Inclined pipe steel 16MnR, thickness of 28mm; the next bend stainless steel capillary pipe as WDL610D, thickness of 28mm; the next level hole pipe, stainless steel pipe hole out WDL610D, the thickness of 26mm.
Installation of measurement and control method - "symmetric 2:00 coordinate method,"
As the pressure pipe are circular hollow tube, the center nozzle is difficult to directly measure the measuring instruments can only be measured through the wall of a point or points to calculate nozzle center position, is generally measured through the center of a circle diameter of both ends of points Control of the center nozzle. In the past, mostly with the water level or the use of theodolite with stainless steel capillary pipe ruler to measure the vertical ball, and it must be the axis point and the installation of point of the first test set out in order to stake out the installation and testing, so these methods are often of low accuracy or Lofting take a long time. Total Station is now widely applied in hydropower projects, and increasingly high precision total station, total station can be directly measured due to the three-dimensional coordinates of a point, and control the network can be used to measure lofting and testing, so leads to coordinate measurement control methods.
Affect the accuracy of penstock installation analysis of the causes
In introducing the "two symmetrical coordinate method", we first affecting the accuracy of the pressure pipe installation simple analysis of the causes. Affect the accuracy of penstock installation of main reasons are the following aspects:
1, materials and production generated when the bias: pressure pipe are normally four rectangular steel plate cutting, coil, welded together, so the plate thickness, circumference measurement error, pipe roundness, in both the phase O-pipe section of the installation, soldering difficult. These errors in the pressure pipe production, just press "pressure pipe manufacture and installation and acceptance norms" DL5017-93 targets the provisions of the precision of control, the construction will be able to meet the installation requirements and specifications.
2, pipe transport, lifting process, due to pipe weight would produce a certain deformation, it will affect the pipe's roundness. The physical and mechanical analysis from stainless steel pipe, although the production of stainless steel pipe into a circle when the diameter of 9.50m would have a certain flexibility, but the 28mm thick steel plate in the circular wall of 16MnR is steel local in nature, and each section of pipe length 2m , in the middle saying goes stiffener ring. So the pressure tube due to transport and lifting the overall uniform deformation resulting from deformation, from the scene of the measured roundness that is almost becomes approximate oval.
3, due to errors inherent in measuring instruments, measurement of different control network and method of measurement error caused by improper deviations, etc., these are the installation of penstock to control the main aspects of measurement, but also the focus of this paper to be discussed.
"Symmetrical two coordinate Law" operation implementation of the
1, in the stainless steel pipe installed prior to the implementation specifications under construction survey to establish a unified measure of local control network, the two water holes civil construction of power generation laying wire networks and power plants, planted control network to re-laid and harmonization of poor observation and evaluation. In this way, you can reduce the measurement and control system caused by differences in measurement error.
2, the establishment of construction coordinate system: the installation of horizontal and vertical direction of X axis direction, vertical direction (elevation) for Y direction, the direction of the axial direction as the mileage three-dimensional coordinate system of construction, the coordinate origin can be located in the installation requires a certain mileage points; and installation design value axis coordinate value converted into the construction.
3, with the first installation of total station Leica TCR402 axis point (at least two points) and the beginning of installation section of install the mileage put on the ground and make a mark in order to facilitate laser-guided instruments or "hanging-line method" to guide tube initially in place. When the steel is transported into the transport trolley a good bit as well as seam welding, will be an axis point total station aircraft, the latter depending on the other axis point of orientation, open the Total Station laser-guided, according to the initial installation of laser-guided guide tube in place in general so that nozzle center offset can be controlled in less than 100mm will be its initial fixed.
4, fine-tuning the pipes in place, it will be good anchorage, with water level elevation of its installation for checking, using theodolite or other method of checking the installation location of its axis to confirm correct after the concrete pouring can be carried out in the next section to install . For other sections of the loft installation, testing, they can operate without this step.
The above method of the slope section, horizontal and vertical bend section bending section shall apply, as long as attention to the installation section of nozzle design of the location of mileage and axis coordinate values can be calculated well.
"Symmetrical two coordinates of Law" is to control the total station network wire directly to frame in the pressure on the pipe installation and testing lofting, so reducing the previous method: start with wire-based network measurement axis points and mount point, and then from the axis point and the mount point setting out and testing pipe installed in the middle sectors of the error and increase the accuracy of lofting. Now the total station's range and angle measurement accuracy is high, such as general engineering use Leica TCR402 ranging accuracy: 2mm +2 �� 10-6; angle measurement accuracy: "2", while the total station Basic can be measured through internal software automatically meteorological data correction. "2:00 coordinate method" has in the implementation of the axis is not fixed points, or restrictions on stainless steel capillary pipe markers, easy, fast, and calculate a simple, accurate and intuitive advantages of be in the future installation of penstock to be reference implementation.