Gas Distribution

Total Performance, Total Solutions

A reliable gas distribution system requires strength, integrity and uncompromising reliability. Not only from your pipe, but also from your pipe supplier.

These qualities make PolyPipe^® the smart choice for gas distribution applications. As one of the largest manufacturers of medium and high - density polyethylene pipe, we understand the critical need for consistent, dependable products. Our MDPE and HDPE pipe are manufactured to the highest quality standards in the industry.

Our staff engineers and technical experts help assure you receive maximum performance and value - from evaluation and design, through job-site assistance and testing. In addition, our network of manufacturing facilities and distribution centers provide timely delivery. The result is a total system solution for your gas distribution project.

A Proven Piping System

Our medium density yellow GDY20, PE2406/2708 and our high density black, GDB30, GDB40 and GDB50 gas distribution products (with or without yellow stripes) are specially designed and produced for natural gas distribution system applications. This pipe offers outstanding environmental stress crack resistance, as well as high chemical and impact resistance.

PolyPipe^® is lightweight and flexible for easy installation and heat fusible for fully restrained joints. It is manufactured to exceed all industry requirements including ASTM D2513 and Department of Transportation (DOT) CFR Title 49 Part 192.

Municipalities and contractors increasingly choose polyethylene pipe for gas systems use, due to its corrosion resistance, weatherability, strength and ease of handling. Polyethylene pipe provides long-term resistance to a variety of service conditions, including abrasion, temperature shifts, bending, internal pressure, direct burial, point loading and squeeze-off. Multiple tests confirm its consistent performance under these conditions.

PolyPipe^® gas products are available in diameters from 1/2" to 1-1/4" CTS, 1/2" to 6" IPS coiled, and straight lengths from 1/2" through 24" IPS.

Design Pressure Rating

The pressure rating of PolyPipe^® is determined in accordance with the Plastics Pipe Institute (PPI) recommended hydrostatic design basis (HDB) for the material, the physical dimensions of the pipe, and the appropriate design and service factors.

Pressure design calculations are based on the following formula, which relates the stress on the pipe wall to the internal pressure.

Refer to the PolyPipe^® Design and Engineering Guide for Polyethylene Piping for additional information.

Thermal Expansion/Contraction

Polyethylene, like other plastics, has a thermal expansion coefficient higher than metals. The coefficient of thermal expansion is 1.0 x 10^-4 in/in/°F. A general rule is one-inch change in length per 100 feet of unrestrained pipe per 10°F change in temperature. This coefficient of expansion is for PE in an unrestrained mode.

When properly restrained at the end connections, PE is not prone to failure due to temperature changes for the following reasons:

• Since PE has a lower modulus of elasticity, the internal stress buildup is considerably less than the long-term strength of the material.
• The passive resistance of the soil prevents some movement when the pipe is direct buried.
• Plastics are viscoelastic; they are capable of relaxing or adjusting with time to stresses imposed by constant strain. However, this relaxation over time may not relieve all of the stresses imposed.

The crucial period for failure due to temperature effects is during installation, when temperature changes may be quite rapid and before heat fusion joints have attained a high percentage of their ultimate strength. Installation of plastic pipe under tension must be avoided to minimize the effects of contraction from thermal changes. Polyethylene should be allowed to cool to ambient temperature prior to final connection.

Bending Radius

An inherent advantage of PolyPipe^® is its flexibility and resiliency. The minimum bending radius is based upon the Dimension Ratio (DR) of the pipe. This radius is determined by multiplying the outside diameter of the pipe by the radius factor for the corresponding DR.

When pipe is used in pressure applications, the longitudinal stress created by the sum of the bending radius, internal pressure and other stress loads on the pipe should not exceed the material's design stress rating. Severe but acceptable bends in polyethylene pipelines should be buried or properly restrained.

Refer to the PolyPipe^® Design and Engineering Guide for Polyethylene Piping for additional information.

Outdoor Storage

The maximum unprotected above ground storage time for PolyPipe^® gas products is dependent upon the type of polyethylene pipe.

For PolyPipe^® GDY20 medium density yellow gas pipe, the recommended above ground storage should not exceed three years.

However, PolyPipe^® black gas products (GDB30, GDB40 and GDB50) are suitable for above ground storage up to 50 years. Refer to DOT CFR Title 49, Part 192, § 192.321 (g) (1) and (3) for additional information.

Joining

PolyPipe^® can be joined by a variety of methods. The preferred method is heat fusion. This encompasses butt fusion, saddle fusion, socket fusion and electrofusion. This type of connection offers a completely leak-proof, fully restrained joint. Polyethylene can also be joined by use of mechanical fittings.

The integrity and versatility of the joining techniques used for polyethylene pipe allow the designer to take advantage of the performance benefits of polyethylene in a wide variety of applications.

For more information, consult PolyPipe^® Recommended Heat Fusion Joining Procedures. Our procedures are in compliance with the joining requirements of DOT CFR Title 49 Part 192 § 192.283 for thermoplastic gas piping systems.

In addition, the recommended procedures for butt and saddle fusions are consistent with PPI TR-33, "Generic Butt Fusion Joining Procedure for Polyethylene Gas Pipe ", and TR-41, "Generic Saddle Fusion Joining Procedure for Polyethylene Gas Pipe."

PolyPipe^® for LPG Service

The most common application for polyethylene gas pipe is distribution of natural gas. However, polyethylene pipe is also approved, per NFPA 58, "Liquefied Petroleum Gas Code ", for the transport of liquefied petroleum gases (LPG) provided the gas is in the vapor state.

The use of polyethylene pipe, manufactured in accordance with ASTM D2513, for the transport of vapor LPG is permitted and defined within DOT CFR Title 49 Part 192. DOT identifies ANSI/NFPA 58 as the installation standard for PE vapor LPG systems.

NFPA 58 imposes certain restrictions on the use of PE piping for vapor LPG distribution. They are as follows:

• The maximum operating pressure is limited to 30 psig.
• The size of PE is limited to 2 "NPS piping with a nominal OD of 2.375".

PPI TR-22, "Polyethylene Piping Distribution Systems for Components of Liquid Petroleum Gases", provides the following use recommendations for LPG service:

• PE gas piping and fittings should only be used in underground gas distribution systems where the operating pressure and temperature are such that condensation will not occur.
• The vapor LPG PE piping system shall be manufactured in accordance with ASTM D2513.
• The PE material shall have a hydrostatic design basis (HDB) category of at least 1,000 psi at 73°F as determined in accordance with ASTM D2837.

Refer to ANSI/NFPA 58 and PPI TR-22 for further information on the use of PE for LPG service.

Quality Assurance in Every Product

At PolyPipe^®, quality throughout the manufacturing process is an inherent value that assures the highest performance. Our manufacturing facilities start with only superior grade, polyethylene resins that have been specifically formulated for long-term integrity and performance in gas distribution systems.

Computer controlled extrusion techniques are utilized in the manufacture of our pipe to ensure quality. In addition, continuous wall monitoring during manufacture results in dimensional consistency.

PolyPipe^®, gas products are produced in compliance with ASTM D2513. In addition to continuous dimension monitoring during manufacture, quick burst tests are routinely conducted to confirm short and long-term performance.

Long-term hydrostatic testing is also performed according to ASTM D1598, ASTM D2837 and Plastics Pipe Institute (PPI) TR-3 to confirm that our products continually meet the established performance criteria.

PolyPipe^® is continually striving to meet the demands of the market today. Our qualification as an ISO 9001:2000 company has given us great confidence in our quality system to ensure quality products are manufactured on a consistent basis. It is the policy of PolyPipe^® to achieve total quality system performance by understanding and meeting its customer requirements without error, on time, every time.

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