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What Is Fusion?

The Fusion Process

The pipe fusion process associated with McElroy fusion machines is a widely accepted process that joins two pieces of thermoplastic pipe together with heat and pressure. While commonly associated with high-density polyethylene pipe (HDPE), our machines are capable of fusing (or welding) a variety of different types and sizes of pipe including medium-density polyethylene (MDPE), polypropylene and polypropylene-random (PP-R), polyamide nylon pipe (PA11 & PA12), Fusible-PVC® and more.

The Theory of Heat Fusion

  • 1

    Clamping the Pipe

    The pipe pieces are held axially to allow all subsequent operations to take place.

  • 2

    Facing the Pipe

    The pipe ends are faced to establish clean, parallel mating surfaces, perpendicular to the centerline of each pipe.

  • 3

    Heating the Pipe

    The melt pattern, that penetrates into the pipe, must be formed around both pipe ends.

  • 4

    Fusing the Pipe

    The melt patterns must be joined with a specified force. The force on the joint must be held until the joint cools.

The principle of heat fusion

Heating two surfaces to a designated temperature, and then fuse them together by application of force. This process develops pressure, causing flow of the melted materials, which causes mixing and fusion. When the thermoplastic pipe is heated, the molecular structure is transformed from a crystalline state into an amorphous condition. When fusion pressure is applied, the molecules from each pipe end mix.

The result of heat fusion

As the joint cools, the molecules return to their original form, the original interfaces are gone, and the two pipes have become one monolithic pipe.

Why use Fused-Pipe?

Heat-fused thermoplastic pipe has numerous benefits over traditional piping systems.

Seamless

Fused thermoplastic pipes create a monolithic pipeline with less mechanical transitions, meaning less opportunities for leaks.

Longer lifespan

Thermoplastic pipes, like HDPE, are expected to last up to 100 years — saving replacement costs.

Cost Effective

Heat-fused pipelines create leak-free systems, reduce maintenance or repair needs, and conserve resources.

Corrosion Resistant

Thermoplastic pipes don't rust or corrode and are resistant to chemical abrasion.

Tough

Thermoplastic pipes can withstand common damages, vibrations and pressure surges.

Where is Fused-Pipe Used?

Natural Gas Distribution

HVAC and Mechanical Systems

Potable Water Delivery

Fire Suppression Systems

Greywater and Sewer Lines

Geothermal Installations

Water Distribution and Transmission

Explore Job Stories

Types of Fusion Machines

McElroy produces the most respected and reliable pipe fusion equipment in the industry.

Manual
Machines

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Rolling Hydraulic Machines

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Tracked Hydraulic Machines

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Specialty
Machines

Learn More

Frequently Asked Questions

Click on a question to see the answer.

McElroy offers a variety of machine styles and sizes to fuse pipe from 1/2" CTS to 2000mm O.D.

Most McElroy fusion machines have a model number that will give you the pipe range of the equipment.

Example: 412 Machines will fuse 4" to 12" pipe sizes, 1236 machine will fuse 12" to 36" pipe sizes, etc.

With a variety of McElroy machines, you can fuse from ½ " CTS to 65 " O.D. pipe sizes.

IPS stands for "Iron Pipe Size" which is a steel pipe sizing standard that has been in existence for years.

DIPS stands for "Ductile Iron Pipe Size" which is a Ductile pipe sizing standard that has been in existence for years.

JIS stands for "Japanese Industrial Standard" which is the piping standard for Japan.

ISO metric stands for "International Standards Organization" which is the piping standard used in many parts of the world.

CTS stands for "Copper Tube Size" which is the copper tubing sizing standard in the United States.

It is the ratio of pipe diameter to wall thickness. It is calculated by dividing the specified outside diameter of the pipe by the minimum specified wall thickness. Any size pipe with a common DR is qualified to operate at the same pressure regardless of pipe OD (e.g. 2" IPS DR 11 pipe can have the same operating pressure as 12" DR 11).

McElroy fusion machines are designed to be operated by one person. Support equipment and personnel may be required to move the pipe and equipment to the job site.

There are a variety of accessory items available depending on the machine size and application. See the machine's product page for more accessories.

Some examples are:

  • Inserts
    Required to fuse different pipe sizes that a machine can accommodate.
  • Pipe Support Stands
    Used to support the pipe about 20' from each end of the fusion machine. These are used to give the pipe proper alignment in the machine.
  • Pyrometer
    Used to measure the heater surface temperature before making the butt fusion joint.
  • Hydraulic Extension Hoses
    Used to operate an 28, 412 or 618 fusion machine off the chassis in a remote application.
  • Stub End Holder
    Used to hold a stub end fitting for a butt fusion connection

The amount of time to make a fusion joint depends on a number of variables such as pipe size, jobsite set-up, and fusion parameters and procedures. With an experienced crew and a McElroy machine, a rule of thumb is 1 ½ to 2 minutes per inch of pipe diameter, depending on the DR. Always consult the pipe manufacturer's recommended parameters and procedures in their installation manual. For pipe outside the United States, use the temperatures prescribed by applicable company, local, state, or federal standards.

Always consult the pipe manufacturer's recommended parameters and procedures. A pyrometer or DataLogger should be used periodically to insure proper temperature of the heater. For pipe outside the United States, use the temperatures prescribed by applicable company, local, state, or federal standards.

Use a surface pyrometer to check the surface temperature of the heater or heater adapter. The dial thermometer on the heater reads internal temperature. Use this as a reference to monitor the heater temperature during the fusion process.

The dial thermometer on the heater indicates internal temperature. Some heat is lost on the transfer of heat to the outside of the heater adapters. Strong wind currents can also drop the surface temperature below the desired setting. Keep the heater in the insulated heater stand, when not being used to heat pipe ends. Loose heater plates or foreign material between the heater and the heater plates will also cause a drop in the surface temperature and the internal reading of the heater plate. Surface readings should be taken with a pyrometer.

Most pipe manufacturer's recommend a certain heating time or bead size against the heater. Always consult the pipe manufacturer's recommended parameters and procedures. For pipe outside the United States, use the temperatures prescribed by applicable company, local, state, or federal standards.

The molten joint must be held immobile under force until cooled adequately to develop strength. The proper cooling times for the joint are dependent on the material, pipe diameter and wall thickness and are established by the pipe manufacturer or by applicable company, local, state, or federal standards. Allowing proper times under force for cooling prior to removal from the clamps of the machine is important in achieving joint integrity.

The pipe ends must be rounded and aligned with each other to minimize mismatch (high-low) of the pipe walls. This can be accomplished by adjusting the clamping jaws until the outside diameters of the pipe ends match. Always make sure the pipe is coming into the machine level and straight, then tighten down the high side until the pipe ends are even. The use of pipe support stands will allow you to bring the pipe into the fusion machine on a level plane, which greatly helps in alignment and also reduces drag on the movable jaws. When working with coiled pipe, if you place them into the machine in an S configuration, the pipe ends are easier to align properly.

McElroy facers are equipped with machined facer stops. These stops provide a square face-off by ensuring the facer is held perpendicular to the pipe ends. This also establishes a controlled stand-off of pipe to the jaw surface to provide optimum rounding and pipe alignment.

A minimum of (1) complete revolution on each pipe end must be removed in order to expose clean material suitable for butt fusion. Always face to the stops to insure a square face-off perpendicular to the pipe.

Always wipe the pipe ends before the facing operation to make sure they are free of dirt and contamination. After facing the pipe, care should be taken to remove all shavings from the fusion area. Brush away loose particles with a clean, non-synthetic cloth. Always consult the pipe manufacturer's recommended parameters and procedures. For pipe outside the United States, use the temperatures prescribed by applicable company, local, state, or federal standards.

After the pipe ends have been properly heated, the heater tool is removed and the molten pipe ends are brought together with sufficient force to properly mix the pipe materials and form a homogeneous joint. The pipe manufacturer's instructions may specify either interface pressure or bead size of molten material as a guide for a proper joint. Always consult the pipe manufacturer's recommended parameters and procedures. For pipe outside the United States, use the temperatures prescribed by applicable company, local, state, or federal standards.

With your information of pipe diameter, wall thickness (or DR), and the recommended interfacial pressure you may use the McElroy Slide Rule Pressure Calculator, the McElroy nomogram pressure calculator, or our online pressure calculator. To determine the gauge pressure in each case, follow the instructions on the calculator to determine the theoretical fusion pressure for use in the fusion mode of the selected McElroy Hydraulic Fusion Machine. Drag pressure should always be added to the theoretical fusion pressure. Always consult the pipe manufacturer's recommended parameters and procedures. For pipe outside the United States, use the temperatures prescribed by the applicable company, local, state, or federal standards.

Drag is the frictional resistance occurring during carriage movement. The amount of drag pressure on a machine should be added to the theoretical fusion pressure from the slide rule or McCalc number to get the fusion pressure.

The molten joint must be held immobile under force until cooled adequately to develop strength. The proper cooling times for the joint are dependent on the material, pipe diameter and wall thickness and are established by the pipe manufacturer. Allowing proper times under force for cooling prior to removal from the clamps of the machine is important in achieving joint integrity.

The minimum power requirement for a McElroy fusion machine represents the minimum power required at the machine to do the work. The generator size will be larger depending on the altitude, temperature, operational distance from the unit, and other variables.

If the blades become dull or chipped, replace the blades. The life of the blades will vary depending on several variables including cleanliness, hours of operation, material being faced, etc.

If the coating on the heater adapters are worn or damaged, remove the adapters and replace them with a new coated set.

Most U.S. pipe manufacturer's have pictures and a good description of a proper butt fusion joint. Always consult the pipe manufacturer's recommended parameters and procedures. For pipe outside the United States, use the temperatures prescribed by the applicable company, local, state, or federal standards.

Cut the joint out and make another butt fusion joint using the proper fusion parameters and procedures. Always consult the pipe manufacturer's recommended parameters and procedures. For pipe outside the United States, use the temperatures prescribed by the applicable company, local, state, or federal standards.

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