Fluke RUSKA 2413, Руководство пользователя

Страница: 13 / 40

2-1
Chapter 2
Applications
Introduction
The RUSKA 2416 may be employed as a null detector/indicator in the following manner:
Gas-to-Gas
The instrument may be used with dry air, nitrogen, carbon dioxide, some hydrocarbons,
and the noble gases, but not with gases containing free hydrogen or oxygen. Although
oxygen will not directly attack the materials of the lower cavity, there is the danger that
an accidentally perforated diaphragm will permit the oxygen to enter the upper cavity.
The organic materials in the upper cavity propose a hazard in the presence of compressed
oxygen. In all instances where a gas is used, no liquid vapors should be permitted to enter
the diaphragm cavity, as the surface tension effects of condensed vapors will surely spoil
the performance of the diaphragm.
Liquid-to-Gas
The instrument is used to separate a liquid pressure medium from a gas. When used with
a dead-weight gage, the transducer affords a means of calibrating elastic sensors with
inert gases. The sensors, such as transducers and bourdon-tube gages may then be used in
systems containing oxygen.
Liquid-to-Liquid
The Differential Pressure Transducer may be employed as a null detector between two
liquid systems. For instance, when calibrating elastic sensors prepared for oxygen
service, it is sometimes more convenient to use a liquid pressure medium than to use a
gas. The liquid medium, of course, must be chemically inactive in the presence of oxygen
in all concentrations. Mixtures of the volatile fluorocarbon solvents are frequently used
for this purpose. The system containing the fluorocarbon may be balanced against the oil
dead-weight gage system to pressures as high as 40,000 psi. Such systems are somewhat
more economical than equivalent liquid-to-gas systems, since the pressurizing apparatus
is less expensive.
With the possible exception of use with the highly volatile fluorocarbons, it is not
recommended that a cell be purchased for alternate use in liquid-to-liquid and
liquid-to-gas service. In order for the cell to perform properly, the diaphragm cavity must
be either completely filled with liquid, or it must be completely dry. A trace of liquid in
the otherwise dry cavity will upset the performance as quickly as will an air bubble in the
liquid cavity. In each instance, the surface tension effects are greater than the
Δ
P error
signal being observed.