Suggestions for Installation and Maintenance of Rubber Expansion Joints
Installation and Maintenance
Alignment
Pipelines containing standard expansion joints should be lined up accurately before installing the joints. If the joints are to be installed with appreciable initial misalignment, compression or elongation, the amount of these deflections should be deducted from the specified allowed movements of the joint. If the total joint deflection due to initial installation and movement of the pipeline during system operation exceeds the published maximum allowable movement, then the pipeline should be altered to reduce the initial installation deflections. Alternately, the pipe may be anchored in some approved manner to limit the pipe movements that the expansion joint must absorb.
Excess Temperatures and Pressures
Expansion joints should never be subjected to operating conditions beyond the pressure and temperature limits recommended by the manufacturer.
Care of Outside Cover
Any damage to the outside protective cover of an expansion joint should be repaired before placing the joint in service. This protective cover is designed to keep harmful materials from penetrating the carcass of the joint. To further protect the exterior of the expansion joint and to help resist acid and ozone attack, a special coating of Hypalon paint is applied. All joints should be painted with Hypalon paint yearly after installation to ensure continued protection.
Mating Flanges
Clean all foreign matter and remove burrs or sharp edges from flanges.
Flange Face Lubricant
Apply a thin film of graphite dispersed in glycerin or water to the face of the rubber flanges before installing the expansion joint. This is a type of lubricant that is safe to use on rubber flanges. Its purpose is to simplify installation and permit easy removal when necessary.
Bolting
Tighten bolts by alternating around the flanges and tighten all bolts equally. The bolts are not considered tight until the edge of the the flange of the expansion joint flange bulges slightly. Check bolt tightness at least one week after going on stream and periodically thereafter. As any rubber-like material takes a set after a period of compression, the bolts may loosen and result in a break in the seal. It is particularly important to check bolts in a hot and cold water system before changing from one medium to the other.
Insulation
When insulation is used over the pipeline adjacent to a rubber expansion joint, the insulation of the expansion joint is not a recommended practice. However, if insulation is required, it should be made removable to permit ease of access to the flanges. This facilitates periodic inspection of the tightness of joint bolting.
Storage
Expansion joints purchased as spares should be stored in a dry, fairly cool, dark place in a flat position – not on the flange edges. No weight should be placed on the flange edges.
Care When Welding
Welding operations should not be performed in the vicinity of a rubber expansion joint due to the possibility of damage to the joint.
Underground Installation
Unusual applications of rubber expansion joints may require the specification of a protective shield, protective cover, or fire cover. These three types of cover have one end which is bolted or clamped to the mating pipe flange. The other end is free, designed to handle the movements of the expansion joint. A protective shield of metal is required when an expansion joint is installed underground. Protective shields should also be used on expansion joints in lines that carry high temperature or corrosive media. This shield will protect personnel or adjacent equipment from injury or damage in the event of leakage or splash. Protective covers or expandable metal are also used to prevent exterior damage to the expansion joint.
