Figure 4-2. Manometer Reading Level
A scratched tube may shatter
(2) Cleaning. When visually determined as
necessary, periodically clean manometer using the
information provided in the following paragraphs.
(a) Mercury cleaning. Use the
following procedures tor mercury cleaning:
handling mercury. A very small
amount of mercury may produce
hazardous vapors. For methods
that are used to dean up mercury
spillage, see paragraph 4-2a (6).
Clean mercury by washing in a
solution of nitric acid, Federal Specification O-N-350 (10
percent acid and 90 percent distilled water), or a solution
of sulfuric acid, Federal Specification O-S-09 (80
percent acid and 20 percent distilled water).
Using apparatus shown in figure
4-3, pour mercury through funnel and filter paper and
allow to pass through acid solution.
After mercury collects at bottom
of glass tube, open pinch cock and let dean mercury
pass into beaker. Control pinch cock carefully to
prevent acid solution from entering beaker.
through distilled water. Place beaker of dean mercury
on a sheet of asbestos and heat until dry over an open
flame not to exceed 230F (110°C).
(b) Manometer tube cleaning. Use
the following procedures for manometer tube cleaning:
When manipulating swab inside
the glass tubing, take care not to
scratched glass tube may shatter
under relatively low pressure.
1 Clean manometer tubes using a
swab attached to a medium stiff piano wire. First swab
Figure 4-1. Manometer
Change 3 4-3