Non return valve is a check valve system which keeps the hydraulic cylinder fixed against external forces. It is normally closed from cylinder side. When oil is sent from one port of helm pump, cylider return port is opened automatically. It is specially designed for manual steering systems to allow high oil flow with minimum pressure loss. It is an essential part of hydraulic steering systems and it can be either integrated on helm pumps or can be used in line. If the helm pump(s) are with integrated non return valves, it is not required to use additional non return valve.
Distribution blocks are equipped with cross relief valves to prevent steering system from external forces which may create high pressures in the system. They are also equipped with a by-pass valve to allow the use of manual tiller. By-pass function is also usefull for air bleed during the start up of the system. Distribution blocks are made of marine grade aluminium and there are models with different number of ports.