Learn with HAYES
About Butt Fusion
What is Butt Fusion
DESCRIPTION
Butt fusion is a thermal welding process used for joining thermoplastic pipe ends or/and fittings, as result of heat fusion and pressure, the molecules of the two pipes melt and mix together and when the joint cools, the molecules of plastics return to their original form and the two parts finally become one monolithic pipe which creates a seamless end-to-end connection.
PROCEDURE / APPLICATION
The HAYES Manual Butt fusion machine is used for welding thermoplastic pipes and fittings made of HDPE (Polyethylene), PPR (Polypropylene), PB (Polybutene) and PVDF by heat fusion and manually controlled force. This method plays a crucial role in joining pipes and fittings, ensuring leak-proof connections and long-lasting joints when maintaining the integrity of fluid transportation networks.
Benefits of Butt Fusion
When to Use Butt Fusion
Butt fusion is commonly used in various industries and applications, including:
- Water and Gas Distribution: It provides leak-free connections that are critical for the safe and efficient transport of these essential utilities.
- Wastewater Management:In sewage and wastewater systems, where pipes are subjected to a variety of harsh chemicals and environmental conditions, butt fusion is the go-to method for reliable, long-lasting connections.
- Industrial Pipelines:Industries such as chemical processing, mining, and agriculture often rely on butt fusion to join pipes that transport a wide range of materials, from corrosive chemicals to irrigation water.
- Geothermal and HVAC Systems:Butt fusion is used to connect pipes in geothermal heating and cooling systems, ensuring efficient heat transfer and long-term durability.
Benefits of Butt Fusion
Butt fusion offers several advantages that make it a preferred choice for many applications:
- Leak-Proof Joints: The resulting joints are seamless and completely leak-proof, ensuring the integrity of the fluid or gas being transported.
- Longevity: Butt fusion joints are highly durable and can withstand the test of time, making them ideal for applications where longevity is crucial.
- No Need for Solvents or Adhesives: Unlike other joining methods, butt fusion does not require the use of solvents or adhesives, reducing the risk of chemical contamination.
- Low Maintenance: Once a butt fusion joint is made, it requires minimal maintenance, reducing operational costs.
- Consistency: Butt fusion offers a high degree of repeatability and consistency in joint quality.
Apparatus—General Recommendation
Butt Fusion Machine— a Butt Fusion Machine has four (4) basic parts:
(1) Heating Tool—The heating tool shall have sufficient area to adequately cover the ends of the size of pipe to be joined. This electrical tool shall have sufficient wattage and control to maintain the specified surface temperature of the tool faces. It shall also be equipped with heater faces that are coated with a non-stick material to prevent sticking to the pipe surface.
Temperature Indicator—The surface temperature of heating tool faces must be 400 to 450°F (204 to 232°C). A pyrometer or other surface temperature measuring device should be used before the first joint of the day and periodically throughout the day to insure proper temperature of the heating tool face. All pyrometers are sensitive to usage techniques. Carefully follow the manufacturer’s instructions for best results.
(2) Alignment carriage or pipe support stands— is a stationary clamping fixture and a movable clamping fixture for aligning and holding each of the two parts to be fused. This may or may not include the power supply to operate the machine. Pipe Support Stands—Optional pipe support stands or racks are used to support the pipe at both ends of the butt fusion machine to assist with pipe loading and alignment.
(3) a facer for simultaneously preparing the ends of the parts to be joined. A facer is a rotating cutting device used to square-off the pipe or fitting ends to obtain properly mating fusion surfaces. If so equipped, facing should continue until a positive mechanical stop on the butt fusion machine is reached.
(4) appropriate inserts for clamping different pipe sizes or fitting shapes. Butt Fusion Machines are operated manually or hydraulically. Some have their own power supply and some require a separate generator. They are available in a variety of sizes to fuse pipe and tubing produced to ASTM and other industry specifications.
Parts of a Manual Butt Fusion Machine
Heating Tool
Alignment
Facer / Trimmer
Insert / Clamps
Support
Operator Experience
According to the American National Standard ASTM F 2620: Skill and knowledge on the part of the operator are required to obtain a good quality joint. This skill and knowledge is obtained by making joints in accordance with proven procedures under the guidance of skilled operators. Evaluate operator proficiency by testing sample joints.
The party responsible for the joining of polyethylene pipe and fittings shall ensure that detailed procedures developed in conjunction with applicable codes and regulations and the manufacturers of the pipe, fittings, and joining equipment involved, including the safety precautions to be followed, are issued before actual joining operations begin.
Before welding recommendations
- Skill and knowledge are required to obtain a good quality joint.
- The machine should be placed on a stable and dry surface to operate.
- Check field generator for adequate power supply and fuel sufficient to complete the fusion joint.
- Pouring water or applying wet cloths to the joint to reduce cooling time is not acceptable.
- Make sure the blades of the trimmer are sharp and the Teflon in the heating plate is in good condition.
- Place the appropriate inserts for the pipe OD or the fitting being fused.
- Non-stick coating (Teflon): Coated surfaces have been treated to reduce polymer adhesion. If the polymer adheres to the heating plate, lightly wipe with a clean cotton cloth to remove. Do not use a wire brush or an abrasive.
- Welding parameters: Pipe manufacturers have established qualified fusion procedures which should be followed precisely. You should obtain a copy of the pipe manufacturer’s procedures or appropriate joining standard for the pipe being fused.
- Heater temperature: Ensure you select the proper temperature according to the pipe manufacturer’s recommendation. The surface temperature of the heating tool plate should be measured periodically with a surface pyrometer prior to initial use and at reasonable time intervals thereafter.
Butt Fusion Welding Procedure
Description of Method
The principle of Butt fusion is to heat to a designated temperature the ends of two thermos plastic pipes until a bead is formed, then fuse them together by application of a sufficient force or pressure. This force or pressure causes the melted materials to flow and mix, thereby resulting in fusion that is stronger that the pipe itself.
The butt fusion procedure has 4 stages:
The Welding Parameters contain the amount of Pressure and Time to apply in each stage. Obtain a copy of the pipe manufacturer’s Welding Parameters for the appropriate joining standard for the pipe being fused. Follow the procedure carefully and adhere to all specified parameters. Failure to follow the pipe manufacturer’s fusion procedures or appropriate joining standard could result in a bad fusion joint.
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PREPARE, TRIM AND ALIGN THE PIPE |
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Process involved
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Parameter Required
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HEATING UP AND HEAT SOAK |
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Process involved
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Parameter Required
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JOINING THE PIPE (FUSE / COOL) |
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Process involved
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Parameter Required
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REMOVING THE PIPE (INSPECTING) |
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Process involved
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Parameter Required
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Step by step welding procedure
Stage #1: PREPARE, TRIM AND ALIGN THE PIPE
Place pipe support stands at both ends of the butt fusion machine and adjust the support stands to align the pipe with the fusion machine centerline. Install the pipes or fittings being joined in the stationary and movable clamps of the butt fusion machine. Leave enough pipe protruding through the clamps to allow for facing and clamp the pipe or fitting in the machine.
Cut and Clean
Cut the pipe and clean the inside and outside of both ends of the pipes with a clean lint-free dry cloth. Remove all dirt from the clamps surfaces where the pipes will be clamped in the butt fusion machine.
Trimming pipes
Face the pipe ends until the trimmer bottoms out on the stops and is locked between the clamps to establish clean, parallel mating surfaces between the pipe ends. Open the clamps, remove the trimmer and clean the inside and outside of both ends of the pipes with a clean lint-free dry cloth.
Alignment
Check the pipe ends for high low alignment and out-of-roundness. If adjustment is needed, adjust the high side down by tightening the high side clamp. Do not loosen the low side clamp or slippage may occur during fusion. Re-face the pipe ends if excessive adjustment is required and remove any dirt with a clean, lint-free cotton cloth. The maximum OD high-low misalignment allowed in the butt fusion procedure must be less than 10% of the pipe minimum wall thickness.
Stage #2: HEATING UP AND HEAT SOAK
Preheat: Verify that the heater surface temperatures are in the specified temperature range according to the standard. ASTM F 2620-13 (204-232°C / 400-450°F). Please follow pipe manufacturer’s procedure. A pyrometer or other surface temperature measuring device should be used before the first joint of the day and periodically throughout the day to insure proper temperature of the heater plate. The thermometer on the electric box indicates internal temperature of the heater which varies from the actual surface temperature.
NOTICE: Incorrect heating temperature can result in questionable fusion joints.
Heat Up with force
Decrease the force at the DRAG (ft/lbs.) to start the Heat Soak. Maintain the contact with DRAG (ft/lbs.) (P2) for the Time (T2) until the Bead size (B) is within the recommended range.
Heat Soak
Face the pipe ends until the trimmer bottoms out on the stops and is locked between the clamps to establish clean, parallel mating surfaces between the pipe ends. Open the clamps, remove the trimmer and clean the inside and outside of both ends of the pipes with a clean lint-free dry cloth.
Change Over
When the proper bead size is observed, quickly remove the heating tool and quickly inspect the pipe ends. The maximum time spent must be less than or equal to (T3).
Bring the pipe togethers and begin the next step. Joining the Pipe.
Stage #3: JOINING THE PIPE (FUSE / COOL)
Fuse pipe together
Close the clamps by bringing the pipe ends together. Raise the force gradually and steadily using the set time until a welding Force (ft/lbs.) is reached during the time (T4). Do not use excessive or insufficient force.
Cooling with pressure
Keep the pipes joined on the carriage aligner under the same fusion Force (ft/lbs.) during the cooling time (T5) until sufficiently cooled. Cooling under fusion Force (ft/lbs.) before removal from the butt fusion machine is important in achieving joint integrity.
Cooling Without pressure
Once the cooling time with force has ended, decrease the force at contact force to 0. For ambient temperatures 100°F and higher, additional cooling time may be needed.
Pouring water or applying wet cloths to the joint to reduce cooling time is not acceptable.
A torque wrench can be used when a specified Interfacial Pressure is required. Hold this force for at least 10 seconds. After 10 seconds, the locking cams will assist by maintaining jaw position during the cooling cycle.
An interfacial pressure of 60 to 90 psi (0.41 to 0.62 Pa) is used to determine the force required to butt fuse the pipe components. Multiply the interfacial pressure times the pipe area to calculate the fusion force required (lb). For manually operated fusion machines, enough force should be applied to roll the bead back to the pipe surface. A torque wrench may be used to apply the proper force. Manual fusion without a torque wrench has been used successfully many times.
Stage #4: REMOVING THE PIPE (INSPECTING)
Cooling time without force
(only 10 minutes additional cooling time is required for IPS 1 in. and smaller pipe sizes). Do not apply internal pressure until the joint and surrounding material have reached ambient air temperature.
Removing Pipe
After pipe has cooled sufficiently, apply closing force on the lever handle and push the locking cams down into the unlocked position. Unscrew the clamp knobs enough that they can be swiveled outward.
Inspecting
Visually check the entire joint. The joint should be smooth symmetry, and the bottom of groove between the beads should not be lower than the pipe surface. The misalignment of two beads should not exceed 10% of the wall thickness.
NOTE: Avoid high stress such as pulling, installation or rough handling for an additional 30 min or more after removal from the fusion machine (only 10 minutes additional cooling time is required for IPS 1 in. and smaller pipe sizes). Do not apply internal pressure.
Optional use of Torque Wrench
NOTICE: Failure to follow pipe manufacturer’s heating time, pressure and cooling time may result in a bad joint.
Torque wrench
If a specified force is required in the fusion procedure, you must use a specialized torque wrench with the reading capacity to apply the proper force.
“The torque wrench is an additional tool supplied by Hayes that measures the force applied over the pipe in the same direction when pushing or pulling”.
Torque units
The reading units shown in the torque could be in ft∙lb (Pound ∙ Foot) for the American System or N∙m (Newton ∙ meters) for the International System.
Make sure you convert your units before using it to set any bearing preloads.
How to use a torque wrench?
Hayes has designed a special torque adapter for the machine.
- Place the adapter into the handle socket and tighten it with the screw provided.
- Insert the torque wrench into the adapter head and tighten it with the screw provided.
NOTICE: Using a different adapter or torque wrench may result in inappropriate forces and torque readings.
IMPORTANT: Add the DRAG value (the force required to move the pipe at or near the point of fusion) to the overcome FORCE for the pipe to be fused and convert the pounds force to torque reading units to assure the proper joining force. This should be determined prior to inserting the heater.
Torque wrench readings: To apply the proper torque reading units ask for the torque wrench readings Chart.
How to calculate fusion force
NOTE: This formula and calculation are based in the ASTM F 2620 American Standard for HDPE pipe using IFP 75 PSI. For the European Standard the IFP recommended is 21.75 PSI or 0.15 Mpa or 0.15 N/mm².
The Fusion Force in the manual machines is calculated in lbs. as the pound of force, in the example above a 4” IPS pipe SRD 11 need 394.12 pound-force (symbol: lbf, sometimes lb f)
When using a torque wrench, you must convert the pound-force to Torque units.
The reading units shown in the torque dial is shown in ft∙lb (Pound ∙ Foot) for the American System or N∙m (Newton ∙ meters) for the International System.
To apply the proper torque reading units ask for the torque wrench readings Chart.
Make sure you convert your units before using it to set any bearing preloads.
CALCULATING ACCORDING TO THE AMERICAN STANDARD ASTM F2620
EXAMPLE: Pipe size: 4 inches-SDR 11 with MACHINE: HAYES COMBAT 6 110V
MACHINE: HAYES COMBAT 6 110V
- Welding ranges: 2″ 3″ 4″ 5” 6”
- Torque Wrench: 16.33″ = 415mm
- Readings: 0-100 ft∙lb or 0-100N∙m
- Voltage: 220 V
- Temperature: 400 – 450 °F
- IFP: 75 PSI = 0.52 Mpa
FORMULAS AND DEFINITIONS
FORCE = IFP x AP + DRAG
- IFP Interfacial Pressure
- ND = Nominal Diameter
- Ap Pipe Area = (OD – T) * T * л
- OD = Outside Diameter
- T Thickness = OD/SDR
- DIN = Internal Diameter
- DRAG Drag pressure – 30 PSI = 0.20 Mpa
- SDR = Standard Dimensional Ratio
- PSI = lbf/in²
- PN = Nominal Pressure
- л / Pi = 3.14
Replace all the values in the formula
OD of 4” = 4.50 In. = 114.30 mm
T = OD/SDR = 4.50 In/11 =
T = 0.40909 In.
Ap = (OD – T) * T * л = (4.50” – 0.409) x 0.409 x 3.14
Ap = 5.25 In²
FORCE = IFP x AP + DRAG | (IFP = 75 PSI and DRAG = 30 PSI)
FORCE = 75 PSI x 5.25 In² + 30 PSI
Replace PSI in the formula (PSI = lbs. / in²)
FORCE = 75 lbs. / in² x 5.25 In² + 30 PSI
FORCE = 394.12 lbs. + DRAG (30 PSI) measured in ft-lbs.
FORCE = 394.12 lbs. + DRAG (30 PSI) measured in ft-lbs.
Glossary of terms
Welding terminology
- T = Time
- P = Pressure
- B = Bead size
- F = Force
Pipe terminology
- ND = Nominal Diameter
- DIN = Internal Diameter
- OD = Outside Diameter
- T = Thickness
- PN = Nominal Pressure
- SDR = Standard Dimensional Ratio
Relation between the Outside diameter and Thickness of the wall
Temperature terminology
Celsius to Fahrenheit
- 1°C = 33.8 °F
- 1°F = -17.22 °C
- ¿°F? = (X°C * 9/5 + 32) = °F
- ¿°C? = (X°F – 32 * 5/9) = °C
Fusion Force terminology (Manual Machines)
- Pound-force= lbf, sometimes lb f
- Pound ∙ Foot= ft∙lb
- Newton ∙ meters= N∙m
- Torque wrench = Measures the force applied over the pipe in ft∙lb or N∙m
Pressure terminology (Hydraulic Machines)
- PSI= Pound square inches
- MPa= Mega Pascal
- 1 MPa= 10 Bar = 145 PSI = 1 N/mm² = 100 N/cm²
- 1 In² = 6.4516 cm²
- 1 cm² = 100 mm² = 0.155 In²
- 1 mm²= 0.01 cm² = 0.00155 In² = 0.00001076 Ft²
FUSION STANDARD ASTM F 2620 (USA)
TEMPERATURE: 400 – 450 °F (204 – 232 °C)
IFP: 75 PSI = 0.517 MPa = 0.517 N/mm² = 5.17 Bar
DRAG: 30 PSI
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HEAT UP |
HEAT SOAK |
BEAD UP (MINIMUN BEAD SIZE) |
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HEAT UP force P1 |
HEAT SOAK P2 |
Time T2 (s) |
If Outside Diameter in. (mm) |
Min. Bead Size in. (mm) |
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IFP*Ap + DRAG
Time T1: 10 s on 14 in. pipe and smaller |
Drag 30 PSI |
4.5 min (270 s) x 1″ (25.4 mm) Wall Thickness (T) |
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CHANGEOVER (Heater Removal) |
JOINING THE PIPE (FUSE / COOL) |
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Wall Thickness in. / (mm) |
Time T3 (s) |
JOINING FORCE P3 |
Cooling under force Time T5 (m) |
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IFP*Ap + DRAG Time T4: T3 & T4 is the max time allow Open/Close |
11 min (660 s) x 1″ (25.4 mm) Wall Thickness (T) For ambient temperatures 100°F and higher, additional cooling time may be needed. |
FUSION STANDARD DVS 2207-1 (EUROPEAN)
TEMPERATURE: (200 – 220 °C) (392 – 428 °F)
IFP: 0.15 N/mm² = 21.76 PSI = 0.15 MPa = 15 Bar
DRAG: 0.01 N/mm²
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HEAT UP |
BEAD UP (MINIMUM BEAD SIZE) |
HEAT SOAK |
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HEAT UP – FORCE |
Wall Thickness (mm) |
Min. Bead Size (mm) |
HEAT SOAK FORCE |
HEAT SOAK TIME – Time T2 (s) 10 times the Wall Thickness pipe in seconds |
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Under Force: 0.15 N/mm²
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Under Force: ≤ 0.01 N/mm² |
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CHANGEOVER (Heater Removal) |
JOINING THE PIPE (FUSE / COOL) |
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Wall Thickness (mm) |
Per Wall thickness (Max. time) Time T3 (s) |
JOINING FORCE |
Joining pressure build-up Time T4 (s) |
Cooling Time Under Joining force Time T5 (m) |
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Under Force: 0.15 ± 0.01 N/mm²
The areas to be weld should meet with a speed of nearly zero.
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Cold weather procedures
- When the ambient temperature becomes colder, it will require a longer heating time to develop an indication of melt and the final bead size. The pipe wall thickness and pipe diameter are primary factors to consider when determining the necessary heating cycle time.
- The heating plate temperature range shall not be exceeded to accommodate cold weather conditions. That could drastically damage the heating iron, ruin the pipe and it also can cause an undesired accident.
- Do not apply additional force during the heat soak to accommodate cold weather conditions
- Cold Ambient Temperatures below -4°F (-20°C) is generally not recommended without special provisions such as a portable shelter or trailer or other suitable protective measures with auxiliary heating.
- Wind— Exposure of the fusion heater plate and pipe to wind can result in unacceptable temperature variations during butt fusions and possible joint contamination. When extreme wind conditions exist, the provision of a suitable shelter is required to protect the pipe and fusion heater plate to ensure a more consistent environment is provided.
- The fusion operator shall be aware of ambient weather conditions to make adjustments to the fusion procedure, these modifications require validation through the production of test fusions and their assessment by comparison to visual guidelines and bend testing.
Quality welding recommendations
Butt Fusion of different wall thicknesses:
The butt fusion procedure is based on joining piping components (pipes and fittings) having the same outside diameter and the same wall thickness (the same SDR) per ASTM or other industry product specifications. Try to butt fusion pipes and fittings that have the same outside diameter but different wall thickness is not recommended.
The quality of butt fusion joints made between pipes of unlike wall thickness is highly dependent on the performance properties of the thermoplastic material used for the pipes or fittings being joined. Consult the pipe or fitting manufacturer for applicable butt fusion procedures for components with dissimilar wall thicknesses.
The correct fusion pressure:
Follow the fusion pressure parameters. If the ends of the pipes (fittings) are brought together with excessive force, molten material may be pushed out of the joint and cold material brought into contact forming a “cold” joint. If too little force is used, voids and weak bonded areas can develop in the joint as molten material cools and contracts.
Preventative Maintenance
The Hayes manual COMBAT series butt fusion machines will give many years of service if operation procedures and maintenance are followed carefully and correctly.
PROPERLY HANDLE ELECTRICAL CORDS
- Yanking or pulling on the cord instead of gently unplugging it can strain the cord’s connections, leading to frayed wires, loose connections, or even short circuits. This can result in costly repairs or the need to replace damaged equipment.
- Following safe handling techniques ensures personal safety and device longevity.
- Regularly inspect and maintain electrical cords to prevent accidents. Avoid overloading outlets, protect cords from damage, and keep them away from moisture, children, and pets.
- Hold the plug firmly, making sure to grip it by the insulated portion. Avoid pulling on the cord itself, as this can strain the connections and potentially damage the cord and the plug.
STORE
- Keep the machine and all its components clean and well maintained to ensure the best performance.
- Store machine inside, in a dry cover area, out of the element of the weather.
CLEAN AND DRY
- Clean the pipe alignment with a soap and water, wash as needed and keep it dry. Never pressure wash.
- Protect the heater, trimmer and the electric power unit from water and other chemicals agents.
- Keep the heater clean to avoid build-up plastic pipe residue, when cleaning the tool don’t use an abrasive pad or steel wool. Use a non-synthetic cloth that won’t damage or scratch surfaces.
- Keep the trimmer and its blades clean and lubricated for optimum performance.
- Make sure all the cables and connections are clean.
- Never allow dirt, water, or other foreign matter to enter the electric power unit.
REMOVE DIRT AND LUBRICATE
- Alignment: Remove oily dirt buildup from guide rods and use WD-40 to lubricate it and wipe it. Do not leave the cleaning agent on the guide rods. Lubricate guide rod bushings with SAE 10W-40 motor oil through the oil holes on the movable jaw.
- Occasionally add a drop of oil to pivot pins and shafts.
- Wash and clean bearings and threads in kerosene or solvent and keep them lubricated.
KEEP EVERYTHING NICE AND TIGHT
- Ensure all screws, nuts, bolts, and snap rings are secure and tight.
ADJUSTING TEMPERATURE
Allow heater to stabilize at the new temperature (5 to 10 minutes) after adjusting.