Sample Conditioning; Contamination Precautions - Emerson Daniel Danalyzer 1000 Hardware Reference Manual

MODEL 1000
Typically, pressure is reduced at the sample point with a pressure regulating sample probe. The input
pressure to the Analyzer can be adjusted between 10 and 20 pounds per square inch, gauge (psig).
Reducing the pressure at the sample point avoids the problem of heavy liquid dropout in the sample
line during cold weather. The flow rate in the sample line is set at 50 cubic centimeters (cc) per
minute with the restrictor valve at the Analyzer.
The Model 1000 is capable of accepting liquid phase samples also. In this case, the pressure is
regulated by means of a back pressure regulator located on the SCS mounting plate. If the stream
is at ambient pressure or under slight vacuum, an educator or pump may be used to force sample
through the sample loop. In this situation, sample shut-off technique with equalizing coil is
employed to ensure consistency of the sample volume.
Use this general rule to approximate sample lag time caused by the length of sample line. Sample
line constructed of 1/8-inch tubing contains approximately 1 cc of volume per foot. Therefore, with
a flow rate of 50 cc per minute, the lag time of the sample between the sample point and the
Analyzer is calculated by dividing the length of the line (in feet) by 50. For example, the sample in
a 100 foot sample line will take 2 minutes to travel the length of the line.
2.1.3

Sample Conditioning

Sample systems should contain at least one filter to remove solid particles from the sample stream.
Most applications require fine-element filters upstream of the Analyzer.
2.1.4

Contamination Precautions

Several precautions are recommended to minimize the possibility of contaminating samples. Except
in special applications, filters should be of either the ceramic or the porous metallic type to avoid the
absorption losses characteristic of fiber or paper filters. Pressure regulators and flow controllers
containing cork or felt filters or absorbent diaphragms should not be used. Sampling lines for
noncorrosive streams should be stainless steel tubing and must be clean and free of grease. Lines
must be pressure tight to prevent diffusion of moisture or atmospheric gases into the sample. Pipe
threads should be dressed only with Teflon tape on pipe threads and never with pipe thread
compounds (dope).
EQUIPMENT DESCRIPTION
SEP 2005
2-3