Checkline TI-25DL - Manual (Page 12)

– 12 –
the surface and does not exceed 0.020" (20 mils or 500 microns) in
thickness. Please note that the paint or coating thickness will be
included in the overall wall thickness measurement.
The surface to be measured should be relatively clean and smooth, free
of any small particulate, rust or scale. The presence of any of these
conditions will prevent stable and reliable readings. Often, a wire
brush, sandpaper or scraper will be helpful in cleaning the measure-
ment surface. In situations where the surface is heavily corroded or
pitted, a rotary sander, or grinding wheel will be necessary to properly
prepare the surface for measurement. If the surface is still “rough”
after preparation, using a more viscous couplant fluid similar to petro-
leum jelly or K-Y jelly will help obtain a stable, reliable measurement.
This type of “thick” coupling fluid is a good choice when measuring
on vertical surfaces or on the underside as it will help adhere the probe
to the measurement surface while also acting as the coupling agent.
Extremely rough surfaces such as the “pebble-like” finish of some cast
irons, will prove most difficult to measure. These kinds of surfaces act
on the sound beam like frosted glass acts on light; the beam becomes
diffused and scattered in all directions.
Rough surfaces also contribute to excessive wear of the probe,
especially in applications where the probe is “scrubbed” along the
measurement surface for use in the Scan mode. The probe should
be inspected regularly for signs of uneven wear on the probe surface
(wearface). If this is detected, the probe should be returned to the
factory for repair or replacement.
– 25 –
6. If two materials are press-fitted or laminated together, the gauge
will only measure the thickness of the sample that contacts the
probe.
9.2 Measurements Of Pipes Or Cylindrical Parts
When using the TI-25DL to mea-
sure the wall thickness of a pipe,
the orientation of the probe is very
important to obtain accurate
readings.
Pipe diameter is greater than 4 inches (100 mm)
Position the probe so the centerline
of the probe wearface is perpen-
dicular to the long axis of the pipe
as shown in illustration “A.”
Pipe diameter is less than 4 inches (100 mm)
Two measurements should be performed at the same location, one
with the centerline of the probe perpendicular to the long axis and one
parallel (Illustration “B”).
The smaller (thinner) of the two measurements should be used as
the actual wall thickness at the measurement location.
Additionally, on applications on pipe diameters less than 1.5
inches (38 mm), we recommend using the optional V-Block
fixture which helps maintain stable probe placement on the
rounded measuring surface.
A
B Parallel
Perpendicular