Ametek 303B, User Manual

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1-2 | 303B Moisture Analyzer Manual
Sample Stream Requirements
Sampling technique is extremely important. Failure to observe needed
precautions can result in poor response, incorrect readings, or both.
Sample gas pressure must be at least 70 kPa (10 psi) gauge or a booster
pump must be used (either pressure on the inlet, or vacuum on the out-
let). See Figure 1-2.
Foreign particles are removed from the gas by the 2-micron filter. The
SAMPLE ADJUST flow controller must be set to 100 mL/min at 1 atmos-
phere. The built-in bypass system permits a portion of the sample gas to
bypass the cell while 100 mL/min flows through it.
Bypassing increases sample flow, thereby reducing the time needed for
sample to transit the line. Since sample flow is constant, the displayed
reading corresponds exactly and linearly to ppm of water vapor in the
sample.
The two most common installation errors are in selecting improper sizes
and materials for sample lines and fittings between the sample source and
the instrument. To assure good results:
• Select a take-off point representative of the sample.
• To minimize dry-down time and response, keep sample line as short
as possible.
• Use no material in the inlet system which can absorb and desorb any
amount of moisture or allow moisture permeation.
• Eliminate water absorbing materials.
• Insulate the system to eliminate large temperature swings.
• Maintain good pressure control.
• Keep the cell as dry as possible between uses.
• Remove contaminating substances from sample if possible.
• Filter out all particulate matter larger than 10 µm; if not, the internal
filter will foul quickly.
• Be sure sample temperature does not exceed 40°C.
• Be sure the sample is free of oil mist.