Dry running of a pump – effects, causes, and the best ways to protect it

Dry Running of a Pump: Causes, Effects, and Effective Protection

Dry running is one of the most common problems associated with operating water-pumping equipment. It occurs when the pump operates without a sufficient amount of liquid, which can lead to serious pump damage and shorten its service life. Modern systems use pump protection devices, such as water level sensors, water level relays, and systems such as SK-13, which automatically switch off the pump if the liquid level drops. Proper pump protection is an investment that helps avoid costly repairs and equipment seizure.

What Is Dry Running and Why Is It Dangerous?

Dry running occurs when the pump draws in water together with air or has no access to liquid at all. This usually happens when the water level in a well or tank is too low. As a result, the pump operates without adequate cooling and lubrication, causing the motor of deep-well pumps to overheat and accelerating the wear of working components. Dry running is particularly dangerous during the operation of deep-well pumps, where a drop in the water level can lead to seizure of deep-well pumps and complete damage to the impellers.

Definition and Mechanism of Dry Running

Dry running is simply pump operation without water flow or at very low pressure. In most cases, it is caused by a drop in the water level, a blocked check valve, or incorrect pump installation. In wells where the water level drops rapidly, a pump installed too high may draw in air instead of liquid. The solution is to monitor the water level and use systems that enable pump protection against uncontrolled interruption of pump operation. Advanced systems may even use an F&F water level relay to respond automatically to changes in the water level.

Effects of Pump Operation Without Water

The effects of dry-running a pump are serious—from overheating working components and burning out the pump motor to complete destruction of the impellers. In many cases, irreversible damage occurs to bearings and seals, requiring replacement of the entire unit. Even brief dry running can reduce pump service life by several dozen percent. That is why thermal pump protection is used to respond to overheating, along with pressure switches that monitor system pressure and pump pressure.

Differences Between Dry Running and Pump Overload

Although dry running and overload are often confused, their mechanisms are completely different. Dry running means pump operation without liquid, whereas overload occurs when the pump operates at excessively high water pressure or against excessive flow resistance. Both phenomena are dangerous to the motors of deep-well pumps and can lead to overheating. Modern systems use pump motor control and pump operation monitoring, enabling the immediate stopping of the pump in the event of a failure.

Pumps Particularly Vulnerable to Dry Running

The most vulnerable are deep-well pumps, pressure booster pumps, and water pumps used in agriculture. In the case of deep-well pumps, the water level and well capacity are particularly important. When pumps installed below the water level are not positioned correctly, the water level may drop below the pump intake, causing a dangerous decrease in the liquid level. Good practice includes monitoring the level and monitoring the liquid level using electronic sensors. It is also worth using pump motor protection and systems for automatically resuming pump operation once the water level has stabilized.

Deep-Well Pump and the Risk of a Drop in the Water Level

A deep-well pump, such as the IBO 3 TI models, must be installed so that its lower edge is sufficiently below the water level. If installed too low, it may draw in contaminants; if installed too high, it may run dry. It is worth selecting the appropriate pressure switch, built-in check valve, and systems such as SK-13, which continuously monitor the pump operating status. Only proper protection of deep-well pumps ensures safety, long pump service life, and stable water flow, even with a variable head.

Various types of pumps used in households, agriculture, and many industrial sectors make tasks involving pumping water out and delivering it to collection points much easier. However, for them to operate reliably, they must be properly protected against dry running and overload, which could seriously damage them. Here is how to protect them against the risk of failure.

Why Can Dry Running and Overload Be Dangerous for Pumps?

Dry running can occur in both deep-well and submersible pumps. There may be several causes, ranging from installing the pump too close to the water level, through a drop in that level, to selecting a device with excessive capacity in relation to the well parameters. It is very dangerous because it is usually difficult to notice that it has occurred, and it may be too late to respond. A pump that runs dry cannot cool its motor, which can result in the seizure of hydraulic components or even serious damage to the control unit.

Another equally dangerous phenomenon is overload, which can have similar consequences. It is most often caused by installing the pump too close to the bottom. This may cause it to draw in sand and silt, leading to faster wear of the pumping components and, consequently, dangerous overheating of the motor. Since both phenomena are dangerous for the pump, it is worth knowing how to prevent them.

Best Ways to Protect a Pump

There are several methods that can help protect a pump against dry running and overload. These include:

- proper pump installation – the pump should be installed at a depth such that the lowest dynamic water level (the water level established during uninterrupted pumping with free discharge) is at least 2 m above the pump discharge outlet. If the well capacity makes such installation impossible (the well has insufficient capacity in relation to the pump capacity), a valve that continuously limits the flow can be installed on the discharge pipeline, or a dry-run protection device can be installed to monitor the water level and, if dry running is about to occur, cut off the power supply to the pump unit,

- installation of pressure switches – this is a fairly simple solution designed to monitor pump operation and switch it off when the pressure drops,

- installation of water level sensors – these sensors are placed in the well and are designed to monitor the water level. When it drops to a specified level, they switch off the pump and switch it on again when the water returns to the proper depth,

- use of modern control devices – a comprehensive solution is to use modern pump controllers. They protect and control the operation of deep-well pumps, submersible pumps, and surface pumps. They protect them against dry running, voltage drops, and overload,

- use of a frequency inverter – this is a device that comprehensively controls pump operation. One of its greatest advantages is that it guarantees constant pressure regardless of water consumption. Eliminating pressure surges also means longer pump and system service life because there is no so-called water hammer. A pump equipped with a frequency inverter is effectively protected against overload, low and high voltage, phase loss and phase asymmetry, as well as dry running.

In summary, there are many ways to protect deep-well and submersible pumps against dry running and overload. It is certainly worth choosing at least one of them to ensure that the pumps operate reliably for many years.

Frequently Asked Questions (FAQ)

The information is provided for educational purposes. Before installation, it is recommended that you read the device manual. Dambat – manufacturer of IBO pumps.