Plastic Pipe Standards
Introduction to Plastic Pipe Standards
Plastics like polyvinyl chloride, polyethylene and styrene rubber are used to make pipes. Plastic pipes do not rust or corrode upon exposure to most household chemicals. However, they do not withstand high pressures or temperatures like metal pipes.
Plastics can be made tougher and stiffer when additives are mixed with the plastic prior to extrusion. For example, chlorinated PVC can withstand higher temperatures than conventional PVC due to post-chlorination of the PVC.
ASTM standards are assigned based on both the use of the material and material type. For example, ASTM F800 is the standard for corrugated PVC tubing while ASTM F405 is the standard for corrugated polyethylene corrugated tubing.
Plastic tubing standards differ from those used for stiff pipe. ASTM D2666 is the standard for polybutadiene tubing while standards like ASTM F809 apply to large polybutadiene pipe and ASTM D2662 applies to smaller diameter plastic pipe.
Given the confusion as to the correct plastic pipe standard to use based on the polymer, size and intended use, the Plastic Pipe Institute or PPI regularly publishes a comprehensive list of plastic pipe standards.
Standard Classification Systems for Plastic Pipe
ASTM D3350 gives the system for classifying polyethylene pipe using a cell classification system. The cell classification system for PE is based on seven physical properties. ASTM D1784 is the classification system for PVC pipe based on five physical properties. ASTM D1784 replaced a previous cell classification class system for PVC types that included types 1, 2, 3 and 4.
AWWA Standards for Plastic Pipes
The American Water Works Association or AWWA issues standards for plastic water pipe used to deliver drinking water and plastic pipes that transport waste water. AWWA standards apply to large diameter pipes that do not fall under ASME B31 piping standards. American Water Works Association standards are incorporated into the state and municipal building codes in many parts of the United States. All AWWA standards are shared with ANSI International. An AWWA standard shared with ANSI is identified as ANSI/AWWA followed by the standard number.
AWWA C900 is the standard for PVC pipe used in water distribution. AWWA C901 covers polyethylene pipe used in water distribution. AWWA C902 is the standard for polybutadiene water piping. AWWA C905 is the standard for PVC plastic pipes. AWWA C906 covers very large diameter polyethylene pipes. AWWA C605 is the AWWA standard for installing PVC pressure piping underground.
AWWA plastic pipe design standards include estimations of the effect of continually high temperatures on the pipe's design, something the ASTM design standards do not include. AWWA standards state that the design stress for plastic pipe should be reduced if the pipe wall is subjected to a sustained temperature above 73°F for prolonged periods of time.
Weathering Tests for Plastic Pipes
Ultraviolet radiation in sunlight breaks down polymer bonds. The effects of UV radiation on plastic are reduced by adding UV absorbers or stabilizing chemicals to the plastic. Water by itself has little effect on plastics, but constant exposure to water can wear down plastic. Furthermore, water reacts with sunlight to break down plastic. Weathering tests simulate exposure to the outdoors and allow engineers to estimate the effect of sunlight and rain on polymers.
Carbon, xenon and fluorescent UV lamps can be used to simulate sunlight. Weathering tests done using fluorescent UV lamps either meet ASTM G53 or ISO 4892. When a carbon arc light and water are used, either ASTM standard D1499 or ISO 4892 are used as the test procedure. The xenon arc light and moisture test is ISO standard 4892 and ASTM D2565. If the weathering is performed outdoors, ASTM standard D1435 applies.
Plastic Pipe Design Standards
ASTM D2837 is the standard method for determining the hydrostatic design basis for plastic pipes. ASTM D2241 is the standard for determining the hydrostatic design stress. The hydrostatic design stress is generally half of the hydrostatic design basis.
Plastic pipe can be specified based on a dimension ratio or standard dimension ratio. The standard dimension ratio is the average outside diameter of the pipe divided by the minimum wall thickness. ISO equations for determining the maximum stress within pipes use the standard dimension ratio or SDR. The pressure rating for a standard dimension ratio is the same no matter the dimensions of the pipe.
ASTM standards even differ when the method of determining the diameter differs. ASTM D2239 is the standard for polyethylene plastic pipe when the SDR is based on its inside diameter, while ASTM F714 applies when the standard dimension ratio is based on the external diameter. ASTM D3000 applies to polybutadiene pipe based on the outside diameter, while ASTM 2662 applies when the conventional SDR is used.
Related Standards for Plastic Piping
ASTM D1600 gives the standard abbreviations used for plastic pipe standards, such as PE being the standard abbreviation for polyethylene. ASTM F412 gives the definitions of terms used in other plastic pipe standards.