Selection of probes for lifting stations and pumping stations
In lifting stations and pumping stations, specific probes or sensors are used to measure the water level in the wastewater tank. Depending on the intended use of the probe in question, this can be used to initiate pumping operations or to trigger an alarm if water accumulates in the tank. There are various types of sensors, each suitable for specific operating conditions. Typical sensors include, for example, pressure sensors, conductivity probes, float switches, hydrostatic sensors or optical probes.
Pressure sensor / Pneumatic level measurement
The water level in a lifting station or pumping station can be determined using a pressure sensor. As the water rises within the lifting station, it compresses the air inside a submersible pressure switch or an immersion pipe. This pressure is transmitted to the pressure sensor, triggering the pumping process as soon as the specified level is exceeded. The water level can be determined with millimetre precision.
Pressure sensors are cost-effective, easy to use and have become the standard in many lifting stations. However, they are not always the ideal solution for Grease wastewater. Furthermore, they are not recommended if the distance between the lifting station and the control unit exceeds 15 metres, or if the pressure hose and cable cannot be laid in a continuously ascending manner from the lifting station to the control unit. In such cases, condensation may form in the pressure hose, impairing the accurate transmission of the water level.
float switch
In a lifting station or pumping station fitted with a float switch, the pumping process is triggered when a floater in the wastewater tank is pushed upwards by rising water. As soon as the floater reaches the required level, the control unit receives a signal to activate the pump.
The float switch is a simple and tried-and-tested type of sensor. However, the options for adjusting the switching heights or switching hysteresis are limited.
Hydrostatic sensor / Level probe
Hydrostatic sensors, also known as level probes, operate on the basis of the hydrostatic principle: this states that the pressure of a liquid in a tank is directly proportional to the height of the liquid column above the measuring point. This type of level probe therefore measures the pressure generated by the water column in the tank to determine the water level.
The advantages of level probes are their reliability and accuracy, as they are less susceptible to external influences such as contamination or temperature fluctuations. Furthermore, signal transmission (wired) can take place over a much greater distance (> 100 m) than with other sensors. This allows the control unit to be positioned much more flexibly. However, they are therefore generally more expensive than other types of probes.
conductivity probe
A conductivity probe triggers the pumping process as soon as the water reaches two closely spaced measuring points. The alternating voltage applied there causes current to flow through the conductive liquid between the measuring points. This sends a signal to the control unit to activate the pump.
A conductivity probe provides a simple and cost-effective way of determining the water level in a wastewater tank. However, it only works with conductive liquids and cannot be used in pumping systems that handle rainwater or condensate.
optical probe
Optical probes are used as alarm probes in lifting stations and pumping stations. They emit an optical signal in the form of infrared light. As soon as the probe detects a change in the infrared light signal, the alarm is triggered.
Compared to other types of probes, optical probes are generally better suited as alarm devices, as they continue to function reliably even after long periods of inactivity. However, they can trigger false alarms if used in lifting stations or pumping stations with heavily foaming wastewater, or if condensation forms on the probe due to warm wastewater vapours.
