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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 really a combination of several types. 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. However, the pressure-balanced elbow is usually required 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

 

How does a pressure balanced expansion joint work?

pressure balanced expansion joint is really a combination of several types. 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. However, the pressure-balanced elbow is usually required 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

 

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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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Flanged and flued expansion joints can take minimal amounts of axial motion due to the thickness of the flanged and flued heads.

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

The flange on an expansion joint can be one of the end connections to allow for connection to the pipe in the piping system.

 

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Flange Indicated on a Neoprene Expansion Joint

Ply refers to the number of sheet metal thicknesses used in the forming of the bellows. Therefore, a 2-ply bellows would be composed of two sheets of metal.

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48″ Tied Universal Expansion Joint with Two-ply Bellows

What is expansion joint ply?

Ply refers to the number of sheet metal thicknesses used in the forming of the bellows. Therefore, a 2-ply bellows would be composed of two sheets of metal.

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48″ Tied Universal Expansion Joint with Two-ply Bellows
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Heat Exchanger shell bellows are used on fixed tube sheet heat exchangers. Bellows deflection is only axial and can be either extension or compression depending on the differential expansion of shell and tubes. In most cases the tubes are hotter than the shell, moreover tube material is sometimes high alloy, i.e. Stainless steel or nickel alloy, which expands about 50% more than carbon steel.

Dye penetrant testing clamshell
Heat Exchanger Clam Shell Bellows

What is a heat exchanger bellows?

Heat Exchanger shell bellows are used on fixed tube sheet heat exchangers. Bellows deflection is only axial and can be either extension or compression depending on the differential expansion of shell and tubes. In most cases the tubes are hotter than the shell, moreover tube material is sometimes high alloy, i.e. Stainless steel or nickel alloy, which expands about 50% more than carbon steel.

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Heat Exchanger Clam Shell Bellows
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The expansion joint fabric is composed of two components: PTFE resins and fiberglass cloth.

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FLEXXCEL Flouroplastic

Yes, it does. This model requires belt attachment nuts to be tack welded.

Style 400b diagram
Style 400B

Expansion Joints should be stored in a clean and dry environment. However, as a minimum, expansion joints must be stored so that water does not penetrate any closed container.

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Fabric Expansion Joints

Yes they do have potential for wet conditions.

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Turbulent Flue Gas/Wet Gas Expansion Joint

Styles Include: Style 200W, Style 100W, Style 300W, Style 600W, and Style 700W

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Dirty Flue Gas Expansion Joint

The biggest limitation is the relatively low-temperature capability.

Elastomeric Fabric Belt Single Ply Reinforcement
1/8″ Thick Elastomeric Fabric Belt With Single Ply Reinforcement

That is called torsional rotation.

Fabric Expansion Joint Torsional Rotation
Torsional Rotation

The belt radius is located at the corner of rectangular expansion joints. The radius corner helps prevent sharp creases that may shorten belt life.

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Rectangular Fabric Expansion Joint

Flexxcell FF1 is manufactured to a high weight without sacrificing the critical flexing properties required for a fabric expansion joint.

Flutter flex
FLEXXCEL FF1