Chapter 2 __________________________________________________________ Product Overview
VAISALA ________________________________________________________________________ 9
Pressure reducing valves of conventional type are provided with built-
in back pressure valves and two pressure meters. The first pressure
meter indicates the pressure inside the cylinder, and is a gauge for
estimating how much gas is left in the cylinder. The second is a low
pressure meter that indicates the highest permissible pressure on the
outflowing gas. This pressure must be adjusted according to the
required speed of gas flow.
The sounding balloons can be inflated either with hydrogen or with
helium. Hydrogen has a slightly greater lifting power than helium, it is
much cheaper than helium, and it is usually available in most parts of
the world. Hydrogen is delivered compressed in steel cylinders, or it
can be generated locally by stationary or portable generators.
Hydrogen is, however, a highly explosive gas when mixed with air.
The risk of fire or explosion can be minimized if precautions are
strictly taken into account in organizing the balloon filling room and
working procedures. See instructions for the safe operation given in
sections Regulations for Balloon Filling Sheds and Safety Instructions
for Balloon Operators.