EAGLEBURGMANN
6
Which type of expansion joint
to use and its design is based on some fundamental
considerations.
It is necessary to state operating data and other con-
ditions as detailed as possible to ensure maximum
operating reliability.
Place and conditions of installation
must be considered before choosing the expansion
joint design. Is the place of installation easily acces-
sible,或者是脚手架,吊车或其他与nt
required to install the expansion joint?
Movements
alone or in combinations, are taken up by fabric
expansion joints:
±
Axial compression
±
Axial elongation
±
Lateral offset
±
Angular offset
±
Torsion
The size and frequency of movements will affect
the choice of expansion joint. For large movements,
复杂的,用剪刀来讲伸缩缝ol
guides are recommended. They ensure controlled
movements and prevent damage to the fabric or heat
pockets from occurring.
Mechanical loads
Fabric expansion joints are also able to take up:
±
Vibrations
±
Structural-borne noise
Essentially, the following should be considered:
±
Overstretching
±
Friction along the sleeve
±
Presetting
±
Combination of movements
Pressure
will affect the design (type of fabric and number of
layers). The following distinctions are made:
±
Positive pressure (normal, peak)
±
Negative pressure (normal, peak)
±
Variations of pressure (pulsations)
±
Pressure surges
±
Design/operating pressure
Flow rates
determine if a sleeve may be recommended. For
higher flow rates an insertion of a sleeve is necessary
for the functionality of the expansion joint.
Medium
represents an important decision factor in choosing
the type of expansion joint and the configuration.
Typical media that fabric expansion joints will get
subjected to are:
Air
±
Clean
±
Dust content
±
Chemical load by acids, solvents, etc.
Flue gases
±
From coal, oil, gas firing etc.
±
Analysis of the flue gas
±
Humidity
±
Contents of soot or fly ashes
±
Flushing/washing of ducts
Leakage requirements
may be necessary, according to the application area and
the medium. In principle, a distinction is made between
the tightness of the expansion joint and the tightness
of the flange area. Single-layer expansion joint can be
made 100% gas tight with appropriate sealing, but
multi-layer expansion joint will always have a certain
lekage through the flange area. Pressure and tempera-
ture will also affect the leakage as both high temperature
and high pressure will result in higher leakage in the
flange area for mulitilayer expansion joints.
The following requirements can be made:
±
Nekal tightness
±
Flue gas tightness
Solid matter
might contaminate the medium which will influence both
the design and the construction. In principle, the expan-
sion joint should be protected from abrasive media.
The main considerations concerning solid matters are:
±
Content (mg/Nm
3
)
±
Grain size (μm)
±
Arrangement of duct (horizontal, vertical, diagonal)
±
Direction of flow (upwards, downwards)
±
Flow rate
Axial elongation
Axial compression
Lateral offset
Angular offset
Torsion
Criteria for Applications & Design