TPi September 2014

In addition to eliminating misalignment issues during installation, a coupling’s 360° orientation capabilities coupled with its smaller profile, compared to a flange, makes the installation of grooved systems ideal for confined spaces. Flanges are roughly twice the width of the pipe they are attached to. On average, grooved couplings are only half this size. The size advantage of the smaller design makes the grooved system suitable for jobs where space is limited – such as mechanical rooms and refurbishment of existing buildings – and any jobs that demand additional flexibility. Speed of assembly Because couplings also have fewer bolts and typically no torque requirements, grooved piping is up to six times faster to install than flanging. Couplings require just two bolts, and for larger sizes (over 660mm, or 26") just four bolts. For comparison, at this higher size range a flange would require a minimum of 20 nuts and bolts. For example, to flange a 150mm (6") joint on Schedule 40 carbon steel pipe requires eight bolts, and would take approximately 1.5 man-hours to complete. This could be completed in just 20 minutes using a grooved solution, or around 10 minutes using a Victaulic Installation-Ready coupling, since these do not require disassembly prior to installation. Both grooved solutions require just two nuts and bolts.

The coupling 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. With both rigid and flexible style couplings available, couplings can be used in virtually every application instead of a flange. Rigid grooved mechanical couplings are designed to provide a rigid pipe joint connection, permitting no linear, angular or rotational movement at the joints. Flexible grooved mechanical couplings, on the other hand, are designed to allow controlled linear and angular movement at each joint that can accommodate pipeline deflection. They offer security whilst also accommodating potential misalignments without the need to install the expensive and delicate specialised equipment necessary with flanged or welded systems. A third benefit can be derived from the use of three flexible couplings used near a source of vibration. Flexible couplings reduce noise and vibration, and eliminate the need for specialised noise reduction components. Flanges, a rigid pipe joining method, are not ideal for environments in which there is pipe movement, such as thermal expansion, vibration or building settlement. Expansion and contraction can stress the flange and piping, which can compromise the gasket over time. When this occurs, the joint is at risk of leaking. Grooved flexible couplings can provide pipe movement in the form of axial movement or angular deflection, and can accommodate thermal pipe movement. In many ways, mechanical pipe joining can offer a more efficient solution than flanging and is a widely accepted method for joining pipe based on the simple system access it provides and the proven reliability – couplings can match the pressure ratings of flanges with no significant difference in flow dynamics. Grooved couplings also reduce the weight of a system and only require two bolts to complete a joint, versus eight bolts in a like-size flange. Flexible installation On initial installation, boltholes of a flange must be precisely aligned, and then tightened to hold the joint. Also the bolt hole index on equipment inlets and outlets must line up perfectly with the flange on the piping to be connected to the unit. With only one of a number of fixed positions determined by the number of holes in a flange, a fitting or valve can only be rotated to match the bolt holes. All this results in an increased risk of misalignment issues in the field. Grooved systems do not have this problem and allow much more convenient installation with a full 360° rotation. There is no bolt hole pattern to line up, and a coupling can be oriented at any angle around the joint. The coupling can be ‘free floated’ around the pipe in the field to provide easy access to the bolts and, in turn, simplify access to the equipment.

A mechanical coupling has 360° orientation capabilities and a low profile, making it suitable for installation in confined spaces

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September 2014 Tube Products International