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Mason SFDEJ Flex Connectors; The result of an evolution leading to, arguably, the best Elastomeric Flex Connector for piping in the HVAC market;

  • Specifically designed to address Vibration Induced Noise associated with HVAC piping
  • Able to deal with large expansion/contraction movements and non-parallel mating-
    flange interfaces.
  • Has the lowest ‘failure rate’ of any elastomeric connector. It’s practically NIL.
  • Will last decades in chilled and ambient temperature applications and longer than any
    other elastomeric connector on the market in hot water applications.
  • One of the few Elastomeric Connectors that has been truly ‘engineered’, as a result of
    working in close concert with the raw material suppliers and ensuring that the
    manufacturing process, involving chemistry, heat and pressure, is consistent with the
    most current knowledge of this critical process.
  • The most appropriate flexible connector for applications in seismic areas.

Regardless how well one has vibration isolated a piece of Electrical or Mechanical equipment, it all goes for naught if one has not also addressed the secondary paths, specifically the electrical, gas and mechanical connections to that equipment. Of the 3 typical connections, the piping connections are by far the most significant in terms of allowing equipment vibration to bypass the primary equipment vibration isolation and transmit that acoustical energy to the structure.

It is important to know that fluid piping transmits vibration both along the wall of the pipe and also in the fluid stream. In the case of the former, the more mechanical devices that are hard mounted to the equipment frame, the broader the range of vibration that will travel down the pipe wall if the pipe is hard attached to any of the equipment. Effectively every vibration signature from every piece of equipment (ie: fans, pumps, compressors, and so on) will be transmitted directly to the structure unless there is an in-stream vibration isolation device in the piping between equipment and the first attachment point to the building. But the piping is there so that fluids can move through them and that takes energy, invariably imparted to the fluid by a pump or pumps. That fluid movement is not a smooth even flow but rather a pulsating flow which is directly related to the rotational speed of the pump times the number impellers in the pump. For example: a pump rotating at 1800r.p.m. (30Hz) and having 4 impeller blades will create a primary fluid pulse of 120Hz (30Hz x 4) throughout the run of the piping. Also, there will likely be harmonic frequencies (ie: 240Hz, 360Hz, 480Hz and so on) generated as well. Whether the vibration travels mechanically down the pipe wall or travels in the fluid steam, exciting the pipe wall throughout the piping run, once the energy gets into the structure and encounters a low density large surface area material (ie: sheetrock), this vibration energy will be shed as airborne noise off that lightweight medium. This is referred to as ‘Vibration Induced Noise’ and it is the underlying cause of most ‘Noise Complaints’. Clearly, any acoustical device installed in a piping system must target BOTH mechanical vibration traveling down the pipe wall and the pulsations traveling in the fluid stream.

Elastomeric flexible connectors (a.k.a. neoprene or rubber flex connectors) have been available for over a century. Like braided metal connectors, which were developed for reciprocating equipment to relieve stresses and alignment issues at the interface between piping and engines and compressors, Elastomeric Connectors were developed for similar reasons for the HVAC industry where forces and movements occur, both transverse and axially at the pipe/equipment connection points. Braided steel connectors are not very flexible in the longitudinal plane and should not be used in HVAC piping systems unless some critical design parameters have been addressed (see Section on Metal Flex Connectors and Expansion Compensators – Braided Flexible Hose/Connectors).

Some 50 years ago, Mason recognized the critical importance of having effective piping isolators working in concert with their equipment isolation systems that they were providing and, accordingly, approached the various elastomeric connector manufacturers at the time to see if they would be interested in developing and manufacturing connectors that would be specifically designed to deal with vibration in piping. None were interested. So Mason decided to do it on their own. In the process they found that were there some inherent design flaws in existing designs and knowledge in the traditional flex connectors, particularly in hot water applications. Mason Flex connectors are the only elastomeric flex connectors on the market that were specifically designed to reduce acoustic energy in piping systems. Acoustical Engineers invariably specify the double convolution (bulges) as the convolutions are specifically designed to knock out the typical frequencies generated by impeller pulsation in the fluid stream and the expanse of flexible elastomer (typically EPDM) of its casing, between flanges, effectively reduces the mechanical acoustical energy in the pipe wall of the upstream equipment-side piping telegraphing that energy to the downstream structure-side piping. That been said, Mason also incorporated many of their findings along- the-way in their connectors, such as: the elastomer best suited for use in HVAC applications; the best available reinforcement; the most effective way of integrating the elastomeric inner and outer surfaces with the intermediary reinforcement; and a way of eliminating pull-out of the elastomeric element from its flanges during a dynamic event. As a result, Mason Flexible elastomeric connectors not only significantly reduce vibration induced noise associated with piping systems and deal effectively with piping expansion, contraction and omni-directional movement but also resulted in the most reliable elastomeric flex connector on the market, with the greatest longevity, particularly in hot water applications. For a better understanding of the historic technical evolution of these connectors, please click on the following link.

SafeFlex Development

Electrical connections to isolated pieces of equipment should be by multi-stranded, not single-solid, wire between equipment and the first junction box that is attached to the structure. Hard protective conduit may be used up to a minimum of 12” (300mm) from the connection at the equipment. This last 12”+ (300mm) must be flexible conduit and easily moved by hand both in all transverse directions and longitudinally.

Gas connections must be flexible using 2 only metal flexible connectors of appropriate flexibility and rated for gas service, (see Section on Metal Flex Connectors and Expansion Compensators – Braided Flexible Hose/Connectors). The two connectors should be installed; one connector at right angles to the other and in relatively close proximity of each other.


  • Good plumbing practice dictates that a shut off valve be installed pipe side of any
    installed flexible connector.
  • For best results, ASHRAE recommends that the first 3 anchor points, downstream of the
    elastomeric connector, be isolated from the structure.

SafeFlex Connectors

MasonFlex Neoprene Connectors


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