The 1278, 2-Wire IS-ASL Subsystem provides an "on-line" alternative to the portable VPAC™II, which is used worldwide for loss control in refineries, gas plants, and offshore platforms. It provides real-time on-line valve leak detection and quantification, with instant response when a valve leaks or sticks. This saves losses that occur between manual surveys. The unit’s on-line capability enables monitoring of difficult to reach valves, such as those on top of towers, which may never be surveyed manually. It is certified as Intrinsically Safe for use in hazardous areas with potentially explosive atmospheres. The system works with any loop-powered 24-volt, 4-20 mA system, and with an Intrinsically Safe sensor, is ready for connection to the plant DCS with a suitable galvanic or zener barrier.