CiDRA SONARtrac GVF-100 - Manual (Page 21)

Copyright © 2006 CiDRA Corporation Page 7-3
20675-01 Rev 02
WARNING
Asbestos containing insulation materials may be present.
Asbestos fibers have been known to cause health problems. If
unsure of the contents of pipe insulation materials contact the
plant representative for that area.
WARNING
Process Heating Tapes may be present. This may present an
electrical shock hazard. Follow plant Lock-out / Tag-out
requirements.
WARNING
Process pipes may be hot. A burn hazard may exist. Use care
when working with hot pipes.
Clean pipe surface using a scraper, sand paper strips, a water (or
solvent for greasy pipes) rinse and final wipe with a clean rag. The
pipe surface under the sensor band assembly should be clean and
free of rust and rust spots, grit, grease, protruding weld spots and
weld splatter. A good guideline is to clean the pipe as if it were going
to be painted.
Avoid dents as they can create flow disturbances within the pipe.
Select a location that ensures full contact between the sensor and the
pipe.
Painted surfaces are normally satisfactory provided they are smooth
and free of chips over 0.25-inch (6.4 mm) diameter. Ensure a smooth
painted finish by sanding the area where the sensor will be mounted.
Finally, wipe the pipe using a damp cloth rag or paper towel.
7.4.2 Determine the Pipe Inner Diameter (ID)
Record the nominal pipe size based on the pipe size and pipe
schedule, as this will be input into the transmitter.
Alternatively, measure and calculate the pipe ID. Accurately measure
the pipe outside diameter (OD). Use an ultrasonic thickness
measurement gauge to determine the wall thickness (t
w
) at a minimum
of 4 locations equally spaced around the pipe and average the
measurements. Calculate the pipe inner diameter (ID = OD – (2t
w
)).
(There are several vendors of ultrasonic thickness gauges.)
Note: The accuracy of the pipe inner diameter measurement is critical
for high accuracy flow rate measurements as there is a direct
correlation between this measurement and the reported flow rate.