POWER August 2015 - 19

tomize your solution for what your facility needs to help keep
personnel safe, " Hickey said.
For more on minimizing arc flash hazards, see " Making Sense
of New Arc Flash Protection Rules " in this issue. ■
-Aaron Larson is a POWER associate editor.
Grooved Mechanical Piping Offers a
Versatile Pipe-Joining Alternative
Two of the most important elements in any construction or upgrade
project are safety and speed of completion. While one way
to increase safety is to eliminate hot work whenever possible,
the reality is that welding is necessary for many tasks around a
power plant. However, one area where welding may not always be
required is in the installation or expansion of piping systems.
Although the pipe-joining method is critical for high-pressure,
high-temperature process piping systems, the same cannot be
said for balance-of-plant piping systems. Services such as cooling
water, reverse osmosis, fire protection, chemical treatment, lube
oil, and compressed air can make use of alternative, flame-free
joining methods-some of which can offer installation up to 10
times faster than welding. Grooved mechanical piping is one of
those alternatives.
A Novel Design
A grooved mechanical pipe joint consists of four elements:
grooved-end pipe, a gasket, coupling housing, and fasteners. The
pipe groove is made by cold forming or machining a groove into
the end of a pipe. A gasket enclosed in the coupling housing is
placed around two abutted grooved pipe ends, and the key section
of the housing engages the grooves. The bolts and nuts are
tightened with a socket wrench, or impact wrench, holding the
housing segments together.
In the installed state, the coupling housing encases the gasket
and engages the grooves around the circumference of the pipe to
create a leak-tight seal in a self-restrained pipe joint. In addition
to pipe-to-pipe joints (Figure 4), grooved couplings can be used
to join pipe to grooved-end valves, fittings, and accessories to
create a complete piping system.
Roll grooving is the most common method for pipe-end preparation.
The roll-grooving process radially displaces a small portion
of the pipe wall, forming a groove around the circumference
of the pipe that is recessed on the outside and indented on the
inside. The method can be used on schedule 5 through schedule
80, carbon steel, stainless steel, copper, and aluminum pipe,
ranging from 0.75-inch to 72-inch diameters.
There are two types of grooved couplings: rigid and flexible.
Rigid couplings do not allow movement and can be used wherever
rigidity in the pipe joint is needed, similar to a welded or
flanged joint. Flexible couplings allow a limited amount of linear
and angular movement to accommodate thermal and seismic
movement as well as vibration and misalignment. The majority of
grooved couplings used in power plants are rigid, with flexible
couplings used only around rotating equipment to isolate noise
or vibration. This enables the system to be supported and guided
in accordance with the American Society of Mechanical Engineers
(ASME) B31.1 Power Piping standard.
Safety, Speed-of-Installation Advantages
A key advantage of grooved piping is its flame-free installation. The
assembly of a grooved pipe joint does not require welding, flame,
or heat, nor does it produce fumes. In terms of preparation, there's
no need to remove or clean the surrounding area of combustible
materials, and no need for increased ventilation or fire shielding.
August 2015 | POWER
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During assembly, torches and tanks are not required, nor are pipe
fitters exposed to flame, sparks, slag, or fumes. There's no need for
a fire watch. As a result, grooved systems reduce risk to personnel
and property.
Minimizing welding allows certified welders to focus on critical
process systems while pipefitters handle the balance-of-plant
systems, which can contribute to on-time completion of a project.
Grooving pipe and assembling couplings do not require specialized
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4. A grooved mechanical pipe joint. This cutaway view
shows the four elements of a joint: the grooved-end pipe, gasket, coupling
housing, and fasteners. Source: Victaulic
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POWER August 2015

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