Mica Shields
are widely used in visual liquid level gages to protect the glass
surface from the corrosive effects of hot alkaline or acidic
solutions. Mica is commonly used in steam water applications to
prevent etching and the weakening of the glass.
Mica Selection: The quality of mica used in visual liquid level
applications continues to be determined by visual examination where
the suitability is assessed on the basis of appearance. In this
process of quality evaluation undue emphasis is placed on clarity,
color, flatness, hardness, stains, visible inclusions and structural
imperfections. As a result of this procedure, Mica is classified
according to grades.
The most common grades used in liquid level gage applications are
as follows:
V2 Ruby Clear and slightly stained - navy grade quality, hard, of
uniform color, may contain slight crystallographic discoloration, free
from all vegetable and mineral stains, cracks, buckles and other
similar defects and foreign inclusions except for a few tiny air
inclusions in more than one-fourth of the useable area.
- Suitable for saturated steam service from 600 to 1500 PSIG
- Conforms to ASTM D351 specifications
- Government spec. number: MILG-18498A
- Thickness from .009 to .012 in single piece or in two pieces (the
thinnest not less than .0045).
V4 Ruby good stained - hard, of uniform color, may contain
slight crystallographic discoloration, free from vegetable and mineral
stains, cracks, buckless and other similar defects and foreign
inclusions, except somewhat wavy but not rippled, may contain some air
inclusions in not more than two-thirds of the usable area.
- Suitable for saturated steam service from 300 to 600 PSIG.
- Conforms to ASTM D351 specifications and the Government spec. number:
MILG-18498A
- Thickness from .009 to .012 in single piece or in two pieces (the
thinnest not less than .0045).
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