VARIVENT® Mixproof Shut-off Valves with Seat Lift

When the valve is closed (unoperated position), there are always two seals between the separate pipelines. If one seal is defective, the resulting leak will be directed through the leak outlet to the outside, without mixing with the product in the other pipe.

This method ensures that there is no mixing between the products from the two pipelines.

To meet the diverse requirements of various industries, applications, and processes, we offer a wide range of mixproof shut-off valves in our product portfolio. The selection guide on the following pages provides an overview of all available options.  

VARIVENT® long-stroke valves are used in the production of products containing relatively large particles or viscous products, such as strawberry yogurt. 

• Certified, hygienic design
• Metal stop
• Flexibility thanks to the modular design
• Proven sealing geometry
• Mixproof separation
• Various valve configurations are available
• Separate lifting linkage for lifting both valve discs
• Optional spray cleaning connection for cleaning the leak chamber

The various versions of the VARIVENT® double-seat valve make it possible to select valves that are optimally suited to the process. The axially sealed valve types D and B result in a small switching leakage with each switch, but they have a very long service life thanks to the axial seals. The radially sealed valve type R, on the other hand, has the advantage of being able to switch with virtually no switching leakage. Valve types B and R are also characterized by a balancer in the lower valve body. This ensures that the valve can reliably remain in the closed position even if there are pressure surges in the lower pipeline. The MX valve type is also equipped with a balancer on the double disc and the valve disc.

Thanks to specially designed balancing devices in both pipelines, the valve remains stable in the closed position even during water hammer, while also retaining its full operational capacity even in the event of hydraulic lock or thermal expansion of the medium.

Sizes

The modular VARIVENT® system is designed to offer a wide range of options for optimally adapting the valve to the process. See the section on options in the catalog for more information.

In axially sealed double-seat valves, there is a brief moment during each switching cycle when the lower valve disc is neither in contact with the center gasket of the upper valve disc nor has reached the axial seating surface of the seat ring. During this brief moment, fluid can penetrate through the resulting gap into the leakage chamber and escape into the atmosphere. This is known as switching leakage.

In radially sealed double-seat valves, this gap does not occur during the switching process, which means that switching leakage is reduced to a minimum (the possibility of product residues adhering to the metal surfaces).

If there is a water hammer in the lower pipeline, the force from the water hammer acts on the lower valve disc and may exceed the force of the actuator spring.

This creates a risk that the lower valve disc will be lifted by the pressure in the pipeline.

In axially sealed double-seat valves, this would result in leakage (see leakage during switching). The connection to the atmosphere would also cause a sudden drop in the overpressure in the pipeline. This would cause the actuator spring to close the valve again.

Valves with a lower balancing mechanism are available to prevent the lower valve seat from lifting during a pressure surge in the lower pipeline. With its downward-facing compensation surface, the balancer adjusts the direction of the pressure and prevents the lower valve disc from moving upward until a certain overpressure is reached.

Radial-seal double-seat valves are always equipped with this lower balancer to prevent the lower valve disc from opening.

Both valve discs in GEA’s MX valve series are equipped with balancers. The valve is therefore pressure-resistant in the closed position in both the upper and lower pipelines and allows for switching while the product is trapped inside.

For more information, please refer to the catalog.