Chapter 1. Installation
1-9
DigitalFlow™ GC868 Startup Guide (1 and 2-Channel)
Figure 1-5: Measuring the OD and Pipe Wall Thickness
5.
Prepare the pipe for the damping material by removing any rust or loose paint
and sanding down any rough spots in an area 14 in. long around the
circumference of the pipe. Take care to preserve the original pipe curvature.
6.
At the approximate location of each transducer, prepare an area 100 mm (4 in.)
long by 50 mm (2 in.) wide for CRV type transducers and 100 mm wide for CRW
type transducers. Remove any paint or rust, and polish the cleared area, taking
care to preserve the original curvature of the pipe.
Note:
If the paint is in a thin, smooth layer, removal is not necessary.
1.4.3
Obtaining the
Transducer
Spacing
1.
Using the measured OD and the pipe wall thickness, program the GC868
(discussed in Chapter 2,
Initial Setup
) to determine the required transducer
spacing.
2.
To determine the GC868 correction factor, calculate the mean inside pipe
diameter (ID) and the pipe ID at the transducer locations. Then divide the square
of the mean ID by the square of the ID at the transducer location, as shown in the
equations below, where OD
X
is the outside diameter at a given point, and W
X
is
the wall thickness at a given point (see Figure 1-5 on page 1-9).
(1-1)
(1-2)
3.
Program the value into the GC868.
Note:
See Chapter 2,
Initial Setup
, pages 2-11 to 2-15, for more details on
programming.
W
1
OD
1
W
8
W
7
W
6
W
5
W
4
W
3
W
2
OD
8
OD
7
OD
6
OD
5
OD
4
OD
3
OD
2
mean ID
OD
1
W
1
W
5
+
–
OD
2
W
2
W
6
+
–
OD
3
W
3
W
7
+
–
OD
4
W
4
W
8
+
–
+
+
+
4
§
=
K
for non-concentric pipe
Mean ID
2
ID at transducer location
2
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=
