Whether they are used in the construction of machinery, apparatus or pipelines, expansion joints offer a wide range of advantages. They compensate for and dampen vibration caused by equipment, reduce pressure thrust and dissipate energy to protect adjacent components from deterioration.
Expansion Joint Types
Generally available in standard sizes, expansion joint rubber are designed to fit and accept a variety of piping types, fittings, flanges and valves. The most commonly used expansion joints are spherical, capped sleeve and spool type, but other configurations are also available to meet the needs of specific applications.
Hand Wrapped Joints
Almost all spherical rubber expansion joints are made by hand, though technology has advanced to make them more efficient and durable than they once were. The traditional hand wrapped joint is a spherical tube, covered with two or three plies of high-performance rubber, laid up on a mandrel and reinforced with nylon tire cord, reversed around the ends of the tube and capped with a steel ring (in a spool style joint) or a steel flange.
The spherical design eliminates steel wire reinforcing, so the sphere is more flexible than an equivalent shaped joint, and its weight is spread more evenly over the entire sphere surface. This makes them easier to maneuver than other designs.
Sleeved Joints
Capped sleeve joint connections are available in a wide variety of pipe diameters and are secured by means of clamps. They are designed for medium to low pressure and vacuum systems. They are primarily used in water, wastewater, chemicals and food processing applications.
Spool Arch Types
The spool arch style is designed for a wide range of industrial applications and offers several times the movement capacity of standard narrow arch type joints. They are available with fluoroplastic liners of TFE or FEP to provide resistance to almost all chemicals carried within the joint.
Spool Arch Type Joints with Fluoroplastic Liners are fabricated as an integral part of the joint and cover all internal surfaces, providing exceptional resistance to chemicals. The liners are abrasion resistant and prevent the build-up of rust or corrosion.
Stainless Steel and Other Materials
The use of a metallic expansion joint is recommended for sanitary or hazardous environments. For this purpose, the joint can be manufactured in a variety of stainless steels including Inconel, Incoloy and Hasteloy, among others.
Stainless steel and other materials are more resistant to chloride, chlorine dioxide and sulfuric acid than are non-corrosive materials. They are also more resistant to oxidation and can be used in areas with frequent re-expanding, especially in chemical plants or power plants.
For corrosive media, the outer ply of the rubber can be replaced by a fluoroplastic liner in an epoxy sealant to prevent damage and rust. This is done to allow the joint to be more easily serviced and maintained.
These are the most common expansion joints installed in sewage and water treatment plant pipelines and on bridge structures, where wide temperature variations are present. They are also widely used for isolation applications between materials with dissimilar coefficients of expansion or to isolate and prevent damage due to thermal growth.