Thermal movement is by far one of the more challenging aspects of construction projects for engineers. This is because all materials, including pipes, experience dimension changes as a result of temperature fluctuation and their coefficient of expansion. In fact, there is a 19mm expansion and contraction rate for every 38-degrees Celsius change in temperature for every 30m of common carbon steel pipe.
When a system is subjected to excess temperature, it may experience horizontal movement, vertical movement and angular deflection simultaneously.
In the instance of horizontal piping, the major obstacle is typically the space constraints around the length and turns of the pipe. For vertical piping, considerations are different and involve dynamic, static and elevation head calculations of the pressures and loads that are exerted on the bottom portion of the pipe. Most often this causes bowing at the mid points of long straight pipe runs, which ultimately lends to stress being inflicted on both the piping system, as well as the equipment fitted. It’s for these reasons that it’s imperative to control these reactive forces to prevent transmission of these stresses throughout the piping system that may potentially damage the building itself.
The resultant factors of inadequate accommodation include excessive stress on the piping system, increased incidence of ruptures and leaks, increased stress on boilers, chillers, valves and other equipment and components. Further, these factors also lead to increased downtime and labour expenses.
While many quick fixes for this thermal movement problem exist, there is only one solution that promises optimal efficiency. Flexible grooved pipe joining systems allow for design flexibility, which greatly reduce stress on the piping systems and provides a more compact, inspectable, and productive method of installation over alternative solutions such as welding or flanging. Moreover, the flexible grooved method is superior as all sealing elements in the joint are combined within a metallic housing.
Flexible grooved mechanical couplings enable movement in the pipe due to the design of the components. The dimensions of the coupling key are narrower than the groove in the pipe, thus allowing the coupling key to move inside the pipe groove. Flexible grooved mechanical couplings are a great alternative to welded U-shaped expansion loops, welded offsets, expansion joints and rubber bellows. Additionally, the width of the coupling housing allows for pipe end separation, leaving roomfor controlled linear and angular movement. The mechanical coupling remains a self-restrained joint, and the unique pressure responsive design provides sealing, even under deflection and pipe movement.
Flexible grooved systems also allow for additional benefits, including a simplified assembly process with mechanical couplings that reduce the need for welding, and a reduction in man hours and material handling, meaning safer job sites. During operation, the simple disassembly of a coupling reduces the chances of deferred maintenance and lengthy downtime for routine or unscheduled maintenance.
Flexible grooved systems offer four common methods when accommodating for thermal pipe movement, which include the following:
Overall, choosing the flexible grooved mechanical method is an efficient way to accommodate excess stress on any piping system, eliminate incidents of ruptures and leaks due to thermal expansion, decrease maintenance needs of equipment, and simplify the commissioning process.
The second part of this article will examine the four methods of flexible grooved systems in more detail and will explain the specific advantages of each when it comes to negating extensive thermal movement.
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