TPi September 2014

Pipe joining techniques examined – a comparison of mechanical grooving and flanging by Andy Carter, product engineer at Victaulic

Gasket replacement may be required, particularly when the flange is taken apart. Also, over time the gasket can bond to the flanged pipe ends. When the joint is disassembled, the gasket will need to be scraped off the flanged pipe end and replaced, again increasing downtime due to maintenance. Because of system expansion and contraction, flange gaskets can also take on compression over time, resulting in leakage. Robust and safe A solution for these common problems is to use grooved couplings in place of flanges. In fact, mechanical connections are becoming more common as they can offer practical as well as economical advantages. A mechanical joint, or coupling, is comprised of four basic but robust elements: the pipe groove, the gasket, the coupling housings, and the nuts and bolts. A pipe groove is formed by cold forming or machining a groove into the end of a pipe. Using a variety of Victaulic grooving tools, it is possible to do this on-site or off-site in a workshop enabling prefabrication.

Traditional flanging Flanging is one of the more ‘traditional’ pipe joining methods and has been around for many years. Because of this tradition many piping components – such as pumps, valves and chillers – are supplied with flanged connections. Flanging is commonly used in certain scenarios where speed and a degree of flexibility are required, although it is not a system that allows for easy system contraction and expansion. Depending on the pipe joining system employed, installation and maintenance time will increase, reducing system efficiencies. A flanged pipe joint is a good example of this. Flanges are bolted together, compressing a gasket to create a seal. The bolts and nuts of a flanged union and gasket absorb and compensate for system forces and, over time, the bolts and nuts can stretch due to surges, system working pressure, vibration, and expansion and contraction. When these bolts yield, the gasket can ‘slip’, which can result in a leak. Depending on the location and service of the piping system, subsequent leaks can be costly and hazardous, resulting in downtime and exposure to risk. M any piping systems, including building services, water treatment and plant utility piping systems, use flanges in pipe runs to join pipe, and to allow pipe sections to be assembled and disassembled if a piping system has to be modified or maintained in the future. An effective alternative to flanging is the use of grooved mechanical joints that offer faster installation and disassembly when maintenance is required, as well as other performance and design benefits. Victaulic product engineer Andy Carter compares the flanged and grooved pipe joining methodologies and the advantages they deliver.

Flanged joints in a mechanical room: flanges are roughly twice the width of the pipe they are attached to

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