1. Service Conditions. Make sure the expansion joint rating for temperature, pressure, vacuum and movements match the system requirements. Contact the manufacturer for advice if the system requirements exceed those of the expansion joint selected. Make sure the elastomer selected is chemically compatible with the process fluid or gas.
2. Alignment. Expansion joints are normally not designed to compensate for piping misalignment errors. Piping should be lined up within 1/8”. Misalignment reduces the rated movements of the expansion joint and can induce severe stress and reduce service life. Pipe guides should be installed to keep the pipe aligned and to prevent undue displacement.
3. Anchoring. Solid anchoring is required wherever the pipeline changes direction, and expansion joints should be located as close as possible to anchor points. If anchors are not used, the pressure thrust may cause excessive movements and damage the expansion joints.
4. Pipe Support. Piping must be supported so expansion joints do not carry any pipe weight.
5. Mating Flanges. Install the expansion joint against the mating pipe flanges and install bolts so that the bolt head and washer are against the retaining rings. If washers are not used, flange leakage can result, particularly at the split in the retaining rings. Flange-to-flange dimensions of the expansion joint must match the breech type opening. Make sure the mating flanges are clean and are flat-face-type or more than 1/16” raised-facetype. Never install expansion joints that utilize split retaining rings next to wafer type check or butterfly valves. Serious damage can result to a rubber joint of this type unless installed against full-face flanges.
6. Tightening Bolts. Tighten bolts in stages by alternating around the flange. If the joint has integral fabric and rubber flanges, the bolts should be tight enough to make the rubber flange O.D. bulge between the retaining rings and the mating flange. Torque bolts sufficiently to assure leak-free operation at hydrostatic test pressure. Bolt torquing values are available from most manufacturers. If the joint has metal flanges, tighten bolts only enough to achieve a seal and never tighten to the point that there is metal-to-metal contact between the joint flange and the mating flange.
7. Storage. Ideal storage is a warehouse with a relatively dry, cool location. Store flange face down on a pallet or wooden platform. Do not store other heavy items on top of an expansion joint. Ten-year shelf life can be expected with ideal conditions. If storage must be outdoors joints should be placed on wooden platforms and should not be in contact with the ground. Cover with a tarpaulin.
8. Large Joint Handling. Do not lift with ropes or bars through the bolt holes. If lifting through the bore, use padding or a saddle to distribute the weight. Make sure cables or forklift tinesdo not contact the rubber. Do not let expansion joints sit vertically on the edges of the flanges for any period of time.
9. Additional Tips.
a. For elevated temperatures, do not insulate over a non-metallic expansion joint.
b. It is acceptable (but not necessary) to lubricate the expansion joint flanges with a thin film of graphite dispersed in glycerin or water to ease disassembly at a later time.
c. Do not weld in the near vicinity of a non-metallic joint.
d. If expansion joints are to be installed underground, or will be submerged in water, contact manufacturer for specific recommendations.
e. If the expansion joint will be installed outdoors, make sure the cover material will withstand ozone, sunlight, etc. Materials such as EPDM and Hypalon® are recommended.
Materials painted with weather paint will give additional ozone and sunlight protection.
f. Check the tightness of leak-free flanges two or three weeks after installation and re-tightness if necessary.
1. Assemble expansion joint between pipe flanges to the manufactured face-to-face length of the expansion joint. Include the retaining rings furnished with the expansion joint.
2. Assemble control rod plates behind pipe flanges. Flange bolts through the control rod plate must be longer to accommodate the plate. Control rod plates should be equally spaced around the flange. Depending upon the size and pressure rating of the system, 2, 3 or more control rods may be required. Contact manufacturer for optional installations.
3. Insert control rods through top plate holes. Steel washers are to be positioned at the outer plate surface. An optional rubber washer is positioned between the steel washer and the outer plate surface.
4. If a single nut per unit is furnished, position this nut so that there is a gap between the nut and the steel washer. This gap is equal to the joint’s maximum extension (commencing with the nominal face-to-face length). Do not consider the thickness of the rubber washer. To lock this nut in position, either “stake” the thread in two places or tack weld the nut to the rod. If two jam nuts are furnished for each unit, tighten the two nuts together, so as to achieve a “jamming” effect to prevent loosening. Note: Consult the manufacturer if there is any question as to the rated compression and elongation. These two dimensions are critical in setting the nuts and the sizing the compression pipe sleeves.
5. If there is a requirement for compression pipe sleeves, ordinary pipe may be used and sized in length to allow the joint to be compressed to its normal limit.
6. For reducer installations, it is recommended that all control rod installations be parallel to the piping.
The following guide is intended to assist in determining if an expansion joint should be replaced or repaired after extended service.
1. 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 unitat 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.
2. Procedures.
a. Cracking. (Sun Checking) Cracking, or crazing may not be serious if only the outer cover is involved and the fabric is not exposed. If necessary, repair on site with rubber cement where 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 is identified by: (1) a flattening of the arch, (2) cracks at the base of the arch, and/or (3) cracks at the base of the flange. To avoid future problems, replacement expansion joints should be ordered with control rod units.
b. Blisters-Deformation-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 O.D. can sometimes be observed and is not a cause for replacement of the expansion joint.
c. 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.
d. 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 fall, adjust the piping and order a new expansion joint to fit the existing installation.
e. Rubber Deterioration. If the joint feels soft or gummy, plan to replace the expansion joint as soon as possible.
f. Leakage. If leaking 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, tighten all bolts. If this is not successful, turn off the system pressure, loosen all flange bolts and then retighten bolts in stages by alternating around the flange. Make sure there are washers under the bolt heads, particularly at the split in the retaining rings. Remove the expansion joint and inspect both rubber flanges and pipe mating 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.
