alves are the most common equipment in chemical enterprises. Installing valves may seem simple, but if not carried out in accordance with relevant technologies, it can lead to safety accidents... 
Taboo 1 
The water pressure test was carried out during winter construction at a negative temperature. 
Consequence: During the water pressure test, the pipes quickly froze, causing them to break. 
Measures: Try to conduct the water pressure test before winter construction, and after the test, the water must be completely drained. Especially, the water inside the valves must be completely removed. Otherwise, the valves may get rusty in mild cases or freeze and crack in severe cases. 
When conducting the water pressure test for the project during the winter, it is necessary to maintain a constant indoor temperature throughout the process. After the test, the water must be completely drained. 
Taboo 2 
Before the completion of the pipeline system, the flushing was not done carefully, and the flow rate and speed failed to meet the requirements for pipeline flushing. Even the water pressure strength test drainage was used instead of flushing. 
Consequence: The water quality fails to meet the requirements for the operation of the pipeline system, and in many cases, it may also lead to a reduction in the pipe cross-section or blockage. 
Measures: Use the designed flow rate within the system or a water flow speed of no less than 3 m/s for flushing. The flushing is considered合格if the color and transparency of the water at the outlet are visually consistent with those at the inlet. 
Taboo 3 
The sewage pipes, rainwater pipes and condensate pipes were concealed without undergoing a water-tightness test. 
Consequence: It may cause water leakage and result in losses for the users. 
Measures: The water-tightness test work should be strictly inspected and accepted in accordance with the specifications. For concealed sewage, rainwater, condensation water pipes and other pipelines buried underground, in the ceiling, or between pipes, it is necessary to ensure that there is no leakage. 
Taboo 4 
During the water pressure strength test and tightness test of the pipeline system, only the pressure values and water level changes are observed, which is insufficient for checking for leaks. 
Consequence: After the pipeline system is put into operation, leakage occurs, which affects normal use. 
Measures: When conducting tests on the pipeline system in accordance with design requirements and construction specifications, in addition to recording the pressure values or water level changes within the specified time, special attention should be paid to carefully checking for any leakage issues. 
Taboo 5 
The butterfly valve flange is made using ordinary valve flanges. 
Consequence: The flange of the butterfly valve is of a different size from that of a regular valve. Some of the flanges have a smaller inner diameter, while the valve disc of the butterfly valve is larger. This results in the valve being unable to be opened or being forced to open, causing damage to the valve. 
Measures: The flange disc should be processed according to the actual size of the butterfly valve flange. 
Taboo 6 
During the construction of the building structure, there were no reserved holes or embedded parts, or the reserved holes were too small in size and the embedded parts were not marked. 
Consequence: During the construction of heating and ventilation systems, the building structure is damaged through demolition and chiseling, and even the reinforcing bars are cut, which affects the safety performance of the building. 
Measures: Thoroughly study the construction drawings of the heating and ventilation system. According to the requirements for pipeline and support/hanging frame installation, actively and conscientiously cooperate with the reserved holes and embedded parts reserved during the construction of the building structure. Specifically, refer to the design requirements and the provisions of the construction specifications. 
Taboo 7 
During pipeline welding, after alignment, the pipe misalignment does not lie on the same center line. There is no gap left during alignment. The beveling of thick-walled pipes is not done, and the width and height of the weld do not meet the requirements of the construction specifications. 
Consequences: If the pipe joints are not aligned on the same center line, it will directly affect the welding quality and appearance quality. If there is no gap between the joints, and if the beveling of the thick-walled pipe is not done, and if the width and height of the weld do not meet the requirements, the welding will not meet the strength requirements. 
Measures: After welding the pipes together, the pipes should not be misaligned and should be on the same center line; there should be an opening at the joint; beveling should be done for thick-walled pipes. Additionally, the width and height of the welds should be in accordance with the requirements of the specifications for welding. 
Taboo 8 
The pipelines were directly buried in frozen soil and untreated loose soil. The spacing and position of the pipeline supports were inappropriate, and even a dry brick stacking method was adopted. 
Consequence: Due to the unstable support of the pipeline, it was damaged during the process of compacting the backfill soil, resulting in rework and repair. 
Measures: The pipeline must not be buried in frozen soil or unprocessed loose soil. The spacing of the supporting piers should comply with the construction specifications. The supports should be stable, especially at the pipe joints, where no shear force should be exerted. The brick piers should be constructed with cement mortar to ensure integrity and stability. 
Taboo 9 
The expansion bolts used to fix the pipeline supports are of poor quality. The diameter of the holes where the expansion bolts are installed is too large, or the expansion bolts are installed on brick walls or even lightweight walls. 
Consequence: The pipe supports become loose, causing the pipes to deform or even fall off. 
Measures: Expansion bolts must be of qualified products. If necessary, sampling tests should be conducted. The diameter of the holes for installing expansion bolts should not be greater than the outer diameter of the expansion bolts by 2mm. Expansion bolts should be used on concrete structures. 
Taboo 10 
The flanges and gaskets used for pipe connections are not strong enough, and the connecting bolts are short or have small diameters. For hot water pipes, rubber gaskets are used; for cold water pipes, double-layer gaskets or inclined gaskets are employed, and the flange gaskets protrude into the pipe. 
Consequence: The flange connection is not tight and may even be damaged, resulting in leakage. The flange gasket protruding into the pipe will increase the water resistance. 
Measures: The flanges and gaskets used for the pipelines must meet the design working pressure requirements of the pipelines. 
The flange gaskets for heating and hot water supply pipes should be made of rubber asbestos; the flange gaskets for water supply and drainage pipes should be made of rubber. 
The gasket of the flange must not protrude into the pipe. The outer circle of the gasket should extend to the flange bolt holes. No inclined pads or multiple gaskets should be placed in the middle of the flange. The diameter of the connecting bolts for the flange should be less than 2mm smaller than the diameter of the flange plate hole. The length of the bolt protruding from the nut should be one half of the thickness of the nut.