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Accurate dosing quantities even with outgassing media

July 2021

When metering liquids, gas bubbles and pressure fluctuations are the main causes of metering inaccuracies. Outgassing media can also block the conveying process completely. Intelligent functions and model-based control behaviour of the gamma/ X and XL solenoid-driven diaphragm metering pumps provide a remedy.

During the dosing process, gas bubbles can occure in the suction line or in the dosing head. This is the case when dosing outgassing media such as sodium hypochlorite. If there is too much gas in the dosing head of an oscillating displacement pump, the dosing process can be disrupted. This means, that the necessary dosing accuracy is not ensured with traditional solutions, such as time-controlled venting or continuous bypass solutions. Conventional pumps dose less liquid than required due to the gas content in the dosing head. In the worst case, and most frequently, the pump can “air lock” and does not meter at all. In order to avoid this, the gas must be detected in good time so that the necessary measures can be initiated; ideally, it should be ensured that the dosage is not only uninterrupted, but also with the exact amount required.

Intelligent functions ensure accurate dosing

Reliable air bubble detection is a prerequisite for intelligent, automatic ventilation. The solenoid driven diaphragm metering pumps gamma/ X and XL use all the advantages of their patented, regulated solenoid drive. The power consumption of the solenoid coil (pressure information), and the position of the diaphragm, allow direct conclusions to be drawn about the dosing behavior at any time during the pressure and suction strokes.

By comparing target values with the measured values even gas bubbles can be precisely identified and selectively monitored. In this way, for example, gas bubbles can be detected and selectively monitored due to a slow pressure rise (as the gas is compressed).

The air bubble detection and the model-based control behaviour of the solenoid-driven metering pump in combination with a special pressure valve enables air bubbles to be pre-compressed by the system pressure even before the actual pressure stroke and to be released into the metering line during the pressure stroke. The intelligent control ensures that exactly the required quantity is metered even during pressure compensation. It adapts the number of strokes and the duration of the compensation to the number and size of gas inclusions. For example, due to several gas bubbles occurring one after the other in the suction line.

This ensures that the dosing capacity is reliably maintained even if several gas bubbles occur one after the other in the suction line. Compared to conventional solutions, the required dosing accuracy is maintained.

Contact us

Wesley Sutton

Managing Director, ProMinent Fluid Controls UK Ltd.

»We are always available to help. Don't hesitate to contact us.«

+44 1530 560 555  Send request   

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