The TWB concept is based on an evaporation principle. The core of the expansion assembly includes a welded bellow which allows pressures up to 35 bar, with a control path of 2.5 mm, a B 10 life of 100.000 cycles is feasible. All TWB´s are helium tested to ensure 100% leak free systems. Depending on the operating fluids, temperature ranges up to 200°C can be accomodated.The lower temperature range is limited by the ambient temperatures.


A robust thermal displacement sensor in a compact design developed specifically for the inlet control of plate heat exchangers allows this TWB to generate a fast response time. The benefit of a fast response time is often achieved at the expense of system stability, Egelhof´s solution to this problem involves the use of new probes which exhibit a larger hysteresis in the range of  1 to 2 K, this is achieved through the phase transitions from liquid to gas. Additionally, the advantage of a small probe results in encoder forces up to 300 N. Therefore, parasitic friction and valve forces habe no impact on the control funktion.

Design an installation

The small probe size of about 1 cm³ enables the use of a slender and short probe and allows the installation into a closed pipe cross section or hard to reach areas directly inside the plate heat exchangers. Length, diameter and material selection of sensors can be adapted easily to the application.


Reduction of Diameter:
The possible volume reduction results in that the diameter is reduced in smaller bellows allowing for more flexibility when designing radiators or thermostatic heads.

Reduction of Installation Height:
In case that volume is reduced due to a reduced installation height, sensor’s distance from radiator can be increased or a more compact thermostatic head can be used.

Testing, Tests, Simulation
System-oriented testing.
All of the EGELHOF products are tested in our state of the art simulation and test benches during product design.
These test installations are also offered as an external service.