Continuous and independent status monitoring:
- of the delivery valves, for leaks
- of the membranes, for material fatigue
- of the temperature loading of the hydraulic oil
Communication of the status to superordinate process control systems:
- via digital outputs
- digitally, via PROFIBUS DP or PROFIBUS PA
Simple to operate and parametrize:
- Locally, via digital display and keys
- PROFIBUS DP and PROFIBUS PA
Mode of operation
Leaks in the delivery valves of oscillating displacement pumps are flows in which cavitation occurs. This results in sound waves that are transmitted to the valve housing, where they are recorded by the structure-borne sound sensor in the SITRANS DA400 on the outside.
The SITRANS DA400 utilizes the fact that with both an open valve and a closed intact valve, no cavitation occurs and the measured sound level thus corresponds to the operating noise of the pump. By contrast, with a closed defective valve cavitation does occur, which can be identified by a period increase in the sound level (see figures). The measured value from the SITRANS DA400 corresponds exactly to this increase in the sound level.
The measurement is carried out exclusively in the ultrasonic range. This filters out the operating noise of the pump and the closing noise of the valves.
Signal from structure-borne sound sensor with intact valve
Signal from structure-borne sound sensor with defective valve
The structure-borne sound sensor works on the piezoelectric principle. The structure-borne sound is injected into the sensor via the sensor base (mounting surface) and inside it is converted into an electrical voltage by a piezo-ceramic element. This is amplified in the sensor and transmitted via the cable.
The sensor frequency range lies in the ultrasonic range (>20 kHz). The sensor is non-directional, i.e. the angle at which the sound wave is incident on the sensor base is not important.
Mode of operation of the electronics
SITRANS DA400, function diagram of the electronics