drawing shows a typical Transparent Glass Level Gauge.
This instrument consists of a metal body, machined to have
an internal chamber and one or more front windows (on each
side of the gauge).On each window a special high resistance
plate transparent glass is applied with sealing joint and metal
cover plate 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 in cross-fittings
or shut-off valves.To protect glass surfaces from corrosive
action of the process fluid, Transparent Level Gauges can be fitted
with Mica shields or Polytrifluorochloroethilene shields.This kind
of indicator is suitable for liquids colorless and very fluid.
variation of transparent level gauges, however equipped with
a special back illuminator, as described in Bicolor
level Gauges, gives a sharp reading
made by contrast between bright colors: green in lower part
(liquid) and red in upper part (steam) of visible window. This kind
of indicator is suitable for water/steam.
some case (i.e. for water / steam) the best reading is obtained
by conveying upwards on the surface of separation (liquid/steam
or vapor interface), a source of light, located on the back
of the gauge, the rays of which are totally reflected down
to the observer.
Transparent level gauges are suitable for all application.
In fact they permit:
use of mica shields or Polytrifluorochloroethylene shields to protect
the glass from the corrosive action of the process fluid;
observation of interface;
observation of the liquid color.
range of transparent level gauges covers from PN 16 up to PN 420/
ANSI 150 up to 2500 lb, and can be manufactured, depending on model
& type, in different materials, as ASTM A105, ASTM A350
LF2, ASTM A182 F304 / F316, Monel, Hastelloy, Incoloy, Carpenter,
Nickel, Titanium, Zirconium, Tantalum, Ebonite, PVC, Polypropropilene,
Level Gauge Material Schedule