Tuesday, May 15, 2012: 08:49:01 PM

Insight

THE RIGHT CONNECT

Pankaj Soni – Country Manager, Victaulic, India, discusses the technology and durability of mechanical pipe joining and its applications

Mechanical grooved pipe joining has been proven through research, testing and extensive evaluation. During its 85-year history, it has stood the test of time in some of the most impressive engineering feats including the Hoover Dam and the Burj Khalifa in Dubai. Grooved mechanical pipe joining provides an attractive alternative to welding and flanging for engineers and owners alike. It allows quick, easy, safe installation and maintenance to meet compressed project schedules, along with maximum operating efficiency and built-in sustainability. Above all, the benefits combine to give a lower total installed cost over the life of the system.

The Essence of the Groove
A mechanical joint consists of four elements in total: grooved pipe, the coupling housings, a pair of nuts and bolts and the rubber gasket ring. This gasket is pressure responsive and is encased by the coupling housing when it engages in the groove around the circumference of the pipe. The gasket then creates a seal unified joint that is enhanced when the system is pressurised.

The method has not only stood the test of time but has been used in some of the most innovative engineering projects in recent years, among them, the Alexandria Library in Egypt and the All England Lawn Tennis Club centre court at Wimbledon, where the state-of-the-art retractable roof over the centre court uses grooved technology for heating and chilled water piping systems in the first project of its type in the world.

The grooved system delivers numerous benefits—the system provides a union at every joint for ease of system maintenance and expansion—plus enhanced design versatility of the joint allows rigidity and flexibility throughout a system. A mechanical joint also provides noise and vibration attenuation, seismic relief, and accommodates thermal expansion and contraction.



The use of flexible groovedpipe couplings reduces the transmission of stresses through a piping system, while the gasket damps vibration. When flexibility is not desired, rigid couplings can be used. Both flexible and rigid couplings provide discontinuity at each joint, which helps to minimise pipeline stresses.

In addition to increasing installation speed, reducing the need for hotworks brings greater onsite safety. As a flame-free method, grooved mechanical 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, and because no electricity is used in the joining process, energy consumption and costs are reduced. The method causes zero emissions: pipe fitters and other workers are not exposed to toxic fumes, which can cause serious health problems.

Roll Grooving Explained
The preparation method most commonly used today in mechanical piping systems is cold forming a roll groove onto the end of a pipe. This method—known as roll grooving—was invented by Victaulic in the 1950’s and is used on 90 percent of grooving applications. Fast and clean, it is suitable for a wide variety of pipe sizes and standard wall thicknesses. Roll grooving is suitable for carbon steel, stainless steel, copper and aluminium pipe or tubing.

Grooved system behaviour is very similar to welded or flanged systems, with all piping remaining in strict alignment and not subject to deflections during operation. This makes grooved systems ideal for use with pumps and valves, or where rigid pipe runs are critical. In addition, the availability of flexible mechanical couplings provides a natural solution to noise and vibration attenuation, removing the need for additional flexible connections around pump sets. With pipe that is roll grooved, any potential increase in pipe hardness, reduction in tensile strength or reduction in elongation has no effect on the integrity of the joint. Pipe material changes are comparable to any other coldforming manufacturing operations.

Strength and Reliability
When it comes to specifying systems, reliability is a top priority for engineers. Mechanical grooved pipe joining has been a reliable and rugged component of a wide range of mission-critical applications, including data centres and flammable chemical cleaning. It has also met the rigorous system demands required for highpressure performance in power applications and in hydraulic elevators.



Grooved systems are verified by independent approval agencies worldwide including Factory Mutual Approvals (FM), Lloyd’s Register of Shipping, Loss Prevention Certification Board Ltd (LPCB), Underwriters Laboratories Inc. (UL), American Society of Mechanical Engineers (ASME), and many more. These are the same agencies that recognise welded, flanged and threaded systems.

Confidence in grooved mechanical piping systems comes from more than 85 years of research and development, exhaustive field observations, and extensive independent and manufacturer testing. Correctly used and installed, the products are safe and effective. Engineers can be assured that grooved technology has been robustly tested in the laboratory as well as in the field to demonstrate its consistent strength and reliability. Details about the grooving process, the strength of grooved pipe, and flow characteristics are further explained in published reports from independent agencies as well as by manufacturers such as Victaulic.


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