1 General 1.1 This instruction is applicable to the fabrication and installation of circulating water underground penstock of Zhejiang Datang XXX Power Plant Project. 1.2 Q235A steel pipe is used as the material of the circulating water underground pressure pipe of the project. See the water structure professional drawings for the construction technical requirements of pipe installation, trench excavation, backfill, etc. and comply with the relevant provisions of the Thermal Power Construction Quality Inspection and Assessment Standards (Part I Civil Engineering). 1.3 Sand cushion is set at the bottom of the circulating water pipeline, and the thickness of the cushion is ≥ 500mm. See the water structure professional drawings for the cushion design requirements. 1.4 This specification includes the construction technical requirements and main precautions for the production, welding, installation, pipeline anti-corrosion protection and hydrostatic test of steel pipes. Relevant matters not specified in this instruction shall be implemented in accordance with the provisions of Technical Code for Construction and Acceptance of Electric Power Construction (Thermal Power Plant Pipeline) DL/5031-94 and Technical Code for Construction and Acceptance of Electric Power Construction (Thermal Power Plant Welding) DL5007-92. In addition to the provisions in the above two chapters, the construction quality inspection standards shall also comply with the relevant provisions in the Thermal Power Construction Quality Inspection and Assessment Standards (Part VII Pipeline Engineering) and the Thermal Power Construction Quality Inspection and Assessment Standards (Part IX Welding Engineering)