It pays to get into the right groove
Efficiency, speed, maintainability and safety are key considerations in hvac installations. Grooved-end pipe joining technology meets all those requirements, says Andy Carter
Grooved-end pipe joining technology - couplings, fittings, valves and accessories - is used throughout the world and is featured in prestigious projects, from the Hoover Dam in the United States, the Grand Arche de La Defence in France, the Alexandria Library in Egypt and the Burj Khalifa in the Middle East, to Wimbledon Centre Court's famous retractable roof in the UK.
The mechanical pipe-joining system begins by cold forming or machining a groove into the pipe end. Piping is secured by a coupling which houses a resilient, pressure-responsive elastomer gasket. The coupling housing fully encloses the gasket, reinforcing it and securing it in position. Only two nuts and bolts are needed to secure the self-restraining joint. The mechanical joint creates a triple seal due to the pipe groove, gasket and housings, which is enhanced when the system is pressurised.
Grooved-pipe couplings are designed to address thermal expansion and contraction, and reduce noise and vibration. Traditional welded or flanged piping systems have rubber bellows or flexible hoses to accommodate vibrations but these materials tend to wear out over time, requiring costly and time-consuming replacement.
No gasket wear
Flexible grooved couplings allow the pipe to move and vibrate within the coupling without wearing out the gasket, localising vibrations generated by equipment and reducing the amount of noise transmitted down the pipeline.
The grooved system takes less time to install: installations are three to four times faster than welded or flanged. Simple fastening of two bolts is all it takes, compared with the multiple bolts needed in a traditional flanged system.
Welding requires high levels of skill, is labour-intensive and time-consuming. With skilled welders in short supply and labour costs high, that makes the grooved method a practical, cost-efficient option. It requires no additional man hours or job site preparation, unlike the extensive preparation necessary for welding, and no electrical energy is needed.
The same advantages apply to maintenance. While the design of the mechanical joint accommodates vibration, thereby reducing the need for repair or replacement, it provides quick and easy access for routine maintenance or repair work. A union at every joint means there is no need to completely drain the system and let it dry out. To access the system, a worker simply unscrews two nuts and drops the section out without the need for a torch, saw or welding machine.
Flame-free pipe joining removes the many health and safety concerns associated with welding. It eliminates the risk of fire and the need for special fire safety precautions during installation and maintenance. Hazards caused by compressed gases and welding equipment leads are also eliminated. The method causes zero emissions: pipe fitters are not exposed to toxic fumes which can cause serious health problems.
Ever tighter structural designs and scarcity of space increases the pressure on contractors to minimise the footprint of mechanical rooms. Eliminating rubber bellows through the use of flexible couplings around pumps or chillers is one way of saving space. Using suction diffusers in place of flanged strainers is another.
These devices straighten out turbulent fluid as it enters a bend, avoiding the need for long, straight runs of pipe into a pump suction, whilst maximising pump performance. Suction diffusers are up to three times faster to install than a flanged strainer and allow quick and easy access for cleaning.
Independent analyses have shown that using the grooved-end piping system gives significant savings on total installation costs compared with welded alternatives. In addition to reduced labour costs due to the speed and ease of installation and less need for higher-level skills, the method brings productivity gains. More people can work in an area if welding is not carried out because shielding is not required, potential delays in obtaining hotworks permits are avoided and man hours needed for a fire watch during and after welding are saved.
Mechanical piping systems offer speed and ease of installation, a reduced need for maintenance and a safe environment for workers. In today's efficiency-driven, cost-led climate, they present a valuable option for effective hvac systems.
// The author is product engineer at Victaulic //
1 February 2012