EN 774 Breather Valve Caps Plastic, with or without Dipstick, with Double Valve

EN 774 breather valve caps with double valve are normally used when the fluid container is under pressure, yet air has to flow in from the outside in case of underpressure (decreasing fluid level).

This is achieved by combining two valves (check / bypass valve). The inlet valve allows air to enter at an underpressure of 30 mbar or higher. The second valve only opens at an overpressure of > 350 / 700 mbar.

The air filter prevents contamination of the fluid from outside (dust). It is made of PU foam with a grade of filtration of 40 µm.

The overpressure inside the container ensures that the air volume, which is flowing in or escaping due to the fluctuating fluid level, is kept to a minimum. This reduces filter fouling and substantially increases the service life, especially in dusty environments.

In addition, a pressurized container has a positive effect on the function of the pump and prevents the formation of foam.

The valve seal ensures that no fluid will leak, especially if the fluid is strongly moved or during transport.

Pressure gradient Δp [mbar] in the container as a function of the air flow rate [l/min] at a valve opening pressure of 350 or 700 mbar.

For the series with dipstick shown above, a shortening and / or the attachment of level markings can be ordered with the service GN 109.
The dipstick is shortened to the length l₁ and the marking notches are milled at l₂ or l₃, making them easily visible. The max. length l₁ is specified in the respective series. 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, the seal must be taken into consideration with a thickness of up to 2 mm, depending on the series.
If required, more than 2 notches may be inserted on request, which are then specified by appropriate details on the position (l₄ ... l_x). Furthermore, texts such as MAX / MIN may be laser-engraved in addition to or instead of the notches by submitting the appropriate template.

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