Heath Consultants Odorator - Manual (Page 5)

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Natural gas (methane) to be tested enters the ODORATOR through
the barbed fitting at the gas supply inlet port. Internally, the gas passes
through an internal five micron filter to the input of a low pressure
regulator. It then passes from the output of the low pressure regulator
to the flow metering valve. This valve, located on the top panel of
the ODORATOR, is operated by the user. After passing through the
valve (when opened), the gas enters the mass flow sensor. This is
the heart of the ODORATOR. The mass flow sensor responds to gas
flow within the range of the flow metering valve.
The signal from the mass flow sensor is then processed, converted to
a digital signal and fed to a liquid crystal display (LCD). The gas from
the mass flow sensor then passes to the mixing chamber where it is
combined with air drawn in by a blower wheel. The user then sniffs
the gas / air mixture at the exhaust port. The flow metering valve
is incrementally opened and the exhaust port sniffed until odorant
is readily detectable at which time the user presses and holds the
READ switch down to display percent gas in air by volume.
The electronics and the speed of the blower wheel are calibrated so
that the concentration of the methane gas / air sample at the exhaust
port agrees with the LCD at the 20% Lower Explosive Level (L.E.L.)
which is 1.00 % gas. All other readings may be corrected using
the correction chart. The correction chart is included to linearize
the instrument within its range. To use the chart, record both the
ODORATOR readily detectable level reading and the corrected actual
value. For ODORATOR readings not specified in the chart, linearly
interpolate between the next highest and lowest points on the chart.
Do not extrapolate beyond the readings in the chart. Depending on
how much the flow metering valve is opened, the concentration of gas
in air at the exhaust port will be anywhere from zero to approximately
2%. The LCD can only indicate up to 1.99%. Concentrations above
1.99% will be indicated by the LCD having its last two digits dashed
out as “1.--”.
INTRODUCTION