There are three basic movements that can be absorbed by an Expansion Joint:
It is the change in dimensional length of the bellows from its free length in a direction parallel to its longitudinal axis. Can be either extension or compression.
It is the rotational displacement of the longitudinal axis of the bellows toward a point of rotation or bending of the expansion joint along its centerline.
It is the relative displacement of one end of the bellows to the other end in a direction perpendicular to its longitudinal axis.
The basic unit of every expansion joint is the bellows. By adding additional components and accessories, the complexity and capability of the expansion joints is increased making them suitable for a wide range of applications and services.
These are some of the main and basic Expansion Joints accessories and components.
A flexible element consisting of one or more corrugations and the end tangents.
The bellows can be singleply or multiply.
The straight un-convoluted portions at the end of the bellows.
The most common types of connection parts are weld ends or flanges. In some cases male or female threaded ends are used.
The ends of an expansion joint equipped with pipe for weld attachment to adjacent equipment or piping. Weld ends are commonly supplied beveled for butt welding.
The ends of an expansion joint equipped with flanges for the purpose of bolting the expansion joint to the matting flange of adjacent equipment or piping.
Flanged ends can be supplied fixed or swivel.
Reinforcing sleeve or ring attached to the end tangent for reinforcement.
Ring placed around the end tangents to facilitate welding.
Devices fitting snugly in the roots of the corrugations in order to reinforce the bellows against internal pressure, and/or to distribute axial movement equally to all convolutions while limiting amount of compression movement per convolution.
A device which minimizes contact between the inner surface of the bellows of an expansion joint and the fluid flowing through it. These devices have also been referred to as liners or baffles.
Internal sleeves shall be specified for all Expansion Joints in the following cases:
A device used to provide external protection to the bellows form foreign objects, mechanical damage and/or external flow and may act as a support for external thermal insulation.
Devices, usually in the form of rods or bars, attached to the expansion joint assembly whose primary function is to continuously restrain the full bellows 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° opposed to the direction of rotation.
Devices, usually in the form of rods or bars, attached to the Expansion Joint assembly whose primary function is to distribute the movement between the two bellows of a universal Expansion Joint. Control rods are not designed to restrain bellows pressure thrust.
Devices, usually in the form of rods or bars, attached to the expansion joint assembly whose primary function is to restrict the bellows movement range (axial, lateral and angular) during normal operation. In the event of a main anchor failure, they are designed to prevent bellows over-extension or over-compression while restraining the full pressure loading and dynamic forces generated by the anchor failure.
Hinged Expansion Joints incorporate a system of articulated supports (a pair of pins through hinge plates attached to the pipe expansion joint ends) which allow for angular movement in one plane only. The hinges and hinge pins must be designed to restrain the thrust of the Expansion Joint due to pressure and extraneous forces, where applicable.
These units do not allow axial movement however, some types of hinge systems can be provided with holes for the hinge pin that are slotted to allow limited axial displacement. These “slotted hinge” types cannot resist the pressure thrust forces and therefore proper anchorage must be provided.
The gimbal system consists in two pairs of hinges affixed to a common floating gimbal ring.
A gimbal ring is either round or square. For round gimbals the torsional moment shall be considered and for square gimbals the instability due to the bending shall be considered.
Gimbal Expansion Joints are designed to allow angular movement in any plane and the gimbal ring, hinged and pins are designed to restrain the pressure thrust due to internal pressure and shear forces.
A scissors-like device. A special form of control rod attached to the expansion joint
assembly whose primary function is to positively distribute the movement equally
between the two bellows of the universal joint throughout its full range of movement.
Pantograph linkages, like control rods, are not designed to restrain pressure thrust.
The use of circular multiply bellows are the ideal solution for Expansion Joints which are exposed to high pressures. This system involves constructing a bellows using several thin sheets instead of one single thick ply. This technique considerably improves the flexibility of the bellows, its most important characteristic.
Main advantages to be gained from using multiply metal bellows:
They guarantee important savings:
MACOGA Expansion Joints are designed, manufactured and tested in accordance with:
If specially requested or included in the terms of the contract, the Expansion Joints can also be designed according to other international standards and codes (AD-Merkblatter B13, CODAP, etc.).
Design control and modifications are set out in the latest version of our Quality Control Manual and the Quality Procedure "Design and Calculation".
Circular Expansion Joints are manufactured with single or multiple ply with a diameter ranging from 15 to 10000 mm.
Our manufacturing range includes Circular Expansion Joints of the following types:
As well as Rectangular Expansion Joints which, with limitless dimensions, can be supplied with different convolution and corner types:
The essential component of an Expansion Joint resides in the degree flexibility of its bellows and this depends upon the design of its convolution and the materials used during the production process.
The choice of metals to be used in manufacturing the bellows, being the basic component of the Expansion Joint, is made taking the following criteria into account:
The tables shows the materials mostly used to produce our bellows:
Stainless steel grades
254 SMO and 253 MA are trademarks of Outokumpu Stainless
Inconel, Monel & Incoloy are trademarks of Special Metals Corporation. Hastelloy is a trademark of Haynes International, Inc.