Table 16-5.--Bolt-Stud Elongation Table
bolts one by one with permanent bolts-studs, and torque
to proper tension.
Stress (psi), based on
(inches per inch
cross-sectional area at root
of effective length)
dieter of thread
MARINE MECHANICAL PIPE
Swage maine fittings (SMF) and elastic strain
preload (ESP) fittings are new processes that have been
approved by NAVSEA for the mechanical joining of
pipe and tubing. These two processes employ
mechanical fittings vice welding and brazing to join
pipe. They have several advantages over welding and
brazing. They may be used when "hot work" is not
allowed. It is a lightweight, portable, one person
operation that greatly reduces the man-hour
requirements of a job. The absence of flux, slag, or
The C-frame spans the bolts-studs, and the amount
oxides eliminates the need to flush pipe interiors. SMFs
of elongation is measured with a dial micrometer. Table
and ESP fittings may be used on high-pressure,
16-5 is a bolt-stud elongation table.
low-temperature systems. The following sections will
The following example illustrates the use of tables
discuss both of these methods in greater detail.
16-3, 16-4, and 16-5. Suppose you are required to make
up a flanged joint in a 150-psi system. You are using a
SWAGE MAINE FITTINGS
metallic-asbestos spiral-wound gasket of the type
covered in specification MIL-G-16265, high-
The tools used to install swage fittings are portable
temperature alloy steel, and studs 1 inch in diameter
and require only one operator. The major tool is a
with an effective length of 6 inches. Table 16-3 shows
hydraulic pump, which is normally air-powered. The
that the amount of stress required for proper
pump drives an actuator that converts hydraulic
compression of the gasket is 30,000 psi 10 percent.
pressure to linear travel and sufficient force to swage
Table 16-4 tells you that approximately 245
the fittings onto the pipe. Different die sets are used with
foot-pounds of torque must be applied to obtain a stress
the different types and sizes of fittings. Specific gauges
of 30,000 psi in a l-inch alloy steel bolt or stud. From
are used to measure the pipe, locate fittings on the pipe,
table 16-5, you find that the elongation of 30,000 psi
and ensure that the fitting has been swaged completely.
should be 0.001 inch per inch of effective length. Since
The following equipment is necessary to install swage
the effective length is 6 inches, the elongation of the
stud when stressed to 30,000 psi should be 0.006 inch.
Power unit--Comes in 13-, 31-, 40-, 70-, and
After applying 245 foot-pounds of torque with a
100-ton units. Requires 5,500 to 10,000 psi of
torque wrench, check the elongation of the stud. If the
elongation is 0.006 inch, then a 30,000 psi stress has
Swage head assembly--Consists of a die holder
been applied and the joint is properly sealed. If the
assembly to hold the lower die half and the yoke
elongation is less than 0.006 inch, increase the torque
assembly to hold the upper die half (fig. 16-24).
until the stud is elongated to 0.006 inch.
Cold Pull-up Joints.--Some flanged joints were
Die set--Two dies. The halves contract radially
originally assembled during the cold springing of the
when force is applied to the die holder assembly.
piping system. These joints are specified on ships'
Retention positioning sleeves--Used for
drawings. By remaking these joints first, you will avoid
6,000-psi fittings in size 3/8 inch NPS and 3/4
excessive misalignment of gasket seats. When
inch OD tubing or above.
remaking cold pull-up joints, install temporary pull-up
bolts-studs and torque to specified tension. The purpose
Marking/inspection gauge--Used to verify the
of installing temporary pull-up bolts-studs is to avoid
OD of pipe or tube, to locate installation and
damage to the threads of permanent bolts-studs. After
inspection marks, and to verify seal retention of
cold pull-up is completed, replace temporary pull-up