Double-seat Valves

VARIVENT® mixproof valves type C and K are used for mixproof separation of incompatible products at pipeline junctions within CIP systems or gas blocks.


When the valve is closed (non-actuated position), there are always two seals between the separated pipelines. If one seal is defective, the resulting leakage will be directed through the leakage outlet into the periphery, without mixing with the product in the second pipeline.

Application Examples

VARIVENT® double-seal valves type C and double-seat valves type K are predominantly used in areas where hygienic is not critical, e.g. CIP systems and gas blocks (brewery)

The Valve Types

Valve type K represents a typical double-seat valve with two independent valve discs in which these two seals are located.

Valve type C, on the other hand, is a double-seal valve in which these two seals are together with the leakage chamber in between them in a valve disc.

In both versions, two seals prevent any mixture between a product line and a line carrying a cleaning media.


Double-seal valves, type C valves
Double-seat valves, type K
DN 25 – DN 150
DN 25 – DN 150
OD 1" – OD 6"
OD 1" – OD 6"
IPS 2" – IPS 6"

Valve Selection Scheme: Mixproof Shut-off Valves

Product Range
Axial Sealing (Switching Leakages)
Modular System
Double-seat Valve, Type D
Product Range
Axial Sealing (Switching Leakages)
With Water Hammer Safety
Double-seat Valve with Balancer, Type B
Product Range
Radial Sealing
With Water Hammer Safety
Radial Sealing Double-seat Valve, Type R
Product Range
Axial Sealing (Switching Leakages)
Viscous Products or Products with large Particles
Double-seat Long-stroke Valve, Type D_/V
Product Range, piggable
Radial Sealing
Pigging Pipe
Piggable Double-seat Valve Upside Down, Type L_H
Product Range, piggable
Radial Sealing
Pigging Pipe Bottom
Piggable Double-seat Valve Upright, Type L_S
Gas Blocks &
CIP Systems
Modular System
Double-seal Valve, Type C
Gas Blocks &
CIP Systems
Modular System
Double-seat Valve, Type K

Cleaning the Leakage Chamber

Double-seal valve type C

In the standard version, two flushing valves are connected to the leakage chamber between the two valve disc seals.

One flushing valve is always used for the leakage outlet, while the second flushing valve is in contact with cleaning media through an olive screw fitting, in order to clean the leakage chamber.

In this case, it is necessary to have a supply valve connected in the periphery to supply the flushing valve with cleaning media at the required time.

Cleaning takes place while the main valve is closed, which means the seal surfaces of the valve disc seals that are in contact are not reached.

Cleaning the Leakage Chamber

Double-seat valve type K

The double-seat valve type K does have neither an external spraying connection nor a lifting actuator. The leakage chamber is flushed by the fluid that emerges from the leakage chamber as a result of the switching leakage during the main stroke.

For this reason, the valve is not suitable for use in hygienic areas.

The advantages of the valve type K are its slightly increased safety against water hammers that could occur in the lower pipeline, as well as having a wider selection of available housing combinations.

Technical Data

Type C & K
Technical Data of the Standard Version
Type C
Type K
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
Ra ≤ 0.8 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
Fixed vertical port
Clamped or welded seat ring
A3, CE