Any device that contain one or several bellows that function by absorbing dimensional changes are considered expansion joints. These dimensional changes are often due to thermal expansion or pipeline contraction. The expansion joints relieve stress on flexures and angles due to slab confinement. Usually, these joints are placed near or between structures that connect fixed elements like buildings, columns, or bolted machinery. These joints allow for contraction and thermal expansion without causing system stress. Although joints function in the same manner, different joints are suited for different structures. Ensuring the use of correct joints guarantees strength and longevity of the building or structure.
A pipeline system that connects vessels and pumps usually require expansion joints with metal bellows. The rotation within the bellow provides lateral, angular, and axial movements. Welded-end or flanged-end joints are usually made by using standard bellows. Adding hinges, ties, and other accessories provides greater lateral and angular movement for the system. Standard bellow designs often include two bellows for support and long wear. The bellows' shape and number, material, and degree of movement determine the speed or rate of wearing out and failure. Of course, unforeseen forces that have strength beyond the bellows' limits and joints' designs inevitably cause weakening and failure.
Piping systems that use large-diameter pipes are usually fitted with thick-wall expansion joints. These systems and joints operate at optimum level in low pressure. These are expensive but are actually more cost-effective over time. Different metals are selected to suit varying temperature and thermal levels. Effective design structure and correct installation ensure longevity of these joints which justify initial investment.
Low-pressure hot gas transfer requires fabric expansion joints. Combinations of fabric layers, metal foils, and insulation accommodate changing system pressures and temperatures. These layers also reduce the abrasiveness of floating solid particles in the gas. To promote endurance of the pipes and joints, gas flow rate, and temperature are often considered in structural designs. Despite these preventions against wearing out, periodical fabric belt replacement is necessary.
Although movement is important in fitting expansion joints, excessive axial rotation is a problem. For this problem, a slip-type joint is usually used. Materials for these joints are chosen based on abilities to accommodate pressures and high temperature. Sealant and packing are added to the design to minimize movement and prevent further abrasions from solids. "Wipers" are special applications that prevent clogging of slip movement space.
It is important to choose appropriate expansion joints in piping projects. Defective joints are usually the cause of collapse, gas leakages, and instability of structures. Pipe fitting is a project that is too large and complicated for a single person to do. It is better to consult and hire professional contractors to do the job for efficiency and safety.