What is pump dry running and how to protect yourself against it?

Dry running is one of those phenomena that in installation practice can destroy a device worth several hundred or several thousand zlotys overnight. At Dambat, we see its effects regularly - in service calls and in conversations with installers who are looking for effective protection for their customers. Below we explain what exactly dry running is, what its consequences are and how to prevent them.

Note: The article is of a technical and informational nature. Always verify detailed data with the documentation for a specific model or with ours technical department.

What is dry running?

Dry running dry run) is a condition in which the engine is running when the device does not have access to water - or the flow is so small that it does not fulfill its cooling and lubricating role. In submersible pumps, water has a dual function: it is the transported medium, but at the same time it cools the winding and lubricates the mechanical seals. When the water level in the well drops below the inlet - or when air is sucked in instead of water - the entire system stops working properly.

In hydrophore installations, the mechanism is identical: the device draws water from a tank or intake, and if the tank is empty or the suction pipeline turns out to be leaky, the rotor rotates without the medium. The temperature rises rapidly and damage occurs.

The most common causes

• Water level falling. It may be seasonal in nature - summer droughts in Poland are becoming more and more intense - or result from excessive abstraction exceeding the capacity of the intake.
• The efficiency of the device exceeds the capacity of the well. A device that is too large will deplete the intake faster than it can regenerate. The operating state then changes cyclically: full capacity → dry running → restart → dry running. Each such episode shortens the life of the installation.
• Leakage in the suction pipeline. Even a slight leak in the connections or a damaged non-return valve causes air to be sucked in instead of water - an effect similar to dry operation.
• Error on first run. A unit that is started without previously filling the installation starts without any cooling medium - damage appears immediately.
• Emptying the hydrophore tank. An expansion vessel that is too small or heavy wear and tear can empty the tank before the well has a chance to refill it.

Effects – what's happening inside?

Working without water triggers a cascade of physical phenomena that quickly lead to a costly failure. The sequence of events is almost always the same:

• Overheating and rupture of mechanical seals. The so-called the grinding is designed for immersed operation - without water, friction increases rapidly, the temperature increases within seconds and seals are destroyed. This is the most common and usually the first visible effect.
• Overload and burnout of the motor winding. Without a hydraulic load, the pump operates outside the optimal point of the characteristic curve. The current consumption increases, and without thermal protection, the winding burns out.
• Rotor seizure. Under the influence of high temperature, the elements deform or sinter with the housing.
• Hidden hydraulic damage. Plastic impellers and diffusers are thermally deformed. The result is a permanent loss of efficiency and noisy operation - even when the device appears to be "working" after an episode of dry running.

In practice, the cost of repairing or replacing the pump after seizing is many times higher than the cost of proper protection installed immediately. A long service life of the installation is absolutely achievable - and with relatively simple technical means. We describe them below.

Methods of protection against dry running

Pressure switches (pressure switches)

The most common protection in hydrophore installations. The pressure switch reacts to a pressure drop below a set threshold and cuts off Power supply – work is resumed after the pressure returns to the starting value. Pressure switches are cheap and reliable, but they respond to the effect (no pressure), not the cause (no water in the well).

Our IBO offer includes a controller IBO PRESS 10 – electronic pressure switch designed for reliable protection against dry running and current overloads. Detailed technical parameters, including the maximum power of supported devices, can be found in the product data sheet.

Water level sensors and transmitters

Probes, electrodes and float water level transmitters monitor the medium directly in the well or tank. It stops before damage occurs - this is a key difference from a pressure switch that reacts after the fact. Resumption of work is possible only after replenishing the intake supplies. Our offer includes many pumps with this type of switches, as well as independent devices performing these tasks.

Important practical note: the installation of the device and the setting of the sensor activation threshold should take into account the dynamic water level - i.e. the level when operating at full flow, not the static level. The difference can reach several meters and has a direct impact on the effectiveness of the entire system.

Thermal motor protection

Temperature sensors built into the winding, otherwise known as thermals they react when the limit value is exceeded - they cut off Power supply and initiate shutdown. After cooling down, restarting is possible. However, such protection should be treated as the last line of defense, not as a substitute for water level sensors or pressure switches.

Controllers and inverters

Pump controllers integrate multiple protection functions in one module: pressure monitoring, operating status, supply voltage parameters, and overload and dry-running protection. This is a solution for professional applications: farms, irrigation systems and wherever operational continuity is critical.

Inverters. (frequency drives) are another level of protection and an optimization tool. They regulate engine speed depending on current demand, limit the number of start-stop cycles and monitor power consumption in real time. A sharp drop in current consumption in the absence of flow is a clear signal for the inverter to turn off - the reaction occurs within seconds. Compatible devices and control equipment for IBO i pumps IPRO can be found on our website, in the tab inverters and accessories.

Warning signals – when to react?

Not every dry run is violent. Often, the installation degrades for weeks in borderline conditions - too little water, but not completely missing. The following symptoms should prompt immediate inspection:

• Irregular or pulsating water flow from taps - a typical symptom of air intake.
• A noticeable increase in operating noise or new sounds (vibration, grinding) - rotor operation without full immersion.
• Shortening cycles with constant demand - more frequent starts and faster shutdowns may indicate incomplete water intake.
• Automatic shutdowns by thermal protection - operation outside nominal parameters.
• A visible drop in pressure during peak consumption hours - a classic symptom of exhaustion of the intake.

Each of these signals requires immediate diagnostics. Ignoring them almost always results in replacing the entire device. If you have any doubts about the operation of your pump, contact a specialist or ours technical department.

Dambat – a trusted manufacturer of pumps and hydrotechnical equipment with quality certificates.

Frequently asked questions – dry running, protection of IBO submersible pumps IPRO