Correct and Incorrect Tube Layout.
Minimum Bend Radius. The metal at the heel of a bend in tubing is
always stretched to some extent. This stretching weakens the tubing
and must be kept within limits.
The radius of the sharpest bend
permissible in a given size tubing is designated the "minimum bend
radius." If this limit is exceeded, the metal at the bend is subject
to rupture under operating pressure.
Bends of a greater radii than
the minimum allowed are always preferred.
The methods of tube
bending and the tools used in bending operations are discussed later
in this section.
The table of minimum bend radii for various types and sizes of
tubing is contained in TM 1-1500-204-23-2. A copy of this table is
shown in Table 2-1 on the following page.