PE (Polyethylene) compounds are the preferred choice for pressure pipes for several compelling reasons, including their unmatched durability, reliability, and adherence to rigorous quality standards. Here’s why PE compounds are the ideal choice for pressure pipes:
Durability of Pipe Systems: PE pressure pipes are engineered for an exceptionally long lifespan, often exceeding 100 years when used in underground infrastructure. This durability is essential because the installation of pipes underground represents the most substantial portion of the project costs (typically 85-90%). Engineers overseeing gas or water systems aim to avoid the costly and disruptive task of replacing pipes within their working lifetime. The longevity of PE pipes provides a “Peace of Mind” and minimizes the need for costly replacements.
Compound Approach: The use of PE compounds has been highly successful in Europe and has led to a significant market penetration of PE in both gas and water distribution systems. In Europe, nearly 100% of new gas pipes and 70% of new water pipes are manufactured using PE compounds. This approach is based on the adherence to European specifications that set high-quality standards and include all the key properties required for long-lasting, leak-free performance. These specifications have been adopted internationally by the International Standards Organization (ISO 4437 and ISO 4427) for PE gas and water pipes. An essential part of these standards is the high level of dispersion of carbon black within the polymer matrix, which allows for lower minimum design factors (2.00 for gas and 1.25 for water), resulting in high-quality pipes available at a reasonable cost.
Proven Quality: Recent data from the UK and Danish water industries confirm the efficacy of this quality-driven approach. PE has demonstrated the lowest failure rate among all materials used for water mains, underscoring its reliability and long-term performance.
Natural and Master-Batch Approach: In some regions, an alternative approach involving natural PE polymers and master-batch methods is used to produce gas and water pipes. However, this method necessitates a distinct quality assurance system and specialized processing equipment. In this approach, pipe producers are responsible for controlling additive levels and dispersion. However, this method poses challenges, including:
- Lack of Guarantee: The use of natural PE material does not guarantee that the resulting pipe maintains the PE100 classification. The introduction of carriers, such as LDPE or LLDPE, to disperse additives may reduce the 50-year strength of the blend.
- Stress Crack Resistance: While the natural material may pass the stress crack resistance of the PE100 specification, the use of a carrier material can decrease the stress crack resistance of the blend.
- Agglomeration: Achieving proper dispersion of pigments and additives, particularly 2-2.5% carbon black, can be challenging with standard extruders. Agglomerates can serve as initiation sites for cracks, potentially causing premature pipe failure.
- UV Stability: Reducing carbon black content to combat agglomeration sacrifices UV stability. A minimum level of 2% carbon black is required to protect the pipe over its lifetime.
- Particle Size: The use of carbon black with a larger particle size reduces the protective qualities of the pipe. A particle size below 25nm is necessary for good UV stability.
Responsibility for Quality: The natural and master-batch approach places the complete responsibility for pipe quality on the manufacturer, as they must control critical factors, including additive content, dispersion, and compliance with various quality and safety standards, such as organoleptic and food approval requirements.
In conclusion, the choice of PE compounds for pressure pipes is driven by their unrivaled durability, adherence to stringent quality standards, and the assurance of long-term reliability. PE compounds offer a cost-effective and dependable solution for underground infrastructure, providing the peace of mind that engineers seek for their projects. (PE100+ Association, 2013)
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