Flexible or expansion joints

Flexible or expansion joints in piping should be eliminated wherever possible. Flexible joints and expansion joints are any corrugated or flexible transition devices designed to minimize or isolate the effects of ... 

Bending or torsional flexibility may be provided by bends, loops, or offsets by corrugated pipe or expansion joints of the bellows type or by other devices permitting rotational movement. These devices must be anchored or otherwise suitably connected to resist end forces from fluid pressure, frictional resistance to pipe movement, and other causes. 

Stability, fluid compatibility and fatigue resistance also are associated with wear resistance. Vibration and pulsation in mechanical systems, or pipelines are common in chemical process industries and can lead to leakages of corrosive fluid. The vibration fatigue is an unavoidable factor which is further aggravated by improper installation of the moving system. Leakages due to these pulsations can be prevented by the installation of flexible rubber expansion joints. 

Flexible expansion Joints of aluminium or copper are essential after every three or four standard lengths... 

Expansion joint A flexible joint in a run of pipework or ductwork that allows expansion or contraction. 

Tolerance Whenever possible, equipment should tolerate poor installation or operation without failure. Expansion loops in pipework are more tolerant of poor installation than are expansion joints (bellows). Fixed pipes, or articulated arms, if flexibility is necessary, are friendlier than hoses. For most applications, metal is friendlier than glass or plastic. 

If unbalanced layouts cannot be avoided, appropriate analytical methods must be apphed to assure adequate flexibility. If the designer determines that a piping system does not have adequate inherent flexibility, additional flexibility may be provided by adding bends, loops, offsets, swivel joints, corrugated pipe, expansion joints of the bellows or slip-joint type, or other devices. Suitable anchoring must be provided. 

Apart from the above three types there are custom built rubber products such as expansion joints, flexible cell covers and large size rubber foils for the caustic soda industry, and many inflatables, fabric reinforced products and thick moulded sheets for specialty applications in certain process plants. These are all hand formed in aluminium or cast iron moulds or forms by laying up process and then cured in autoclave. Here the flow of the un-vulcanized rubber during cure is not very important as the shape is already formed rather the green strength and the stiffness of rubber stock with a low scorch time are the important requisites. A rubber expansion joint made by a hand layup method and cured in autoclave is shown in the following figure 14.1. 

Expansion Joints All the foregoing applies to stiff piping systems, i.e., systems without ejq)ansion joints (see detail 1 of Fig. 10-169). When space limitations, process requirements, or other considerations result in configurations of insufficient flexibility, capacity... 

Expansion joints provide a flexible connection between components such as piping, pumps, and vessels to counter expansion, contraction, bending, torsion, and other operational forces such as vibration (Fig. 8.39). PTFE is the material of choice. Unlike hoses, an expansion joint is used either with a cover, usually elastomeric, or merely with rib supports between the convolutions. Expansion joints are available in two or three convolutes. The choice depends on the requirements of the installation. 

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