Chapter 2. Installing the Pipe Nozzles
12
Model T17 Installation Guide
2.2.4 Installing the First Welding Boss - Diametrical
To install the first welding boss, complete the following steps:
1.
Before welding the first boss, you must add another scribe line to the pipe, known as the oblique center line.
The oblique center line compensates for the slope or oblique angle of the boss. The oblique center line is offset
from the true vertical center scribe line marked earlier by a distance
X
, which is dependent on the pipe outside
diameter and the welding boss diameter as follows:
where, D = pipe outside diameter
d = welding boss outside diameter (1.660 in.)
Using the above equation, values of
X
for some common pipe sizes were calculated and are listed in
2.
Scribe the oblique center line on your pipe at the calculated distance from the true center line for your pipe
size. The oblique center line should be marked on the side of the true center line that is closer to the second
nozzle location, as shown in
below.
Figure 17: Scribing the Oblique Center Line
Table 1: X Values for Common Pipe Sizes
Pipe OD
X Dimension
NPS (inches)
DN (mm)
inches
mm
12
300
0.058
1.37
14
350
0.049
1.24
16
400
0.043
1.09
18
450
0.038
0.97
20
500
0.035
0.89
22
600
0.031
0.81
24
650
0.029
0.74
26
700
0.027
0.68
X
D 2
⁄
d 2
⁄
sin
-1
d D
⁄
(
)
[
]
tan
-----------------------------------------
–
=
True Center Line
Oblique Center Line
Side View
