case study
Deng Peng I Hydropower Station is located in Maoergai Town, Songpan County, Aba Prefecture. The first hub is located in the Ronagou reach 6.6 km upstream of the intersection of Ronagou and Hayasongou and the Hayasongou reach 6.5 km upstream of the intersection of Ronagou and Hayasongou respectively. The diversion tunnel is located on the left bank of the downstream section of Ronagou, a secondary tributary of the Maoergai River, and on the right bank of the downstream section of Hayasonggou. Surge well, pressure pipeline and site are located at the right bank of Lingou, about 60m upstream of the intersection of Luonagou and Lingou, the second tributary of Maoergai River. The power station is a high-head diversion power station with an installed capacity of 2× 10000=20000KW, rated flow of 6.6m3/s and working head of 370m.
The pressure pipeline adopts the combined water supply arrangement of one pipe and two machines. Pipes shall be laid with open pipes. The main pipe has an inner diameter of l.4m and a total length of 703.84m, of which the upper flat section is 65.3lm, the inclined pipe and the upper and lower elbows are 63l.4m, and the lower flat section is 7. L3m. The bifurcated pipes are arranged in a tree shape, with crescent rib bifurcated pipes and a bifurcation angle of 60o. The inner diameter of the branch pipe is 0.8m, and the total length of the two branches is 23.0m The main material of the penstock is l6MnR, with a thickness of l0-22mm. The branch pipe material is l6MnR, and the branch pipe material is 16MnR.
1, organization plan for construction quality of pressure pipeline
In the process of pressure pipeline installation and construction, in order to ensure the overall engineering quality and construction period of the hydropower station project of the water control project, it is necessary to scientifically formulate the pressure pipeline installation quality control scheme and organization management mode to ensure the quality management of the project construction. Establish a quality assurance system with the project manager as the person in charge in the construction site, comprehensively control and manage the installation quality of the pressure pipeline, and strengthen the quality control of the unit project (or process quality) according to the national Code for Acceptance of Building Equipment Construction and Installation Water Supply Project BJ242-82 and the Evaluation Form for Construction Quality of Water Conservancy and Hydropower Projects. In the process of construction, the construction should be carried out in strict accordance with the three inspection system. Without acceptance, the previous procedure shall not be carried out. After the completion of each unit project, the quality evaluation of the unit project must be carried out. The quality control of pressure pipeline construction should include the quality control of preparatory work inspection before construction, quality control during construction and quality acceptance at completion.
2, pressure pipe installation and quality control
In this project, in order to effectively control the installation quality of pressure pipeline, in view of the installation technology and engineering conditions of pressure pipeline, during the installation and construction of pressure pipeline, attention should be paid to the construction technology and technical methods of each link, and the whole process of quality control should be carried out.
1) quality control of pressure pipeline before installation
According to the actual situation of this project, a steel pipe factory is set up at the construction site. Both the straight pipe section and the bent pipe section are manufactured in the steel pipe factory, assembled on site, and then transported to the construction site factory for anti-corrosion treatment. After fabrication, the pipe joint will be transported by car to the pressure pipe tunnel by road, and will be transported by trolley and rail in the pressure pipe tunnel. After transportation is in place, pressure pipes will be installed. Strict quality inspection shall be carried out before installation, and the pressure steel pipe delivered to the site must have a product certificate. On-site steel pipe joints shall be marked for installation, with obvious joint number, flow direction and horizontal and vertical center lines. The thickness of steel pipe, welding quality and paint quality must be checked and guaranteed to be qualified. Before installation, the steel pipe should be free from deformation, paint stripping and pollution to ensure the installation quality of the penstock.
2) Installation process of pressure pipeline
In order to ensure the installation quality of pressure pipeline, nondestructive testing should be carried out for the installation of pressure pipeline at first. Non-destructive testing of pressure pipeline mainly includes non-destructive testing of weld surface and weld interior, aiming at the quality problems of pipeline surface and interior.
2. 1 surface nondestructive testing
There are five main types of surface nondestructive testing: X-ray, ultrasonic, magnetic powder, penetration and eddy current. Usually, ultrasonic inspection is used for the weld of steel pipes, while radiographic inspection is usually used for bifurcated pipes.
Used to detect defects on the surface of pipelines. The following problems were found during supervision and inspection:
Some design units do not test according to the surface nondestructive testing standards; Non-destructive testing on pipeline drawings is inconsistent with the actual testing position; Some unqualified welds, the expansion ratio of nondestructive testing did not meet the requirements during the implementation process;
2.2 Internal NDT
Internal nondestructive testing adopts ultrasonic flaw detection or radiation according to the design requirements of the design unit, mainly to detect welding defects such as cracks, slag inclusion, porosity and incomplete penetration, and generally has the following problems:
Failure to strictly check the testing equipment and testing environment before testing; Some inspection units' inspectors' certificates are invalid, and even some personnel are external non-professional inspectors; During the inspection, the inspectors did not carry out effective supervision and control, and did not conduct spot checks on the negatives; Adjust the elevation and center of the installed pressure pipeline, which requires surveyors to have professional survey qualifications. The specific installation process of pressure pipeline in this project is as follows:
pipeline transport
At the beginning, the horizontal pipe of the bent pipe is transported from the construction branch hole, transported to the installation position in the hole by 5T winch, jacked up by screw jack on the transport trolley and reinforced, and the steel pipe is installed to the design position.
② Marking, cutting and groove treatment of steel plate.
Draw a line on the standard platform. Steel seal, paint and punching marks are used to mark steel pipe number, water flow direction, axis, grouting hole position, groove angle and cutting line.
The semi-automatic cutting machine is used to cut and groove the steel plate, and the angle grinder is used to polish it.
Slag, burr and crack produced in the cutting process are removed and trimmed by the grinder.
③ coil plate
After the press performs radian prefabrication. "Full-range rolling" is carried out by a rolling machine, and the radian is checked by a template, and the longitudinal seam is butted on the rolling machine.
(4) steel pipe welding reinforcement and joint repair.
The welding method of longitudinal seam is mainly manual welding, supplemented by automatic submerged arc welding. The welding deformation of longitudinal seam is corrected by special orthopedic tooling prepared by press.
The connection of the steel pipe is completed on the connecting trolley, and the girth weld of the pipe section is completed on the roller welding trolley in the girth weld area; The welding method is automatic submerged arc welding, and the weld defect treatment is manual welding.
⑤ Inspection and acceptance of steel pipe installation quality
In the process of steel pipe installation, inspect and accept each field weld (including grouting sealing weld) together with the supervisor. Unqualified welds shall be repaired and re-inspected until they are deemed qualified by the Supervisor. The acceptance record must be signed by the supervisor.
When installing the pressure pipeline, the construction must be carried out in strict accordance with the technological process and specification requirements, and the quality of each construction link must be strictly controlled. Only after the previous procedure completely meets the specification requirements can the next procedure be carried out.
3. Quality control of pressure pipeline installation
Installation technology and quality control of the first section
The installation quality of initial installation is very important. According to the construction sequence of this project, it is proposed to use the horizontal section of the lower elbow as the initial installation section. After passing the inspection, the steel pipe can be temporarily fixed on the embedded anchor bar with section steel. After checking and fixing firmly, transport the second section of steel pipe to the installation position, adjust the center and elevation of the second section of steel pipe based on the first section of steel pipe, and carry out connection and steel bar welding. In order to prevent steel pipe displacement caused by welding shrinkage during steel bar welding, one end of the steel bar has a weld, which should be lap welded and welded at the end. After the installation of the first and second lower elbow sections, in order to ensure that the pipeline will not shift, the second-stage concrete can be poured first, and the welding of this section should be tested before pouring, and it can only be poured if it is qualified.
Installation of riser section and elbow, concrete pouring and quality control
In order to ensure the quality of this project, attention should be paid to the coincidence of the lower center of each elbow and the inclination of the nozzle when installing the elbow, that is, the lower center of the elbow should be aligned with the lower center of the first assembled steel pipe. After the deviation was found in the structure, a positioning plate was welded on the adjacent nozzle. When the locating plates of two pressure pipes are engaged with each other, the centers of the two pressure pipes coincide. The elbow must be checked and adjusted 2~3 days after installation to avoid error accumulation and bring difficulties to future treatment.
Installation and quality control of bifurcated pipe
After the bifurcated pipe is assembled and inspected in the processing plant, it will be transported to the construction site by car for sectional installation. The installation process is basically the same as the straight pipe section. Firstly, the bifurcated pipe is divided into two parts, transported to the installation site for assembly, and then docked with two branches at the same time. When all bifurcated pipes are assembled correctly, the temporary support shall be welded firmly before welding.
4. Welding and inspection of pressure pipelines Welders are the most indispensable backup force in the welding of pressure pipelines and the inspection of their results. If the manufacture of steel pipe is the most important first procedure in the welding technology of pressure pipeline in hydropower station, then the second important procedure is the inspection of welder. This is why welders are an indispensable part of steel pipe welding in hydropower stations. 4. 1 Welder Qualification Welders must be trained by the training center and hold the Qualification Certificate for Welders of Boilers and Pressure Vessels issued by the Ministry of Labor and Personnel of China, the Qualification Certificate for Boilers and Pressure Vessels issued by the General Administration of Quality Supervision, Inspection and Quarantine, or the certificate issued by the competent department of electric power and water conservancy. The certificate must be valid within the time limit. 4.2 The welding and inspection of pressure pipeline welders are also graded. Due to the different types of welders, the types of steel they are responsible for will be different, and the welding position will be different. The inspection is also divided by region. Appearance inspection, appearance inspection is nothing more than looking at the quality of the surface weld, that is, cracks and unevenness are not allowed in the details, the edge of the appearance weld must meet the actual requirements, and the raw material connection should be smooth to achieve a certain degree of beauty. Infiltration technology is mainly used to check the cracks on the toilet surface. 5. Post-welding treatment After welding, the pressure lamp will have a certain amount of heat, so it is very important to reduce the heat. Some steel pipes are difficult to be heat treated as a whole, and low alloy steel is one of them. In this case, we can do it from two aspects: one is to measure the width of weld heating, and then cool it from the inside. When cooling, the temperature inside and outside the steel pipe should be uniform to prevent the deformation of the steel pipe and affect some properties of the smooth pipe. Before eliminating heat treatment, it is necessary to go through many tests and then specify a set of corresponding schemes, otherwise many unnecessary problems will appear, so do not carry out heat treatment at the same time, and start from the local. In order to eliminate welding residual stress, explosion method will be adopted. The so-called stress means that the steel pipe will be elastically compressed after being subjected to a series of forces, resulting in a certain residual stress, which is very destructive to the bearing capacity of the steel pipe, so we will take corresponding measures to eliminate the stress. In fact, it is very simple to effectively relieve stress by shortening the plasticity of steel pipe itself.
In a word, during the installation and construction of the pressure pipeline in the hydropower station of the water control project, the effective control of the installation technology and quality of the pressure pipeline not only ensures the engineering quality, but also improves the engineering benefit to varying degrees, which provides a lot of engineering experience for the installation of the pressure pipeline in hydropower projects. The above data can be modified.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd