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Internal liners are an expansion joint accessory used to protect the convolutions from direct flow impingement, which can cause erosion and flow-induced vibration. They are recommended to extend the life of metallic expansion joints.

Accessories internal liner
Internal Liner on a Metallic Expansion Joint

What is an internal liner?

July 30, 1990

Internal liners are an expansion joint accessory used to protect the convolutions from direct flow impingement, which can cause erosion and flow-induced vibration. They are recommended to extend the life of metallic expansion joints.

Accessories internal liner
Internal Liner on a Metallic Expansion Joint
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Yes for a simple bellow, the tie-rods main purpose is to hold the pressure thrust.

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12″ Single Expansion Joints With Tie Rods

Pressure thrust can be absorbed by placing anchors in a system or by using an expansion joint with tie rods.

In line pressure balanced expansion joint diagram
In-line pressure balance

directional anchor restrains the pressure thrust from the expansion joint and allows for movement in a direction perpendicular to the pressure thrust.

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Single Expansion Joints

The tie rods are used to take the pressure thrust forces. Most universal expansion joints use tie rods to eliminate the requirements for main anchors

Pantographic linkage is an accessory that is used to distribute axial movement between two bellows, allow lateral motion and support the weight of the center pipe section between the bellows.

Olympus digital camera
Expansion Joint with Pantographic Linkage

What is meant by pantographic linkage?

Pantographic linkage is an accessory that is used to distribute axial movement between two bellows, allow lateral motion and support the weight of the center pipe section between the bellows.

Olympus digital camera
Expansion Joint with Pantographic Linkage
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The number of tie-rods used is determined by the design pressure of the expansion joint. It can range from two to eight tie rods in extremely high-pressure conditions.

Universal ej drawing
Universal Expansion Joint with Tie Rods

Control rods are used to control axial and lateral movements of the expansion joint.

Olympus digital camera
Single Hinged Expansion Joint with Control Rods

Limit rods are used to limit axial expansion or compression to prevent the bellows from over-compression. Limit rods are designed to absorb the pressure thrust of the expansion joint in case of anchor failure.

Accessories limit rod
Limit Rods

The function of tie rods on an expansion joint is to continuously restrain the full pressure thrust during normal operation while permitting only lateral deflection. Angular rotation can be accommodated only if two tie rods are used and located 90 degrees opposed to the direction of rotation.

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20″ Diameter Tied Universal Expansion Joint

What is the purpose of tie rods on an expansion joint?

The function of tie rods on an expansion joint is to continuously restrain the full pressure thrust during normal operation while permitting only lateral deflection. Angular rotation can be accommodated only if two tie rods are used and located 90 degrees opposed to the direction of rotation.

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20″ Diameter Tied Universal Expansion Joint
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When there is an axial movement, the in-line bellows will start compressing and the balancing bellows will extend and vice versa. Both bellows will be moving.

Yes, axial as well as lateral expansion joints can be absorbed together in a single bellows design, but the lateral movement would be very minimal compared to a double or universal type expansion joint.

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Single Tied Expansion Joint

 

No, you cannot use an axial expansion joint because thrust force will be acting until the gap is closed between the tie rod nuts. When the nuts touch the lugs, the thrust force will not act upon the equipment.

By using an in-line pressure balanced expansion joint.

In line pressure balanced expansion joint diagram
In-line pressure balanced expansion joint diagram

The preferred method to design universal expansion joints would be to use a larger diameter bellows and use a reducer at the end of the expansion joint. This would ensure angular rotation and axial movement between the two bellows.

 

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72″ Inch Tied Universal Thick-wall Expansion Joint

To decrease the thrust force in an axial expansion joint you must decrease the height of the bellows. However, this method will also increase the forces necessary to deflect the bellows.

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Expansion Joint Designed for 2″ Axial Compression

The expansion joint is designed to accommodate all the needed displacements. The tie-rods are part of the expansion joint and designed to absorb all the specified displacements.

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20″ Diameter Tied Universal Expansion Joint

Universal expansion joints are usually used when there is large lateral motion.

Tied universal expansion joint
Tied universal expansion joint