Metal joints manufacturers

In modern expansion joints, the metal bellows are often produced with a so-called multi-ply design. To increase both flexibility and stability, multiple thin plies of metal are layered to form the bellow walls. There are two basic design types: The multi-ply and the multi-walled bellows structure. The multi-ply structure consists of a pressure-tight, longitudinally welded outer and inner cylinder of stainless steel. In between these cylinders is an open, spiral cylinder which forms multiple plies depending on the design. The multi-walled structure consists of several concentric, longitudinally welded cylinders. Each cylinder forms a pressure-tight and closed "wall".

Single-plane three-hinged Metal joints make do with one-sided angularly flexible expansion joints, while multi-plane three-hinged systems for absorbing thermal expansion in three axial directions require at least two gimbal expansion joints that are angularly flexible on all sides. The following basic rules apply to angular compensation


The axial expansion joint absorbs movement in an axial direction. Standard connectors of the axial expansion joint are welded ends, fixed flanges and loose flanges. Axial expansion joints are often equipped with a guiding tube on the inside of the metal bellows. This reduces the flow resistance and prevents damage caused by direct contact with the flowing medium. Axial expansion joints, which can absorb large movements, frequently consist of two metal bellows and an inside or outside sleeve that protects against buckling under internal pressure. For small nominal diameters, protective tubes prevent mechanical damage during installation and operation. Axial expansion joints are suitable for internal and external overpressure. 


Unlike Metal joints  unanchored axial and universal expansion joints, lateral expansion joints do not load adjacent pipe supports with the axial compressive force from internal pressure since this force is absorbed by the tie rods. Angular expansion joint

If pressure is applied to the outside of the metal bellows of axial expansion joints, the expansion joints permit very large axial movements in case of internal pressure in a pipeline. Because there is no danger of buckling when an external overpressure is applied, very long metal bellows or combinations of bellows with very large movement absorption can be used in this case.


There are two main types of bolted Metal joints designs. In one method the bolt is tightened to a calculated clamp load, usually by applying a measured torque load. The joint will be designed such that the clamp load is never overcome by the forces acting on the joint (and therefore the joined parts see no relative motion).


Expansion joints are required in large ducted air systems to allow fixed pieces of piping to be largely free of stress as thermal expansion occurs. Bends in elbows also can accommodate this. Expansion joints also isolate pieces of equipment such as fans from the rigid ductwork thereby reducing vibration to the ductwork as well as allowing the fan to "grow" as it comes up to the operating air system temperature without putting stress on the fan or the fixed portions of ductwork.


The torque value is dependent on the friction produced by the threads and by the fastened material's contact with both the fastener head and the associated nut. Moreover, this friction can be affected by the application of a lubricant or any plating (e.g. cadmium or zinc) applied to the threads, and the fastener's standard defines whether the Metal joints torque value is for dry or lubricated threading, as lubrication can reduce the torque value by 15% to 25%; lubricating a fastener designed to be torqued dry could overtighten it, which may damage threading or stretch the fastener beyond its elastic limit, thereby reducing its clamping ability.