McNab Model S/D Stack Opacity Monitor/Controller
monitors smoke or dust density by measuring attenuation of calibrated beam
of light passing through exhaust stream
Related Technical Papers/News Releases:
If you must continuously monitor the
density of particles passing through a smoke stack or an exhaust duct, the
McNab Optical Products Model S/D opacity monitor/controller should be your
instrument of first choice. Here's
All that is required are two holes on
opposite side of the smoke or exhaust stack fitted with flanged nipples.
Stacks up to 75 inches in diameter can be accommodated. The light source
assembly is bolted to the flange on one side of the stack; the photo-cell
scanner assembly to the other; no obstructing sampling devices are placed
in the stack. When required,
a source of instrument clean air is connected to both assemblies to
continuously purge optical elements of contaminants.
No focusing is required.
A unique laminar-flow air-sweep
system keeps optical elements clean and clear for a minimum of three
months between cleanings. Wing-nut
clamps permit easy removal of optical modules for cleaning.
Advanced electronic circuitry permits
use of minimal optical surfaces, further reducing need for periodic
cleaning. Optical surfaces have been reduced by 50 per cent for increased
optics provide long-term stability. The
graph below compares the opacity of a McNab Model S/D over a 14-hour
period with that of a typical competitive unit under actual and identical
operating conditions. Note
that the competitive unit would have to be cleaned every six hours to
prevent false readings. The McNab unit remains accurate throughout the
period and would continue to do so for months to come, thanks to its
unique air-sweep system.
The light source and the photo-cell
scanner are optically pre-focused individually and together at the McNab
factory so a field optical technician is not required for installation or
operation. A clear stack
gives a 0 Ringelmann (0 per cent opacity) reading, and a totally opaque
stack gives a 5 Ringelmann (100 per cent opacity) reading.
Field focusing is not needed.
Electronic control circuitry keeps the intensity of the light
source uniform throughout lamp life. For those who require periodic
calibration records, McNab can supply kits of calibrated, graduated glass
optical filters with known smoke-density ratings.
Optional Output Devices
McNab can supply output devices to meet your particular requirements. Simplest are panel assemblies, AP-I SD, with meters and repeater relays which provide alarm contact closures (rated at 5A @ 230V). Where environmental regulations require continuous records, strip chart recorders, AP-IIl SD, can be provided.