During the construction of the project, the technical personnel of the civil engineering and the initial installation project, because there is not much research on the hydropower specification, resulting in many fatal diseases of the hydropower installation project during the construction, today I will list the taboos in the hydropower installation project for your reference.
1. There is no identification or qualification certificate for the main construction materials and equipment
The quality of the project is not up to standard, there are hidden dangers of accidents, and it cannot be delivered and used on schedule, so it must be reworked and repaired; it will cause delays in the construction period and increase the input of labor and materials.
Solution:
In strict accordance with national standards, the factory inspection is carried out.
2. Unnecessary quality inspection before valve installation
During the operation of the system, the valve switch is not flexible, the closing is not strict and water (steam) leakage occurs, resulting in rework and repair, and even affecting the normal water supply (steam).
Solution:
Before the valve is installed, the compressive strength and tightness test should be done. In the test, 10% of the batches shall be randomly checked, and there shall be no less than one. For the closed-circuit valve installed on the main pipe to cut off, the strength and tightness test shall be carried out one by one. Comply with the "Construction Quality Acceptance Specification for Building Water Supply and Drainage and Heating Engineering" (GB50242-2002).
3. Valve specifications and models do not meet the design requirements
Affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even caused the valve to be damaged and forced to be repaired during the operation of the system.
Solution:
Familiar with the application range of various valves, select valve specifications and models according to design requirements. The nominal pressure of the valve should meet the requirements of the system test pressure. According to the requirements of the construction specification: the water supply branch pipe diameter is less than or equal to 50mm, the stop valve should be used; when the pipe diameter is greater than 50mm, the gate valve should be used. Hot water heating dry and vertical control valves should use gate valves, and fire pump suction pipes should not use butterfly valves.
4. Valve installation method is wrong
The water (steam) flow direction of the globe valve or check valve is opposite to the sign, the valve stem is installed downward, the horizontally installed check valve is installed vertically, the handle of the rising stem gate valve or butterfly valve has no opening and closing space, and the valve stem of the concealed valve is not facing Check the door.
The above problems cause the valve to fail, the switch is difficult to repair, and the valve stem often causes water leakage.
Solution:
Strictly follow the valve installation instructions for installation. For the rising stem gate valve, leave enough valve stem to extend the opening height. Butterfly valve fully considers the handle rotation space. Various valve stems cannot be lower than the horizontal position, let alone downward. For concealed valves, not only should an inspection door meet the needs of valve opening and closing, but also the valve stem should face the inspection door.
5. Ordinary valve flanges for butterfly valve flanges
Butterfly valve flanges are different in size from ordinary valve flanges. Some flanges have a small inner diameter, while the disc of the butterfly valve is large, resulting in failure to open or hard opening and damage to the valve.
Solution:
Process the flange according to the actual size of the butterfly valve flange.
6. No reserved holes, embedded parts and marking problems
In the construction of heating and sanitary engineering, the building structure is chiseled, and even the stressed steel bars are cut off, which affects the safety performance of the building.
Solution:
Familiarize yourself with the construction drawings of the heating and sanitary engineering, and actively cooperate with the construction of the building structure to reserve holes and embedded parts according to the needs of the installation of pipes and supports and hangers, and refer to the design requirements and construction specifications for details.
7. The pipeline elevation is not on a center line
The misalignment of the pipe directly affects the welding quality and appearance quality. No gap is left between the counterparts, thick-walled pipes are not shoveled, and the welding seam width and height do not meet the requirements.
Solution:
After welding the pipes, the pipes should not be misaligned. They should be on the same center line, and there should be a gap between the counterparts. Thick-walled pipes should be beveled. In addition, the width and height of the weld should be welded according to the requirements of the specification.
8. Improper spacing and position of pipeline piers
Due to the unstable support, the pipeline was damaged during the backfill compaction process, resulting in rework and repair.
Solution:
Pipes shall not be buried on frozen soil and untreated loose soil. The spacing of buttresses shall meet the requirements of construction specifications, and the support pads shall be firm, especially at the pipe joints, which shall not be subjected to shearing force. Brick buttresses shall be built with cement mortar to ensure integrity and firmness.
9. Quality and installation of expansion bolts
The pipeline support is loose, the pipeline is deformed, or even falls off.
Solution:
Expansion bolts must be qualified products. If necessary, samples should be taken for test inspection. The diameter of the installation expansion bolts should not be greater than the outer diameter of the expansion bolts by 2mm. The expansion bolts should be used on concrete structures.
10. Insufficient strength of flange and gasket
Rubber gaskets for heat pipes, asbestos gaskets for cold water pipes, and double-layer gaskets or bevel gaskets with flange gaskets protruding into the pipes.
The flange connection is not tight, or even damaged, and leakage occurs. Flange gaskets protrude into the pipe, increasing the resistance to water flow.
Solution:
Flanges and gaskets for pipelines must meet the requirements of the design working pressure of the pipeline. Rubber asbestos gaskets should be used for flange gaskets of heating and hot water supply pipes; rubber gaskets should be used for flange gaskets of water supply and drainage pipes. The gasket of the flange shall not protrude into the pipe, and its outer circle should reach the bolt hole of the flange. No inclined surface pads or several pads shall be placed in the middle of the flange. The diameter of the bolt of the connecting flange should be less than 2mm than the diameter of the flange plate, and the length of the nut protruding from the bolt rod should be 1/2 of the thickness of the nut.
11. Water pressure strength and tightness test of piping system
Leakage occurs after the operation of the pipeline system, which affects the normal use.
Solution:
When the pipeline system is tested according to the design requirements and construction specifications, in addition to recording the pressure value or water level change within the specified time, it is especially necessary to carefully check whether there is any leakage problem.
12. No closed water test for sewage and condensate pipes
cause water leakage and cause loss to users.
Solution:
The closed water test work should be checked and accepted in strict accordance with the specifications. Buried underground, in the ceiling, between pipes and other hidden sewage, rainwater, condensate pipes, etc. should be installed to ensure no leakage.
13. Pipe flushing requirements are not up to standard
The water quality does not meet the operating requirements of the pipeline system, which often results in the reduction or blockage of the pipeline section.
Solution:
Flush with the maximum juice flow in the system or a water flow speed that should not be less than 3m/s. The water color and transparency of the outlet should be visually consistent with the water color and transparency of the inlet water.
14. Water pressure test under negative temperature in winter
Due to the rapid freezing of the tube during the hydrostatic test, the tube was frozen.
Solution:
Try to carry out the water pressure test before winter application. After the pressure test, the water should be blown out, especially the water in the valve must be removed to the net, otherwise the valve will freeze and crack. When the water pressure test is carried out in winter, the project must be carried out at a positive indoor temperature, and the water must be blown out after the pressure test. When the hydrostatic test cannot be carried out, the test can be carried out with compressed air.
