Domestic large-scale hydropower plant under construction artificial sandstone system and concrete mixing system equipment management mode 1 artificial sand system equipment 1.1 Process Currently domestic hydropower station artificial gravel aggregate processing system, the production process has two broken sections plus sand , Three broken sections plus sand, and set the second sieve, three sieves, four sieves, aggregate wash, aggregate plastic. According to the system of production capacity, source rock, product fineness, concrete grading, quality requirements of finished products to ensure reliable operation of the system, advanced technology, economic rationality and the advanced nature of major equipment and matching, through technical and economic comparison, to determine System production process. 1.2 equipment selection Various crushing equipment, sand equipment for material sources, advantages and disadvantages of equipment selection problems, see Table 1. Example 1: The Three Gorges Project The downstream sandstone processing system is the main base of the finished sand and part of the aggregate required for concrete placement of the Three Gorges Dam and the main body of the plant. The rock lithology is a plagioclastic granite with a few diabase vein distributions. Rock compressive strength, abrasion index. According to the design of construction organization, the system designed 556,000 m3 of artificial sand and 129,000 m3 of crushed stone required for concrete pouring at the peak of 2000, designed the coarse crushing, medium crushing, fine crushing, 1020,1440,200 t / h, and to produce four pre-cooling concrete aggregate based. The system selected MK-II-50-65, HP-500ST, B9100 crushing equipment, Department of the first domestic use. Example 2: The Artificial Sand and Gravel System at Xiluodu Hydropower Station Center Center provides 2.8 million m3 of aggregates needed for concrete and shotcrete for diversion tunnels, spillway tunnels, underground powerhouse systems and other construction facilities. The source of the diversion tunnels is basalt, Compressive strength of 219 ~ 293MPa. System design gross processing capacity of 850t / h, finished product production capacity of 700t / h, of which artificial sand production capacity of 240t / h, the fineness modulus of 2.6 ± 0.2), stone powder content of 10 to 15%, the surface moisture content 6%. 1.3 related issues (1) stone powder recovery methods: to be naturally precipitated and dried, dredged stone powder mixed with sand; negative pressure water absorption, speed up sedimentation stone powder drying; spiral machine and high-frequency vibration dehydration screen. (2) RCC RCC Dams on Finished Sand Requirement RCC content requires up to 17 ± 2%. If the use of wet process production, better finished sand quality, but there is the phenomenon of fine sand and finished sand loss, and the recovery of poor results in the lower the content of stone powder in the finished sand; if the use of dry process production, finished sand powder content Satisfy the requirements, but finished sand gradation is not ideal (intermediate grade with low). (3) basalt artificial sand fineness modulus is high and the content of stone powder is not enough, especially the content of stone powder is too low, which has a great impact on the workability and performance of concrete. In addition to the system design and equipment configuration Fully consider the selection of stone powder recycling device, but also should increase the sand production equipment to increase the content of stone powder technology research. 2 Concrete mixing system equipment 2.1 Mixing floor (station) At present, there are two types of self-supporting and forced-type concrete mixing towers used in China's hydropower station under construction. The main parameters of productivity (m3 / h) are as follows: 30,45 50,60,75,90,120,150,180,240,270,320,360. Blender has double cone tipping self-inverted, inverted discharge from the next type, double horizontal axis mandatory, one horizontal axis mandatory and planetary type, the nominal capacity (L) series are: 750,1000,1500, 2000, 3000, 4500, 6000, 7500. The domestic mixing tower (station) technology is mature, able to meet the needs of mixing conventional concrete, pre-cooling concrete and RCC roller compacted concrete for hydropower projects. In order to meet the need of rapid pouring of RCC dam in recent years, the market share of periodic self-rolling or forced-type mixing equipment for mixing RCC, especially for forced concrete mixing plant (station), is increasing day by day. Continuous production of domestic concrete mixing equipment has been put into use in some medium-sized hydropower projects, but can not fully meet the requirements of temperature-controlled pre-cooling of high-strength RCC production. At present, the latest technical status of domestic mixing tower is as follows: the main node of the steel structure of the mixing tower is connected by a pin (shorten the installation period); the control system adopts the dual-screen dual standby hot backup three-screen display technology (which improves the reliability of the microcomputer control system) Control, diagnosis, troubleshooting and other new technologies. The main external components, such as the main control and implementation of components used in the selection of mature and reliable and cost-effective world-renowned manufacturers of products, nominal capacity of more than 3m3 mixing console (double-horizontal axis and double-cone tilt self-falling) Using imported products (not yet made). Three phases of the Three Gorges Project are arranged on five concrete mixing systems with different elevations. The total normal capacity normalized concrete production capacity is 2360m3 / h and the total pre-cooling concrete production capacity is 1870m3 / h (see Table 4). Mixing of concrete mainly through six feed lines directly to the six towers (top) with the conveyor belt cloth warehousing; This new factory assembly line production mode, an anti-past the traditional single-pot pouring operation, the concrete Speed ​​continuous pouring can be achieved, thus greatly improving productivity, but also ensure the quality and duration of the Three Gorges Project. The annual pouring volume for the three consecutive years from 1999 to 2001 was more than 4 million m3 (in 2000, the annual pouring strength of concrete was 5.48 million m3 and the monthly pouring intensity of 553,000 m3 was the highest in the world). From 1999 to 2004, a total of 20.55 million m3 of concrete was poured into the Three Gorges Project. 3 large-scale hydropower station sand and gravel system, mixing system equipment procurement mode 3.1 crushing equipment procurement mode artificial sandstone system equipment generally purchased by the contractor, but crushing equipment, especially to the main project of the hydropower station gravel aggregate gravel system imported crushing equipment Including stone powder recycling device), but also the owners purchase. Domestic crushing equipment manufacturers are more, such as Luoyang Dahua, Guiyang Cheng Chi, Shanghai Shanbao, foreign manufacturers are: the United States nordberg, Astec, Finland metso, Sweden svedala, sandvik, Japan kobelco and so on. 3.1.1 Contractor Procurement contractor choose the best imported crushing equipment for sand and gravel systems engineering bidding, after the successful bidder, the contractor will undertake the equipment purchase according to the project bidding phase commitment. The proprietor may give the contractor financial support in the form of advances or payments. For example: Yunnan Xiaowan Hydropower Station, Pubugou Hydropower Station, Three Gorges Project sand and gravel system capacity expansion period, the construction of Xiluodu hydropower sand and gravel system. Advantages: The contractor is responsible for purchasing equipment, and the owner has less coordination work. Disadvantages: contractors in the project after the bid in order to minimize the input of new equipment, often on the gravel system equipment to "optimize": the old new generation, small generation, reducing the configuration of the equipment is not conducive to project protection. 3.1.2 Owner Purchases Major Imported Crushing Equipment Under the condition that the key equipment is procured by the owner through international bidding, the contractor will use the equipment to carry out project bidding for the sand and gravel system with the proposal and is responsible for the system design, construction and operation. After the bid opening, the owner purchases the imported equipment and submits the imported equipment to the contractor for installation. At the completion of the project, the contractor shall repurchase the equipment according to the bidding commitment. For example: Guangxi Longtan Hydropower Station, Yunnan Jinghong Hydropower Station, Chongqing Pengshui Hydropower Station. Advantages: Owners can effectively control the procurement of equipment, to avoid the old new generation, with a small generation. Disadvantages: In the equipment procurement, installation, commissioning and operation, the owners assume the responsibility of supply, and thus need to invest more energy to coordinate the relationship between equipment manufacturers, contractors. 3.2 Procurement system of mixing system equipment Currently used in the hydropower station mixing host nominal capacity greater than or equal to 3m3 concrete mixing plant (station), generally by the project owner to pay the contractor to install the operation and management, and at the end of the project by the contractor Value repurchase. Among them, the nominal capacity of more than 3m3 mixing host (double horizontal axis and double-cone tilt self-falling), due to the current domestic can not be manufactured, it is generally imported products; mixer nominal capacity of less than 3m3 mixing plant (station) Usually purchased by the contractor (the project owner will provide financial support). At present, the domestic concrete mixing plant production enterprises are: Zhengzhou Hydraulic Concrete Machinery Co., Ltd., Zhengzhou Sanhe Hydraulic Machinery Co., Ltd., Guodian Mechanical Design Institute, Shaanxi Construction Machinery Co., Ltd., the major foreign manufacturers Japan IHI, Germany BHS, Italy CIFA, Italy SICOMA, the United States JOHNSON-ROSS and so on. 4 sand and gravel system, mixing system management mode (1) the owners commissioned by the design unit preparation of sand and gravel systems, concrete mixing system tender documents, contractors with the program bid general contracting methods, is responsible for geological exploration, design, equipment procurement, construction and operation management. Advantages: the owners bear the responsibility of system construction and operation of small, less coordination. Equipment purchase costs, depreciation charges and other costs into the unit price of finished aggregate or concrete unit, the residual value of equipment owned by the contractor. The end of the project owners do not bear the custody of equipment storage, asset disposal pressure. Disadvantages: As the owners of equipment procurement, system JianAn intervention less likely due to financial problems caused by the contractor equipment ordering is not timely, delayed delivery, or the contractor failed to purchase the tender commitment to configure the tender documents required equipment, etc., Reduce the project protection, so there is a certain degree of engineering risk. (2) The owners provide the main equipment (such as the imported crushing equipment and large mixing plant). Other equipment of the system is configured by the contractor. The contractor is responsible for the system equipment installation, commissioning, operation and maintenance. After the project is completed, the repurchase will be undertaken according to the bidding documents Owner equipment. Advantages: As the main equipment is the owner of the procurement department, the timely ordering of equipment, equipment, performance, etc. in the controllable range of the owners, help to improve the reliability of the system. Disadvantages: the owners assume the main supply of equipment and system construction and operation of the larger contractual responsibility, and the actual operation of equipment manufacturers involved in the installation of more coordination between units. 5 Conclusions and Suggestions At present, the common production technology and equipment selection and configuration of sand and gravel material processing system for hydropower station engineering have been relatively mature. However, the sand making technology, such as the recovery of the stone powder from basalt sand and RCC sand, is yet to be further studied and explored. In order to prevent the contractor from purchasing old equipment and equipment on behalf of the new generation and substituting the bidding promises, the owner or supervisor shall participate in the procurement of equipment which is undertaken by the contractor and make use of the equipment Owners in the credibility, financial advantages, to assist the contractor on equipment selection, price, service and other issues with the equipment manufacturers contract negotiations. The owner provides capital support to the contractor in the form of advanced fund or advance payment to ensure timely ordering and supply of major equipment. An open, fair and just selection of a strong hydropower station sand and gravel mixing system construction team won the bid to facilitate the owners, supervision units follow-up of sand and gravel mixing system construction and operation and management. (This article picture, the table is slightly, see "Construction Machinery Technology and Management" magazine in 2006 eleventh period)