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.
Pressure thrust can be absorbed by placing anchors in a system or by using an expansion joint with tie rods.
A directional anchor restrains the pressure thrust from the expansion joint and allows for movement in a direction perpendicular to the pressure thrust.
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
Read MoreControl rods are used to control axial and lateral movements of the expansion joint.
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.
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.
| 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.
Read More
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.
Read MoreBy using an in-line pressure balanced expansion joint.
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.
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.
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.
Universal expansion joints are usually used when there is large lateral motion.
