4 Advice to Choose a grooved mechanical tee

Mechanical tees help you retrofit and expand sprinkler systems

Tees are pipe fittings with three outlets&#;two in a line and a third 90 degrees between them. In fire sprinkler systems, a heavy main water line carries water through the building, and lighter branch lines distribute it to the sprinkler heads. Tees connect branch lines to the main lines, and account for various changes in elevation and the direction of pipe and water.

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When renovations or retrofits are necessary&#;such as for building additions or changes in code&#;new branch lines and tees may also be required. And even though grooved pipe couplings are made to come apart easily, disassembling an extensive sprinkler system to add standard tees can be a burdensome process. Mechanical tees make that task easier: Simply attach them to the existing pipe, drill a hole, and fasten a water-tight outlet to get new water and pipe direction.

In this article, we explore:

How mechanical tees work

Mechanical tees, as part of grooved piping systems, use gaskets secured by housings to attach a new line of pipe to an existing one. The mechanical force from the bolts and nuts combined with the gasket and lubricant creates a tight seal around a hole drilled into a run of pipe. This eliminates the need to cut or disassemble pipe, potentially reducing man-hours and materials costs for something like the installation of a simple branch line.

The components of a mechanical tee

Mechanical tees have the same basic parts as grooved couplings&#;nuts and bolts, housings, and gaskets. In grooved couplings, the gasket fits around the circumference of the two butted pipes, and the housing holds them together end-to-end. Read our previous blog for more information on grooved piping systems. In mechanical tees, the gasket fits around the circumference of a hole drilled perpendicular (on center-line) to a pipe. The housing and its hardware secure the outlet to the drilled hole.

Mechanical tees have the following components:

• An upper housing, which accepts the gasket and has an outlet
• A lower housing, which secures the upper housing to the pipe
• A gasket for creating a seal
• Bolts and nuts

Some mechanical tees use a U-bolt instead of a lower housing. The U-bolt fits around the pipe in the same way the lower housing would. U-bolt mechanical tees can be good cost-saving alternatives.

Pipe size for fire sprinkler mechanical tees

The housing of a mechanical tee fits around the pipe that is receiving an outlet. The inner diameter of the housing matches the outer diameter of the pipe. Mechanical tees are sold based on the nominal pipe size (NPS) they fit. For instance, the housing of a 3&#; mechanical tee fits around a 3&#; nominal pipe. The housing&#;s inner diameter is 3.5 inches, the same as the pipe&#;s actual outer diameter.

Outlet size and type for mechanical tees

Mechanical tees create outlets that exit pipes, but the outlet is not necessarily the same size as the main pipe. Indeed, many mechanical tees are reducing, meaning that the branch pipe is smaller than the main pipe. Outlet size is also given in nominal pipe size, not actual size.

Note that outlet size, whether nominal or actual, does not correspond to the size of the hole drilled into the pipe. For instance, a 1.5-inch nominal outlet (whose actual outer diameter is 1.9 inches) needs a 2.7-inch hole. Manufacturer instructions will specify the size of the hole required.

Mechanical tee outlets accept different kinds of pipe, the two most common being grooved and threaded. Threaded outlets are female, and their size is given in Female National Pipe Thread (FNTP).

Materials, listing, and performance for fire sprinkler mechanical tees

Properly manufactured mechanical tees conform to several standards. Look for UL and FM markings when shopping for mechanical tees to know that the fittings are listed and approved. Like all pipe fittings, different tees have different performance limits. For one, mechanical tees can only withstand internal pressure up to a certain point&#;their maximum working pressure. The manufacturer will provide this value. Beyond this, also consider the housing material and the gasket material.

Housing materials

Commonly used for pipe and pipe fittings, ductile iron makes up the housing of many mechanical tees. Ductile iron offers high tensile strength and wear resistance and dissipates heat and vibration well. The ductile iron in a mechanical tee should conform to specifications from ASTM International; in particular, ASTM A536: Standard Specification for Ductile Iron Castings. Copper, steel (stainless and carbon), CPVC, and HPDE tees are also on the market.

Types of gaskets for mechanical tees

A synthetic rubber gasket creates a tight seal for a mechanical tee. Because different materials react differently to heat and various chemicals, the type of gasket used determines what the pipe can be used to transport. Three primary gasket materials are available: EPDM, nitrile, and silicone.

EPDM rubber works well in wet, hot (up to 230 °F/110 °C), and even acidic and salty conditions. This makes it perfect for fire sprinkler pipes. However, EPDM breaks down when exposed to nonpolar hydrocarbons, so it&#;s unsuitable for transporting petroleum products, hydrocarbon solvents, and aromatic compounds.

Nitrile rubber fills a different niche, tolerating water and heat only up to 150 °F or 65 °C but resisting nonpolar compounds. Nitrile is thus ideal for petroleum products, hydrocarbon solvents, transmission and hydraulic fluids, and more.

Silicone gaskets don&#;t resist petroleum and other hydrocarbons very well. But they have an exceptional range of temperature tolerances, remaining flexible at incredibly cold temperatures (anywhere from -76° to -148° F/-60° to -100 °C) and not breaking down even at extremely high temperatures (446° to 572° F/230° to 300° C). Silicone gaskets are common in food and medical applications.

Check out our selection of FM and UL-approved mechanical tees with ductile iron housings, 300 psi working pressures, and EPDM gaskets&#;perfect for fire sprinkler systems. Our fittings are sized for pipe ranging from 1 ¼ inch to 6 inches and feature groove or threaded outlets. U-bolt options are available.

Applications and installation of mechanical tees for sprinklers

Mechanical tees make retrofitting and remodeling easy because they save you the trouble of having to cut or disassemble a lot of pipe. Perhaps you need to put a new branch line to come off a fire sprinkler main. If you need the branch near the end of the run of pipe, undoing a few grooved couplings and adding a conventional tee should be easy enough. But if the branch needs to come off a central part of the network, you could have a lot of pipe to cut and move. And if you have soldered, welded, or another kind of connection instead of grooved, you could spend a lot of time and materials to disassemble and reassemble your sprinkler lines.

To install a mechanical tee:

1. Start by draining the pipes.
2. Then, locate the center-line on the length of pipe that will receive the tee and mark the center of the new outlet.
3. Using an industrial hole-saw, drill a hole perpendicular to center-line. Note that the hole size is not the same as the outlet pipe size. For instance, a tee with a 1 ½&#; nominal grooved outlet (1.9&#; actual outer diameter) requires a 2.007&#; hole per manufacturer instructions.
4. Once the hole is cut, prepare the pipe and tee for installation. Deburr the edges of the hole and clear away debris. Inspect the quality of the gasket and the pipe surface around the hole for anything that might impede a good seal&#;dirt, lumps on the pipe, tear in the gasket, etc.
5. With that done, lubricate the gasket according to manufacturer instructions. Assemble the housings around the pipe so that the outlet is over the hole and tighten the nuts. Under- or over-tightening the bolts can damage the hardware or affect the performance. Tighten the nuts to the torque specified by the manufacturer using a torque wrench.

This video provides a good illustration of installing a mechanical tee:

Different manufacturers give different guidance. For some systems, contact between the metal housings indicates sufficient torque. For others, this is not necessary. The 100Tong Handbook, for example, says that the outlet housing should make metal-to-metal contact with the pipe, but that gaps between the two housings are acceptable as long as they are symmetrical.

Fire sprinkler mechanical tees make retrofits and system changes easier

Ideal for system modifications, mechanical tees let you change direction and add branch lines to fire sprinkler systems easily. Simply drain the system and cut a hole where you need it. Nuts and bolts, a housing assembly, and a gasket seal an outlet to the newly-drilled hole. Mechanical tees should be UL-listed and FM-approved, be rated for the intended working pressure, and have an appropriate gasket.

To get started on your project, browse our selection of mechanical tees. We have grooved-outlet tees in the following dimensions:

Want more information on fire fighting pipe? Feel free to contact us.

Our mechanical tees with FNPT threaded outlets are available in the following dimensions:

-bolt mechanical tees with FNPT threaded outlets are available in the following dimensions:

To round out your shopping list, check out our other grooved fittings, including standard tees, elbows, caps, drain caps, and grooved couplings. You&#;ll need a lubricant to install mechanical tees properly. And if you&#;re adding branch lines, pipe hangers may be a must.

Shop for all your pipe fitting needs in our full online inventory. If you have questions, reach out to us at 1 (888) 361- or .

This blog was originally posted at blog.qrfs.com. Check us out at Facebook.com/QuickResponseFireSupply or on Twitter @QuickResponseFS.

Posted on September 23,

Grooved mechanical coupling systems are the most versatile, economical, and reliable grooved pipe joining system available today. Benefits of grooved pipe connectors to contractors include safer job sites, reduced total installed costs, and ease and speed of installation.

What is a Grooved Pipe Joint?

A grooved pipe joint consists of four elements

1. the grooved pipe
2. the gasket
3. the coupling housings
4. the nuts & bolts.

A pipe groove can either be cold formed or machine formed. A gasket encompassed by the coupling housing is wrapped around the two pipe ends, and the coupling housing key sections engage the grooves. The pipe coupling&#;s bolts and nuts are tightened with a socket wrench or impact wrench. In the installed state, the mechanical pipe 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.

Grooved pipe couplings can employ one of two basic styles: flexible or rigid. There are benefits to both styles. To read more on the differences between flexible and rigid grooved pipe couplings and when to use them, check out this blog post.

Top Five Benefits of Grooved Pipe Joints

1. Safer Jobsites

Not only do benefits of grooved pipe couplings include being fast and easy to install, but it&#;s also safer than any other pipe joining method. Grooved mechanical coupling systems are installed without the need for flame, eliminating the fire hazards typically associated with welding/brazing or soldering.  Welding is one of the most dangerous industrial activities; its hazards include fire risk, electric shock, compressed gases, and toxic fumes. As such, welding requires personal protection for the eyes, hands, feet, and body. Welding activities also require a fire watch during and following the work, which can slow the construction schedule and increase costs.

The safety of installers on the job site is of the utmost importance; however, it becomes even more critical during expansion and/or retrofit projects where buildings such as hospitals and schools may remain open and operational during construction. The benefits of grooved mechanical couplings can decrease the risks to workers and in the projects mentioned above, building tenants. The grooved pipe joining method is the hands-down winner in a side-by-side safety comparison to welding, one of the most dangerous industrial activities.

2. Accommodating Piping System Expansion and Contraction

When accommodating thermal expansion and contraction in a piping system, the grooved pipe joining method conforms to industry practices. Simultaneously, it provides design flexibility, reduces stress on the mechanical piping system and provides a more compact, easy-to-inspect, and productive method of installation over other pipe joining methods.

Grooved mechanical couplings allow for movement of the pipe due to the design of their components. The dimensions of the pipe coupling housing key are narrower than the pipe groove allowing room for the pipe coupling housing key to move in the pipe groove. Additionally, the width of the pipe coupling housing allows for pipe end separation which in turn allows the grooved pipe joint to accommodate linear and angular movement. The mechanical coupling provides a self-restrained joint, and the unique pressure-responsive design of the pipe connector enables positive sealing even under deflection and linear pipe movement.

3. Less Downtime

In retrofit projects, avoiding disruption to building occupants while minimizing cost overruns associated with night and weekend work can be a challenge. Grooved mechanical pipe joining systems can address these issues as a reliable alternative to welding and flanging. The widely-accepted flame-free technology is fast and easy to install and maintain, providing compatibility between new system design and existing systems.

In many cases, existing piping systems can be rerouted and kept in operation while work is performed on old systems or while new systems are installed. The grooved system eliminates the need for complete system shutdowns because there is no need to drain and dry the system, and an arc or flame is not required to disassemble or reassemble the joint. As a result, buildings can return to full operating capacity very quickly. The benefits of grooved in this situation are simple: avoid downtime. To access a piping system joined with grooved components, a worker simply disassembles two couplings to drop out a pipe section. To complete the job, the grooved couplings are easily placed back on the pipe, and the nuts are tightened.

4. Reduced Total Installed Costs

Although there might be a higher upfront materials cost than with welding, the benefits of grooved are found in the reduction of labor time and labor costs. Based on the elimination of welding, and the need for highly skilled and relatively expensive labor, the assembly of mechanical coupling systems reduces labor man-hours as well as the labor rate. This contributes to an overall reduction in piping system costs, known as total installed costs. Victaulic estimates that jobs requiring welding applications demand up to 45 percent more man-hours on average over grooved piping solutions, and at a much higher labor rate.

5. Ease and Speed of Installation

Grooved mechanical piping is inherently faster to install than any other pipe joining method because the gasket and coupling housings simply need to be positioned onto the grooved pipe ends. The bolts and nuts are tightened with standard hand tools. Following installation, most grooved systems can be visually inspected. Metal-to-metal bolt pad contact confirms that the pipe coupling has been properly installed and secured into place. Welding, on the other hand, often requires X-ray inspections to ensure a sound joint. The benefits of grooved pipe couplings are demonstrated in the ease and speed of installation savings. Victaulic&#;s Installation-Ready&#; mechanical pipe couplings can be installed up to ten times faster than welding and six times faster than flanging.

It&#;s easy to see the benefits of grooved piping systems and how it is quickly becoming the standard on commercial building job sites. With the ability to improve job site safety, speed and simplify installation, reduce total installed costs, and ease maintenance and expansion, grooved mechanical piping will long hold a place in contractors&#; toolkits. When you add the engineering benefits to the mix&#;design versatility; accommodation of thermal expansion and contraction, deflection and seismic movement; and noise and vibration attenuation&#;grooved piping is in a class of its own.

Check out some of our case studies to see the benefits of grooved in action.

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