In domestic pumps, the main material of the impellers is thermoplastic (plastic, which is durable). It is characterized by great potential of work and low cost. The material has served its purpose well for many years. But if it works without water, which acts as a lubricant and a source of heat removal, then the internal components of the pump are deformed. In the most extreme cases, the shaft may jam and the motor may fail. Usually, after this, the pump cannot supply water, or it supplies very poor quality water.
Who can diagnose a breakdown?
Dry running can be easily diagnosed by a specialist when disassembling the pump. It does not apply to warranty damage.
Rules to follow
Any device manufacturer indicates that the pump cannot be used without water. Therefore, it is important to follow certain rules, especially in places with a high level of risk.
The main reasons for the breakdown of the unit include the following:
- Wells and wells with a low flow rate. The fault of dry running may be the selection of an unsuitable pump configuration, which is distinguished by a high power level. Or the cause may be natural phenomena. For example, in hot summers, the water level in wells and wells drops, and their flow rate becomes lower than the pump performance level.
- The process of pumping water from tanks. It is recommended to carefully monitor that the device does not pump out absolutely all the water, and turn it off in time.
- When pumping water from the network pipeline, the pump is embedded directly into it. It helps increase blood pressure. Since the pressure in the system is low, this is a fairly common use of a pumping station. It is very difficult to determine the moment when there will be no water in the network.
Protection of the pump against dry running is mandatory. When emptying the container, the device is not able to automatically turn off. It will continue to function until it breaks or until inattentive users turn it off.
Float
Protection of the pump from dry running when pumping water is carried out by means of a float. The cost of such a switch is low.
The following types of device are distinguished:
- Appliances that are designed only to fill the container. Raising the water level to a certain limit causes the contacts inside the unit to open, and the pumping system stops its work. This type of float serves as protectionfrom transfusion, but not from dry running.
- Another modification involves work on emptying containers. This is exactly what is required. The cable of the device is connected to a break in one of the phases that feeds the pump. The contacts inside the device open, and if the liquid level in the tank drops to a certain level, the pump will stop. The required response limit is determined by the place where the float is mounted. The cable of the device is fixed at a fixed level in such a way that when the float is lowered, at the moment the contacts open, there is still water in the tank. If water is pumped out of the well by a pump with a surface (self-priming) design, then the fastening should be carried out in such a way that when the contacts open, the water level is above the grate that sucks in water.
It should be noted that such pump protection against dry running is used in almost all wells with pumps. Devices are produced by various companies.
Unfortunately, the float is not versatile. It simply will not fit in a well or network pipeline. Other types apply here.
Using a dry-running pressure switch
The pump dry-running protection relay is an ordinary device equipped with an additional function of opening contacts when the pressure drops below the extreme level.
Usually this level is set by the pump manufacturer and is between 0.4 and 0.6 bar. This indicator is not regulated. When used correctlythe pressure in the system will not drop below this mark, since all pumps used for private needs operate at high pressure.
A drop to the limit threshold can only be observed in the absence of water in the pump. Without water, there is no pressure, and the relay, reacting to a dry run, opens the contacts that power the device. The pump can only be started manually. Before doing this, the cause of the failure must be identified and eliminated. The pump is filled with water again before the next start.
What type of construction is this pump guard intended for? Dry running of the pressure switch will help to avoid only automatic configuration (together with a hydraulic tank). Otherwise, the operation of the device loses its meaning.
As a rule, the relay is designed for a deep pump configuration, as well as a surface system or stations. The submersible pump is also protected against dry running.
Flow switch equipped with pressure function
Many manufacturers offer to replace the hydraulic tank and pressure switch with another compact device - a flow switch, or a press control. This device sends a command to start the pump when the pressure in the system drops to 1.5-2.5 bar. After the water supply stops, the pump turns off, since the liquid no longer passes through the relay.
Protection of the pump against dry running is provided by a sensor built into the relay. System shutdownoccurs after a dry run is fixed, which takes a little time and does not affect the functionality of the pump. In addition, press control provides protection against increased voltage in the mains.
The main advantage of the unit is its small size and weight. Unfortunately, the market is overflowing with devices that are produced by unknown countries. Understanding the quality of a particular model is sometimes very difficult.
On average, the device works for about 1.5 years, provided that the assembly is done at a high level. The device, which has been certified and has high performance, is manufactured by ACTIVE. Its cost is about $100.
Using a level switch
The basis of the level switch is an electronic board, to which sensors are connected to protect the dry running of the pump. As a rule, the design of the device involves three electrodes, one of which performs a control function, and two - a working one. They are connected to the device by means of an ordinary single-core electrical wire. The electrodes are used to give a signal.
How the device works
Protection against dry running of the borehole pump is carried out when the sensors are immersed in the tank at different levels. When the water drops below the control sensor, which is installed a little higher than the installation of the pump itself, the electrode sends a signal to the level switch, and the pump stops.
After the water rises above the control sensor, the automatic pump is activated. Protectiondry running has a high level of reliability, but the cost of such a relay is much higher than that of other devices. Also, the device is used for pumping water from wells and wells. The level switch itself is installed indoors or in any place where there is no moisture.
Which device to choose?
The use of the device depends on the pump model and the taste of the user. Experts note the following.
Protection against dry running of the borehole pump, as well as devices located in tanks or wells, will be fully implemented with the simultaneous use of a pressure switch and a float. These devices will complement each other. At a cost, this option will not be more expensive than installing an expensive level switch.
It should be noted that to protect the pump, designed to work in wells, more often resort to the use of a pressure switch. It is better to use models of an expensive segment, as well as a level switch, which is distinguished by a high degree of reliability.
Note that the use of protective equipment is optional if:
• the well is deep and has a good flow rate, as indicated in the technical data sheet;
• you have the proper experience in using pumps in a well or well;• you are sure that the water level in the system practically does not crash.
Use extreme care when operating the pump. As soon as you notice that the water has disappeared or the thermal relay has tripped, which caused the pump to turn off, try to find out the cause of the incident, and only thenactuate the pumping system.
Electrical modifications
Despite the fact that protective equipment has been developed that operates on elementary principles and clear criteria, it should be remembered that in addition to mechanical components (pipes, pressure switches, receivers, valves and valves), there are configurations that operate on electricity.
Do-it-yourself pump protection from dry running can be done using relays, transistors and resistors. The process is not particularly difficult.
But there are a wide range of electronic devices on the market these days, and that makes things a lot easier. There are even special automatic units that combine the function of a protection relay and a pressure relay. Some models have a soft restart of the pump.
For example, reviews indicate that the LC-22B model can cope with all the problems that arise in the pumping system quickly.
Users note the EASYPRO pressure controller from the Italian manufacturer Pedrollo. It maintains a constant water pressure, automatically starts and stops the pump. The pressure regulator in this device is supplemented with an expansion tank and the function of changing the outlet pressure in the range from 1 to 5 bar. In addition, the display of the device displays all the necessary information about the operation of the pumping system.
Conclusion
Applying your knowledge andskills when implementing a pumping system protection scheme is not so difficult. Any mechanical configuration is simple. With not only a theoretical base, but also the knowledge of several options for solving this problem, you can ensure the smooth functioning of your pumping system.
