Traditional noise and vibration attenuation methods may be unnecessary for heating, ventilating and air-conditioning systems, as well as industrial utility piping and fire protection systems, when using grooved mechanical piping systems.
According to pipe joining systems manufacturer Victaulic chief technical officer Larry Thau, independent tests have shown that grooved pipe joinings are as effective in sound attenuation as flexible arch connectors, within common frequency ranges.
He states that grooved joinings maintain noise and vibration attenuation qualities, as well as the ability to accommodate deflection, expansion and contraction throughout the life of the piping system.
Designers have traditionally specified elastomeric flexible arch connectors to diminish noise and vibration from equipment connected to a circulation system; however, the weakness of flexible elastomeric flexible arch connectors may result in ruptures or leaks, expense and lengthy installation time.
Thau explains that testing confirmed that a substantial vibration reduction is achieved in pipe systems that employ the Victaulic Style 77 coupling. The actual reduction measured ranges from 2.3 dB to 12.1 dB.
Acoustic consulting firm SSA Acoustics, based in the US, undertook a field measurement test that showed three Victaulic couplings, placed in series in a pipe section, have comparable performance to twin-sphere neoprene connectors and a superior performance to braided metal hoses. Victaulic couplings dampened the overall vibration amplitude by between 80% and 90%.
“Sound attenuation depends on three couplings being placed near to one another, in close proximity to the source of the vibration, so that there are numerous opportunities for design flexibility,” says Thau.
Further, each successive joint creates a reduction in vibration. Independent test laboratory Nutech Testing Corporation used Victaulic mechanical couplings in its testing and concluded that, for any given pipe diameter, less vibration is transmitted with each additional Victaulic coupling, regardless of whether they are rigid or flexible couplings.
Victaulic regional manager for South Africa Barry van Jaarsveld states that, although flexible and rigid couplings have vibration and noise attenuation characteristics, attenuation is more advanced in flexible couplings.
“Flexible couplings allow thermal expansion and contraction in piping systems, and need to be specified at the design phase,” says Van Jaarsveld, adding that rigid couplings act more like a welded joint in the way they hang, with only limited allowance for expansion and contraction.
The elastomeric gasket contained in the internal cavity of the ductile iron housing, creates discontinuity similar to that when using a flex connector and the material from which the gasket is made absorbs vibration.
The flexibility of the grooved pipe couplings reduces the transmission of stress through a piping system, while the gasket and ductile iron housing combine to dampen vibration.
The grooved pipe joint over a flex connector is the proprietary design of the coupling, which enables the gasket to seal the pipe, while the ductile iron housing provides both space for the elastomeric material to flex, and containment to prevent stretching. The coupling works to create a permanent leak-tight seal with no need for additional reinforcement.