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PE 3408 EHMW PipeButt Fusion Procedures

BULLETIN NO.108


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This manual is a training guide for the butt (heat)fusion technique for joining PLEXCO PE 3408 ExtraHigh Molecular Weight (EHMW) High DensityPolyethylene Pipe. Butt fusion is the preferred methodfor joining high density polyethylene pipe. It has beenan accepted procedure in the gas and municipalservice industries for over 30 years.The PLEXCO P34CH resin used in making PLEXCOPE 3408 Pipe has been specially engineered toprovide a quality piping material that can be easilyfused to form tough, strong joints. The averagemolecular weight is in the extra high molecular weightrange (250,000 -1,500,000) and is comparable to thatof any other polyethylene piping material on themarket. The broad molecular weight distribution of thisresin makes it possible to easily produce quality buttfusion joints with greater control than is possible withpipe made from resins having the same molecularweight but a narrow weight distribution. This meansthat in PLEXCO EHMW High Density Polyethylene PE3408 Piping, you have the pressure rating andabrasion resistance of a high density, extra highmolecular weight material plus easy assembly by buttfusion joining.Described here are the recommended procedures forusing heat fusion to form strong and durable jointswith PLEXCO PE 3408 Pipe. Experience has shownthat a joint made by a properly trained person, using aproven fusion procedure, which passes a visualinspection based on proper bead formation, will havestrength characteristics comparable to the pipe itself.Heat fused pipe sections become, in effect, a singlepiece of pipe.NOTE: Butt fusion procedures recommended by Plexcohave been qualified in accordance with Title 49, Codeof Federal Regulations, Part 192.283. Under the Title 49regulations, gas pipeline operators are required to havequalified joining procedures, and per Part 192.285, toensure that persons making joints in their gas pipingsystem are qualified to make joints using the gaspipeline operator's qualified joining procedure.

This bulletin is intended to be used as a guide for butt fusion techniques. It is not intended to be used asinstallation instructions, and should not be substituted in place of the advice of a professional designengineer .


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3. At the end of every heating cycle, quickly observethe parts to be joined to insure sufficient and uniformmelting patterns.Join parts within 3 seconds.If a non-uniform pattern is obtained, allow the pipe tocool, cut off the pipe ends, and repeat the procedure.4. Check heater surface temperature at least once aday with a device such as surface pyrometer orcrayon indicators for 440 :t 10F or 500 :t 10F fusionsurface temperature. The heater thermometer willprobably read a higher temperature than the fusionsurfaces. Check the thermometer frequently forconsistent readings.5. NEVER lay a hot heating unit on the soil or grasswhen the heat cycle is completed.Return it to the holder, if possible, or at least lay it ona board.Soil can contaminate the joint and damage thecoating; grass may burn and char the heater surface.Temperature for Butt FusionPLEXCO Technical Services personnel haveconducted extensive testing to qualify the butt fusionprocedure under laboratory conditions at a number ofdifferent temperatures over the range of 350 to525F. This work has shown that there are a numberof "time-temperature-pressure" conditions that can beused to make acceptable joints.The laboratory proven procedures have beenmodified based on field experience to provide twoheater iron surface temperatures that arerecommended for butt fusion of PLEXCOPolyethylene Pipe and Fittings: 440F and 500F.The choice of temperature should be based on theoperating procedures and operating conditions ofthe individual installer.The principal difference in the procedures used for440F and 500F is the heating time necessarybefore making a joint. The lower temperature requiresa slightly longer heating time. This extra time doesallow some advantages in control and reproducibilityof bead size.

PLEXCO PE 3408 EHMW High Density PolyethylenePipe is joined by a simple heat fusion process. Thebasic steps in this process are:1. Be sure that the surfaces of the fusion tools, pipeand fittings are free of contaminants.2. Heat the surfaces to be joined -both the pipe andfittings -simultaneously at a prescribed temperaturefor a specified time.3. Remove the heater -bring melted surfacestogether.4. Hold until solidified.A correctly made fusion produces a joint that is asstrong as the pipe itself and has a record of provenperformance.Before you begin fusing, here are some points toremember:1. All heater surfaces have a thin layer of non-stickcoating that is easily scratched or scraped off. Thiscoating prevents melted polyethylene from adheringfirmly to the heater surfaces, but occasionally it alsomust be cleaned.Metal tools should NEVER be used to clean theheater surfaces because they scratch and remove thecoating.Wooden implements and clean, dry, lint-free rags arerecommended for cleaning. All-cotton rags arerecommended because rags containing a substantialamount of synthetic fibers may melt and char againstthe heater surface.If the non-stick coating becomes worn or scratched,the heating unit should be recoated.Melted polyethylene adheres firmly to the heatingiron and is more difficult to remove at places wherethe coating has been scraped off. In addition, sincethe coating acts as an insulator, heat transfer inthese uncoated areas is greater, and localoverheating can occur.2. Just before using, wipe heaters to remove dirt andforeign material. As soon as possible after use, cleanheaters with wooded implements and clean rags toremove melted or charred plastic.

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Butt Fusion ProcedureButt fusion of PLEXCO PE 3408 EHMW HighDensity Polyethylene Pipe and Fittings is easilyperformed utilizing the equipment available today.For pipe sizes 4" IPS and larger, hydraulicfusion machines are normally used, and thefollowing procedures are presented for suchmachines. Pipe sizes of 4" IPS and smaller are fusedusing manually operated equipment. Theprocedures and principles for manual fusionequipment are essentially the same as thosewhich follow.

Butt fusion machines are available from severalmanufacturers. Various machines will have slightlydifferent procedures for use, care, set-up, andoperation. Consult the equipment manufacturer'smanuals for correct instructions on the use, care, set-up, and operation of the butt fusion machine.Hydraulic fusion machines typically have controls forsetting pressures used for facing, heating, and fusing.It may be necessary to add pressure to overcomemachine internal drag pressure or external forcesacting on the pipe..Facing should be conducted at a pressure thatproduces properly faced pipe ends..Heating pressure should be set so that the pipeends maintain contact against the heater, but arenot forced against the heater (zero contact

pressure)..Fusing pressure may be determined using theinterface pressures presented below.Fusion Interface Pressure Guidelines

Interface Pressureeater SurfaceTemperature

440F :f: 10F 60:t 15 psi500F :t 10F 80:t 15 psi

Industry studies indicate that polyethylene ofdifferent trade names andlor different polyethylenes,such as 2306, 2406, 3406, and 3408 materials,can be successfully joined by heat fusion.Melt times prescribed at 500F by each manufacturerfor his product should be used. Apply the heatingtool first to the material requiring the longestmelt time. Then apply the product requiring thelesser melt time to the heater so the melt cycle forboth products will be completed at the same time.All other fusion conditions and procedures remainthe same as when joining PLEXCO products.The Plastics Pipe Institute has issued a document,PPI Technical Note TN-13, on "General Guidelinesfor the Heat Fusion of Unlike Polyethylene Pipesand Fittings." PLEXCO recommends that theseguidelines be utilized when joining differentpolyethylenes. However, the mixing of differentpolyethylenes should not be done indiscriminately -optimum conditions will be achieved when joiningpipe and fittings from the same manufacturer's system.Upon request, PLEXCO will provide additionalinformation and technical assistance in properfusion procedures for joining the PLEXCO systemwith polyethylene systems of other manufacturersand material designations.

Install appropriate inserts in the pipe clamps asnecessary. IPS sizes are for IPS (steel) pipediameters; DIPS sizes are for ductile iron pipe sizes.Heater surfaces must be clean and free ofcontaminants such as dirt, oil, grease, and melted orcharred plastic. To clean the heater, use only woodenimplements and clean, dry, lint-free non-syntheticcloths. Take care not to damage coated surfaces.With a surface pyrometer, check the heater foruniform surface temperature. Adjust the heater asnecessary for 400F :t 10F or 500 :t 10F surfacetemperature. (Heater thermometers indicate internal,not surface temperature.)

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2. Place the facer between the pipe ends. Face thepipe ends until continuous ribbons are produced onboth side or the facer. Turn off the facer, move thepipe ends apart, and remove the facer. Clean outribbons and shavings from around and inside thepipes. Do not touch the newly faced surfaces with thehands, as perspiration and body oils couldcontaminate the surfaces.IMPORTANT: The pipe ends are properly faced whencontinuous ribbons are produced on both sides of thefacer unit. If the facing stops are reached beforecontinuous ribbons are produced, re-install the pipeends in the machine (Step 1 , and continue facinguntil continuous ribbons are produced on both pipeends. Facing down to the stops is preferred.

3. Bring the two pipe sections together and, with thefingers, feel for any high-Iow difference at the junctionof the two ends. If necessary, tighten the appropriateinside clamp until the two sections are aligned asclosely as possible. Tighten the high side, neverloosen the low side.IMPORTANT: After facing the pipe ends, ifanyadjustment at all is made on one or both insideclamps, then the facing unit should be re-installedand the pipe ends given several turns with the cutteruntil the motor speeds up, before continuing withheating and fusing.

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With a clean dry cloth wipe both inside and outsidesurfaces of the two ends to be joined to remove dirtand foreign material. It is important that the endsprotruding past the jaws be absolutely clean and freeof contaminants.1. Install pipe in machine. Ends should extendapproximately an inch past alignment clamps forfacing. Check alignment and adjust as necessary.


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4. Separate the two pipe sections. Slide heater to aposition where it will come between pipe ends. Usecaution in this operation to avoid coming in contactwith pipe. Bring the movable pipe section against theheater until both pipe ends are in firm contact withthe heater.IMPORTANT: As soon as the pipe ends are firmlyagainst heater; immediately move control valves to aneutral position to remove pressure of pipe againstheater.If pressure of the pipe against the heater ismaintained during the heating period, melt will besqueezed away from pipe ends, causing a concaveeffect in the heated pipe ends. This could result in aweakened joint after fusing.

5. Heat the pipe ends until properly sized melt beadsare formed on both pipe ends. As the pipe ends aremelted against the heater during the heating period,the molten plastic will swell and form melt beadsaround the pipe ends. The melt beads should be thesame size on both pipe ends, and uniformly sized allthe way around.Approximate Melt Swell Bead Size

Depending upon wall thickness, melt swell bead sizemay vary.6. After melting has been completed as above,separate the pipe ends just enough to remove theheater. Quickly observe the parts to be joined toensure sufficient and uniform melting patterns. Thenquickly bring the pipe ends together with the pressurerecommended by PLEXCO. Join parts within 3seconds. If melted plastic sticks to the heater, don'tjoin the two ends -discontinue making the joint, letcool, and start over again from Step No.1.IMPORTANT: Do not use pressures above the rangeindicated. Excessive pressures will squeeze too muchmelt out of the fusion area and result in a weakenedjoint.The force applied will cause each bead to roll backonto the pipe as shown. Insufficient rollback is oneindication of a faulty joint.


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7. While maintaining the pressure used in makingjoints, allow the joint to cool for 30 to 90 seconds perinch of pipe diameter before removing from machine.Heavier walled pipes (lower SDR) will require morecooling time. If upon examination the joint appearsfaulty, cut open and start again with Step No.1.

8. Remove fused pipe sections from fusion machine.Allow joint to cool at least 20 minutes after removalbefore subjecting it to testing, bending or backfillingstresses. Reposition fusion machine so that end ofthe newly fused section lies in the stationary clampswhile a new pipe section is placed in the movableclamps. Repeat fusjon procedure beginning withStep No.1.

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