Interstitial Sensors (DIS, EIS, HFS)

A double-wall tank only protects the ground if someone notices when the inner or outer wall fails. Franklin's interstitial sensors sit in the dry gap between the two walls and alarm as soon as liquid collects there. Three models cover different tank builds and monitoring needs.

The DIS is the discriminating option. A light beam travels through the probe tip to tell whether it is wet, and a microprocessor in the sensor decides whether the liquid is petroleum or water before reporting to the EVO™ console. Its fail-safe digital link raises an alarm if the sensor itself fails. The EIS also works optically, with LEDs and prisms, but only reports that liquid is present. Its polysulfone body resists chemicals, and it can also be used in sumps.

Installation depends on the tank. In a steel double-wall tank, the DIS or EIS is lowered straight to the bottom of the interstitial space through the 2" NPT fitting provided on the tank. In fiberglass tanks it is pulled into the space with a fish string or wire. For tight fiberglass interstices Franklin offers the HFS, a 2-wire magnetic float and reed switch sensor whose rounded shape makes it easy to pull out for cleaning and refit after an alarm. Riser cap kits TSP-KI2 (2") and TSP-KW4 (4") complete the installation.

Apex supplies and installs interstitial sensors in Lebanon for new double-wall tanks and for monitoring upgrades on existing ones.