Protecting the pump from dry running: methods, features, step-by-step instructions and reviews. Dry-running protection: selection, connection, configuration, principle of operation Which dry-running relay for the pump is better

“Dry running” is a pump operating mode during which no water is pumped through the pump. This mode is extremely undesirable and emergency; it reduces the service life of the pump. The water pumped by the pump is both a lubricant and a coolant. Without it, the pump overheats, when long work in the “dry running” mode, the working elements of the pump can be deformed and the motor can burn out. To ensure long and reliable operation of the pump and all water supply systems in general, this should not be allowed. To protect the pump from dry running, automation is used: dry running sensors, dry running relays, float sensors, etc. They will turn off the pump when running dry.

Causes of dry running

The very first and most obvious reason is the lack of water. It doesn’t matter where the water is pumped from - a tank, a reservoir, a well, the water may run out, or its level will be lower than the position of the submersible pump (or the surface suction pipe). In the case of a well, this situation may mean that the pump itself is incorrectly selected and its productivity is greater, or its location is incorrectly chosen - it is located higher.

Other cases of dry running are typical for surface pumps: the water suction pipe may become clogged and water will stop flowing in the required quantity, or the tightness of this pipe may be broken, air will leak in and enter the pump.

For pumps that are connected to the water supply network (for example, in gardens or villages) to increase the water pressure in the home water supply network, dry running can occur not only when there is a complete absence of water in the centralized water supply system, but also when the pressure in it is low.

Thus, dry running has similar causes in all cases and is associated with a complete or partial absence of water and air entering the pump. In the very simple case When the pump is used only to supply water from a well or a well and there is a person nearby when it is operating, there is no need for protection against dry running. There is also no need for it if pumping occurs from a known inexhaustible source, for example from a lake. But if you have an automated plumbing system, such protection is necessary.

Dry running protection for the pump

To protect against dry running, sensors and relays are used that turn off the power either immediately after dry running occurs, or in advance. Dry running is detected by determining one of three quantities:

water level
pressure at the pump outlet
water flow through pump

Float sensors and level switches work by monitoring the water level. located above the submersible pump (or above the suction pipe surface pump) and when the water level drops below it, it opens electrical circuit turning off the pump. Restarting the pump after the water level has been restored is most often done manually. A pressure switch is a more advanced tool that has two sensors located at the minimum and maximum water levels. When the water level drops below the minimum, the pump is turned off, and when it is restored to the maximum, the pump is turned on again (if necessary). The advantage of such devices is that they turn off the pump before it runs dry.

The second approach is to measure the pressure at the pump outlet. It is logical that if the pressure there drops below critical (usually considered 0.5 bar or less), then the pump has stopped pumping water and needs to be turned off.

And finally, the third option is to measure the water flow through the pump using a flow sensor. As soon as the flow rate drops below a critical level, the power to the pump is turned off.

The last two methods involve short-term operation of the pump in dry running mode: first dry running occurs, then the sensor detects this and turns off the pump. This can be considered a disadvantage, although in order for the pump to be damaged and fail in dry running mode, it must operate for several minutes (or even tens of minutes).

Protection of the pump from dry running is necessary in water supply systems of country houses, but most often it is not used on its own, but in combination with other automation devices, the installation methods of which depend on the water supply system, the availability

The equipment installed in the water intake system is not cheap and requires professional installation skills. A prerequisite for uninterrupted operation is well-organized protection. well pump from dry running. The danger of working in dry mode lies in the difficulty of diagnosis: 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 well pumps.

Well protection must be comprehensive. It is necessary to take into account all the main factors that can render the water pumping device unusable:

Water hammer: a sharp increase in inlet pressure. As a result of sharp pressure fluctuations, mechanical damage housing elements, impeller.
Suspensions of solid particles. Poor filtration is the reason why small insoluble impurities get inside the device.
Dry run. The device works by pumping water. If air appears inside instead of water, the situation is fraught with overheating, deformation of parts, and loss of power.

Consequences of dry running: damaged impeller

Causes of breakdowns of well pumps

Situations when downhole equipment begins to operate abnormally can be caused by:

Incorrect power calculation. The most common mistake is installing a powerful submersible device in a well with 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 installed at an insufficient depth, there is a risk of dry running at the slightest drop in level. If the device is lowered excessively, a situation may arise when the equipment sucks in sand along with silted liquid, and the inlet hole becomes clogged with dirt.
Seasonal change in flow rate. Protection of well pumps 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 deal with the problem

Why is dry running dangerous for equipment? Model design submersible pumps provides for the use of water as a means of protection. Cold liquid cools internal surfaces mechanism, provides operating pressure. In addition, for equipment used at depth, it is not possible to organize classical system lubricating rubbing parts: water also performs this function. The result of even short-term operation in dry mode is overheating, deformation of parts, and engine combustion. To protect the equipment, it is necessary to install devices that immediately turn off the pump when the water supply stops.

How to choose the right mechanism to protect against dry running

Protection of a well pump from dry running must be selected taking into account the type of equipment and characteristics of the well. Manufacturers offer systems for wells, general centralized pipelines, and wells of different depths. Experts also recommend taking into account the performance of the source and the power of the pump. The specifics of the well design can significantly limit the choice: pipe diameter, location and type pumping equipment. It is definitely worth getting advice from an experienced specialist before purchasing and installing.

Ready solutions with pressure sensors

Types of devices and features of their application

All electronic protection systems operate according to general principle: turn off the pump if there is a danger of dry running or if a lack of water is detected inside the device. After the water level normalizes, the equipment starts up as usual.

Device types:

Self-installation or professional installation: is it possible to save money?

It is better if the 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 promptly identify mistakes during well construction and equipment installation.

The choice of a system that will reliably protect 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 specific conditions.

You won't be able to save on self-installation: the process requires preliminary calculations. Some systems involve intervention in the design and power supply system of the device, so it is better if the installation is carried out by a qualified specialist.

Video: how to protect the pump from dry running

When setting up your water supply, any owner should think about additional protection. In addition, it is not only the well or well itself that needs to be prevented from malfunctions, but also the equipment that performs the work: the so-called drainage systems and external pumps.

To avoid work Grundfos pump In the order of dry running, specialized devices are installed on water pipelines, which, first of all, should be chosen correctly.

Dry pump running - what is it?

No matter where the pump pumps water from, sometimes a situation arises when the water runs out. If the well's flow rate is small, you can simply pump out all the water. If water is pumped from a central water supply, its supply can easily be interrupted. The operation of a Grundfos pump in the absence of water will be called dry running. Sometimes the word " idling", but this is not entirely correct.

What's wrong with dry running, other than wasting energy? If the pump operates without water, it will overheat and then burn out - the pumped water is used to cool it. Therefore, protecting pumps from dry running is one of the elements of automation that will need to be purchased. There are, however, modifications with integrated protection, however, they are not cheap. It is more economical to buy an automatic one.

How can you reliably protect the pump?

There are several different devices that will turn off the pump if there is no water.:

All these pumping devices are designed for one thing - turn off the unit without water. They just function differently and have different areas of use. Next we'll look into distinctive features their work and when they are most effective.

Dry running protection relay

Pump relay to protect the unit from dry running - a simple electromechanical device that monitors the presence of pressure in the system. The price for it is reasonable. As soon as the pressure drops below the threshold, the supply line breaks and the pump stops working.

The relay consists of a membrane that reacts to pressure and a contact group that is normally open. When the pressure decreases, the membrane presses on the contacts, they close, turning off the power.

The pressure to which the device reacts - from 0.1 atm. up to 0.6 atm. (depending on factory settings). A similar situation is likely if there is not enough water or there is none at all, the filter is dirty, the suction part is very high. In each case, this is a dry running situation and the pump needs to be turned off, which is what happens.

A protective relay against dry running is installed on the surface with a connection, although there are modifications in a sealed housing. Naturally, it functions in an irrigation scheme or any other system without a hydraulic accumulator. It works most productively with shallow pumps if the opposite valve is installed after the pump itself.

You can install it on a system with GA However, you will not get 100% protection of the unit from dry running. There is a problem with the quality of the structure and operation of such a system. A safety relay is installed in front of the water pressure switch itself, as well as the built-in hydraulic accumulator. In this case, between this pump and the protection there is, as a rule, check valve, in this case, there is also a membrane that is under pressure generated by the accumulator. This is a common scheme, however, with this method of administration it is possible that a functioning pump without water will eventually not turn off and burn out.

For example, a dry running situation has been created: the pump is connected, there is no water in the well, there is a certain number in the hydraulic accumulator. Since the lower pressure limit is usually set at about 1.4-1.6 atm, the safety relay membrane will not turn on - there is pressure in the system. In this state, the membrane is pressed out, and the pump will operate dry. Will it stall or in this case if it burns out? When most of the water supply is used up from the accumulator, a breakdown may occur. Only in this case will the pressure drop to the limit and the relay can have an effect.

If such a situation arose during a period of intensive use of water, nothing terrible will happen in principle - a certain number of tens of liters will quickly dry up and everything will be normal. However, if this happened at night- they flushed the water in the tank, washed their hands and went to rest. The pump is connected, but there is no signal to turn off. By the morning, when water is drawn in, the unit will be inoperative. That is why in systems with hydraulic accumulators or pumping stations it is more correct to use other dry-running protection devices.

Water flow sensor

To measure the flow of water passing through the pump, a submersible flow sensor with a connection was created. The price for it in Moscow is affordable. The downhole regulator consists of a valve (“petal”) located in the flow part and a microswitch. The petal is spring loaded and has an integrated magnet on one side.

Working diagram pump sensor Dry running protection is as follows:

Pumping immersion sensor the flow is built into boosting stations with low productivity. Functions in establishing two values of degree of pressure and flow. The device stands out for its compact dimensions (light weight and size).

At a pressure level whose range is 1.5-2.5 bar (depending on the modification of the automation) in the pump there is a command to start its work. The pump performs its own functions until the water intake stops. Due to the flow meter integrated into the relay, the pump stops working. The downhole regulator very quickly detects the occurrence of a “dry run”, which makes it possible to eliminate a long stay in the operating “waterless” mode.

Situations when it is permissible not to use protective devices

It is possible to do without installing a downhole dry running sensor only in certain cases:

continuously monitoring the water supply from a well or borehole (you will need to be close in order to respond in a timely manner to changes in the water flow);
pumping is carried out from an inexhaustible source;
the well has a high flow rate;
person checking work Grundfos station, has experience, understands the operating principle of the pump system.

If the pump’s condition has become intermittent or it has switched off completely, it cannot be restarted without identifying and eliminating the fault factors.

Which safety device should I choose?

The choice of a dry-running protective device is determined by modification of the pump itself and problems, which he needs to cope with. A suitable type is when a dry running sensor is used in the form of a float and protective relay pressure. Connecting these devices to the pipeline will make it possible to absolutely reduce the risks of pump equipment malfunction.

The use of safety elements is not necessary if:

the depth of the well or tank is quite large;
servicing of the unit is carried out by an experienced specialist;
The water level of the system does not change - there is no point in connecting with protective devices.

The operation of the Grundfos pump requires high user attention. As soon as the water disappears or the relay operates and the engine turns off, you must immediately find out the root cause and eliminate it, and only after this is it possible to resume operation of the unit.

Modern pumping stations Quite often they are equipped with either full protection against dry running, or at least protection against engine overheating. The benefit of having such elements in the design is obvious: where necessary, protection can prevent pump failure.

But the presence of protective modules makes the design more expensive. That is why it is worth considering in advance how important protection against “dry running” is for you, and whether it is worth spending money on a more expensive station - such as.

Having a device that will turn off the pump when water stops flowing into the system is highly desirable in the following cases:

The pump is used to increase pressure by inserting a pumping station into the network water supply. This is done quite often, and in order to insure equipment in case of a water supply outage, protection is installed.
The station is used to draw water from the reservoir. Here, the relevance of protection against “dry running” is obvious: as soon as the container is emptied, the pump will begin to “grab” air, and if it is not turned off in advance, it will quickly fail.
As a source autonomous water supply a well or a well with low flow rate is used. Here, too, there is a risk that the hose used for sampling will be above the water level, and this will lead to breakdown.

The last case is relevant for almost all private households. IN summer time The water level is already falling, but it is further reduced due to intensive selection for irrigation. So a pumping station that pumps water out of a well or shallow well must be carefully protected.

Methods for implementing protection

Dry running protection can be implemented in different ways. Here are the most common schemes.

Float switches

A float is the simplest device that is used when equipping autonomous water supply systems based on tanks or wells:

The float is fixed in such a way that the system is activated when the water is slightly above the level of the intake pipe.
When the water level drops, the float opens the contacts.
When the contacts open, the phase supplying the pump is broken and the pump stops working.

Pressure/flow switch

Another device (example -), which is equipped with many pumping stations. It works quite simply:

The manufacturer sets a certain pressure level at which the switch is triggered. Typically this value does not exceed 0.5–0.6 bar and cannot be changed by the pump owner.
As soon as the pressure in the system drops below this level (and this does not happen even with intensive simultaneous water withdrawal), the relay registers “dry running” and the pump is de-energized.

Note! Restart must be carried out manually, after eliminating the cause of the relay operation and filling the system with water.

A prerequisite for efficient work The pressure switch is the presence of a hydraulic accumulator. However, automatic alluvial stations are equipped initially.

If there is no hydraulic accumulator, then instead of a pressure switch you can use a compact flow switch. But it works on a similar principle, but turns off the system when water stops flowing through the device. The response time of such devices is short, so the pump receives effective protection.

Level relay

If the water source is a well, then a level switch can be used to protect the pump from “dry running”:

A relay is a board to which electrodes are connected (usually two working and one control).
The electrodes are lowered into the well and fixed so that the control one is located just above the installation level of the well pump.
As soon as the water level in the well drops, the control sensor is triggered and the pump is turned off. After the water level rises, the system is automatically started by a relay signal.

Reliable operation of any devices is possible only if the conditions set by the manufacturer are met. It is especially important to adhere to this rule for those who work with devices that use mechanical components, for example, pumps. It is not advisable to operate most of them “dry”. Such expensive industrial and household equipment must have protection against dry running.

Dry running sensors

Reasons for installing protection

When it happens correct operation pump, then water flows through its cavity in a continuous flow. It performs several important functions simultaneously:

the rubbing surfaces are lubricated, and the force to be overcome is reduced;
During friction, heating occurs; heat is picked up by water flows and carried away from the friction area.

Excessive overheating without a pump dry-running protection relay leads to rapid wear and tear of the mating surfaces. The resulting heat during prolonged operation can deform working parts, sometimes irrevocably. The electric motor also receives excess heat, and if it is significantly overheated or there is no dry-running protection relay for the pump, it can burn out.

Hydraulic equipment with faulty dry-running protection sensors should not be allowed to operate.

Design features

Let's take a closer look at the dry running sensor for the pump and its operating principle. The dry-running protection relay is a block with several springs. It limits the operation of the entire device.

Everything is adjustable with a few nuts. The pressure force from the water is measured using a membrane. It either weakens the spring at low force or counteracts its resistance at high load. The principle of operation of the dry-running relay comes down to a power load on a spring, which is capable of opening the contacts that supply voltage to the pump.

This protection against dry running of the pump during pressure reduction to the minimum indicated by the built-in algorithm closes the electrical circuit. With this action, the voltage on the electric motor decreases, and it automatically turns off itself. The pump remains sensitive to pressure increases. As soon as this works, the dry-running relay, according to its operating principle, will open the circuit and re-apply voltage to the motor.

You need to know that in most cases the relay on/off interval is from one to nine atmospheres.

Water level switch

Often pumps come with a factory setting of a minimum of 1.2 atm and a maximum of 2.9 atm, when they are completely turned off, without waiting for a drop to 1 atm.

Making adjustments

The direct mutual influence between the following quantities is derived:

setting the pressure on the relay;
hydraulic accumulator volume;
water pressure.

When starting adjustment work, it is necessary to check the pressure level in the hydraulic accumulator.

The unit must be disconnected from the power supply and wait a few minutes for complete discharge capacitors. Water must be removed from the accumulator cavity. We also remove the cover on it and measure the readings on the pressure gauge, which should be about 1.4-1.6 atm. If necessary, increase the air pressure.

VIDEO: Automation for protecting pumps from dry running

Carrying out setup

The dry-running relay for the pump must be adjusted under pressure while the system is running. It is worth starting the pump first to pump the level up to desired value. The system will automatically turn off the power supply, as the relay will operate.

Adjustment work is carried out with a pair of screws located under the cover of the machine. To clarify the operation limits, you must perform the following steps:

record the switching pressure;
unplug the pump cable from the power supply;
remove the sensor cover and slightly loosen the clamping nut of the smaller spring;
the desired pressure parameter is adjusted by tightening/loosening the spring marked “P”;
then open the tap, relieving pressure, and monitor the start of the electric motor;
record the readings on the pressure gauge, repeat the operation several times and display the most optimal values pressure empirically.

During adjustment work, it will be necessary to take into account the physical capabilities of the pump. Given the rated value with all the losses, there may be a manufacturer’s limit of 3.5 bar, so we must go to 3.0 bar so that the pump does not burn out from overload.

High-quality protection against dry running

Operating a pump without water is the most common cause breakdown of this equipment with normal power supply. A popular material for the manufacture of pumps is thermoplastic, which can withstand long-term use and is affordable.

During load without water, the rubbing surfaces warm up. This happens more strongly the more the device operates without liquid. A natural consequence of heating is plastic deformation, and almost immediately the motor jams and burns out from overload.

There are certain risk areas that are more likely to run dry:

wells or wells with low water flow. The reason may also be excessive power of the device, which does not correspond to the liquid flow. During dry periods, the inflow per unit time also decreases at most sources;
large containers serving as reserve collection tanks process water. Care must be taken to ensure that the pump does not operate in an empty cavity without liquid;
network pipeline with an embedded pump to equalize the pressure in the system. During the dry season, there may be interruptions in water supply, leading to a drop in pressure.

External elements for protection

The following external elements are used as protection against dry running:

Float switch

The element relates to budget decisions. It is used to pump water from accessible containers. It only protects against overflow.

Pressure switch

Many devices have a contact opening when pressure thresholds are reached. Most of them have a low shutdown level and adjustment is not available in many models.

Flow switch with functions

If there is no water pumping through the relay, automatic shutdown power supply A small delay does not have a significant effect on the result.

Before purchasing additional protections, you should carefully read their threshold values.

VIDEO: How to protect the pump from dry running