These level gauges are particularly suitable for liquids :
- Very Fluid
- Non-corrosive for glasses (e.g. ammoniacal solutions, trichlorethylene, water steam up to 32bar, etc.)
Bicolour level gauge will parallel glasses. Working Principle :
It is a variation of transparent level gauge, however equipped with two reflex glasses and a back illuminator, fitted with suitable coloured fitters. The reading is given by the contrast between the bright colour (usually:red) of fitters in the lower part containing liquid and the colour of upper part of visible window.
The drawing shows a typical Reflex Glass Level Gauge. This instrument consists of a metal body, machined to have an internal chamber and one or more front windows (on one side only of the gauge).
On each window a special high resistance plate reflex glass is fitted with sealing joint and metal cover plates hold by bolts and nuts.
The chamber is connected to vessel with cross fittings and flanged, threaded or welded ends. Usually, between the instrument and its connecting ends, valves are fitted to consent shut-off piping and to disassemble the level gauge without to empty the vessel. Drain valves can also be fitted to cross fittings device.
To avoid leakage in case of glass breakage, safety ball-check device can be provided.
Working Principle :
Reflex level gauges working principle is based on the light refraction and reflection laws.
Reflex level gauges use glasses having the face fitted towards the chamber shaped to have prismatic grooves with section angle of 90°. When in operation, the chamber is filled with liquid in the lower zone and gases or vapors in the upper zone; the liquid level is distinguished by different brightness of the glass in the liquid and in the gas/vapor zone. The reflex level gauges do not need a specific illumination: the day environmental light is enough. Only during the night an artificial light must be provided.