25RECT Low Pressure Rectangle Bellows Expansion Joint

Hyspan standard LOCORR profile.

Hyspan LOCORR convolutions are recommended for ducting with dimensions ranging from 2.5 feet through 10 feet of length. The saw-tooth cross section provides high flexibility. They can be used with single or double miter, or camera fold corners.

Material: 0.040″ thick.
Axial Stroke: 0.375″ per convolution
Axial Spring Rate: 279 pounds per inch of stroke per foot of periphery

Most rectangular expansion joints are used to absorb thermal expansion as axial travel or as connectors to isolate fans and other mechanical equipment. As a result most configurations are single unrestrained joints. There are no standard sizes since the ducts are individually fabricated and designed to accommodate the system design. Although Hyspan can fabricate other convolution profiles, the standard LOCORR and HYCORR profiles will accommodate most sizes, and they can be used with one of corner designs pictured. The end attachments are generally selected to conform with attachments used in the system or to mate with equipment. The most common end attachments are bolted flanges. The flanges have the added benefit of reinforcing the duct work.

Hyspan performs a design analysis on all designs in conformance with the method of analysis outlined in the Standards of the Expansion Joint Manufacturers Association, Inc.(EJMA). Rectangular expansion joints have stresses, and angular and lateral spring rates associated with the “long side” and “short side” sometimes referred to as the “easy way” and “hard way” and accordingly must be individually analyzed. In addition to these calculations Hyspan performs an analysis on the duct to determine if internal or external stiffeners are required to react the pressure forces.

Rectangular expansion joints are commonly furnished with flow liners to reduce pressure drop and prevent impingement of the flow on the bellows. The material used is frequently the same as the duct material. Most rectangular expansion joints are used in applications where the ducting is supported and anchored and the joint motion is axial; however, limit rods or tie rods are frequently incorporated into the design to prevent over travel.

Single rectangular metal expansion joints have limited ability to absorb lateral offset or deflection. If lateral offset is a requirement a universal configuration is recommended or two single joints spaced apart. If the motion is limited to one plane, hinges or slotted hinges are frequently included. Slotted hinges have the benefit of stabilizing the expansion joint, limiting the axial travel and supporting the weight of adjacent ducting. The joint pictured is used in the exhaust stack of a ship. The rounded . ends are made from round expansion joints cut in half. This is the same technique is used to made round corners of rectangular expansion joints.

Although not common because of the added complexity, “race track” or “bath tub” joints are sometimes used. The joint pictured is used in the exhaust stack of a ship. The rounded ends are made from round expansion joints cut in half. This is the same technique is used to made round corners of rectangular expansion joints.