Joining Polyethylene Pipe
Pipe Joining Guidelines
There are four common sizing systems used for polyethylene pipe. Each has a recommended joining method.
SIDR/IDR (Standard Inside Dimension Ratio) ASTM D 2239 - This pipe is sized based on inside diameter and should be joined with insert fittings and clamps or with special OD Fittings designed to meet ASTM D2239 specifications.
CTS (Copper Tube Size) ASTM D 2737 - This pipe is outside diameter controlled and is most commonly joined with stab fittings or O.D. (outside diameter) Compression fittings.
IPS - Iron Pipe Size - ASTM D3035 & F714 - This pipe is outside diameter controlled and the preferred method for permanent, leak free joints is Heat Fusion. It may also be joined with O.D. Mechanical fittings for ASTM D3035 & F714 specifications.
DIPS - Ductile Iron Pipe Size - ASTM F714 - This pipe is outside diameter controlled and the preferred method for permanent, leak free joints is Heat Fusion. It may also be joined with O.D. Mechanical fittings for ASTM F714 specifications.
Overview of Heat Fusion
Heat fusion is the preferred method for joining IPS or DIPS pipe to pipe or pipe to fittings. When done properly, heat fusion creates a monolithic piping system.
During Heat Fusion, the fusion surfaces are prepared by removing the outside layer of material. A heating tool is applied to the prepared fusion surfaces until the material begins to melt and a melt bead is visible. The heating tool is then removed and the molten surfaces are gently brought together. The molten material flows together and then cools forming permanent, leak free joint.
Key Points of Quality Fusions
Fusion Equipment and tools must be properly sized and in good working order.
Insure the fusion tool surface is clean, undamaged and operating at the proper fusion temperature.
The fusion operator should be certified in the use and operation of fusion equipment and procedures.
Proper care must be taken to clean and prepare the surfaces of both pipe and fittings. Cleanliness is key in conducting a successful fusion.
Fusion procedures provided are intended for use as guidelines. Acceptable fusion joints depend on visual verification, fusion experience and quality heating tools.
Ambient conditions such as wind, rain and temperature are a factor when fusing pipe.
Check the power supply to your fusion iron to verify proper voltage and amperage.
Always conduct test fusions before you begin installations. Random test fusion are also recommended if your fusing pipe for an extended period of time to insure continued validity of the joints.
Federal Regulations for Joining Gas Pipe
D.O.T. Regulations require that each joint in a gas piping system be made in accordance with written procedures that have been proved by test or experience to produce strong, leak free joints (see CRF 49, PART 192, 192.273)
D.O.T. Regulations require that written procedures for Butt fusion joining of polyethylene gas pipe must be qualified before use by subjecting speciment joints to required test procedures. (see CFR 49, PART 192, 192.285)
D.O.T. Regulations require that all persons who make joints in polyethylene gas piping must be qualified under the operator's written procedures (CFR 49, PART 192, 192.285)
D.O.T. Regulations require that the gas system operator must ensure that all persons who make or inspect joints are qualified (CFR 49, PART 192, 192.285, 192.287)
Charter Plastics fusion certifications do not qualify the individual to contduct gas pipeline fusions.
Liquid Hydrocarbon Permeation
Liquid Hydrocarbon Permeation may occur in polyethylene pipe. It can be a factor if the pipe is exposed to:
- Ground that is permeated with Liquid Hydrocarbons
- Fluid inside the pipe that has a 2% or greater liquid hydrocarbon concentration
- Liquid hydrocarbon condensates that may form in gas pipelines.
Liquid Hydrocarbon exposure may cause swelling of the pipe. Once polyethylene pipe has been permeated with liquid hydrocarbons, joining by heat fusion is not recommended. The hydrocarbons will leach out during heating and contaminate the joint. Hydrocarbon contamination is indicated by a bubbly, potmarked or sandpaper like surface. It may also be indicated by discoloration or by a fuel odor. When this observed, you should join the pipe with O.D. Mechanical type fittings. Fusion should not be used.
Charter Plastics has recommended fusion procedures.
Charter also endorses and has tested to the Generic Butt Fusion Procedures established by PPI in TR33.
Charter Gas pipe has been qualified under both procedures and complies with the Code of Federal Regulations 49, part 192.283.
All persons conducting Heat fusion should certified by the pipe manufacturer, the fusion equipment manufacturer or a certified fusion trainer. When fusing Charter Pipe, they should follow the Fusion Guidelines published by Charter or the Generic Fusion Procedures Published by PPI in TR33.