Optical Scientific Inc
OFS 2000CW User’s Guide
P/N 1910-905
Rev. 03/28/13
15
2.5 Flange Pipe Extension
In some instances it may be to the customer’s advantage to have the mounting flange pipe section extend into
the stack instead of fitting flush with the stack wall. Flush fit or protrusion makes no appreciable difference in
accuracy of OFS flow measurement.
If the pipe end is to extend into the stack interior, a general rule to follow is not to let the end extend into the
RATA measured stack flow area which begins at a little less than 90% of the stack inner diameter.
The 10% difference may be regarded as a laminar flow area where the flow is dampened somewhat by the
stack interior surface. Since this falls outside the RATA test area, pipe protrusion should not pose a problem.
For example:
Figure 2.4 Measured Flow Cross Section
In this instance, the stack inner diameter is 65 inches. A 10% difference results in a measured area diameter
of 58.5 inches. Therefore the flange pipes may extend up to 3.25 inches into the stack interior without
impinging into the RATA measurement area.
The OFS 2000CW
has a wide range of applications, and each application has it’s own individual conditions.
Proper flange installation and alignment is basic to them all. The guidelines shown here in brief should provide
insight to most common considerations in planning or upgrading your installation.
For further help or answers to other OFS questions, see Section 13
“Technical Support”.
