棉花滩水电站4号机座环及蜗壳安装

Installation of supporting ring and spiral case of No.4 generating unit of Mianhuatan Hydropower Station

棉花滩水电站安装 4台单机容量为 15 0MW的混流式水轮发电机组。座环总重 41t,分两瓣在工地安装场拼装焊成整体 ,材料为Q345D ,Z35。蜗壳为Q345C钢制 ,钢钣厚为 19～ 41mm ,共 2 9节 ,总重 132t。制造厂已将其中2 1～ 2 4节蜗壳和 2 5～ 2 7节耳板与座环焊在一起 ,工地共需挂装 2 5节 ,每节由 2～ 3块瓦块组成。座环和蜗壳的焊接均预热 ,预热温度为 10 0～ 12 0℃ ,焊接采用分段、退步、对称焊 ,焊后进行后热处理 ,后热温度为 2 0 0～ 2 2 0℃。工件冷却后对焊缝进行无损检测 ,质量属于优良。通过实践认为 :良好的焊接工艺是质量保证的前提 ;座环、蜗壳安装及混凝土浇筑过程中应有牢固的支撑 ;设计应考虑现场施工条件 ,便于施工 。

There are 4 mixed flow hydro generating units each with an installed capacity of 150 MW in the Mianhuatan Hydropower Station. The supporting ring, made by the material of Q345D and Z35, is 41 ton in total and is divided into two parts firstly and then is welded into one in the site. The spiral case is made by the steel plate of Q345C with the thickness of 19 41 mm and is divided into 29 sections with the total weight of 132 ton. The factory has welded the No.21 24 cases and No.25 27 ear plates with the supporting ring. In the site, there are 25 sections to be assembled. The welding of supporting ring and spiral case should be pre heated. The pre heat temperature is 100 120 Celsius degree. After welding, the post heat treatment also should be made, with the temperature of 200 220 Celsius degree. The test on the welding joint after cooling by the non destructive test method showed that the quality of welding is excellent. It is concluded that good welding technique is the prerequisite of high quality; the firm support is needed in the installation of supporting ring and spiral case and in the pouring of concrete; the construction conditions should be considered in the design.