Double-seat valves

VARIVENT® mixproof divert valves are used for distributing liquid in pipelines, i.e. for distributing a liquid from one pipeline into two others, in which case one of the two pipelines must be shut off from the outlet line with a mixproof function.

Function of the Valve

When the valve is closed (non-actuated position), there are always two seals between the middle and upper pipeline. If one seal is defective at this point, the resulting leakage can be deliberately channeled through the leakage outlet into the periphery, without mixing with the product in the second pipeline.

The shut-off between the middle and lower housing is performed with only one seal, and is not suitable for separating two incompatible media.This method ensures that there will not be any mixture between a product line and a line carrying cleaning fluid.

Special Features

  • Certified, hygienic configuration
  • Metallic stop
  • Flexibility because of the modular principle
  • Proven seal geometry
  • Mixproof separation
  • Optional separate lifting actuator for lifting the two valve discs
  • Optionally spray cleaning connection for cleaning the leakage chamber

Valve Selection Scheme: Mixproof Divert Valves

VARIVENT® Double-seat Valve, type Y
Mixproof Divert Valves
Seat Lifting
VARIVENT® Double-seat Valve, type Y_L, Y_C

Application Examples

The typical application for this mixproof valve with changeover function is the divert function after a pasteurizer.

For this application, the VARIVENT® mixproof divert valve type Y has been approved by the German Federal Dairy Research Centre in Kiel for use after a pasteurizer.

Switching Leakage

In axial sealing double-seat valves, with every switching procedure there is a short time during which the lower valve disc is neither in contact with the middle seal of the upper valve disc, nor has it reached the axial seat surface of the seat ring. During this brief moment liquid can percolate through the resulting gap into the leakage chamber and flow out into the atmosphere. This is referred to as the switching leakage.

Double-seat divert valves
DN 25 – DN 150
OD 1" – OD 6"
IPS 2" – IPS 6"

Cleaning the leakage chamber

Lifting actuator (type Y_C, Y_L)

The valves are equipped with a lifting actuator which permits individual lifting of an individual valve disc during the particular pipe cleaning. In this case, the cleaning media passes the seal of the lifted valve disc, cleans the leakage chamber and then flows out through the leakage outlet into the periphery. In this way, it is possible to clean all surfaces that come into contact with the product, including the seal surfaces of the valve disc seals.

Spray cleaning (type Y, Y_L)

The valves have a cleaning connection to be connected at the level of the lantern either on its own (type Y) or additionally next to the lifting actuator (type Y_L). This connection allows the leakage chamber to be supplied with cleaning media from an external source in order to clean this chamber (in addition to the lifting actuator) by means of an integrated spray nozzle.

After that, the cleaning media flows through the leakage outlet without pressure into the periphery. Cleaning takes place with the valve closed, which means the seal surfaces in contact are not touched during cleaning.

Technical Data

Types Y, Y_L, Y_C
Technical Data of the Standard Version
Type Y
Type Y_L, Y_C
Material in contact with the product
1.4404 / AISI 316 L
Material not in contact with the product
1.4301 / AISI 304
Seal material in contact with the product
Ambient temperature
0 to 45 °C
Air supply pressure
6 bar (87 psi)
Product pressure
5 bar (73 psi)
Surface in contact with the product
DN, OD Ra ≤ 0.8 µm
IPS Ra ≤ 1.2 µm
DN, OD Ra ≤ 0.8 µm
IPS Ra ≤ 1.2 µm
External housing surface
Matte blasted
Control and feedback system
Connection 0 (without control top)
Actuator type
Pneumatic actuator air / spring
Connection fittings
Welding end
Adhesive ID tag
Valve seat version
Clamped seat ring
3A, CE
3A, CE