Article

Chlorine Resistance Testing for classification and life time evaluation of plastic pipes

 A guide to understanding the procedures of evaluating the oxidative resistance to chlorinated water for plastic pipe materials and systems

The thermo-oxidative chlorine resistance of polyolefin plastics pipes has been investigated during the past 30 years, and Element has played an active part in the progress ever since. The test data is used by manufacturers for product certification to industry specifications.



While many plastic pipe materials have proved to be resistant to oxidative degradation, under more aggressive circumstances, the ageing process can be accelerated and become a critical factor in the lifetime and durability of the pipe systems.

For example, the common use of chlorine for water disinfection purposes means it’s important to evaluate the oxidative resistance of piping materials and systems. Chlorine is an oxidizer and potential aging accelerator of water piping systems.  

Standardized Testing

With the adoption of standardized test methods such as ASTM F2023 and ASTM F2263, evaluations of the thermo-oxidative resistance to chlorinated water are conducted on cross-linked polyethylene (PE-X), polyethylene with raised temperature resistance (PE-RT), polyethylene (PE), polypropylene (PP) where the oxidative performance of these materials are demonstrated. 

Element follows ASTM F2023 (PEX, PP, PE-RT), ASTM F2263 (PE) and PPI TN-43 for testing and evaluation of the long term thermo-oxidative chlorine performance. The chlorine resistance for a material is then demonstrated in a material designation code (cell classification) according to material standard specifications for each material and application; ASTM F876 (PEX), ASTM F2389 (PP), ASTM F2623 (PE-RT), ASTM F2263 (PE). The material designation is then used by pipe companies and printed on the pipe as evidence of performed testing and as information for users.  

Principle

Chlorine resistance testing is conducted under accelerated conditions at three elevated temperatures and duplicate pressures. The chlorinated water (free chlorine) conditions are chosen from the highest amount chlorine that is allowed in drinking water in North America (EPA). The most commonly accepted approach is to perform exposure under a worst case condition scenario, that is, the most aggressive media that may be encountered in a specific application in combination with the smallest pipe dimension for the specific application. 

The testing of hot and cold water materials and piping systems (ASTM F2023) are conducted until failure and the project length for the testing program is given by the material’s actual performance. 


Figure 1:   Schematic example of ASTM F2023 testing results and following extrapolation

For cold water material PE a different approach is currently accepted by the industry where pipes are tested for a minimum testing time criteria as given in PPI TN-43. Still the approach to test smaller pipe dimensions until failure is described in ASTM F2263, but material specifications and material designations are based on the single point testing approach. 

Product Certification

Mutual recognition of ISO/IEC 17025 accredited testing results allows our customers to use the results for product certification according to industry specifications such as NSF/ANSI 14.

Research & Development and new materials

One way to reach successful development of new material recipes is screening of many different recipes. To test actual pipe is not always possible and this is why Element may use the standard pipe testing equipment for immersion testing of samples in other formats, for example tensile sample, impact strength sample, film, granule, etc. The samples may then be analyzed following the degradation process with different analytical methods. 

Post Exposure Analysis

Post exposure analyses on exposed samples are used to follow the degradation and failure propagation mechanism in the pipe. Test programs will be developed in close collaboration with our customers and analytical experts taking into account the latest research and developments within the specific application area. 

Testing Conditions

Temperatures
20-115°C
Chlorine concentration 4.3 ppm free chlorine as standard
Free chlorine up to 100 ppm
Chlorine dioxide (ClO2) 0.5 and 1.0 ppm
pH 6.8 is set as standard, others on request
Flow rates
Standard up to 54 dm3/h 
Dimensions Dimensions up to OD 110 mm can be tested

PEX (1/2” DR9 / 16x2 mm)
  PE-RT (1/2” DR9 / 16x2 mm)
  PP-R and PP-RCT (20 mm DR7.3)
  PE (16x2 mm or 4” DR11)
Pressures
Up to 20 bar
  Standardized 2.76 bar (40 psi), 4.14 bar (60 psi), 4.83 bar (70 psi)
Chlorine types
Free Chlorine (hypochlorite)
  Chlorine Dioxide (chlorite + acid generation system)

 

The Element Advantage 

Element’s plastic pipes testing facility in Sweden is one of very few independent laboratories globally in this field with a capacity of more than 5,000 test positions.

Since 1992 we have built our expertise around polymer degradation mechanisms and developed and expanded our ISO/IEC 17025 accredited testing facility, capable of generating reliable and reproducible test data for an extensive range of materials and pipe constructions for product classification and life time evaluation. The team and facility is trusted by resin and plastic pipe manufacturers and around the world.

Sample drop off points in USA and Canada

For our North American customers, local delivery points are recently set up to simplify sample shipping to our Element laboratories in New Berlin, WI, USA and in Mississauga, Ontario, Canada. We’ll provide you with all necessary details.

Contact us today

Contact our experts to discuss how we can assist as an accredited, independent testing provider.


References

  • EPA, National Primary Drinking Water Regulations (2020-08-17)
  • ASTM F2023, Standard Test Method for Evaluating the Oxidative Resistance of Crosslinked Polyethylene (PEX) Pipe, Tubing and Systems to Hot Chlorinated Water
  • ASTM F2263, Standard Test Method for Evaluating the Oxidative Resistance of Polyethylene (PE) Pipe to Chlorinated Water
  • ASTM F876, Standard Specification for Crosslinked Polyethylene (PEX) Tubing
  • ASTM F2769, Standard Specification for Polyethylene of Raised Temperature (PE-RT) Plastic Hot and Cold-Water Tubing and Distribution Systems
  • ASTM F2389, Standard Specification for Pressure-rated Polypropylene (PP) Piping Systems
  • PPI TN-43, PE Compound Categorization for Potable Water Applications
  • NSF/ANSI 14, Plastics Piping System Components and Related Materials
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