HERION & RAU Fluidtechnik | Anwendungen | Commercial and Heavy Vehicles

Pressure Switches for Commercial and Heavy Vehicles

In commercial vehicles, brakes, axle systems, lifting devices, and protection systems depend on pneumatic or hydraulic pressure, which must be correct. If it drops unnoticed, a control function quickly becomes a safety issue. Our pressure switches monitor it under shock and continuous vibration, during temperature changes, humidity, and dirt. High IP ratings and switch points that remain within the defined window over the service life are prerequisites here and ensure long-term stability.

Typical Application Areas

From truck trailers to pantographs: six systems in which our pressure switches are installed.

Truck Trailers

Lift axle, pneumatic brake

Construction Vehicles

Hydraulic brake systems

Field sprayers

Pressure monitoring

Railway Applications

Pantograph contact pressure

Overload monitoring

For lifting systems

Fire extinguishers

Pressure monitoring

Application Case 01

Pneumatic Brake – Safety Principle through Pressure Monitoring

The brake of a truck trailer or rail vehicle is held open pneumatically. If the pressure drops, it engages automatically. This fail-safe principle only works as long as the system pressure is monitored: our pressure switch keeps it within the defined window and reports when there is no longer enough pressure to keep the brake open. Vibration-resistant and with stable switch points, even when weather and ground conditions change.

Why our pressure switches are ideally suited:

Application Case 02

Overload Monitoring – Protection Against Overload

In hydraulic lifting systems, such as in excavators or cranes, the system pressure increases with the load. If it exceeds the defined threshold, the limit has been reached, usually because there is too much material in the bucket. Our pressure switch detects this and triggers a shutdown or warning message. The small, precisely defined hysteresis is important here: it ensures that the driver clears the overload message as soon as some material is removed, instead of having to empty the bucket completely.

Why our pressure switches are ideally suited:

FAQ

Frequently Asked Questions

Why are mechanical pressure switches still used in commercial and heavy vehicles?

Not every pressure monitoring application requires a continuous measured value. For many vehicle functions, clear information on whether a certain pressure has been reached or fallen below is sufficient. A mechanical pressure switch generates this switching signal directly and does not require any additional evaluation electronics or power supply. This is suitable, for example, for release, warning, or control functions in pneumatic and hydraulic systems and enables a robust, clearly defined interface to the vehicle control system.

What is the significance of hysteresis for fluctuating pressures in the vehicle?

In pneumatic and hydraulic systems, pressure is rarely perfectly constant. Pumps, valves, load changes, or vehicle movements can lead to short-term pressure fluctuations. If the switch and reset points are too close together, undesirable frequent switching can occur in this range. A suitably designed hysteresis creates a defined distance between the two switching states. How large this distance should be depends on the function – for a lift axle, for example, it is different than for overload monitoring.

What information do we need to select the right pressure switch?

For vehicle applications, in addition to operating pressure and the desired switch point, the specific function in the system, switching direction, and reset behavior are particularly important. We also require information on the medium, temperature range, and possible pressure peaks. The installation location, vibrations, humidity, electrical load, connection type, and desired protection rating also play a role. For mobile applications, it is also helpful to know whether the switch is used in the protected interior, on the chassis, or in a particularly exposed area.