envea STACK 602, User Manual

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9 Maintenance STACK 602
20
(PC-000848-MA Issue 5, December 2021)
ENVEA UK Ltd
3.2 Principle of Operation
Figure 4: Principle of Operation – DynamicOpacity
®
sensors.
The STACK 602 measures the effect of particles on a light beam transmitted across
the stack. The instrument measures the ratio of the temporal variation in intensity,
unlike traditional opacity instruments, which simply measure the beam intensity.
The variation in intensity derives from variations in the distribution of particles in
the flue gas stream. A linear relationship between instrument output and dust
concentration has been demonstrated in third-party, independent approvals, such
as TUV. This permits the instrument to be calibrated in mg/m³ by comparison to
the standard reference method (SRM) of isokinetic sampling (refer to ISO
9096)
for specific applications, such as fixed-load power plants and electrostatic
precipitator (ESP) applications. The STACK 602 measures dust using dynamic
opacity mode and provides concentration (mg/m³) outputs.
What is Dynamic Opacity?
DynamicOpacity
®
technology measures the amount of variation in the light
reaching the Receiver as a proportion of the total received light.
dynamic opacity
=
light variation/total light intensity
The advantage of dynamic opacity is that it is less affected by window
contamination (accurate up to 90% window contamination). Window
contamination will reduce the total light intensity showing up as an artificial
opacity reading. However, the light variation due to dust moving in the stack
should decrease by a similar amount, so the dynamic opacity ratio is unaffected.