Modern commercial buildings have increasingly intricate and multifaceted demands. To effectively meet the current and future needs of these spaces, plumbing, heating and air (PHA) system designers must evaluate numerous factors, including cost, lifespan, energy efficiency, and ever-changing building codes and regulations. In addition, they must fit all requirements for these complex systems into shrinking building footprints.

The type of pipe joint engineers specify can heavily influence how simple or challenging performing system installation, commissioning and maintenance will be. Over the course of two articles, we’ll compare common pipe joints used in commercial PHA systems and discuss their impact on the construction process and end-user. Part 1 focuses on grooved, welded and flanged joints.

What Is a Grooved Joint?

Grooved joints are comprised of four components: grooved pipe ends, an elastomer gasket, a coupling housing, and nuts and bolts. To install these joints, contractors stab the couplings onto grooved pipe ends, then use standard hand tools to tighten bolts until the coupling housings close flush against each other.

Pipefitters employ two grooving techniques to prepare pipe for a mechanical joint, selected based on project needs:

1. Roll grooving uses a cold-forming process to indent pipe ends, effectively creating a groove without removing any pipe material. This method is 20 to 30 seconds faster than its counterpart, cut grooving, and does not require cutting oil or additional cleanup since it doesn’t generate metal shavings.

2. Cut grooving requires removing pipe material, leaving no impression on the inside of the pipe. While pipe preparation is slightly slower than roll grooving, cut grooves are advantageous in certain applications where roll grooving cannot be used, such as when the pipe needs to be internally lined or coated to preserve the integrity of the lining and coating.

• Features. Grooved joints are compatible with various pipe materials, sizes, temperatures and pressure ratings. Their versatility allows engineers to specify a flexible or rigid grooved system for their plumbing and HVAC systems, depending on the system criteria. The flexible coupling design leaves room for controlled linear and angular movement, while rigid couplings are used to avoid movement, and can be supported similar to a flanged or welded joint. 

Both rigid and flexible couplings provide a self-restrained joint and contain a pressure-responsive gasket that preserves positive sealing when pressurized.

• Installation. Grooved joints are an efficient and flame-free pipe-joining method. Contractors may see increased material spending for grooved components, but these connections are quick and easy to perform, reducing total installed cost and yielding considerable time-savings on projects of all sizes. The joints are compatible with a wide variety of systems, simplifying retrofit projects for engineers tasked with connecting new and existing systems. 

A coupling’s simple design — housing, gasket, nuts and bolts — also reduces material handling and can be assembled without specialty equipment, enhancing installation speed.

Pipefitters are not exposed to fire, sparks, slags or fumes since grooved pipe assembly is a flame-free process. There is no need to remove combustible materials, increase ventilation or fire shielding, or coordinate a fire watch. By eliminating hot works, grooved systems reduce safety risks during installation and are easier to coordinate in active buildings. 

In addition, contractors can often visually verify proper installation by confirming pad-to-pad contact of the coupling housing, unlike alternative methods that may require steps like performing X-rays to check joint integrity.

• Maintenance. A mechanical joint’s design improves pipe access and helps minimize maintenance downtime in active buildings since components are easily taken apart and reinstalled. They typically require no maintenance after commissioning.

What Is a Welded Joint?

In this method, certified welding professionals use welding torches to fuse metal pipe. Butt-welded and socket-welded connections are commonly seen in commercial buildings, and their usage depends on pipe materials and system requirements:

1. Craft workers use butt welds to join same-size pipe, creating a smooth, continuous connection.

2. For socket welds, a smaller-diameter pipe is first inserted into a larger-diameter pipe and then welded together. 

• Features. Welding techniques create strong pipe connections resistant to high pressures and temperatures. Contractors do not need additional materials to create seams; different piping materials can be joined via welding when necessary. When performed correctly, a welded system’s continuous joints help reduce potential leak points. The seamless connection also streamlines the insulation process. 

• Installation. Welding is one of the most used pipe-joining methods because of its mechanical strength. However, welding not only requires extensive coordination — such as meticulous planning, scheduling welding activities, obtaining necessary permits, implementing fire watch protocols and cordoning off active welding areas — it also exposes welders to potential safety hazards, including fire, sparks, slags and fumes. 

Construction teams must take additional precautions when welding in cold environments, as the ambient temperature can expedite the cooling process, impacting welding time and quality.

In addition, the time required to ensure 100% weld penetration increases with pipe thickness. Even a highly skilled welder can take hours to perform a single weld, potentially adding to total labor and installation costs. Additional testing methods are often needed to inspect penetration and joint integrity.

• Maintenance. Welded systems are permanent, preserving a system’s structural integrity and reliability long-term. However, welded systems can be challenging to alter since the process involves scheduling available craft workers to cut, adjust and reweld the system. 

During expansions that require engineers to accommodate new hydraulic requirements, welds may need reinforcement or alteration to meet pressure requirements. Welding projects can also disrupt active buildings due to the additional safety precautions required for hot works.

What Is a Flanged Joint?

Flanged joints are usually concentrated around equipment connections like pumps, tanks and valves. To create a flanged connection, installers place high-load gaskets between threaded or plain end pipe, then align mating flange faces. Fitters secure flanges by tightening a series of four to 20 bolts in a star pattern with specific torque requirements, a technique ensuring equal load distribution during installation. 

• Features. The bolted pattern in a flanged joint creates an even load distribution, making the joint resistant to vibration and pressure thrust forces. Torque requirements ensure a tight seal within the specified system parameters and help prevent pipe misalignment in the long term.

Flange assembly doesn’t require heat, improving jobsite safety and eliminating many time-consuming hot work procedures. Unlike welding, specialized certifications and extensive coordination are not needed to perform flanged connections, which can streamline system installation and free up labor to focus on more technically intricate tasks. However, specialty equipment is needed to meet torque requirements on some systems. 

• Installation. The most critical and challenging part of installing a flanged system is ensuring proper alignment. Installers must precisely align components, as misalignment adds stress to the pipe and structure that can lead to failure.

Pipefitters must meticulously follow recommended bolt-tightening procedures to achieve even load distribution on the joint. They will also need to do multiple tightening passes to meet torque requirements, which can be time-inefficient, particularly in larger systems. Some contractors choose to manufacture flanged spools off-site to improve jobsite productivity.

When installing, pipefitters should confirm that they have the right flanges and size-specific tools. Flange fittings have their own pressure ranges and bolt patterns; installing the wrong one could lead to leaks.

• Maintenance. Flanges must be regularly inspected and maintained to ensure bolts maintain proper loading or that pipe movement is not causing cracking or bulging that could lead to system failure. 

Flanged systems offer a crucial advantage in that they do not require pipe cutting to disassemble, offering easier system access. However, flanges are not the most time-efficient or economical to maintain, repair or alter, particularly in large-diameter applications, since disassembly requires applying the same bolt-tightening sequence used during the initial installation.

Grooved, welded and flanged joints are among the most used pipe-joining methods in commercial PHA systems. They’re often preferred thanks to their compatibility with many materials and ability to withstand the demands of a commercial building. 

In Part 2, we’ll discuss threaded, brazed, soldered and compression joints. These joining methods are often used in systems or zones with smaller-diameter pipe, whereas grooved, welded and flanged systems can be employed in both small- and large-diameter applications.

Mark Gilbert is vice president at Victaulic, a global manufacturer of pipe-joining, flow control and fire protection solutions for the most complex piping applications. Contact applications.engineering@victaulic.com or visit www.victaulic.com to learn more.