Dry-boil protection
Run-dry protection or dry-run protection refers to a measure that is intended to prevent a device from being operated without a liquid medium (usually water).
Dry run protection for shaft bearings
With shaft bearings , the medium is supposed to cool and sometimes also lubricate. For this reason, a dry run protection is often built into the control of pumps . A sensor monitors the presence of the medium and actuates a contact. In the closed- circuit principle , this contact should be open in the dry and de-energized state, i.e. without any control voltage . Only in exceptional cases is the circuit principle used.
Dry run protection for household stoves
Electric household stoves usually have, in addition to the boiling shut-off protection in the upper part of the cooker, a dry boil protection in the bottom of the cooker. Both react to reaching certain temperatures.
The boiling switch-off protection reacts to the rising water vapor and switches off the cooker shortly before the water reaches the boiling point, usually at 95 ° C. The heat capacity of the heating plate in the bottom of the cooker is sufficient to bring the water in the cooker to a boil after switching off. The boiling point of water is under normal conditions at sea level at 100 ° C and decreases with increasing altitude.
On the other hand, the boil-dry protection in the cooker reacts to temperatures of just over 100 ° C, since the temperature of the floor only rises when all the water in the cooker has completely evaporated and the bottom of the cooker is dry. The temperature sensors for temperature protection are either bimetal switches or thermistors .
Dry run protection in industry
A vibrating level switch is often used in industrial applications . This is based on the principle that liquids dampen vibrations more than air. Other types of sensors, such as float switches , can be found in the Wikipedia article on level measurements .
Individual evidence
- ↑ Kettle safety. Kettle.com, accessed December 5, 2014 .