April 2004
3-6
Performing a Pipe Survey
Finding a location where the pipe is concentric is important for
optimum accuracy and performance. If possible, perform a pipe
survey with an ultrasonic thickness gauge to find the best
location.
2. Clear rust or loose paint and measure the wall thickness at five
points along the pipe axis at 25 mm (1-in.) intervals using an
ultrasonic thickness gauge, as shown in Figure 3-4 below.
Check each point three times and record the mean values. If
the maximum variation between the five points exceeds 0.25
mm (0.010 in.), find another location.
Figure 3-4: Measuring Thickness Along the Pipe Axis
3. Measure the outside diameter (OD) of the pipe using a tape
measure or the supplied layout tape. Using the entire layout
tape, mark two circumferential lines along the edges of the
wrap, as shown in Figure 3-5 below.
Figure 3-5: Measuring and Marking Circumference
Lines