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Loads on a tied universal bellows are not transferred because pressure thrust is contained within the tie rods and is not transferred to the piping system equipment.

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Diameter Tied Universal Expansion Joints

The lateral movement in a tied universal expansion joint is achieved by having the bellows work together in angular rotation in order to obtain the correct lateral deflection.

72" Diameter Tied Universal, Thick-wall Expansion Joint for a Sulfuric Acid Plant
72″ Diameter Tied Universal, Thick-wall Expansion Joint for a Sulfuric Acid Plant

Universal expansion joints are typically used in z-bend or l-shape pipe arrangements where the expansion joint allows for lateral motion

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Universal Expansion Joints

The length of a universal expansion joint is dependent upon the amount of lateral motion to be absorbed by the expansion joint. This is determined on a case by case basis.

30 inch double hinged expansion joint with duct work
Universal Expansion Joint and Duct Work

Yes, a tied expansion joint is a correct application for tied expansion joints to eliminate pressure thrust on the turbine exhaust nozzle.

Single joint
12″ Single Expansion Joints with Tie Rods

The number of tie-rods on a universal expansion joint is calculated according to the amount of pressure thrust that the particular expansion joint will absorb. Low-pressure expansion joints may have two rods, for example, while high-pressure expansion joints may have four or more.

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12″ Universal Expansion Joint with Tie Rods

Yes, hinged expansion joints do need to be designed to accommodate for pressure thrust.

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Hinged Expansion Joint

Expansion joints have one loose flange when specified to facilitate the alignment of flanges on the piping system during installation.

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Single Tied Expansion Joints with Carbon Steel Flanges

We do not recommend the annealing of stainless steel bellows because the bellows strength increases while decreasing the cycle life.

Metallic expansion joints should be replaced if they are leaking or can simply be replaced on a scheduled maintenance program in order to avoid leaks that may occur in the future.

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36″ Rectangular Metal Expansion Joint

We get inquiries for steel and rubber expansion joints for pump suction and discharge.

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Rubber Expansion Joints

If bellow thickness is increased, then the bellows spring rate will increase substantially.

72 inch thick wall expansion joint for a sulfuric acid plant
72″ inch thick wall pipe expansion joint
You can find a slide show on an introduction to U.S. Bellows that covers a wide variety of metallic expansion joints at the following link:

Unreinforced bellows do not have any external type of reinforcement such as root rings or equalizing rings.

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Unreinforced Single Metallic Expansion Joint

The gimbal expansion joint is basically the same as the hinge type, except that instead of being limited to deflection in only one plane, it can accept bending or angulation in any plane. It contains two sets of hinge pins or pivots, the axis of each set perpendicular to the other. Each set of pins is connected to each other with a central gimbal ring, in much the same way that a universal joint on an automobile works.

72" Double Gimbal and Single Hinged Flanged and Flued Head Expansion Joints
72″ Double Gimbal and Single Hinged Flanged and Flued Head Expansion Joints

What are gimbal expansion joints?

The gimbal expansion joint is basically the same as the hinge type, except that instead of being limited to deflection in only one plane, it can accept bending or angulation in any plane. It contains two sets of hinge pins or pivots, the axis of each set perpendicular to the other. Each set of pins is connected to each other with a central gimbal ring, in much the same way that a universal joint on an automobile works.

72" Double Gimbal and Single Hinged Flanged and Flued Head Expansion Joints
72″ Double Gimbal and Single Hinged Flanged and Flued Head Expansion Joints
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Expansion joint thickness can vary from .010 inches to .125 inches thick depending upon the design requirements for your application.

The effective diameter of the bellows is the mean diameter of the convolutions.

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42″ Diameter Neoprene Fabric Expansion Joint for a Generator Cooling Fan in a Power Plant

pressure balanced expansion joint is a combination of several types of expansion joints. Its purpose is to retain and balance the pressure thrust so that main anchoring of the pipe or adjacent equipment is not required, and forces and movements on attachment flanges of delicate equipment, such as turbines, are kept to acceptably low levels.

Why are pressure balanced expansion joints used?

A piping system typically requires pressure-balanced expansion joints because axial deflections are also present. In order to accept these movements, a bellows is added beyond the elbow with the same cross-sectional area as the ones in the universal section.

This balancing bellows is connected by the tie rods to the pipe beyond the universal section; in this way, the pressure thrust is contained as tension in the tie rods. The section of the expansion joint between the tie rods, which includes the elbow, is now free to move axially, with the only resistance being a function of the spring rates of the bellows.

Because of their arrangement, however, the spring rate of the entire expansion joint is the sum of the spring rates of the balancing and the universal bellows. This is a constant volume system, in that when the universal end compresses, the balancing end extends the same amount. All of the lateral deflection is absorbed by the universal end, and there is no lateral deflection imposed on the balancing end. Therefore, the balancing bellows is almost always a single bellows type.

60" Pressure Balanced Expansion Joint with Turning Vanes for a Power Plant in Washington
60″ Pressure Balanced Expansion Joint with Turning Vanes for a Power Plant in Washington

Looking for pressure balanced expansion joints? Visit our product page or speak with an engineer to know exactly what you need.


Did you know that US Bellows is a Piping Technology Company?
We are proud to be a one-stop solution from expansion joints to pipe supports and engineering services. We work hard to simplify your supply chain, and ensure system reliability with quality assurance.

How does a pressure balanced expansion joint work?

pressure balanced expansion joint is a combination of several types of expansion joints. Its purpose is to retain and balance the pressure thrust so that main anchoring of the pipe or adjacent equipment is not required, and forces and movements on attachment flanges of delicate equipment, such as turbines, are kept to acceptably low levels.

Why are pressure balanced expansion joints used?

A piping system typically requires pressure-balanced expansion joints because axial deflections are also present. In order to accept these movements, a bellows is added beyond the elbow with the same cross-sectional area as the ones in the universal section.

This balancing bellows is connected by the tie rods to the pipe beyond the universal section; in this way, the pressure thrust is contained as tension in the tie rods. The section of the expansion joint between the tie rods, which includes the elbow, is now free to move axially, with the only resistance being a function of the spring rates of the bellows.

Because of their arrangement, however, the spring rate of the entire expansion joint is the sum of the spring rates of the balancing and the universal bellows. This is a constant volume system, in that when the universal end compresses, the balancing end extends the same amount. All of the lateral deflection is absorbed by the universal end, and there is no lateral deflection imposed on the balancing end. Therefore, the balancing bellows is almost always a single bellows type.

60" Pressure Balanced Expansion Joint with Turning Vanes for a Power Plant in Washington
60″ Pressure Balanced Expansion Joint with Turning Vanes for a Power Plant in Washington

Looking for pressure balanced expansion joints? Visit our product page or speak with an engineer to know exactly what you need.


Did you know that US Bellows is a Piping Technology Company?
We are proud to be a one-stop solution from expansion joints to pipe supports and engineering services. We work hard to simplify your supply chain, and ensure system reliability with quality assurance.

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metallic expansion joint device is used to absorb thermal movement. It is generally fabricated from stainless steel or other high nickel alloys.

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Single Flanged Metallic Expansion Joint

We typically only use carbon steel material for the bellows rectangular expansion joints which are installed in duct systems. Round expansion joints don’t typically have carbon steel bellows, however for both round and rectangular expansion joints, the flanges, pipe, and hardware may be carbon steel.

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Metallic Expansion Joint with Carbon Steel Flanges

Where should we use carbon steel expansion joints?

We typically only use carbon steel material for the bellows rectangular expansion joints which are installed in duct systems. Round expansion joints don’t typically have carbon steel bellows, however for both round and rectangular expansion joints, the flanges, pipe, and hardware may be carbon steel.

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Metallic Expansion Joint with Carbon Steel Flanges
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