BELLOW

Do's Dont's
 Inspect for damage during  Do not drop or strike
shipment, i.e., dents, carton.
broken hardware, water  Do not remove shipping
marks on carton, etc. bars until installation is
 Store in clean dry area complete.
where it will not be  Do not remove any
exposed to heavy traffic or moisture-absorbing
damaging environment. desiccant bags or
 Use only designated lifting protective coatings until
lugs. ready for installation.
 Make the piping systems  Do not use hanger lugs as
fit the expansion joint. By lifting lugs without
stretching, compressing, approval of manufacturer.
or offsetting the joint to fit  Do not use chains or any
the piping, the joint may lifting device directly on
be over stressed when the the bellows or bellows
system is in service. cover.
 It is good practice to leave  Do not allow weld splatter
one flange loose until the to hit unprotected bellows.
expansion joint has been Protect with wet chloride-
fitted into position. free insulation.
 Make necessary  Do not use cleaning
adjustment of loose flange agents that contain
before welding. chlorides.
 Install joint with arrow  Do not use steel wool or
pointing in the direction of wire brushes on bellows.
flow.  Do not force-rotate one
 Install single Van stone end of an expansion joint
liners, pointing in the for alignment of boltholes.
direction of flow. Ordinary bellows are not
 Be sure to install a gasket capable of absorbing
between the mating flange torque.
and liner.  Do not hydrostatic
 With telescoping Van pressure test or evacuate
stone liners, install the the system before
smallest I.D. liner pointing installation of all guides
in the direction of flow. and anchors.Pipe hangers
 Remove all shipping are not adequate guides.
devices after the  Do not exceed a pressure
installation is complete test 1-½ times the rated
and before any pressure working pressure of the
test of the fully installed expansion joint.
system.  Do not use shipping bars
 Remove any foreign to retain thrust if tested
material that may have prior to installation.
become lodged between
the convolutions.
INSTALLATION
The necessary steps for installing all expansion joints shall be pre-planned. The installers shall be made aware of
these steps as well as the installation instructions furnished by the manufacturer. The most critical phases of the
expansion joint installation are as follows.

 Care shall be exercised to prevent any damage to the thin bellows section, such as dents, scores,
arc strikes and weld spatter.

 No movement of the expansion joint (compression, extension, offset, rotation and especially
torsion) due to piping misalignment, for example, shall be imposed which has not been
anticipated and designed into the movement capability of the expansion joint. If such movements
are imposed, they can result in system malfunction, damage to the bellows or other components
in the system. Specifically, cycle life can be substantially reduced, forces imposed on adjacent
equipment may exceed their design limits, internal sleeve clearances may be adversely affected,
and the pressure capacity and stability of the bellows may be reduced.

 Any field pre-positioning shall be performed in accordance with specific instructions which include
both the direction and magnitude of the movement.

 Anchors, guides and pipe supports shall be installed in strict accordance with the piping system
drawings. Any field variances from planned installation may affect proper functioning of the
expansion joint and must be brought to the attention of a competent design authority for
resolution.

 The expansion joint, if provided with internal sleeves, shall be installed with the proper orientation
with respect to flow direction.

 After the anchors or other fixed points are in place and the piping is properly supported and
guided, the expansion joint shipping devices should normally be removed in order to allow the
expansion joint to compensate for changes in ambient temperature during the remainder of the
construction phase.

POST INSTALLATION INSPECTION

PRIOR TO SYSTEM PRESSURE TEST
A careful inspection of the entire piping system shall be made
with particular emphasis on the following.

 Are the anchors, guides and supports installed in

accordance with the system drawings?
 Is the proper expansion joint in the proper location?
 Are the expansion joint flow direction and positioning
correct?
 Have all the expansion joint shipping devices been
removed?
 Are all guides, pipe supports and the expansion joints free
to permit pipe movement?
 If the system has been designed for a gas, and is to be
tested with water, have provisions been made for proper
support of the additional dead weight load on the piping
and expansion joint? Some water may remain in the
bellows convolutions after the test. If this is detrimental to
the bellows or system operation, means shall be provided
to remove such water.
 Has any expansion joint been damaged during handling
and installation?
 Is any expansion joint misaligned? This can be determined
by measuring the expansion joints' overall length,
inspection of the convolution geometry, and checking
clearances at critical points on the expansion joint and at
other points in the system.
 Are the bellows and other movable portions of expansion
joint free of foreign material?

Expansion Joints with Shipping Bars that Must be Removed

 Post Installation

 
 INSPECTION DURING AND
IMMEDIATELY AFTER SYSTEM
PRESSURE TESTS
  WARNING: EXTREME CARE MUST BE EXERCISED WHILE INSPECTING ANY PRESSURIZED
SYSTEM OR COMPONENT.

A visual inspection of the system shall include checking for the following.

 Evidence of leakage or loss of pressure.

 Distortion or yielding of anchors, expansion joint hardware, the bellows and other piping
components.

 Any unanticipated movement of the piping due to pressure.Evidence of instability (squirm) in

the bellows.

 The guides, expansion joints and other moveable parts of the system shall be inspected for
evidence of binding.

 Any evidence of abnormality or damage shall be reviewed and evaluated by competent design
authority.

 PERIODIC INSERVICE INSPECTION

WARNING: Extreme care must be exercised while inspecting

any pressurized system or component.
 
Immediately after placing the system in operation, a visual inspection shall be conducted to insure that
the thermal expansion is being absorbed by the expansion joints in the manner for which they were
designed.

The bellows shall be inspected for evidence of unanticipated vibration.

 
  U.S. Bellows, Inc. Field Service Team
A program of periodic inspection shall be planned by the system designer and conducted throughout
the operating life of the system. The frequency of these inspections will be determined by the service
and environmental conditions involved. These inspections should include the items noted previously as
well as an examination for signs of external corrosion, loosening of threaded fasteners and
deterioration of anchors, guides and other hardware.

WARNING: IT MUST BE UNDERSTOOD THAT THIS INSPECTION PROGRAM, WITHOUT ANY

  OTHER BACKUP INFORMATION, CANNOT GIVE EVIDENCE OF DAMAGE DUE TO FATIGUE,
STRESS CORROSION OR GENERAL INTERNAL CORROSION. THESE CAN BE THE CAUSE OF
SUDDEN FAILURES AND GENERALLY OCCUR WITHOUT ANY VISIBLE OR AUDIBLE WARNING.

Where the critical nature of the system warrants, it may be necessary to devise means for minimizing
the probability of this type failure, including periodic preventative replacement of critical system
components. Where any inspection reveals evidence of malfunction, damage or deterioration, this shall
be reviewed by competent design authority for resolution.

 
TYPICAL CAUSES OF EXPANSION
JOINT FAILURE
Bellows expansion joints which have been properly designed and manufactured for specified piping
system conditions have given many years of satisfactory service. Failures, of course, have occurred
which are of concern both to users and to reputable expansion joint manufacturers. Failures can occur
  for many reasons, but experience has shown that certain causes of failure fall into fairly distinct
categories. The following list, which shows some typical causes but is by no means all-inclusive, is
presented with the intent that, as knowledge of the causes of failure becomes more widespread, action
can be taken to prevent or minimize these occurrences.

 Shipping and handling damage. Examples: Denting

or gouging of bellows from being struck by hard
objects (tools, chain falls, forklifts, adjacent
structures, etc.); improper stacking for shipping or
 storage; insufficient protection from weather or other
adverse environmental conditions.
 Improper installation and insufficient protection.
 During and after installation .
 Examples: Joints with internal liners installed in the
reverse direction with respect to flow; installing an
expansion joint in a location other than as prescribed
by the installation drawings; premature removal of
shipping devices; springing of bellows to make up for
piping misalignment; insufficient protection from
mechanical damage due to work in the surrounding
area; insufficient protection of bellows during nearby
welding operations and failure to remove shipping
devices before placing system in operation.
 Improper anchoring, guiding and supporting of the
system.
 Anchor failure in service.
 Bellows corrosion, both internal and external.
 System over-pressure (in-service or hydrotest).
Bellows vibration (mechanical or flow induced
resulting in high cycle fatigue).
 Excessive bellows deflection (axial, lateral, angular
deflections greater than design values).
 Torsion.
 Bellows erosion.
 Packing of particulate matter in the bellows
convolutions which inhibits proper movement of the
bellows.

  48" Expansion Joint Failure

INSTALLATION MISALIGNMENT
During the erection of piping systems, the accuracy of the
location of equipment, pipe supports, structure and the piping
itself is never perfect. Since the expansion joint is usually far
more easily deflected than any of these other components, it is
tempting for piping installers to use it to correct for
misalignment. The installation instructions of PT&P's expansion
joints, as well as other manufacturers, require that the piping be
aligned to the expansion joint during installation. The expansion
joints will arrive from the factory with rigid restraints which
maintain their length and ends in the position and dimensions of
the specification in this catalog.

If some misalignment must be accepted by the expansion joint,

this can be accommodated by the addition of devices such as
limit rods which can be used during the installation to adjust the
expansion joints to fit. Any proposed misalignment should be
clearly stated to PT&P so that the amount of deflection possible
can be considered in the total deflection capability of the proper
selection. As an example, one would not want to have a needed
cyclic axial compression capability of 0.5 inch (12.7 mm) cut in
half by a compression due to pipe misalignment of .025 inch
(6.4 mm).

SYSTEM OPERATION
A record shall be maintained of any changes in system operating conditions (i.e. pressure, temperature,
thermal cycling, water treatment) and piping modifications. Any such change shall be reviewed by
competent design authority to determine its effect on the performance of the anchor, guides and
expansion joints.

SQUIRM OR INSTABILITY
SQUIRM OR INSTABILITY
As described above, all bellows have a critical pressure at which they become unstable. Instability can
occur in either of two modes, column instability (or squirm), or inplane deformation of the convolution side
wall.

Squirm is the phenomena whereby the centerline of a straight bellows develops a sideways or lateral
bow.

The critical pressure at which this instability occurs is a direct function of the diameter and spring rate,
and an inverse function of the length. If the bellows is bent, or angulated, the centerline can begin to
move away from the center of curvature. In each case, the effective length of the bellows increases,
lowering the material available to withstand the pressure, thereby increasing the hoop stresses. As the
length increases, the tendency to squirm increases and the stresses become higher and higher until
catastrophic failure occurs. A simple way to visualize this phenomena is to remember that the bellows is a
cylinder of given volume. Internal pressure tries to increase a vessel's volume. Since a bellows is flexible
in the axial direction, it can increase its volume by increasing the length of its centerline. With the ends
fixed, it does so by simulating the appearance of a buckling column.