Every offset press operator in Augsburg and beyond depends on this non-return valve to keep ink and dampening solution flowing in one direction only. Inside the dampening unit of a sheet-fed or web press, the valve sits between the metering roller and the fountain pan, preventing backflow when the roller stops. Without it, air bubbles or ink residue would travel upstream, disrupting the precise film of dampening solution that keeps the plate clean and the print sharp. On high-speed presses running coated stock, the valve also stops water hammer from the oscillating roller, so the fountain stays at constant level and pH. When the operator adjusts impression on the fly, the valve ensures the change in roller speed doesn’t pull ink back into the water circuit, avoiding ghosting and reducing waste. In newspaper plants, the same valve is fitted in the ink recirculation loop of flexo presses, where it keeps solvent-based inks from contaminating the return line during splice changes.