PROCESSING | PIPE INSPECTION AND STANDARDS
Right: Parallel HDPE pipes installed as part of a buried geothermal header system
“Materials that were never designed for UVC are
increasingly seeing repeated exposures – often without the required testing or even knowledge of manufacturers,” said Vince. “Studies have shown significant degradation of materials under UVC, which could reduce performance or – in the worst cases – potentially render components unfit for service.”
Geothermal guidance The Plastics Pipe Institute (PPI) has released a new model specification document providing guidance on plastic pipe materials for ground source geothermal systems. The document, PPI MS-7 Model Specification for
users to securely access their instrument test data from anywhere in the world. This method of data collection allows researchers to identify critical points of degradation at key junctures and better understand the progression of ageing mechanisms.
UVC exposure Although UVC radiation is not a component of natural sunlight, there are areas where plastics are exposed to it. UK-based Radical Materials uses accelerated testing techniques – and says UVC radiation testing now plays a key role in its business. UVC radiation has been used in applications such as disinfecting water supplies, using a method called Ultraviolet Germicidal Irradiation (UVGI). “Whilst UVA and UVB radiation will reach the
earth’s surface as components of sunlight, UVC never does as it is filtered by the ozone layer,” said Chris Vince, technical director at the company. This means many materials are not designed to withstand UVC, which is higher in energy than either UVA or UVB and potentially more damaging. UVC exposure causes significant degradation if a material is not designed for it, and the speed and extent of this is still largely unexplored. “UVGI doses received in-service can be unpredict- able and their application and subsequent material testing is currently poorly standardised,” he said. Due to increasing use of UVGI and its poorly understood effect on material performance, new dedicated UVC test machines have been devel- oped. Radical says they are not designed to admin- ister UVGI, but to simulate and accelerate the UVC dosage of repeated UVGI cycles and test the effects on defined material parameters and properties. A typical way of using such a machine would be to develop a simulation based on the UVC cycles that a material will be exposed to in service.
30 PIPE & PROFILE EXTRUSION | October 2023
Plastic Piping Materials for Ground Source Geother- mal Applications, applies to plastic piping materials for open- and closed-loop, horizontal and vertical, direct-buried, and submerged water-based, ground-source geothermal heat exchange systems. Aimed at specifiers, engineers, and designers, it includes detailed specifications for four plastic piping materials used in ground-source heat exchange systems: HDPE, PE-RT, PEX, and PP (PP-R and PP-RCT). PPI says the definitions, terms and other information can be used in bid documents. “High-density polyethylene (HDPE) has been the primary piping material used in geothermal ground loops for decades and is a proven resource for this application,” said Lance MacNevin, director of engineering for PPI’s building and construction division.
He added that product standards and specifica- tions for HDPE piping have evolved, meaning that a specifier who uses outdated language for piping systems may accidentally specify a product that is no longer on the market – or is less capable. “Two other types of HDPE-based piping materi-
als – PEX and PE-RT – are also now approved in model codes for geo ground loop and are impor- tant options for certain projects,” he added. “In addition, PP-R and PP-RCT piping systems are recommended for indoor piping.”
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.inoex.com �
www.aquatherm.com �
www.laserlinc.com �
www.cnrs.fr �
www.gtu.ac.in �
www.enivibes.com �
www.slb.com �
www.atlas-mts.com �
www.radicalmaterials.com �
www.plasticpipe.org
www.pipeandprofile.com
IMAGE: GEOSOURCE ENERGY
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