21 of 49 Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 05: Earth Works, Pipe Works and Ground Improvement  HDPE pipes shall comply with DIN 8074 and DIN 8075 in connection with DIN 19537 or equivalent.  The pipes shall be designed for a nominal working pressure Class PN 6, have a hydrostatic design  stress of 50 kg/cm² at 20 °C and be jointed with pushfit couplings.  5.3.5.7 Corrugated HDPE pipes  The length of coiled pipes shall be in general 100 m. The minimum diameter of the rollers for coiled  pipe should be such that kinking of the pipe is prevented. The minimum internal diameter of the rollers  shall not be less than 24 times the nominal outside diameter of the pipe. The ends of the pipe shall be  plugged or covered.  The pipes shall be manufactured from high-density polyethylene containing only those antioxidants,  UV stabilisers and pigments necessary for the manufacture of potable water black pipes. The Contrac- tor shall provide an approved third party certificate to verify the above.  Mechanical couplings and fittings shall be used. The mechanical joints shall be push-on types. They  shall be produced in acetal-homo-polymer or be combined with gunmetal adaptors. The joints have to  provide the system with strength in tension and water tightness. Push fit jointing type shall consist of a  PVC grip ring and nitrite elastomer or equivalent O ring.  The couplings and fittings shall be designed for a nominal working pressure of 16 bars and a tempera- ture of 40°C and shall fit the HDPE pipes in this contract.  All fittings (couplings, bends, tees, reducers) and adaptors shall be deemed to be included in the unit  rates of HDPE pipes.  5.3.5.8 Glass fibre reinforced pipes (GRP)  GRP (Glass Fibre Reinforced Pipe) pipes and fittings shall be manufactured by quality assured manu- facturer in accordance with ISO 9001. GRP pipes shall be centrifugally cast or produced with continu- ous filament wound technology and shall comply with DIN 19565, DIN 16858, prEN 1796 and prEN  1636. GRP pipes with a diameter greater than 200 mm shall be provided for the following principal  categories:  Pressure rating, bar Stiffness, N/mm$^{2}$  PN 6  SN 5,000  PN 10  SN 10,000  All pipes shall be jointed using collar or sleeve joints incorporating an integral full width EPDM rub- ber seal. All joints shall comply with DIN 19565.  Fittings including flange joints, bends, tee pieces, tapped pieces and junctions shall be standard GRP  fittings and shall comply with DIN 19565.  All flanges shall be drilled and comply with EN 4504 unless otherwise specified. The nominal pres- sure rating for particular flanges shall be at least equal to the highest pressure rating of the pipes or  fittings to which they are attached, but with a nominal pressure of PN 10. All flanges shall be provided  with all necessary nuts, bolts washers and gaskets, as specified herein. After cleaning the flanges, the  gasket shall be fitted smoothly to the flange and the joint made by tightening the nuts to finger pres- sure first. Thereafter the final tightening of the nuts shall be made by gradually and evenly tightening  the bolts in diametrically opposite positions using only standard spanners of type approved by Engi- neer.  Gaskets and joint rings shall be manufactured from natural or approved synthetic rubber.  5_Vol3_d4.3_Section 5 Earth and pipe works_en_GIR_rev6.docx 