts in the phases of the power supply system. When it comes to submersible systems, then the pump dry-running protection sensor is located above the protective grill of the branch pipe or the bottom valve. The device can be integrated as an option, or in the basic design it can be part of the pump.

Flow switches with pressure sensors

In this case, press control is implemented. The normal operating mode of the control system fixes temperature regime and pressure indicators. The second parameter is considered as a target value for determining the risks of idling. By default, the press control is set to a standard value of 1.5-2 atm. This is the threshold level at which the system turns on or off depending on the up or down dynamics. Of course, the user can adjust the dry running sensor for the pump to different peaks, taking into account the characteristics of the equipment and the conditions of the water supply in general. Some models of downhole units with such controllers do not provide for automatic activation. After stopping in the operating mode, they are entered only manually if the water level has risen to an acceptable level.

Level sensors

The principle of operation of electrical liquid level meters is the most common in the industry. Such devices are used to accurately control the level of technical environments in production tanks, and recently they have begun to be used in plumbing.

How does a dry running sensor work for this type of pump? The monitoring relay includes an electronic board and several electrodes. Sensitive elements are installed at different points of the tank, in which water is pumped out, and during operation they exchange signals with each other. Liquid acts as a conductor for currents of low frequency, therefore, the termination of communication will mean that there is no water at a sufficient level. When the signal is interrupted, the circuit is opened and the power supply is cut off.

What to consider when choosing a sensor?

In addition to determining the appropriate mode of operation for the device, it is important to consider the conditions in which it will be used. The control unit itself can be installed in a technical room. It doesn't have to be immersed in the work environment. But the sensor should be selected with an emphasis on temperature range and risks of physical damage. As for the first parameter, the optimal spectrum is from -1 to 40 ºС. In case of circulation pumps can be serviced and hot water, therefore, the upper temperature bar increases to 70-90 ºС. From a workflow point of view, the pressure range that a dry running sensor for a pump in a particular system can in principle be able to control will be important. This indicator on average varies from 0.5 to 3 atm, and some versions reach a maximum at 10 atm. The protection class is also taken into account. The optimal solution for home use will become a model marked with IP44.

Dry-running relay connection

Installation of control valves is performed at the stage of assembling the pumping structure. First of all, a check valve with a filter is mounted on the suction line, after which you can start integrating the protective relay. Again, the controller and sensors are located at different points. The main thing is that physically the moment of registration of the critical level is ahead of the start of idling.

The electrical connection of the dry running sensor for the pump is carried out in the following sequence with power supply from 200 V: socket - relay - pressure gauge - motor. Wiring loops usually operate with a current strength of the order of 10 A, while you should not forget about grounding and installing a stabilizing fuse.

Controller setup

The electrical circuit after installation will be an open two-pole relay. In this state, the pump cannot be started, since it will start operating at the same idle speed. Initially, the accumulator should be filled with water until the pressure reaches optimal level... During this technological period, the dry-running sensor for the pump should be activated. The principle of its action on this stage is configured for the service mode, in which idle operation is allowed, but without an alarm, followed by shutdown of the equipment. When the accumulator is able to maintain sufficient pressure, the relay with the sensor is transferred to normal operation. But before that, you should also set the threshold pressure value at which the electrical circuit will open again.

Pump controller manufacturers

High-tech relays with automation and the ability to prevent dry running are produced by Sturm, Elitech, Metabo, etc. The most successful developments are offered by direct pump manufacturers. For example, Grundfos is working on combining centralized control panels, which include water supply fittings and a multifunctional safety automation package. Domestic developers of controllers have also succeeded in this direction. The dry-running sensor of the Whirlwind 68/4/4 pump, for example, is distinguished by the support of a switching current of 12 A and a maximum pressure of 10 atm. Its features include a high protection class - IP65. Decent in price and quality offers are also produced by the companies "Belamos", "Dzhileks" and "Zubr".

When should you not use dry run protection?

The additional load in the form of sensors is far from always justifying itself. Obviously, pumping water from a lake, reservoir or pond does not involve dry running risks. Another thing is that a change in the position of the equipment itself can lead to a shift in the water intake level, but such problems should be solved by a more reliable installation. It is also not recommended to use a pump controller in high flow wells. The dry running sensor in this case simply will not work, wasting energy in vain. At least for wells and wells, a seasonal schedule can be set when the risks of sudden changes in water levels rise and fall. Accordingly, for these periods it is necessary to adjust the operating mode of the control equipment.

Finally

It is also not worth underestimating the consequences of idling for pumping equipment. For some models, long-term operation in this mode will make itself felt in the form of breakdowns of individual consumables, which can be replaced with minimal cost... But there are also whole groups of units that directly depend on water supply. In versions with rotary units, the pumped liquid can be used as a technical lubricant or as a cooling medium. Therefore, a dry running sensor for the pump can prevent very significant damage to the motor. For the same reason, manufacturers themselves in basic configurations increasingly provide for the presence of monitoring equipment. Moreover, refusal to use protective devices is a condition for the loss of warranty, since the instructions for operating the equipment are violated. These nuances should be taken into account even when developing a water intake scheme, assessing the connection possibilities of the most effective means control.

For long-term and trouble-free operation of the pump (pumping station), a prerequisite for operation is the availability of a sufficient amount of water. Regardless of where the intake comes from (well, well, open reservoir, centralized or drainage systems), pumping equipment must be equipped with protection against idle. This is due to the fact that water, when passing through the pump, provides its lubrication and cooling. In the absence of water or insufficient amount of water, the operating pump overheats and fails.

In order to exclude damage that does not fall under the manufacturer's warranty, a dry-running protection relay should be installed on the pump.

1 Causes of dry running

It is necessary to connect a dry-running relay to protect pumping equipment in the following cases:

when the productivity (power) of the borehole pump significantly exceeds the resource capabilities of self-healing of a sufficient volume of water in the well;
the natural water level in the source is well below the installation level of the pump;
there is constant clogging with sand, silt, foreign objects in the intake pipe or filter mesh;
the tightness of pipes and their connections from the physical effects of the soil or due to improper installation is broken;
the circulation pump operates at low water pressure or insufficient water in heating (cooling) systems;
water intake comes from a source to be filled - a well (well) that slowly restores the water level, storage tank, unstable water supply system.

Connecting the idle relay to the pumping station is a prerequisite, since it works in automatic mode without outside control.

2 Dry-running protection devices

The main devices that exclude the possibility of pumping equipment operating without water in automatic mode include:

dry running sensor for the pump;
dry running relay for the pump;
pressure switch;
float switch.

Under certain conditions, sensors and relays interrupt the power supply to the pump motor, which causes it to stop. Protection operation is determined by the following parameters:

water level;
pressure at the outlet;
by the strength of the flow of water.

Combined control of several parameters at the same time is possible.

2.1 Float sensor

Float-type dry-running sensors work effectively when installed in wells, drainage systems and storage tanks. The actuation process (power off) occurs when the water level in the source falls to a minimum value. When, together with the decreasing water, the float drops to the lower operating level, the contacts open on the pump power supply phase, which leads to its stopping.

The float sensor can be connected to submersible or surface pumps... In this case, its location should be above the bottom valve or the protective grill of the suction inlet with fixation of operation due to insufficient water level.

Installation of such a sensor is impossible when taking water from wells and centralized systems water supply.

2.2 Level switch

This device monitors the water level in the source (container). When the level drops to a critical value, a monitoring relay is activated to adjust the operation of the flow valves or turn off the pump.

The main advantage of this protection is that the power supply to the pump is cut off before it starts to idle.

The level switch consists of an electronic board and three electrodes (sensors), which are installed on different heights in close proximity to each other. The electrodes, when immersed, exchange low-frequency currents, since water is a good conductor of electricity. When the water level drops to the lowest control sensor, the electrical connection between the electrodes is interrupted, which triggers the relay to stop the pumping device. When the operating water level is restored, the pump switches on again.

2.3 Pressure switch

The principle of operation of the pressure switch is based on determining the sufficient pressure (from 1 bar) at the outlet of the device pumping water. If the pressure drops below 0.5 bar, the contacts are opened by means of a pressure switch.

When the pressure is restored, with a pressure sufficient for safe operation of the pump, manually fill the dry pump with water and turn it on yourself.

Pressure switches are used when installing domestic pumps connected to centralized water supply networks, water supply and fire extinguishing stations. Installation is recommended at pumping stations that work with a hydraulic accumulator (storage tank).

2.4 Flow sensor

The device is a petal valve that is installed in the flow path of the pump. The principle of its operation is to react to the strength of the flow (the passage of a certain volume of water in the pipe per unit of time).

The spring-loaded sensor petal, under the action of passing water, compresses the spring and, through the magnet attached to it, interacts with the reed switch. In this case, the contacts are connected, included in the pump power supply circuit. In the presence of high flow, the lobe sensor is constantly deflected and the pump motor runs.

Without liquid in the pipeline or its weak movement, the spring deflects the petal with the magnet to its original position, which leads to the opening of the contacts and stopping the pumping device.

The flow sensor has a compact size and low weight, which allows it to be used not only in industrial, but also in household devices.

3 Is it possible to do without dry-running protection?

In some cases, this is acceptable, provided that:

the pump does not work often and for a short time (seasonal water supply in the country);
constant control (observation) over the operation of the pumping device is carried out;
water intake comes from a guaranteed inexhaustible source;
the user has sufficient operating experience, is familiar with the structure and technical characteristics water supply device.

3.1 How to connect a dry-running relay to the pump? (video)

The operation of the water pump, which is part of the hydraulic water supply system, must be carried out under the conditions specified by the equipment manufacturer. It is customary to refer to undesirable extreme conditions as operation without liquid. A similar phenomenon it is usually called "dry running".

Operation specifics

Pumped water in home systems involves several parallel processes:

transportation of liquid to the consumer;
cooling of pumping equipment;
lubrication of elastic elements of the pump

The negative consequences of improper operation are especially noticeable in vibration equipment, which is most popular in household water supply circuits. The phenomenon for submersible, surface and drainage devices is also considered unacceptable.

If protection against dry running of the borehole pump is not provided, the result is the following:

moving elements warm up and increase the temperature of adjacent nodes;
most parts are subject to deformation;
in a certain situation, jamming occurs, which leads to the failure of the electrical part.

In the design of the pumping station, it is necessary to carry out the installation of protection in a timely manner, since the consequences of "dry running" are not repaired under warranty, the work will have to be carried out at their own expense.

When checking the condition of the failed equipment, it will not be difficult for a specialist to determine the cause of this condition. It is evidenced by the characteristic deformation signs of structural elements. In the instructions for the equipment, the manufacturer clearly indicates the inadmissibility of operating the pumps in the absence of liquid poured into the working cavities.

Suspected "culprits" of the breakdown

There are several common causes that lead to extreme pump performance:

Unbalanced pump power. In such a situation, fluid is quickly pumped out due to insufficient well flow rate or for pumps in which the intake part is located above the dynamic level.
The connection diagram has a section of the intake pipe, in which there is a depressurization. Air will pass through the hole.
The pumping pipe is clogged, which is often the case with surface pump models.
The hydraulics work under reduced pressure.
When pumping liquid from any container, it is necessary to avoid air entrapment.

Without installed automatic systems, it is quite problematic to cope with the prevention of dry running.

VIDEO: Disassembly, revision and cleaning submersible pump"Aquarius"

What is dry-running protection for a pumping station

One of the main factors in obtaining a reliable circuit is the installation of automation. Such equipment includes the following components:

dry running sensor for the pump;
dry running relay for stations or pumps;
pressure switch;
float switch.

Float switch-off

One of the universal bollards is a dry-running float sensor for submersible pump... This chain element is a relatively inexpensive aid to protect hydraulic equipment. Due to the ease of installation, this dry running sensor for the pump is used in many schemes, for example, when pumping out from classical wells or some containers.

A dry-running sensor for a submersible pump is connected to the electrical circuit for one of the power phases. A special contact inside the device will break the connection at a certain position of the float body. This will stop pumping in a timely manner. The actuation height is set when adjusting the float installation location. The cable that connects the dry-running sensor for the pump is set at a certain level so that during the lowering of the float an absolutely complete withdrawal of liquid does not occur. Should stay a certain amount of liquid at the moment of opening the contacts.

During water withdrawal by surface or submersible units, the sensor is mounted so that even after the contact is broken, the liquid level is still higher than the intake grill or valve.

The disadvantage of the float is zero versatility - you cannot install it in a narrow shaft.

In such a situation, it is necessary to look for other methods by which protection against dry running of the borehole pump will be carried out.

Water pressure switch

The dry running protection relay used is structurally electrical, which makes it possible to break the contact in the circuit at a critical drop in pressure and, accordingly, the water level in the source. The manufacturer sets the initial minimum value. It usually varies in the range of 0.5-0.7 atmospheres.

Dry-running pressure switch

The vast majority of dry-running relay models for household needs self-adjustment does not provide a threshold value.

Under normal operating conditions of the pumping station, the pressure in the system always exceeds one atmosphere. The underestimation of the indicator indicates only one thing - air has entered the intake pipe. The automation immediately breaks the contact feeding the pump, preventing the current from flowing through the cable. Start after a break is carried out exclusively in manual mode, which is an additional protection.

The use of such a relay makes sense if certain conditions are met:

the presence of a closed water supply system;
mounted hydraulic tank;
use of a pumping station with a surface or submersible pump.

The principle of operation of this relay is relevant for systems with deep pumps.

Water flow sensor

The circuits use special dry-running sensors that record the speed of the water passed by the pump. The sensor is designed with a valve (petal) located on the duct section and a reed switch microswitch. There is a magnet on one side of the spring loaded valve.

The algorithm used by this sensor is as follows:

water pushes the valve;
due to the push, the spring is compressed;
the contacts are closed and the equipment starts to work.

As soon as the flow weakens or completely ends, the pressure on the valve stops, respectively, the spring weakens, the magnet moves away from the switch and the contact is broken. The pump stops. When water appears, the entire cycle is repeated automatically.

This sensor is built into low power hydraulic equipment. Its job is to balance two quantities: flow and pressure level. Positive qualities are the following characteristics:

compact dimensions;
ease of installation;
quick response to disconnection.

The fast response speed ensures that the power is cut off in a timely manner, which reduces the risk of waterless operation.

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If it is necessary to install universal protection, experts recommend using the device for emergency modes of mini AKN. It is based on the electronic protection of self-priming equipment, which reacts to the set parameters.

The advantages of the device are:

minimum power consumption;
small parameters;
comprehensive protection against extreme modes;
high degree of reliability;
ease of installation.

Work without installed protection

In certain cases, you can do without the installation of additional protective assemblies. This is possible in the following situations:

the selection of liquid is carried out from a source in which there is always water;
direct visual control of the liquid level is carried out;
high rate of debit in the well.

If you hear that the unit starts to stop, or rather "choke", it must be disconnected from the network yourself. It is not recommended to restart the hydraulics without checking.

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