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Platform Position Monitoring for Tank Car Wash System


When cleaning tank cars in a car wash, a folding bridge is automatically lowered pneumatically to serve as a fall protection for personnel.

The pistons of the two 5/2-way pneumatic cylinders are indexed in and out using compressed air. A leakage in the system would result in the folding bridge returning to its parking position and thus causing severe physical damage to the wash head of the cleaning system. To prevent this, the position of the platform must be reliably monitored.


After entry of the tank car the folding bridge is lowered until it rests on the tank car.

Fig. 1: After entry of the tank car the folding bridge is lowered until it rests on the tank car.

The position value captured by the inductive analog measuring system NBB3-F90-104-IU-V1 is accepted as the setpoint. The folding bridge may still move within a tolerance window of a few centimeters. Once a specified threshold value is exceeded the complete system is switched off. This prevents mechanical damage to the wash head.

Fig. 2: Folding bridge with position monitoring

Customers' benefit

The high resolution of 125µm allows for the exact calculation of the folding bridge position. A minimum temperature drift of ± 0.5mm (-25 °C ... 70 °C) guarantees reliable position calculations in almost any environment. Even high humidity or splash water as found in a car wash do not impede the function of the IP67 protected sensor in any way, and the long-term operation of the system is secured.

Fig. 3: Inductive analog measuring system for position calculation