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PLATING AND ANODIZING: STACK TESTING

FIGURE 7: MINIMUM NUMBER OF TRAVERSE POINTS FOR FIGURE 9: AN EXAMPLE OF TRAVERSE CALCULATIONS.
VELOCITY MEASUREMENT WITH FLOW DISTURBANCE.

FIGURE 10: LOCATION OF TRAVERSE POINTS FOR
CIRCULAR AND RECTANGULAR CROSS SECTIONS.
FIGURE 8: PERCENT OF STACK DIAMETER FROM INSIDE

WALL TO TRAVERSE POINT.
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• Remote sensing

• Visual observation (Ringleman charts, opacity)

• Senses (e.g. odor)

Conclusions
Stack sampling is a somewhat more complex process than waste-
Isokinetic Sampling water sampling due to the nature of a gas over a liquid.
For particulate sampling or sampling micron-sized particles, it is Several estimation methods are available to industry for
necessary to sample at isokinetic rates. In isokinetic sampling, the compliance purposes in addition to stack testing or for NPRI re-
velocity of gas entering the nozzle is the same as the velocity of the porting.
gas in the stack at that point so as to obtain representative samples. Several pollutants are amenable to stack testing but some are
A large error can be introduced if sampling at other than isokinetic easier to assess by other methods.
velocities. Sampling at greater or less than the isokinetic rate caus- Sample location (eight downstream and two upstream rule) is
es a larger or smaller volume of gas to be withdrawn from the stack important in establishing the number of traverse points.
than the nozzle area would account for. Traverses on two perpendicular axes and the 8/2 rule deter-
mines number of points on each traverse.
Methods of Estimating Releases Isokinetic sampling is important for particulates and micron-
There are several other methods available for estimating stack re- sized particles. n
leases in addition to stack testing. Some of the methods available to
industry are:
• Material balance (mass, energy) Peter J. Paine is CEO of P. J. Paine and Associates. For additional
• US EPA AP 42 emission factors information on stack testing or if you are a chromium plater
• EEEquipment efficiency planning a stack test, contact pjpinc@rogers.com
• Continuous emission monitoring or (613) 884-9029.

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