"AVK" series 859 diaphragm actuated pressure reducing control valves (PRV) automatically reduces a higher inlet pressure to a lower constant outlet pressure, regardless of flow demand or changes in inlet pressure. A replaceable spring inside the pilot makes it possible to operate in different pressure ranges and still keep the high precision. Setting and adjustment on a control knob on the pilot. Reduced bore, for water and neutral liquids to max. 70° C.