Page 55 - Pipeline Rules of Thumb Handbook

42 Pipeline Rules of Thumb Handbook

for permanent record. Additional printouts of Results Recap Table 1
may be made by XEQ “DATA.” Examples of Computations Using the Cold Bend Program
Fig. 1 and Example 1 are a typical offset bend.

Fig. 2 and Example 2 are a conventional direction change.
Fig. 3 and Example 1 show receiver and launcher scraper
trap connections, where the traps are not level.

Fig. 4 and Example 3 are a crossing under a foreign line,
where offset bends are used.
The oil and gas codes differ in bending requirements.
These are defined by the radius of bend/diameter ratio. The
oil code, B31.4, specifies the R/D ratios as follows: for 12in.
and less, use 18; 14in., 21; 16in., 24; 18in., 27; 20in. and
larger, use 30.
The gas code, B31.8, specifies for all pipe 12in. and larger,
the ratio is a constant of 38.1987. (The code states “longitu-
1
dinal axis of the pipe shall not be deflected more than 1 / 2
degrees in any length along the pipe axis equal to the diam-
eter of the pipe.”)
The program prompts: Gas pipeline greater than 12in. Yes?
or No? (Gas PL => 12Y?N?). Is line gas or oil? When this
information and other data are keyed in, the proper radius is
determined and the results computed and printed out.
If the scraper trap routine is desired, it should be run
immediately after “Bend” while pertinent data are in storage;
XEQ 15 for each receiver and each launcher.
Here again the program asks if this is a receiver (R trap)
Y? or N? Note that trap angle is requested for R & L traps
(they could differ), and the length of the traps may not be
equal.
The direction change, Example 2 (XEQ 17), can be run at
any time since it prompts for input data. If this is a code bend,
then R must be determined for pipe size and service of line
by—“bend” (use results of previous run for same diameter or
key in data as shown on Example 1 to obtain R). Use this
minimum radius or any larger radius. Points on a circle of
given radius may be calculated for any angle. Subdivide angle,
and for each subdivision key in R and let T = 0, thus deter-
mining points on curve.

Formulas for reverse bends

(
R -
V = 21 cos 1 )+ 2 T sin 1
R
H = 2 sin 1 + 2 T cos 1 + 2 T
1
L = 2 R + 4 T
.
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