The Series 55 is an electrical indicator with automatic reset.

With its optional manual and automatic reset capabilities, the Series 55 is a highly sought after member of Apache’s pigPRO™ Series, a patented line of intrusive pig passage indicators that reliably detect the precise location of a cleaning pig as it travels within the pipeline network. When a cleaning pig passes the system’s intruding plunger, it activates the plunger and triggers a visual flag indicator, signaling the pig’s location.