Reflex Level Gauge

A reflex level gauge uses a single glass with prismatic grooves on the process side. Where there is vapour the light reflects off the grooves and the glass looks bright and silvery; where there is liquid the grooves are wetted, the light passes through and the glass looks dark. The contrast is strong enough to read from across the plant without illumination, and with only one glass and one gasket the gauge is the most economical and the most robust of the glass types.

Gauges are made in sections up to 2.5 m and combined for longer ranges, with pressure ratings to 400 bar and temperatures from −160 to +400 °C. Bodies are carbon steel, 316 or 316L stainless steel, or LF2 for low-temperature service, with borosilicate or aluminosilicate glass. Mounting is side-side, side-bottom, top-side or top-bottom with flanged, threaded or weld-stub connections, and the gauge is fitted with isolating valves incorporating ball checks that close automatically if a glass breaks. A graduated scale, insulation, electrical tracing and anti-frost protection are available, and a relay output where a switch is needed.

Reflex gauges are not suitable for interface between two liquids or for fluids that must be seen in colour, and on steam above about 30 bar the prisms erode; those services take a transparent gauge.

Applications are level indication on clean liquids, cryogenic services and general process vessels in oil and gas, petrochemical, chemical, power, water treatment, marine and general industry.