Sample Transport Tubing; Bypass Flow Control; Pressure Regulator; Flow Controller - Endress+Hauser SS2100 Series Operating Instructions Manual

Operating Instructions
3.5

Sample transport tubing

Sample transport tubing must be made of an appropriate material, which may be coated, and of an appropriate
diameter for the application. The sample transport tubing may be heat-traced to prevent sample condensation or to
prevent fluctuations in measurement due to changes in ambient temperature.
3.6

Bypass flow control

A sample flow control valve and flow meter are provided to maintain a flow of fresh sample to the SCS even during
system shutdown. The flow control valve is a needle valve and should be closed gently if used to shut off flow
completely, to avoid damaging the valve. If the bypass flow meter has a glass tube, perform an occasional check for
evidence of liquid in the tube. If liquid is found in the bypass or sample cell flow meter tubes, investigate and correct
immediately.
3.7

Pressure regulator

All Endress+Hauser TDL cells are limited to a maximum 0.7 barg (10 psig) pressure. To ensure that this pressure is
not exceeded, a pressure regulator is provided inside the sample system.
3.8

Flow controller

A sample flow controller is provided with the SCS in which a flow control needle valve and flow meter similar to the
sample bypass are used. In some cases, a differential flow controller is used. As with the bypass flow control valve, if
the flow control needle valve and flow meter must be used for sample shut-off, close the valve gently to avoid
damage.
3.9

Scrubber

All trace measurement applications require the use of a scrubber. The scrubber is switched into the flowing sample
going to the measurement cell to remove the trace moisture component. A spectrum of the sample gas that is free of
H O is acquired and saved in the analyzer controller memory. This is the "dry" spectrum. The scrubber is then
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bypassed, and the sample spectrum is acquired with H
controller subtracts the dry spectrum from the wet spectrum and the concentration of trace moisture is measured.
The same dry spectrum may be used for 10 to 30 minutes, depending on the controller's program, before a new dry
spectrum is acquired.
The automatic valves that control switching the sample stream into the scrubber or bypassing the scrubber are
pneumatically operated valves.

3.10 Validation systems

System validation is accomplished in the SCS using a permeation device. Refer to Validation for trace moisture (H
or ammonia (NH ) systems →.
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3.11 Sample return and vent

Tunable diode laser spectroscopy is inherently sensitive to sample pressure in the measurement cell, so all
Endress+Hauser analyzers are calibrated for a range of sample pressures. Most applications benefit from operation
at low pressures instead of high pressures. Sometimes the analyzer is designed to vent the sample to atmosphere, or
an atmospheric pressure return system. Return to a flare or other sample return must recognize the pressure
limitations of the cell and the calibration of the analyzer.

3.12 SCS heaters

Differential analyzers have heated SCS enclosures to avoid condensation of sample components. For these trace
measurement systems, temperature stability of the SCS is critical to the measurement. Precise temperature control is
accomplished with a PID temperature controller, which maintains close tolerance on the system's temperature.
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SS2100-series Sample Conditioning System
O in the sample. This is the "wet" spectrum. The analyzer
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O)
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