Introduction to Grooved Pipe & Fittings - MeyerFire

We previously have introduced different types and combinations of threaded fittings - which have been around for more than a century.

Here we're introducing another common way to join pipe; using grooved fittings. 
An attic sprinkler system using a grooved elbow with couplings.  Use of "mechanical" couplings that could allow faster joining of pipe came to life in by Lieutenant Ernest Tribe. Just a few years later the Victory Pipe Joint Company renamed itself to Victaulic (a combination of "victory" and "hydraulic"), and grew to expand the technology worldwide. 

Today, Victaulic and other manufacturing leaders provide grooved fittings that are often used for pipes in fire sprinkler systems. It is not uncommon for both mains and branch lines to be grooved today.

What are common grooved fittings, and how do they work? Let's introduce them.  An in-rack sprinkler with a branch line using (starting with the sprinkler) a groove x thread reducing elbow
​with a grooved coupling, a grooved piece of pipe, and a grooved tee (connection not shown). PIPE
Let's start with the pipe. In order to give grooved fittings an opportunity to "grip" the pipe and remain in place, they need an opportunity to resist the pressure of the water that is trying to "pull away" the pipe from the fittings which join them together. A grooved coupling about to connect two grooved-end pipes. Note the loose nut and bolt on the right-hand side, allowing the coupling to be expanded and "slip" over the pipe on the left. In order to create a groove in the pipe, steel can either be "roll groove" or "cut groove". Roll groove pipe involves pressing an indentation into the pipe near the end of the pipe. This allows a grooved fitting to slip over the end of the pipe and fit into the groove. Roll groove pipe has the advantage of not reducing the pipe thickness, so it can have more tolerance for corrosion than thinner pipe, similar pipe with threads, or pipe with cut grooves.

Pipe which is cut groove involves cutting into the pipe rather than pressing it. This cutting removes a portion of the pipe wall, making a thinner but smooth interior pipe wall. This thinner wall makes it more susceptible to corrosion, however, for pipe systems with a minor slope, the smooth inside of the pipe does not create a ridge where water can sit and corrode the pipe. Roll Grooved Pipe (top) and Cut Grooved Pipe (bottom). Note the ridge on the inside of the pipe wall for roll groove pipe, and the thinner pipe wall along the cut groove pipe. A tape measure with a "go" or "no-go" measurement to determine if the groove is within manufacturer tolerances. ELBOWS & TEES
Let's start with the basics. Elbows allow bends of 90-degrees (most common), 45-degrees, 22-1/2 degrees, and 11-1/4 degrees.

Why not every possible angle? What if I need to have a 60-degree bend because of my building?

First, it wouldn't be economical to make a fitting of every bend. Second, is that using just two 90-degree elbows back-to-back we're able to create a "swing joint" and make any angle we could want, just by changing the elevation of the pipe that's being joined. Victaulic "FireLock" Grooved Fittings; 
90-Degree Elbow #001 (left), 45-Degree Elbow #003 (center), and Standard Tee #002 (right) One notable specialty with the grooved elbow is a "Drain Elbow", which has the elbow except it includes a drain outlet at the bend of the elbow. This is used all the time with fire department connections which come down a wall and need to be capable of being drained (to avoid having water-charged pipe freeze and burst). This is also called a "Drain-El" or is a Victaulic #10-DR. A wall-mounted fire department connection that is away from the riser, here showing the "Drain Elbow" with a ball drip below. The portion upstream of the check valve is intended to be dry unless the FDC is actively being used in order to avoid freezing water inside. COUPLINGS
Nice sketches, Joe, but that's not how things look in the field!

That's because unlike threaded fittings, the actual pipe joining is by a grooved coupling. The coupling has malleable iron bumps that grip the indent of one groove (pipe/fitting) and connect it to the second groove (the other pipe/fitting).  A grooved coupling (here a Victaulic #009N shown). OTHER FITTINGS
There are a host of other fitting types. Grooved Reducing Tees? Yep. Less common. Less common can equate to more expensive, or at least that's what I hear from contractors familiar with all the pricing nuances.

What other grooved fittings do I often see? 

Reducing fittings, which is a concentric, single-cast piece of metal that has a large groove on one end and tapers down to a smaller groove on another end. One note of caution is using these in the vertical orientation; I've heard it is much better, more stable, and stronger to use a reducing-fitting as opposed to a reducing-coupling when in a vertical orientation. One of my clients goes so far to say to not use reducing couplings at all (where the coupling itself has two different groove sizes). I wouldn't have the expertise to gauge that myself. A flange x groove reducer (left) and a grooved cap (right). There are also reducing adapters, than can accept a flange connection and convert it to a reduced groove connection. 

Crosses are also available, as are caps (like the Victaulic #006 shown above on the right) which can terminate the end of a branch line. These caps even have 1-inch threaded opening options for easy auxiliary drains. 
Many manufacturers have equipment and components with grooved ends that can readily attach to pipe and fittings.

What are grooved fittings?

Groove fittings are a new type of steel pipe connection fittings, also known as clamp connections, which have many advantages. Automatic sprinkler system design specifications put forward, the connection of the system pipeline should be used grooved connectors or fillet, flange connection; system diameter equal to or greater than 100mm pipeline, should be segmented using flange or grooved connections.

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Grooved fittings connection technology, also known as clamp connection technology, has become the current preference for liquid and gas pipeline connection technology, from the beginning of development in to the present, after just a few years of development and application, has gradually replaced the flange and welding of the two traditional pipeline connection methods. Not only is the technology more mature, but the market is also generally recognized. 　

Common fire engineering groove pipe fittings types

Just card, elbow (90 degrees 45 degrees), positive tee, reducer tee (fillet, groove), positive four-way, reducer four-way (fillet, groove), groove mechanical tee, fillet mechanical tee, mechanical four-way, conversion flange, split flange, groove reducer, fillet reducer, blind piece.

Dimensions include clamp connections 76 89 114 165 219 (galvanized pipe) 108 159 (seamless pipe)

Threaded connections include 33 42 48 60 76 89 114    

Generally 100 (i.e. 114 OD) or more with grooved connections and 100 or less with fillet connections

Advantages of grooved fittings

Easy to operate 　　

The operation of grooved fittings is very simple and requires no special expertise, and can be operated by ordinary workers with simple training. This is due to the fact that a large number of technical details have been incorporated into the finished product in a factory-like manner. A single pipe connection takes only a few minutes, which simplifies the technical difficulties of on-site operations to the maximum and saves man-hours, thus also stabilising the quality of the work and increasing efficiency. This is the general direction in which installation technology is developing.

The original characteristics of the pipe are not affected

Grooved pipe connections are made only by extruding a groove on the outer surface of the pipe to be connected with a groove-rolling machine, without damaging the inner wall structure of the pipe. Norms stipulate that galvanized pipes, plastic-lined steel pipes and steel-plastic composite pipes must not be connected using welding and flanges, otherwise they require secondary treatment.

Good stability and easy maintenance Grooved pipe connections have a unique flexible character, making the pipeline resistant to vibration, shrinkage and expansion, and more suitable for temperature changes. When the pipeline needs to be repaired and replaced, only two pieces of clamps need to be loosened to replace, rotate and modify a section of pipeline at will.

Scope of application

Groove pipe connection as an advanced pipeline connection, that is, can be set up in the open or buried, that is, there are steel joints, but also flexible joints. Therefore, it has a wide range of application. 　　

According to the system: it can be used for fire-fighting water system, air-conditioning hot and cold water system, water supply system, petrochemical pipeline system, thermoelectric and military pipeline system, sewage treatment pipeline system, etc; 　　

By pipe material: can be used to connect steel pipes, copper pipes, stainless steel pipes, plastic-lined steel pipes, ductile iron pipes, thick-walled plastic pipes and hoses and valves with steel pipe joints and flange joints.

Groove fittings selection principles

The principle of pressure

Working pressure of 1.6Mpa pipe fittings, is grooved and threaded together.

If the working pressure of the main pipe and branch pipe of the piping system is greater than 1.6Mpa less than 2.5Mpa should all use grooved fittings; such as working pressure less than or equal to 1.6Mpa should try to use grooved fittings with threaded connections, the main pipe working pressure is less than or equal to 2.5Mpa, the branch pipe is less than or equal to 1.6Mpa, the main pipe should be selected with grooved fittings, branch pipe with threaded grooved pipe fittings.

Economic principles.

In order to reduce the cost of the project, in order to meet the strength and rigidity of the pipeline system, three, four-way class should try to choose mechanical three, mechanical four-way.

Strength principle.

If the strength and rigidity of the pipeline system has special requirements, in the selection of tee, four-way is, should try to avoid the use of mechanical tee, mechanical four-way class.

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Tee class selection principles.

Tee is divided into groove tee, groove reducer tee, threaded reducer tee (groove and thread combination), groove mechanical tee, threaded mechanical tee five categories. Select according to the above 3 principles, reasonable selection.

Four-way class selection principles.

Four-way is divided into groove four-way, groove reducer four-way, threaded reducer four-way (groove and threaded combination), groove mechanical four-way (double-branch pipe equal diameter), threaded mechanical four-way (double-branch pipe equal diameter), groove reducer mechanical four-way (double-branch pipe unequal diameter), threaded reducer mechanical four-way (double-branch pipe unequal diameter) seven major categories. Select according to the above 3 principles, reasonable selection.

General piping system.

The use of mechanical tee class should be noted to meet the following conditions: branch pipe outside diameter must not be greater than 2/3 of the main pipe outside diameter size. mechanical four-way class should be met: double branch pipe equal diameter, the branch pipe outside diameter should be lower than the corresponding main pipe outside diameter size three; double branch pipe not equal diameter, the size of the largest branch pipe outside diameter size than the main pipe outside diameter size lower than 2, the size of the largest branch pipe outside diameter size than the main pipe outside diameter lower than four

Example: Mechanical four-way on 8" mains

International pipe size series: 8, 6, 5, 4, 3, 2, 1

Maximum mechanical four-way of 4" for double branch pipes of equal diameter

Double branch pipe is not equal in diameter, using the maximum mechanical four-way, for one end 5 inch, the other end 3 inch

The use of groove pipe fittings should be noted when the problem

#1 When the galvanized pipe diameter is greater than or equal to 100 when using groove connection, 100 pipe can also be set wire, but the wire teeth can not be guaranteed;

#2 Whether the size of the opener matches the pipe fittings;

#3 Whether the sealing rubber ring has bulging, serious wear and cracking, etc;

#4 Whether the pressure depth of the grooving machine matches the grooved parts, which are generally available on the grooved parts.

Maintenance of groove pipe fittings

#1 If water seepage is produced, the bolt should be loosened after the pressure is relieved first to see if the rubber ring is extruded and deformed, if the rubber ring is deformed change the rubber ring directly;

#2 If the riser has been fixed, the rubber ring can not be replaced, in the steel card shell body pad some rubber, increase the amount of compression;

#3 If the rubber ring is not a problem, check the sealing surface of the pipe fittings to see if the paint has an area off, such as off the entire sealing surface paint scraping clean or replace the pipe fittings;

#4 After-sales service purposes: fast, decisive, accurate, thoughtful, thorough; points: listening, roundabout, fast, honest, flexible.

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