configuration. The installation of an expansion joint can or operating pressure oscillations. Both conditions can
be performed either internally or externally. Specific cause a premature failure and must be identified in the
frames are designed for each application depending on
quotation/evaluation stage. This condition is commonly
preferences or accessibility.
found adjacent to turning vanes, ID fan and stacks. This
pressure oscillation typically exists in ductwork locations
EXTERNAL ENVIRONMENT
where the static pressure is very low ±1 to ±2” w.c (±25 to
Correct operation of high temperature expansion joints
±50 mm H
2
O).
requires that a portion of the system heat be dissipated to
the external environment. Abnormally hot ambient
INSTALLATION
conditions or an adjacent heat source, reflective surface,
CONSIDERATIONS
or duct insulation may create temperatures that exceed
The system designer must consider all installation
the limits of the gas seal membrane and should be
requirements such as mating duct flanges, adjacent
considered when designing the system.
ducting equipment, insulation, painting/ finishing, field
An external cover may be desirable to help protect
assembly, erection and necessary qualified supervision.
against failing objects or the accumulation of combustible
materials such as coal or saw dust. Covers should be
RESPONSIBILITY
designed by the expansion joint manufacturer to ensure
The system designer must evaluate whether the lines of
that proper air circulation requirements are satisfied.
responsibility are clear between the ducting supplier,
erector, and the expansion joint supplier, and if they will
EXPANSION JOINT FLUTTER
result in a system that meets specification requirements
The inherent flexibility of expansion joints can cause
at an optimum overall cost. It is usually in the best
fatigue problems as a result of physical fluctuations interests of the end user to specify and/or order the
known as flutter. Flutter is a result of either flow induced expansion joints themselves.
10
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