Standard_Parts_Catalogue

Page 1619 | 3.5 Controlling, Venting, Sealing of Liquids and Gases 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 GN 764 Breather Caps continued Breather caps GN 764 with double valve are normally used if the oil container is under pressure and if outside air has to flow back in to compensate for the vacuum caused by falling oil level. This is achieved by combining two valves (non-return / bypass valve). The inlet valve opens at a vacuum of 30 mbar or greater. The second valves opens at an overpressure > 350 mbar. The air filter prevents the oil from being polluted from the outside (dust). The filter is made of PU foam with a filtration of 40 µm. The overpressure inside the container ensures that the air volume flowing in or escaping owing to fluctuations of the oil level is kept to a minimum. This reduces filter fouling and substantially increa- ses the useful filter life, especially in a dusty environment. Also, a container under pressure has a positive effect on the function of the pump and prevents foaming. The valve seal ensures that no oil will leak even if the oil is heavily agitated or during transport. Description of function Air flow rate [l/min] in reliance on the pressure difference Δp [mbar] container / outside space (Type F, with filter). Pressure curve Δp [mbar] in the container as factor of the air flow rate [l/min.] at a valve opening pressure of 350 mbar (Type FD, with filter and double valve)