Edgetech PPM1, Руководство оператора, Страница: 12 / 29

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5.0 OPERATION
5.1 STARTUP
IT IS RECOMMENDED THAT A NEWLY INSTALLED INSTRUMENT BE DRIED
DOWN WITH DRY INERT GAS SUCH AS BOTTLED NITROGEN BEFORE
FINAL CONNECTION IS MADE BETWEEN THE SAMPLING SYSTEM AND
THE PROCESS GAS STREAM.
5.1.1 DRY DOWN PHASE 1
THE DRY GAS SHOULD FLOW THROUGH THE SAMPLING SYSTEM ONLY
(BYPASSING THE SENSOR) FOR THE FIRST FEW HOURS.
This procedure is recommended because during construction of the sampling
system, the components are exposed to the moisture in the ambient air, which
under normal conditions, can easily exceed 30,000 ppmv. These components
will be in equilibrium with the ambient air (having adsorbed moisture on their
surfaces). This water vapor will be desorbed from the walls of the tubing and
other surfaces of the sampling system components once the gas sample starts to
flow.
Unless steps are taken to remove any moisture in advance by following the
PHASE 1 dry down procedure, much of the moisture desorbed from the surfaces
of the sampling system will enter the electrochemical cell, most probably
exceeding the moisture concentration that the cell is designed to handle.
5.1.2 DRY DOWN PHASE 2
THE FLOW OF DRY GAS SHOULD THEN BE ROUTED THROUGH BOTH THE
CELL AND THE SAMPLING SYSTEM ASSEMBLY FOR AT LEAST ONE OR
TWO HOURS.
This procedure is recommended to dry down the measurement cell, and to
equilibrate the entire sampling system.
NOTE: ONCE THE ANALYZER HAS BEEN POWERED, THE POWER
SHOULD NOT BE SHUT OFF. FAILURE TO ADHERE TO THIS PROCEDURE
COULD SHORTEN THE USEFUL LIFE OF THE MEASUREMENT CELL.
The rationale behind this recommendation is that if power is always applied to
the measurement cell, any moisture that accidentally gets into the sampling
chamber will be eliminated by electrolyzing the water vapor molecules. This
keeps the moisture level on the phosphorous pentoxide low, lengthening its life.