20 of 49 Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 05: Earth Works, Pipe Works and Ground Improvement  All pipes of ND 250 or smaller shall have an external electrolytic zinc protection. In addition all pipes  shall have an external coat of black varnish applied at the factory.  A special external bitumen-based hot applied coating, having a minimum thickness of 0.3 mm, shall  be sprayed onto the pipes before laying to provide protection against corrosion.  Bends and tees  5.3.5.4 Polypropylene (PPRC) pipes  Bends and tees shall be lined inside with epoxy as specified for accessories and coated outside as spec- ified above for pipes.  This kind of pipe shall be used for drinking water systems in the buildings. The installation, material  and fittings shall be compatible with TS 9937 and international requirements. The Contractor shall  provide the material catalogues with related standards to the Engineer’s approval.  All PVC and PP pipes shall be manufactured by a quality assured manufacture in accordance with the  ISO 9000 system. Un-plasticized PVC pipes and fittings for gravity drainage and sewerage shall com- ply with the relevant provisions of CEN Standard EN 1401, PP pipes shall comply with CEN Standard  EN 1852. Un-plasticized PVC pipes and fittings for pressure pipes shall comply with the relevant pro- visions of CEN-standard EN 1452.  All connections to PVC and PP pipes must be performed by using single 45 branch; no saddle must be  used.  Only pipes with a ring stiffness greater than 8 kN/m² may be used. Reference is made to ISO 9969.  5.3.5.5 PVC and PP pipes  5.3.5.6 High density polyethylene (HDPE) pipes  All HDPE pipes and fittings shall be manufactured by a quality assured manufacturer in accordance  with the ISO 9000 system. HDPE pipes shall be manufactured from PE 100 material, as classified by  the European Technical Committee Report CEN/TC 155. In accordance with ISO 12162 the PE 100  material shall have a minimum required strength (MRS) value of 10 MPa. The pipes and fittings shall  be coloured blue (potable water), yellow (gas) or black (wastewater) and be suitable for below-ground  use. Gravity pipes shall be engineered light weight pipes with (structured wall pipe type) with ring stiffness  larger than SN 8 kN/m2. The pipes shall be manufactured so that the cavity between the inner and out- er pipe can be water filled.  Pressure pipes shall be in pressure class PN6 minimum.  PE pipes and fittings shall comply with the relevant provisions of CEN-standard EN12201 (water and  wastewater) and EN1555 (gas).  Generally, all buried pipes shall be jointed using either butt or electro fusion welding techniques.  Small diameter pipes (diameter<63 mm), pipes within structures and pipes connecting to metal fittings  shall be jointed using mechanical jointing techniques, such as compression, flanged joints or push-fit  joints.  Jointing of large pipes of the light weight type shall be made by extruder welding. All welding shall be performed by certified welders holding licences not older than 12 months, and  issued by a recognised institution approved by the manufacturer and the Engineer.  5_Vol3_d4.3_Section 5 Earth and pipe works_en_GIR_rev6.docx 