Metallic Expansion Joints - Thorburn Flex Inc

THORBURN
FLEXIBLE PIPING SPECIALIST
WHY USE THORBURN'S METAL BELLOWS
TYPE EXPANSION JOINTS?
All piping or ducting systems are subjected to changes in their geometry due to various factors, some of which are:
a) Thermal:
i.e. • Startup to operating temp.
• Variations in ambient temp.
• Emergency or fault conditions
b) Pressure:
i.e. • Deformation, due to constant pressure
• Deformation, due to pulsating pressure
• Deformation, due to vibration
c) Mechanical:
i.e. • Movement of other
equipment
• Thermal growth in
other equipment
Where the incorporation of sufficient natural flexibility in such a
piping or ducting becomes a problem, three basic alternative
solutions are open to the systems analyst.
1) The expansion loop
2) The slip type expansion joint
3) Thorburn bellows type expansion joint
1) EXPANSION LOOPS
The "loop" is the oldest method of dealing with pipe movement
and probably the most expensive when one considers today's
high costs of material and labour. In addition, pressure drops,
heat loss, high anchor loading together with the large space
requirement, can make this method economically unsound for
the relatively small amount of movements that can be
accommodated with the pipe loop.
3) HOW A THORBURN METALLIC BELLOWS WORKS
Thorburn's metallic bellows is a flexible seal. The convoluted
portion of an expansion joint is designed to flex when thermal
movements occur in the piping system. The number of convolutions
depends upon the amount of movement the bellows must
accommodate or the force that must be used to accomplish
this deflection.
The convoluted element must be strong enough circumferentially
to withstand the line pressure of the system, yet responsive
enough longitudinally to flex. The longitudinal load (pressure
thrust) must then be absorbed by some other type of device.
These are usually anchors, tie rods, hinges, or Gimbal structures.
Pressure thrust can be calculated by multiplying the effective
area shown in the catalogue by the working pressure.
2) SLIP TYPE EXPANSION JOINTS
Derived from the "Stuffing Box", the slip type expansion joint is
an improvement on the Expansion Loop but is somewhat limited
in its applications, being suitable for axial motion only. Small
amounts of lateral or angular displacement will cause binding
and eventually premature leakage. The design of this product is
such that a regular examination and maintenance program must
be introduced so that if leakage occurs, packing is tightened or
replaced.
In most cases the initial cost of the Slip type expansion joint
greatly exceeds that of the Bellows expansion joint designed for
the same application. Another factor to be considered is maintenance
costs of Bellows type vs. the Slip type, as the bellows type
requires no maintenance once correctly installed.
Graphic illustration
of Thorburn's
tied universal expansion joint
BELLOWS MOVEMENTS
BELLOWS TYPICAL SHAPES
Types of bellows movement Principle for operation of Toroidal shape, extremely Lyre shape, pressure
a bellows corrugation pressure resistant resistant and flexible
Collars
Axial Angular Lateral
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