4.2.12 Student Book © 2004 Propane Education & Research CouncilPage 1 4.2.12 Installing Buried Distribution Lines Using Polyethylene Tubing and Mechanical

4.2.12 Student Book © 2004 Propane Education & Research Council Page 1

4.2.12

Installing Buried Distribution Lines Using Polyethylene Tubing and

Mechanical Fittings Persons who install polyethylene (PE) tubing and mechanical fittings must be aware of the code requirements and material standards that apply to the operation. Installing personnel must be qualified to perform this task, and aware that more rigorous qualification requirements apply to installers who install or repair PE distribution lines in jurisdictional pipeline systems.


4.2.12

Installing Buried Distribution Lines Using Polyethylene Tubing and

Mechanical Fittings

In this module you will learn to identify:(1) Characteristics and standards that apply to polyethylene pipe,

tubing, and associated fittings (2) Qualifications/functions required of installing personnel (3) Appropriate responses to abnormal operating conditions (4) Mechanical fittings for joining PE pipe (5) Techniques for connecting PE tubing to field assembled

service head adapters and anodeless risers


Characteristics & Standards that Apply to PE Tubing,& Associated Fittings

Polyethylene (PE) pipe and tubing is the only type of plastic listed for use for [buried distribution] gas piping in NFPA 58, LP-Gas Code. Polyethylene is what is known as a thermoplastic and may be joined either by heat fusion (welding) or by mechanical fittings.

Polyamide (PA) tubing is approved for use in emergency shutdown systems for bulk plant and cargo tank tanks in the 2004 edition of NFPA 58.

4.2.12 Student Book © 2004 Propane Education & Research Council Pages 1 & 3


All fittings used to join PE pipe or tubing shall be tested & recommended by the manufacturer for use with PE pipe and shall be installed according to the manufacturer’s written procedure.

PE pipe cannot be joined by a threaded or miter joint.

PE tubing can be joined by qualified installers using manufacturer prescribed procedures using:• Heat fusion methods including

1. Butt fusion welding 2. Socket fusion welding 3. Electrofusion welding

• Mechanical fittings recommended for use with PE by the manufacturer



Figure 1. Sample Manufacturer’s Production Code Markings

The required markings must appear at least every two feet of pipe or tubing length.


PE Installation Personnel Qualifications

1.5 Qualification of Personnel. Persons… whose primary duties fall within the scope of this code shall be trained in proper handling procedures. Refresher training shall be provided at least every three years. The training shall be documented.

NFPA 58

2001

NFPA 58

20044.4

PE tubing and pipe installed in jurisdictional pipeline systems must be installed by persons qualified to install PE materials, valves and fittings as required by 49 CFR Part 192.

In some cases, such as repair of existing PE piping, personnel qualifications must be documented in compliance with the pipeline operator’s written Operator Qualification Plan. Persons working on jurisdictional pipelines, and pipeline operating companies must comply with requirements of 49 CFR 192.285 and 287 that apply where NFPA 58 is silent or any that exceed the requirements of NFPA 58.


PE Installation Personnel Required Functions

Inspecting PE Pipe— When shipments of pipe are delivered they should be inspected to ensure a quality product is received.

PE pipe must be carefully inspected for cuts, gouges, deep scratches, and other defects before use.

The segment of pipe containing defects shall be cut out. The only exception is that pipe with scratches and gouges with a depth less than 10% of the wall thickness can be used.

Storing PE Pipe— PE pipe and tubing should be stored to minimize the material being damaged by crushing, piercing, or extended exposure to direct sunlight.



Figure 2. Cutting Polyethylene Pipe

Handling PE Pipe

4.2.12 Student Book © 2004 Propane Education & Research Council Pages 5 - 7


Trenching and Backfilling—

1. PE pipe or tubing shall be laid and continuously supported on undisturbed or well‑compacted soil. Do not use blocks or allow pipe to rest on rocks or large clods of dirt, because this will set up shearing stresses in the pipe, or may cut or puncture it during backfilling.

2. In rock excavation, pad the ditch line with at least six (6) inches of clean fill material such as sand.

3. Allow for contraction by "snaking" the pipe from one side of the ditch to the other.

4. Prior to beginning backfilling, the entire trench is to be examined to make sure the PE pipe is continuously supported at all points on undisturbed or well‑compacted soil.



Figure 3. Critical Stress Area

Trenching and Backfilling— The area of the service line extending out from the point where it is connected to the main is a critical stress area. The backfill in this area should be compacted around and under tie‑ins. Also, a protective bridging sleeve should support the service line in this critical area.



Figure 4. Trench Construction and Terminology

Placing Pipe in Trenches— PE piping may be joined in the trench or above grade, although most joining is done above grade prior to lowering pipe into the trench. When heat fusion is used, sufficient time must be allowed for the joint to set‑up before moving the pipe.

Allow [heat] fusion joints to cool at least 10 minutes before stressing pipe either by lowering into ditch or pressure testing.



Figure 5. Installing Tracer Wire

Installing Tracer Wire— A metallic wire called a "tracer wire" or electrically conductive warning tape is placed in the trench with the pipe during the backfilling operation. It is inserted after the pipe is installed and half-way through the backfilling process. The tracer wire is used as a conductor of the electrical signal when an underground pipe locator is used to locate the polyethylene pipe.

Tracer wire should be placed in the trench above and separated from the PE pipe by approximately 6 inches of soil before the trench is completely back filled with soil.


Appropriate Responses to Abnormal OperatingConditions

Damaged Pipes and/or Fittings— Each imperfection or damaged pipe or fitting that would impair the serviceability of PE pipe must be repaired by a patching saddle, or removed and/or replaced.

Leaking Pipe and/or Fittings— When a leak is found it should be promptly scheduled for repair according to company procedures.

Exposed Piping— PE piping that has been exposed or deformed must be appropriately supported and covered.


Identifying Mechanical Fittings for Joining PE Pipe

Figure 6. MechanicalTapping Saddle

Many types of mechanical connection styles and methods are available. Each has particular advantages or limitations of performance in certain applications. As illustrated in Figure 6, a mechanical tapping saddle for connecting the main to the service line is one type of connection used when fusion is not used.



Figure 7. Style 90 PE Lok Courtesy Dresser Industries

Mechanical Compression Fittings It is important that the inside of the pipe wall be supported by the stiffener under the seal ring and under the gripping ring (if incorporated in the design), to prevent collapse of the plastic.



Figure 8. Various Styles of Stab Fittings Courtesy Perfection Corporation

Stab-Type Mechanical Fittings


Connecting PE Tubing to Field Assembled Service Head Adapters and Anodeless Risers.

Figure 9. PE Tubing and Risers in a Typical Propane Installation

2 n d -Sta g e o r2 -PSI Se rv ic eRe g u la to r

Fie ld -A sse m b le dSe rvic e H e a d A d a p te r

A n o d e le ss Rise r

1 st-Sta g eRe g u la to r

PE Tu b in gTra c e r W ire

Buried PE tubing is terminated in typical residential and small commercial distribution systems with an anodeless riser at the service entrance to the building and a field-assembled service head adapter at the propane tank.

4.2.12 Student Book © 2004 Propane Education & Research Council Pages 12 - 15

Time to See If You Got the Key Points of This Module…

• Complete the Review on pages 12 & 13.

• See if you are ready for the Certification Exam by checking off the performance criteria on pages 14 & 15.

Documents

4.2.12 Student Book © 2004 Propane Education & Research CouncilPage 1 4.2.12 Installing Buried Distribution Lines Using Polyethylene Tubing and Mechanical