Field inspection guide of installed rubber expansion joints
After Installation. After installation, the rubber expansion joint should be properly protected against damage. Nothing should be in contact of with rubber. The rubber parts must not be painted or exposed to solvents or chemicals. The best performance is obtained when the expansion joint is able to function stress-free under normal operating conditions. Pressure testing of rubber expansion joints. A rubber expansion joint relies on its rubber sealing face pressure testing before supply can adversely influence the integrity of the sealing face. Random batch pressure testing of the rubber expansion joint is performed by the manufacturer. Pressure testing to 1.5 times the working pressure can be performed by Convoluted Technologies on special request by the customer, only if the customer takes note of the information stated above. Convoluted Technologies Pty Ltd will be recording our recommendations on the provided test certificates. System pressure test should take place only after the rubber expansion joints have been fully installed in the piping system. If leaks should occur in the flange connection, the bolts can be re-tightened not exceeding the torque recommendations. All rubber material tends to relax over a period of time. It is good practice to check the tightness of the bolts for 80% of the installation torque, about two weeks after the installation date. If temperature cycling is part of the installation, it is recommended to check the above on an ongoing monthly basis, until such time that the last check shows no further tightening is required. Field inspection guide of installed rubber expansion joints The following guide is intended to assist in determining if an expansion joint should be replaced or repaired after extended service. Replacement Criteria: If an expansion joint is in a critical service condition and is five or more years old, consideration should be given to maintaining a spare or replacing the unit at a scheduled outage. If the service is not of a critical nature, observe the expansion joint on a regular basis and plan to replace after 10 years’ service. Applications vary and life can be as long as 30 years in some cases. Cracking; Cracking or crazing may not be serious if only the outer cover is effected and the inner fabric is not exposed. If necessary, repair on site with rubber cement if the cracks are minor. Cracking where the fabric is exposed and torn, indicates the expansion joint should be replaced. Such cracking is usually the result of excess extension, angular or lateral movements. Such cracking can be identified by; flattening of the sphere, cracks at the base of the sphere, and/or cracks at the base of the flange. To avoid future problems, replacement expansion joints should be ordered with limit or control rods. Blisters/Deformation and Ply Separation; Some blisters or deformations, when on the external portions of an expansion joint, may not affect the proper performance of the expansion joint. These blisters or deformations are cosmetic in nature and do not require repair. If major blisters, deformations and/or ply separations exist in the tube, the expansion joint should be replaced as soon as possible. Ply separation at the flange outside diameter can sometimes occur and is not a cause for replacement of the expansion joint.
Metal Reinforcement; If the metal reinforcement of an expansion joint is visible through the cover, the expansion joint should be replaced as soon as possible. Additionally, if any external metal reinforcement is exhibiting signs of fatigue or wear, the expansion joint should be replaced as soon as possible. Dimensions; Any inspections should verify that the installation is correct; that there is no excessive misalignment between the flanges; and, that the installed face-to- face dimension is correct. Check for over-elongation, over-compression, lateral or angular misalignment. If incorrect installation has caused the expansion joint to fail, consider ordering a new expansion joint sized to fit the existing piping dimensions. If neither option is available, adjust the piping and order a new expansion joint to fit the existing installation. Rubber Deterioration; If the joint feels soft, gummy or too stiff to move, plan to replace the expansion joint as soon as possible. Leakage; If leakage or weeping is occurring from any surface of the expansion joint, except where flanges meet, replace the joint immediately. If leakage occurs between the mating flange and expansion joint flange, tighten all bolts (note the recommended torque settings). If this is not successful, turn off the system pressure, loosen all flange bolts and then re-tighten bolts in stages by alternating around the flange. Remove the expansion joint and inspect both rubber flanges and pipe mating flange faces for damage and surface condition. Repair or replace as required. Also, make sure the expansion joint is not over elongated as this can tend to pull the joint flange away from the mating flange resulting in leakage. If leakage persists, consult the manufacturer for additional recommendations.