Media
Your medium to be controlled influences which valve body material and which sealing materials must be used. Different materials have different chemical resistance.
Valve body material
- Stainless steel: suitable for all kinds of chemicals and food-safe media.
- PPSU: suitable for all possible chemicals and food-safe media. Can be manufactured more rationally compared to stainless steel in high quantities.
Seal material
EPDM is well suited for alcohol and acidic media. EPDM tends to swell with oil-containing media and is therefore unsuitable for this. In addition to alcohols and acids, FKM can also be used for oily media. Both materials are used in dialysis valves.
Temperature
Knowledge of medium temperature, ambient temperature, and duty cycle is essential to find a suitable solenoid valve:
Continuous temperature stress
Continuous temperature stress is a critical issue when selecting valve components. In particular, plastics degrade over time and temperature and retain only a fraction of their original properties. The temperature a component will experience depends on the ambient temperature in the device, the media temperature, the heat generated by the solenoid system when energized, and the duty cycle of the valve. But also knowledge of the installation situation in the device is important.
The components in a dialysis valve, for example, have to endure extreme continuous temperature stress: In a hemodialysis unit with typical ambient temperatures of 80°C, the valve components sometimes feel temperatures of 150°C. Since the valves are expected to operate maintenance-free for 10 years or 50,000 hours, the continuous temperature stress is enormous. Even after this stress, the valve must still function perfectly – the material properties must therefore not have fallen too far. Accordingly, great care must be taken in the selection of the materials used.
EPDM and FKM as sealing material, PPSU as valve body material, and PTFE as bellows material cope well with extreme temperature stress (150 °C for 50,000 hours).
Stainless steel is of course also very well suited as a valve body for high-temperature chemical resistant solenoid valves.
Maximum temperature
The maximum temperature to which the valve is exposed has a significant influence on the sizing of the solenoid system. This is because the current that can flow through the coil decreases with increasing temperature, as its resistance increases. The solenoid system, therefore, has less force to switch the valve open.
Pressure Tightness
When considering pressure tightness, it makes sense to think about the necessary flow at the same time, since they are negatively correlated. In concrete terms: for the same spring force and solenoid system size, the requirement for a higher pressure tightness simultaneously means that the flow through the valve must be smaller.
In addition, it is important to know that there is a preferred direction of media flow through the valve where higher pressure tightness is possible.
Our valves have flow rates from 2.5 l/min to 4.3 l/min at a pressure difference of 1 bar. Max. pressure tightness in both directions from 2.5 to 3.0 bar. In preferred direction up to 6.0 bar.
Please call us to discuss your application – customizations are also available; call +49 9723-938917 for more information.