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Chapter 2. Installing Pipe Nozzles
2.5 Installing the First Welding Boss
1. Before welding the first boss, you must add another scribe line known as the oblique center line. The oblique center
line compensates for the slope or oblique of the boss. The oblique center line is offset from the true center (vertical)
scribe line marked earlier by a distance of "X," which is dependent on the pipe outside diameter as follows:
where:
D = pipe outside diameter
d = welding boss outside diameter, 1.660 in. (4 cm)
Table 1 below shows values of X for various pipe sizes.
2. Scribe the oblique center line on the pipe at the prescribed distance from the true center line. The oblique center
line should be marked on the side of the true center line that is closer to the second nozzle location.
10
D 2
X
=
Table 1: X Values for Various Pipe Sizes
Pipe
NPS (DN)
6 in. (150 mm)
6.625 in. (17 cm)
8 in. (200 mm)
8.625 in. (22 cm)
10 in. (250 mm)
10.75 in. (27 cm)
12 in. (300 mm)
12.75 in. (32 cm)
14 in. (350 mm)
14.00 in. (35.5 cm)
True Center Line
d 2
–
------------------------------------------ -
1 –
tan
sin
d D
O.D.
X Dimensions
0.106 in. (2.69 mm)
0.081 in. (2.06 mm)
0.064 in. (1.62 mm)
0.054 in. (1.37 mm)
0.049 in. (1.24 mm)
Oblique Center Line
Side View
Model T9 Ultrasonic Flow Transducer Installation Guide
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