|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 special instructions furnished with the expansion joint by the manufacturer, which will provide information necessary for proper handling and installation of expansion joints. 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 splatter.No movement of the Expansion Joint (compression, extension, lateral offset, rotation) due to piping misalignment, for example, shall be imposed which has not been anticipated and designed into the movement capability of the Expansion Joint. Imposing such movements can result in systems malfunction or 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 movement. Anchors, guides, and pipe supports shall be installed in strict accordance with the piping systems drawings. Any field variances from planned installation may affect the proper functioning of the Expansion Joint and must be brought to the attention of 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.
- Once the pipeline anchors or other fixed points are in place, the piping is properly supported and guided and the Expansion Joint installed, the shipping devices (usually yellow in color) should 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 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 pre-positioning correct? Have all of the Expansion Joint shipping devices been removed? If the system has been designed for gas and is to be tested with water, has provision been made for proper support of the additional dead weight load on the piping and Expansion Joint? Are all guides, pipe supports, and the Expansion Joints free to permit pipe movement? Are any Expansion Joints misaligned? This can be determined by measuring the joint overall length, an 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 the Expansion Joint free of foreign material?
WARNING: Extreme care must be exercised while inspecting any pressurized system or component.Inspection During and After System Pressure Tests A visual inspection of the system shall include checking any pressurized system or component for:
- Evidence of leakage or loss of pressure, Distortion or yielding of anchors, Expansion Joints 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 movable 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 In-Service Inspections Immediately after placing the system in operation, a visual inspection shall be conducted to ensure 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. A program of periodic inspection shall be planned by the system designer and conducted throughout the operating life of the system. The frequency of this inspection will be determined by the service and environmental conditions involved. These inspections shall include the items in the 2 inspection lists above, as well as an examination for signs of external corrosion, loosening of threaded fasteners and deterioration of anchors, guides, and other hardware. 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 of failure, including periodic preventive replacement of critical system components. When any inspection reveals evidence of malfunction, damage, or deterioration, this shall be reviewed by competent design authority for resolution.
System Operation A record shall be maintained of any changes in system operation conditions (such as pressure, temperature, thermal cycling, water treatment, and piping modifications. Any such change shall be reviewed by the competent design authority to determine its effect on the performance of the anchors, guides, and Expansion Joints.
Causes of Failures Bellows expansion joints will give many years of satisfactory service when they are properly designed and manufactured for specified piping system conditions. Failures can occur for many reasons, but experience has shown that certain causes of failure fall into distinct categories.
The following are some typical causes:
- 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:
- Direction with respect to flow.Joints with internal liners installed in reverse. Installing a 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 a nearby welding operation.Failure to remove shipping devices before system operation. Improper anchoring, guiding supporting of the piping system.
- Anchor failure in service.
- Bellows corrosion. Examples:
- Improper selection of bellows material for the flowing medium and/or adverse external environment. Specifically, chlorides leaching from insulation, have been frequently the causes of stainless steel bellows corrosion.
- Stress corrosion cracking (consult the material manufacturer for proper selection).
- System over-pressurization (in-service or hydro test).Bellows vibration (mechanical or flow-induced) resulting in fatigue failure.Excessive bellows movement (axial, lateral, and angular movement greater than design values).Bellows erosion. Example:
- Bellows without internal liner installed in a system having a very high velocity and/or erosive flowing medium.
- Packing of particulate matter in bellows convolutions which inhibits proper movement of the bellows.
Expansion Joints: Do’s and Don’ts From the “Standards of the Expansion Joint Manufacturers Association, Inc”
- Inspect for damage during shipment, i.e., dents, broken hardware, watermarks on the carton, etc.
- Store in a clean dry area where it will not be exposed to heavy traffic or damaging environment.
- Use only designated lifting lugs.
- Make the piping systems fit the expansion joint. By stretching, compressing, or offsetting the joint to fit the piping, the joint may be overstressed when the system is in service.
- It is good practice to leave one flange loose until the expansion joint has been fitted into position.
- Make necessary adjustment of loose flange before welding.
- Install joint with the arrow pointing in the direction of flow.
- Install single Van stone liners, pointing in the direction of flow.
- Be sure to install a gasket between the mating flange and liner.
- With telescoping Van stone liners, install the smallest I.D. liner pointing in the direction of flow.
- Remove all shipping devices after the installation is complete and before any pressure test of the fully installed system.
- Remove any foreign material that may have become lodged between the convolutions.
- Do not drop or strike carton.
- Do not remove shipping bars until installation is complete.
- Do not remove any moisture-absorbing desiccant bags or protective coatings until ready for installation.
- Do not use hanger lugs as lifting lugs without the approval of the manufacturer.
- Do not use chains or any lifting device directly on the bellows or bellows cover.
- Do not allow weld splatter to hit unprotected bellows. Protect with wet chloride-free insulation.
- Do not use cleaning agents that contain chlorides.
- Do not use steel wool or wire brushes on bellows.
- Do not force-rotate one end of an expansion joint for alignment of bolt holes. Ordinary bellows are not capable of absorbing torque.
- Do not hydrostatic pressure test or evacuate the system before installation of all guides and anchors. Pipe hangers are not adequate guides.
- Do not exceed a pressure test 1-½ times the rated working pressure of the expansion joint.
- Do not use shipping bars to retain thrust if tested prior to installation.
Refer to EJMA Standard for proper guide spacing and anchor recommendations.
NOTE: The manufacturer’s warranty may be void if improper installation procedures have been used.