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Tandem Way Valve T-WSR

Tandem Way Valve, Proportional Directional Control Valve with Redundant Control Magnet Unit (Dual Coil System)

Voith tandem way valves are way valves with two control magnets (dual coil system). The control magnets are connected in series and create a redundant unit. Tandem way valves with integrated position control adjust hydraulic positioning cy­lin­ders by means of a pilot valve in processes requiring high availability. The positioning cy­linders operate a valve that controls the mass flow needed to drive machinery. Voith tandem way valves ensure very precise and high dynamic control of the mass flow.

A tandem way valve consists of two electromagnets with integrated position control connected in series and a 3/3 way hydraulic unit for single-acting positioning cylinders or a 4/3 way hydraulic unit for double acting positioning cylinders. Working in con­junc­tion with a hydraulic cylinder, the way valve converts a constant input pressure into a variable stroke. A standard 4 – 20 mA signal specifies the stroke of the positioning cylinder. An additional pilot valve is no longer needed with the Voith electrohydraulic tandem way valve.

In the event of a malfunction, control magnet 1 switches off automatically and control magnet 2 switches on. The switching logic is located in the external control system and monitors the control magnets.

The Mean Time Between Failures (MTBF) for Voith tandem way valves is over 360 years. Your equipment runs for a very long period of time without unplanned down­time; productivity is increased.


Voith Digital Solutions GmbH
Actuators and Governors
Voithstr. 1
74564 Crailsheim, Germany

Tel. +49 7951 32-470
Fax +49 7951 32-605

Product inquiry

Technical data

Flow rate Up to 600 l/min [158 gpm] at 1 bar [14.5 psi] differential pressure
Input pressure Up to 200 bar
MTBF (Mean Time Between Failures) 360 years (calculated in accordance to MIL‑HDBK‑217 and Siemens SN 29500, actual MTBF evaluations from installed products show even higher values)
Supply voltage 24 VDC
Current consumption 1.0 A (3.0 A for t < 1 s)
Input signal 4 – 20 mA
Communication (optional)
  • Sercos
  • EtherCAT
  • EtherNet/IP
  • others on request
Fail-safe operation Internal return spring
Redundancy 2 Control magnets (cold redundancy)
Ambient temperature -20 to +80°C [-4 to 176°F] (standard version, not rated for
use in potentially explosive areas)
Explosion proof rating (optional)
  • ATEX (II 2G IIC T4, Ta = -30...+60°C)
  • CSA C/US (Class 1, Div. 1, 2, Group B, C, D, Temp. Code T4)
  • IECEx (Ex db llC T4, Ta = -30...+60°C)
  • KOSHA (Ex db llC T4, Ta = -30...+60°C)
  • others on request
Protection class IP 65
Safety integrity level SIL 2 (on request)

Advantages and benefits

  • Thanks to the redundancy provided by the two way valve magnets, the Mean Time Between Failures (MTBF) for the tandem way valve is over 360 years. Your equipment operates with maximum availability. Productivity increases and the costs associated with lost production remain low.
  • Voith tandem way valves are not sensitive to contaminated pilot oil. Turbine lubricating oil is suitable as the operating fluid. A common oil supply system for both lubricating and pilot oil suffices. Maintenance is simple, which helps you lower operating costs.
  • During load rejection, the way valve shifts the control valve to the partial-load position very rapidly (approx. 300 ms). When a shutdown command is received, the way valve shifts the control valve to the safe position (open or closed) very rapidly (approx. 300 ms). This ensures high availability of your equipment.
  • The way valve incorporates fast and exact position control. Very good control response, almost no hysteresis and a resolution better than 0.1% ensure very fast and accurate control. You benefit from having a stable process with high product quality.
  • The tandem way valve mounts to your equipment easily. This reduces the costs for integration.
  • The stroke and positioning function can be adjusted easily on-site by means of potentiometers. This allows you to adjust the stroke to the application quickly and without any delays.
  • For use in hazardous areas, we offer explosion proof tandem way valves with the required certificates.

Typical fields of use

  • Operation of the control valve of
    • steam turbines
    • gas turbines
    • compressors
  • Retrofit of mechanic-hydraulic valve controls
  • Upgrade of systems with Voith DSG I/H converters or WSR way valves
  • Upgrade of systems with partially or non-redundant Woodward CPC or CPC-II converters

Technical information


3/3 T-WSR Tandem way valve
for single-acting hydraulic cylinders

4/3 T-WSR Tandem way valve
for double-acting hydraulic cylinders

A redundant control system provides the two setpoints w1 and w2 in the form of standard 4 – 20 mA signals for the two control magnets. A separate position sensor (x1in and x2in) is connected to each control magnet. The armature of control magnet 1 acts through control magnet 2 to move the control piston of the hydraulic pilot valve. If control magnet 1 is energized, control magnet 2 is de-energized, but powered. In the event of a malfunction, control magnet 1 is de-energized and control magnet 2 is energized via setpoint w2 with a brief delay ("warm redundancy"). The switching logic is located in the external control system and monitors the control magnets (position sensor displays x1out and x2out). The switching logic also generates the switching signals.

F Force
FMag Magnetic force
FF Spring force
U Voltage
UHall Hall voltage
UMag Voltage applied to magnetic force
X0, X1 Parameters for stroke adjustment (potentiometers)
KPU, KPD Control gain settings (potentiometers)
w1, w2 Position setpoints
x1in, x2in Position sensor
x1out, x2out Position sensor display


Control schematic

Control schematic for a 3/3 T-WSR Tandem way valve

Control schematic for a 4/3 T-WSR Tandem way valve