1 Preface
With the increasing urban population in China, the amount of urban sewage is also increasing, so that China's requirements for environmental protection is also higher and higher, the urban sewage must be treated to meet the standards before being discharged into the rivers and bodies of water, so our country has built a large number of new sewage treatment plants. Sewage treatment plant often has a large scale, more equipment, pipeline complexity and other characteristics, these are to the construction of sewage treatment plant has brought some difficulty.
2 main construction techniques for process piping
2.1 Pre-construction preparation
1) Measurement and placement. Wastewater treatment plant pipeline intricate and complex, distributed throughout the site, the plane position and elevation accuracy requirements, the quality of the measurement work directly affects the quality of the project, the measurement work is the key control link of the project, should be arranged in the plant measurement control network.
2) pipeline alignment. Calculation of pipeline centerline coordinates, according to the coordinates of the control network has been measured and placed, with a total station measuring and placing each section of the pipeline pipe center control points, and marked with wooden stakes every 10m ~ 20m pipeline centerline, while the centerline piles cited outside the excavation surface set up the centerline control piles, in order to facilitate trench excavation and retesting. And then according to the center line measured out the pipe trench excavation edge line, with white ash powder put out the trench edge line after earth excavation construction.
3) Foundation compound. In order to ensure the plane coordinate position and elevation of the pipeline, before the installation of the pipeline, the centerline and elevation of the pipeline should be rechecked, and the construction can be carried out only after checking the correctness, and at the same time, make a good record of inspection.
2.2 Pipe trench excavation, support
According to the center line of the pipe trench excavation edge line, put out the trench edge line with white ash powder can be earth excavation, and according to the construction site of the soil and the actual conditions of the requirements of the trench slope support.
2.3 Carbon Steel Pipe Installation
1) Installation of bends and inclined pipes. Bend pipe installation should pay attention to the center of each section of the bend pipe under the coincidence and the mouth tilt, when the lower bend pipe installation, that is, the center of the lower center of the first installed section of the steel pipe to the center of the lower. If there is a shift in the adjacent mouth of each welded a baffle, between the baffle with a jack to turn the steel pipe, so that the center is the same. Bend the center of the upper and lower and horizontal sections of the same steel pipe, you can hang pendant ball or latitude and longitude determination; bending pipe installation 2 ~ 3 sections, you must check the adjustment, so as to avoid the accumulation of errors, resulting in difficulties in dealing with the future. Inclined pipe installation method and the same bend.
2) fork pipe installation. Fork pipe assembly and inspection in the processing site, and then subsection with the car to the construction site installation method; installation process and straight section is basically the same, the first fork pipe is divided into two parts of the installation site combined, and then with the two pipes at the same time for docking. When the fork pipe is fully assembled, the center, elevation and tilt of the two branch pipes must be reviewed, and the temporary support will be welded firmly after the error, before welding work.
3) Flexible joint installation within 2m outside the structure. Pipeline through the wall is generally used in the wall pre-embedded casing and steel pipe filled with oil-impregnated hemp wire and asbestos cement, in order to ensure tightness, pay attention to the casing and the gap between the steel pipe can not be too large, nor too small, appropriate for about 25mm, and should be uniform. Flexible joints, axial tilt angle allowable deviation shall not be greater than 3 °, if encountered when the foundation is not good, may make the flexible joints produce radial displacement, and make the axial tilt more than the permissible value, the installation of the joints is best made for the base of concrete foundations and concrete piers, in order to avoid the flexible joints due to the foundation of the uneven settlement of the damage is too large. Rigid joints and flexible joints to do closed water test, qualified before backfilling the pipe trench.
4) pipeline and equipment connection, the weight of its pipeline should not be pressed on the equipment, the valve in the horizontal pipeline, there must be a fixed point; pipeline valves, instruments and accessories should be installed, should be operated, observed and maintained for convenience, the valve installation should be tight, tight, perpendicular to the center line of the pipeline, and can be operated and flexible and convenient; pipeline through the reserved holes in the pipeline transverse weld shall not be placed in the casing, the casing and the flexible joint shall not be placed in the casing, the casing and the flexible joint shall not be placed in the casing. When the pipe passes through the reserved hole, the transverse weld of the pipe shall not be placed in the casing, and the gap between the casing and the pipe shall be filled with oil-impregnated sesame wire and sealed with asbestos cement.
5) Removal of the internal support and paint patching inside the pipe. Pipe internal support removal should be carried out after the second phase of concrete pouring, removal of steel pipe clamps, lugs, internal support and other temporary components, it is strictly prohibited to use the hammering method, the application of carbon arc planer or oxygen - acetylene flame in its removal from the wall of the pipe more than 3mm, it is strictly prohibited to damage the parent material. After excision, the traces and weld scars remaining on the inner wall of the steel pipe are smoothed with a sander and carefully checked for microcracks. After checking and passing the manual painting of the excision part of the filler paint.
2.4 reinforced concrete pipe installation
Check the buried pipe trench bottom foundation in line with the installation conditions, the reinforced concrete pipe for lifting in place buried work. Pipe installation should be done before the internal and external pressure test. Reinforced concrete pipe installation, it is appropriate to start from the downstream, bearing mouth toward the construction of the forward direction, and each pipe mouth butt tightly, according to the design requirements of each section of the pipe interface at the installation of rubber water stop ring. The internal surface of the pipe should be kept smooth and any protruding aggregate must be removed. Socket interface structure and the filler used should be in line with the design requirements and construction specifications, gray mouth dense, full, filler surface recessed into the edge of the mouth is not more than 5 mm. try to make the ring gap uniform, gray mouth flat, smooth, well-maintained. After wiping into a sack cover, 3 h ~ 4 h after sprinkling maintenance. After the installation of the pipeline, the test is qualified before allowing backfill.
2.5 Mechanical pipe jacking construction
1) The flow chart of pipe jacking construction process is shown in Fig. 1.
Figure 1: Flow chart of pipe jacking construction process
2) Support of working pit
Pipe jacking working pit and receiving pit adopt the combination of anchor spraying and I-beam steel reinforcement as the support method, and the support of vertical shaft adopts the method of "steel grid + vertical connecting bar + mesh spraying C20 concrete". The shaft support adopts "steel grill + vertical connecting bar + net spraying C20 concrete joint support system", plus I-beam support. The locking ring adopts C25 cast-in-place reinforced concrete ring beam.
Construction process:
Construction preparation→measurement and positioning→excavation of earth at the wellhead→concrete filling of locking ring beam→erection of gantry→excavation of soil→installation of steel grid→hanging of reinforcing bar mesh→spraying of concrete→I-beam support→starting of the next cycle→sealing of bottom of the shaft.
3) construction quality inspection standards
More about engineering/service/procurement tender writing production, to enhance the winning rate, you can click on the bottom of the official website customer service free consultation:/#/?source=bdzd