The Expansion Joints Blog

Single Tied Expansion Joints for a Pipeline in Alaska

The expansion joint assemblies are fabricated entirely from stainless steel with a design pressure of 50 PSIG. They are designed with tie rods that do not permit axial movement, but allow for lateral movement up to 1/2″. The expansion joints will be used on a process line that contains exhaust gas and hydrocarbon vapor at a low concentration. It will connect an oil tank with a vapor control system.

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Universal Metallic Expansion Joints with 300 lb. Raised Face Stainless Steel Flanges

The expansion joint assemblies are fabricated for a 12″ pipe and are designed for 2-1/2″ lateral movement. The design pressure is 276 PSIG with a design temperature of 626°F. 316L stainless steel was used for the bellows and tie rods. The expansion joints include 300 lb. raised face stainless steel flanges to accommodate low spring rate requirements.

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Hinged Expansion Joints with Refractory Lining

Hinges cause the unit to bend in a single plane. The hinge mechanism is designed to accept the full pressure thrust.

• Design Pressure: 75.4 PSIG
• Design Temperature: 1400°F
• 100% X-ray Tested
• Pneumatically Tested weld seams to 83 PSIG

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View Information on Refractory-lined Expansion Joints

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Elbow Pressure Balanced Expansion Joints

The expansion joints are fabricated for a 36″ pipe and are designed with Inconel® 625 grade LCF bellows. They include a liner provided with drain holes to prevent accumulation of corrosive condensation.

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Inline Pressure Balanced Expansion Joints

- Design: 125 PSIG, Temperature: 244°F

- 304 SS Bellows, Flanges & Liners

- Designed to Balance 48,000 lb. of Pressure Thrust

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Externally Pressurized Expansion Joints

These expansion joints are fabricated for a piping system in a steam plant. They include 304 SS bellows and carbon steel shell and flanges, and are designed for 150 PSIG and 350°F.

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In order to properly specify expansion joints for piping systems, the piping specialist and must be aware of the various types of deflections that can be taken by an expansion joint bellows. Piping flexibility programs can determine where stresses are excessive, and if an expansion joint is necessary or not. Expansion joint placement and proper selection still depends on understanding the different types of bellows deflections.

Axial Deflection (View Axial Movements)

Axial deflection refers to movement of the bellows along the longitudinal axis of the bellows. Compression is the axial deflection which will shorten the bellows length, while extension is the axial deflection which extends the expansion joint. Often confusion occurs because thermal expansion in the piping will cause the expansion joint to compress. The specification for an expansion joint should always state the movements as they affect the expansion joint, and not as they are produced by the system. Piping which is operating at temperatures lower than ambient, such as in cryogenic systems, will contract, causing the expansion joint to extend.

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This tied universal expansion joint with a 45 degree mitered elbow will be installed in a flue gas system. The assembly is 60″ in diameter and 215″ long. The pipe is fabricated from A 516 GR 70 carbon steel and the bellows are Inconel® 625 LCF. The bellows were 100% x-rayed and hydro-tested to 15 PSIG prior to shipping.

Rectangular metal expansion joints have a variety of applications in the power, petrochemical, refining, chemical, and steel industries. Since there are no standard duct sizes, and due to the wide range of pressure and temperature combinations, each rectangular metal expansion joint is custom-engineered to provide the most economical design that will absorb the thermal movements of the system in which it is installed.

General arrangement of rectangular expansion joints with supported sides

Features:

- Absorbs axial and lateral movements

- Variety of bellows geometry (for long straight sides)

- Normal guiding is required

- Manufactured for a wide variety of materials

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Like circular expansion joints, rectangular expansion joints absorb three types of movement: axial, lateral and angular. For the purpose of designing rectangular bellows, it is critical to know in which direction the lateral and angular movements will occur, i.e. parallel to the long and/or short side of the bellows.

Unlike circular bellows where the pressure stress is a circumferential membrane (hoop) stress, the rectangular bellows must be designed for longitudinal (beam) bending stresses. Long unsupported lengths must frequently be supported to prevent excessive deflection and stresses of the bellows element. In certain applications, covers and liners can perform the function of pressure supports.

View more information of Rectangular Metallic Expansion Joints