Sample Conditioning System
Hardware Installation and Maintenance Manual 4
–3
Sample conditioning system filters
The sample system is equipped with a membrane separator, which is ideal for
the removal of relatively small amounts of liquid present on a continuous basis
(i.e., aerosols and suspended liquids). If two-phase fluids and free-flowing
liquids flow through the analyzer and sample system, it may flood and require
cleaning. Permanent damage from liquid flooding is not likely.
A guard filter is typically installed at the inlet to the SCS with a fine element to
protect the flow controllers, flow meters and pressure regulators from fine
particulates.
A bypass filter with a fritted metal, glass fiber or polymetric membrane filter
may also be in place to remove larger quantities of particulates or entrained
liquids and mists. Some filters may fit with liquid knock-out traps to protect the
system from free liquids.
Accumulation of liquids in the guard and bypass filters or a steady flow of liquid
from a liquid knock-out trap should be investigated and corrected immediately
as this is generally an abnormal condition.
Sample regulator heaters
In most applications, the process sample is at high pressure. When the
pressure is reduced, the sample cools due to the Joule-Thompson effect.
1
The
amount of cooling varies greatly depending on the application, but oftentimes
must be offset using a heated sample regulator to prevent condensation of
1 Named for James Prescott Joule and William Thomson, the Joules-Thompson
effect describes the increase or decrease in temperature that accompanies
the expansion of gas without production of work or transfer of heat. The
cooling occurs because work must be done to overcome the long-range
attraction between the gas molecules as they move farther apart. (www.bri-
tannica.com)
SSI
Analyzer
Heated Enclosure
Heat Trace
Heated
Enclosure
Probe
Regulator
Figure 4–1 Probe to analyzer interface
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