GN 774 Breather Caps Plastic, with Filter and Double Valve

Breather caps GN 774 feature a double valve and are used for venting vessels, such as hydraulic tanks. The valve limits the overpressure inside the vessel by releasing air whenever the pressure value specified in the table is exceeded. Conversely, the valve allows air to enter into the vessel once an underpressure of -30 mbar is reached, preventing the formation of a vacuum. The respective flow rate depends on the pressure difference and can be read from the diagram.

The integrated air filter prevents dust and dirt from entering the vessel. With fluctuating liquid levels, the overpressure reduces the air exchange, resulting in reduced filter contamination, especially in dusty environments.

The pressurized air pocket above the liquid counteracts foam formation. The valve seal ensures that no liquid escapes, such as due to vigorous movements or during transport.

Level markings and special lengths GN 109 for oil dipsticks are available for the standards shown above. The dipstick is shortened to the length l₁ and the marking notches are milled in at l₂ or l₃ with the effect that they are easily visible. The maximum length l₁ is given in the appropriate standard. The length specifications l₁ to l₃ refer to the contact surface without seal, with a tolerance of ±1 mm to be taken into account. For critical applications and depending on standard, the seal must be taken into consideration with a thickness of as much as 2 mm.
If required, more than 2 notches may be cut which are then specified by the appropriate details on the position
(l₄ ... l_x). Also, texts such as MAX / MIN may be laser-engraved in addition to or instead of the notches by submitting the
appropriate template.

The level markings / special lengths GN 109 are to be ordered as a separate item in shopping cart step 1 under note.