Epson XDT manual In-situ Installation, Not Recommended

Section 2: Sensor and Sampling Techniques

2.3.1 In-situ Installation

In-situ installation is recommended only for measurements where the gas pressure is expected to vary little, the gas is expected to be free of contaminants, the gas temperature is within the operat- ing specifications of the sensor, and there is no chance of liquids coalescing. Examples of applica- tions suited for in-situ installations are: pure gases, output of desiccant dryers (for instrument air), glove boxes, etc. For most other applications in-situ installation should be avoided for the follow- ing reasons:

•Sample conditioning is almost always necessary to avoid exposure of the sensor to liquid water and other contaminants, such as hydrocarbons, which may damage the sensor or affect accuracy over time.

•Variations in line pressure affect the reading of the sensor because dewpoint varies with pres- sure.

•If the gas line is under pressure, it is more likely that water condensation occurs which may damage the sensor.

•Under a pressurized system removal of the sensor without the installation of isolation valves can be dangerous.

If in-situ installation is required, bypass mounting is preferable; make sure to install the sensor at the upper surface of the gas line to minimize its exposure to liquid water, should condensation occur, the XTR65W sensor is best suited for these applications. Also consider the need to isolate (depressurize) before installing or removing the sensor.

In-Line Installation, Sensor

Measuring at Line Pressure

NOT RECOMMENDED

Main

Gas Line

Safety shut-off Valve

Sample Cell

Bypass Installation, Sensor Measuring at Line Pressure

Safety shut-off Valve

	Bypass
Main	Control
Gas Line	Valve *

* maintain differential pressure to provide adequate flow through sample cell

The sensor measures the dewpoint at whatever pressure it is at. The instrument is equipped with a pressure correction feature which allows reporting the dewpoint at a different pressure.

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