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Joint Fabrication Procedures for 3" - 8" Swaged Piping with Polyvinylidene fluoride (PVDF) Liners

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1. To arrive at the required finished length "X", select the proper cut-off length "D" from the cutting dimensions table for your liner material.

NOTE: Although PP is shown, the process in steps 1-6 is identical for PVDF.

2. Cut pipe to proper cut-off length "D" using a sharp angled tip cutter to assure an accurate cut. DO NOT USE hacksaw or wheel-type cutters. A hacksaw tends to "lead", which produces non-right-angle cuts. A wheel-type cutter produces a slightly beveled cut that leaves burrs and can cause severe stress risers in the plastic liner.

3. Determine the cut-back dimension "E" from the cutting dimensions table. Using the same angled cutter, cut through the metal just to the surface of the plastic liner at this distance "E" from the end of the steel shell. Once the tool begins to "break through" the steel, extra care should be taken in feeding the tool further to avoid cutting the plastic liner. A clear indication that the cutting tool is near the plastic is the appearance of "pick-marks" in the steel.

4. Remove the cut steel ring from the end of the pipe by inserting the proper size guide plug into the pipe and pulling with a modified gear puller.
NOTE: A guide plug has two diameters. Choose the end that fits snugly in the pipe bore.

5. Cut a standard tapered pipe thread on the end of the pipe with any conventional threader to accommodate a chamfered threaded flange. Use standard thread length and adjust thread depth to allow flange to be turned on hand tight until the last 1½ turns.

6. Place flange on pipe with chamfer facing outward. Tighten flange with wrench until turn-up dimension "F" between end of plastic stub and face of flange matches requirement shown in the cutting dimensions table. Also be sure that bolt holes on flanges at either end of pipe spool are aligned. Flanges must be tightened with a flange wrench and must be beyond hand tight.
Rotatable Flange Option. Place flange and stub assembly on pipe with chamfer facing outward. Tighten to turn-up dimension "F" measured from end of plastic face of stub assembly.
NOTE: Stub assembly must be beyond hand tight like the chamfered flange.

7. Clamp prepared pipe in horizontal or vertical position. File away any notches on end of exposed plastic stub. Using a clean rag and a non-flammable degreaser that is compatible with the liner, wipe away cutting oil, shavings and dirt from stub.




8. Set up forming tool to proper size and "dry run" into flange bolt holes, checking alignment and centering. Check the guide pins fit freely in the bolt holes with the clamping dogs behind the flange. If adjustment is needed, loosen the adjusting nuts, center the tool and retighten the nuts. Remove tool, attach hydraulic hose and set aside.

9. Lightly grease the proper size of aluminum flaring die and preformer with a high temperature grease.
Preheat die to temperature between 280°F (138°C) (min.) and 300°F (149°C) (max.) with hot plate, oven or torch. Use 300°F (149°C) temperature-sensing crayon or a pyrometer to monitor while proceeding to next step.
NOTE: DO NOT HEAT PREFORMER "CONE" DIE. It is used at room temperature.

10. Attach proper size of heat cup to hot air gun, set heater dials and allow gun to preheat for 15-20 minutes.
Heat Dial Settings
3" 6-7 3-4
4" 7 4
6" 7 5-6
8" 7 6

11. Place the proper locking collar over the plastic stub and place tight against the flange face, with curved crimped edge inward, fitting into flange chamfer.
NOTE: For forming faces of PVDF, be sure to use only stainless steel locking collars with large holes. DO NOT USE nickel-plated collar with small perforated holes, which is designed for use with PTFE-lined pipe.

CAUTION: When field forming, use adequate ventilation (indoors, use exhaust fans). Avoid breathing of vapors resulting from overheating and possible degradation of the plastic. Do not consume food or beverages and do not smoke during fabrication process. Please refer to the Material Safety Data Sheet before heating the material. Also, to prevent electrical shock, do not use heat gun near water.

12. Place heat gun and heat cup to flange and heat plastic stub for 2-4 minutes to temperature between 240°F (116°C) and 250°F (121°C). Use 250°F (121°C) crayon to make sure you do not exceed maximum temperature of 250°F (121°C). Frequently rotate gun for uniform heating and monitor the plastic temperature with 250°F (121°C) crayon.

13. Attach the preheated forming die to the hydraulic cylinder on the forming tool. (CAUTION: Remember die is HOT.) With die centered in plastic stub, insert tool reaction arms through flange holes and insert locking pins in arms.
CAUTION: Make sure the pins do not bear on the raised lettering of the flange. Apply sufficient hydraulic pressure to eliminate the air gap between the heated die and the formed face. Note this pressure and maintain it for at least 2 minutes. Maintaining the pressure will require repeated pumping as the plastic slowly flows.

14. Attach bolts through free flange holes and secure flaring die to flange. Retract the hydraulic cylinder, remove locking pins and forming tool. Cool the plastic to room temperature using cool air or water. Remove die from flange.
NOTE: To assure properly flared face, it is extremely important to cool plastic and flange to room temperature. Also, be sure you achieve the minimum flare diameter listed here.

15. Visually inspect the finished flare for a flat, smooth surface and a smooth bend radius. Also, be sure the locking collar is firmly embedded in liner.

16. Spark test the finished face for defects the may not be readily visible. Adjust the sparker to arc about 1" to the flange. Insert probe into the pipe end and circle the inside near the liner. A defect is identified by apparent major arcing through the liner. DO NOT USE pipe with a defective liner.



17. To identify PVDF liner, always be sure to attach black color-coded plastic band to pipe spool.

18. A ½" thick plywood cover should be bolted to the flange to protect the plastic face and to prevent the face from "remembering" its preformed shape and pulling away from flange.

19. Attach proper label to the plywood cover.

Standard Thread Length (in.)
Pipe Size Thread Length
1 13/16
1 1/2 1
2 1 1/16
3 1 7/16
4 1 1/2
6 1 11/16
8 1 7/8

Cutting Dimensions for PVDF with locking collar Temp.
1 X + 1 3/16 15/16 3/4 X + 5/8 300°F 230°F
1 1/2 X + 1 11/16 1 3/16 1 X + 7/8 300°F 230°F
2 X + 1 3/4 1 1/4 1 1/16 X + 7/8 300°F 250°F
3 X + 2 1/8 1 7/16 1 1/4 X + 1 1/16 300°F 250°F
4 X + 2 1/4 1 1/2 1 5/16 X + 1 1/8 300°F 250°F
6 X + 2 3/8 1 5/8 1 7/16 X + 1 3/16 300°F 250°F
8 X + 2 5/8 1 3/4 1 9/16 X + 1 5/16 300°F 250°F
† PVDF locking collars are stainless steel with large holes.

"This page is a machine translation of the source page, which is written in
English. This translation is intended to provide a general idea of the
page's content, and is not guaranteed for accuracy."