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2.3.4 Installing the First Welding Boss - MR1 Mid-Radius
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
diameter as follows:
D 2W
–
------------------ -
Y
=
0
2
Note: For convenience, refer to Table 5 on page 30 for tabulated values of the
sizes. For any values not listed in the table, calculate your
•
Example: To demonstrate the calculations, consider an
a. From standard pipe tables: pipe OD (D) = 48.000 in. and pipe wall thickness (W) = 0.375 in.
b. From GE documentation: welding boss OD (d) = 1.660 in.
c. From the 1st equation: Y
d. From the 2nd equation: Y
e. From the 3rd equation: X = SQRT ((48.000/2)
Note: In the above example, the tabulated pipe OD of 48.000 in. was used in the calculations for clarity. Ideally, the
measured average pipe OD would be used instead.
Model T17 Installation Guide
×
(
)
Chord Location
d
-- -
Y
Y
where, d = welding boss OD = 1.66 inches
=
+
1
0
2
2
D
2
--- -
(
)
X
Y
=
–
–
0
2
= (48.000 - (2 x 0.375))/2) x 0.5 = 11.813 in.
0
= 11.813 + 1.660/2 = 12.643 in.
1
where, W = 0.375 inches and Chord Location = 0.5
2
D
2
--- -
(
)
Y
where, D
–
1
2
dimension with the equations above.
X
installation for a STD Schedule, 48" pipe.
MR1
2
2
- 11.813
) - SQRT ((48.000/2)
Chapter 2. Installing the Pipe Nozzles
, which is dependent on the pipe outside
X
pipe OD
=
X
dimension for some common pipe
2
2
) = 0.492 in.
- 12.643
29
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