Manholes are, beside pipes and fittings, an essential element of underground pipe-systems. They are used for maintenance and inspection of sewers, sampling point or are fixed part of process technology / fluid engineering. The fabrication of thermoplastic manholes can be done in different ways of production. While, in smaller dimensions (DN ≤ 800), blow molded, injection molded or rotation molded manholes are in the market, manholes made of profiled pipes (helical extruded pipes) and semi-finished products will be used in medium sized and large diameters (DN800 to DN4000). Especially, the materials Polyethylene (PE) and Polypropylene (PP) are popular, due to their very long service life (> 100 years), good flexibility, high impact resistance, high strength, safety and low weight.
The authors of this report have large experience in the production and application of plastic pipes in the Sultanate of Oman. The Sultanate of Oman is well known for the high investments in the build-up and renewal of the infrastructure. Consequently, high quality materials will be used which high safety and guarantee a maximum service life. This has a direct implication in the use of very high quality-standards and specifications for testing during the production of large diameter manholes, which are more stringent and comprehensive than those used in many European countries.
NEW PLAYER in the corrugated pipe business
Two former Fränkische Rohrwerke employees founded their own company.
In the beginning of April 2010 Reinhard Gruber and Joachim Schuster have founded the company G&S Plast GmbH & Co. KG, located in Haßfurt – Germany.
Polypropylene has an excellent track record after more than 30 years of service for non-pressure sewage and drainage applications. The inherent material properties and their development, energy and cost efficiency, pipe design and ease of manufacture and installation have contributed to this success. The traditional cornerstones of the requirements profile such as impact resistance, stiffness and chemical resistance are increasingly being supplemented by demands for purity, sustainability and recyclability. Consequently, the continuous development seen in both material and pipe design has brought additional benefits to pipe producers and end users and is contributing to a more sustainable environment.
The first generation of PP with higher modulus PP was introduced in 1998 and provided a major step forward with an optimized balance of the stiffness-impact properties. A few years later, this product was improved and an E-modulus of 1700 MPa was achieved, representing the first PP-HM to meet the requirements set in the modified EN1852 standard in 2002 (which was adjusted based on the development of this new class of polypropylenes). The journey has continued and recently, the next generation PP for underground drainage and sewage has been introduced. It presents the first and unique 2000 MPa PP-HM from Borealis – BorECO™ BA2000, achieved without the use of fillers, meeting and exceeding the requirements set in the recently - again - modified EN1852.
Pipes are getting larger and larger in diameter, but while plastic pipes are entering the huge market of concrete pipes, the main barrier is still the high price of the raw material. Some authorities still don´t accept and consider the importance of the advantages of a long life time and a sustainable pipe system, or they just don´t want to spend the money for the future of their country. So the question is how producers of plastic pipes made of High Modulus Polypropylene (PP-HM) can deal with this problem.
How can existing “conventional” pipe producers enter these markets with technically better products and very competitive prices? Today large sewage and drainage pipes are mainly produced with standard polyethylene or polypropylenes. Mostly, structured wall pipes are used for these applications according to international standards like:
DIN16961, EN13476, NBR7373,JIS, ASTM F894
Short term E-module (E) of different polyolefin materials (usually they can be used in normal single screw extruders):
To make an easy calculation, we should start with reducing a solid wall thickness by increasing the E-modulus of the material (standard material can also have a higher short time E-modulus).