A pump that pumps well or well water performs its functions correctly only in the presence of a working environment. If there is no water to reduce the frictional force and cooling, due to idle operation, the parts of the device will quickly wear out. The control of the presence of liquid is carried out using dry-running protection devices.
Danger of dry running
If there is no working environment:
- The parts heat up, grow in size and transfer thermal expansion to the nearest nodes through metal joints.
- Gradually, the elements inside the pump are deformed.
- The unit "wedges" due to the transformation of the internal parts, which causes a voltage surge.
- The windings burn out in the electric motor, which finally disables the pump.
Drainage of submersible pumping equipment occurs when the productivity of a deep source is low. If the water intake is large, the well will empty quickly. It will take time for the reservoir to fill up again. The reason for the dry running of the surface pump is the clogging of the pipe through which the pumping is going. If the water intake is carried out from the city-wide network, the water may run out due to a break in the main line or technical work on the water supply branches.
Any type of borehole pump for long-term operation requires a special device that turns off the pump in the absence of the required volume of fluid.
Devices for effective protection of pumping equipment
The principle of operation of all types of dry running relays for a borehole pump is similar. A safety device switches off the pump if there is a risk of idle operation or a lack of liquid inside the pressure unit is detected. After bringing the water level back to normal, the pump equipment starts up in standard mode.
However, each type of device has its own characteristics:
| Category | Device | Structure | Operating principle | Features of the |
Water level sensors | Float switch | A group of contacts is located inside the camera - "float". The device wire is built into the electric circuit of the pump. | When the water level drops, the contacts open, no current flows to the pump, and the unit shuts down. When the amount of liquid increases to the required criteria, the contacts are closed and the pump is connected. | Simple and inexpensive equipment, but limited in use for narrow wells due to the volume of the chamber. |
| Water level control sensor | Consists of two meters lowered to different depths. | The first sensor is immersed to the minimum at which the pump will work. The other drops a little lower. If they stop contacting, the power supply circuit is opened. | The device turns off the pumping equipment even before the body rises above the water surface. Versatile design, but requires professional customization. |
| Protection relay | Includes membrane, contact group, multiple wires. | When the pressure drops, the diaphragm clamps the contacts, the power supply circuit opens. | Able to work when the pressure drops from 0.6 to 0.1 atmosphere. | |
Flow relays | Petal | The line contains a flexible plate - a petal. | If the liquid does not enter the pressure unit, the petal deviates from the initial position, the contacts diverge and cut off the power supply. | Ideal for pressure equipment used to maintain pressure inside the pipe during active drawdown. |
| Turbine | Equipped with an electric magnet in the rotor. | When water passes through the turbine, an electromagnetic field is generated, the pulses of which are read by sensors. If there is no signal, the pump is turned off. | ||
| Flow controllers | An electronic device with a complex circuit, connected directly or through a transformer. | Automatically monitors several parameters of the aqueous medium at once, gives a signal to stop the supply of liquid, independently connects and disconnects the pump. | Reliable devices, equipped with check valves, but not cheap. | |
There are combined controllers. Also, protection of a submersible pump against dry running can be carried out using frequency converters. But such options do not apply to the home water supply network: they are unnecessarily expensive, cumbersome and energy-intensive.
Criterias of choice
Before purchasing the device, carefully study the passport of the dry running sensor and make sure that by design parameters it is suitable for your downhole pump.
Place an emphasis on whether the body of the device is protected from water penetration. Only such devices are allowed to be mounted on deep pumps.
Check that all electrical wiring and parts of the future circuits are sufficient for the applied power. Otherwise, there is a danger of burnout of the sensor or adapter.
Connection features
- the well is deep;
- professional maintenance of pressure equipment is carried out;
- the water level in the system does not change.
In all other cases, a device connection is required. Simple mechanical and electromechanical devices can be embedded independently. For installation, you will need the protection device itself, a suitable cable, tools for working with electrical wires and keys for mounting on a pipe, as well as sealants and seals.
The relay is mounted before the first start of the water supply network. This allows problems to be anticipated and faults identified. To make a mechanical connection, you need skills in working with shaped elements. You will need to thread and seal the structure with flax fiber or fum tape. The device is cut into the pipe using an adjustable wrench. Then the electrical part is connected. The conductors on the relay must correspond to the indicators of the pressure unit.
The safety device must not be connected before the water meter, otherwise it will not work properly.
Pressure control sensors are mounted with open contacts. To start the device, press and hold the red button until the pressure level reaches the required value. If the number of atmospheres is not enough, the device will be turned off.
To connect the water flow switch, it is required to place them in series in the electrical network together with the pressure equipment. When the pressure drops, the dry-running protection activates, opening the energy circuit.
Even a perfect protective device will be useless if you don't learn how to use it. If any sensor is triggered, do not restart your pump until you know what the problem is and fix it. Each sensor requires regular calibration. In order for the system to work effectively, it is necessary to replace the elements that have expired in time.
