This component comes in many shapes, sizes and types designed to detect changes in the condition of the interstitial space (the space between two walls of a double-wall tank) of a double-wall tank.
Some are designed to operator in a "dry" mode. When a liquid comes in physical contact with the sensor it will send a signal to an electronic console or trip a switch to initiate an audible and/or visible alarm. Some interstitial sensors are designed to operate in a "wet" mode. The most common configuration for this type is the hydrostatic sensor.
This sensor is usually mounted inside a column connected to the interstitial space of the double-wall tank. The column and interstitial space of the tank are filled with a liquid (usually a brine solution). When a leak occurs the level of liquid in the column changes. The sensor is designed to detect this change and will signal an electronic console to generate an alarm (audible and/or visible) when the change in level reaches a preset distance, which is determined by the volume of the liquid that leaks from the interstitial space.
There are other types of sensors designed for monitoring changes in the pressure or vacuum placed upon an interstitial space. When preset amounts of change in either are detected the sensor will send a signal or trip a switch to generate an audible or visible alarm.
Interstitial sensors (regardless of type or design) must be UL® rated, compatible with the product stored in the tank, and have a COMM 10 Material Approval for use in UST systems within the state of Wisconsin.
Consult with the manufacturer of the sensors installed at your UST facility to determine their capabilities, setup, operating, and maintenance requirements.