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ATI A15/66 Residual Sulfite Monitor

O&M Manual

Rev-W (8/10)

INTRODUCTION

The Model A15/66 is an on-line monitoring system designed for the continuous measurement of

sulfite ion (SO

) in solution. The full scale operating range of the system may be selected by the user for

0-2.000 PPM or 0-20.00 PPM, and the sensing system will operate on water streams with temperatures

from 0 to 50C. The Monitor is designed for dechlorination applications where sulfur dioxide gas or

sodium sulfite or bisulfite are used to remove chlorine from water streams.

Sulfite ion measurement is made in the A15/66 system by pumping a small amount of sample out

of the inlet overflow assembly, mixing the sample with acid to convert the sulfite ion to sulfur dioxide gas,

and then air stripping the SO

for measurement in the gas phase. A sulfur dioxide gas sensor located in

the flow block next to the air stripping chamber measures the concentration of SO

in the gas stream, and

is connected to an electronic module with converts sensor signals to a direct concentration display.

The measured sulfite concentration is displayed on a backlit liquid crystal display on the front of

the instrument. Depending on the full scale operating range selected, the unit will display sulfite with a

resolution of either 0.01 PPM (10 PPB) or 0.001 (1 PPB). A 4-20 mA output is provided for recording or

data logging. The output can be programmed for a variety of ranges as is described later in this manual,

with a minimum range of 0-0.1 PPM and a maximum range of 0-20 PPM. Alarm contacts are also

standard in the electronic package and may be used either for simple control schemes or for signaling

operators of abnormal operating conditions.

The standard model A15/66 system includes three main components, a wall mounted NEMA 4X

electronics unit, a chemistry module housed in a wall-mount enclosure, and a sample inlet overflow

chamber with standoff bracket. The electronics is also available in a panel mount version if preferred for

a particular application. For connection of the chemistry module to the electronics, a 20' sensor cable is

supplied, and the cable length can be increased to 100' maximum.

Figure 1 on the following page shows a typical installation of this monitoring system. For

convenience in installation, a special stainless steel mounting panel is available. This panel provides

mounting locations for the monitor, chemistry module, and overflow chamber. In addition, it contains a

shelf at the bottom for locating the reagent containers used in normal operation. The drawing in figure 1

provides mounting hole dimensions for the optional stainless steel mounting panel.

While the monitor is suitable for outdoor mounting, the chemistry module should have additional

protection mounted outdoors. It is best to mount the chemistry module and reagents inside a general-

purpose enclosure to keep wind driven rain off of the pumps located on the bottom of the chemistry

module. Do not put the chemistry module in a sealed enclosure. Sample leakage from the overflow

chamber must have a place to drain in case of an overflow or sample line break.

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Analytical Technology A15 Dokumentacja Strona 6