Installation taboo 1:
Taboo:
The main materials, equipment and products used in construction lack technical quality appraisal documents or product certificates that comply with current national or ministerial standards.
Consequences:
The quality of the project is unqualified, there are hidden dangers of accidents, it cannot be delivered on time, and must be reworked and repaired; resulting in delays in the construction period and increased investment in labor and materials.
Measures:
The main materials, equipment and products used in water supply, drainage and heating and sanitation projects should have technical quality appraisal documents or product certificates that comply with current standards issued by the state or the ministry; their product names, models, specifications, and national quality standards should be marked. Code number, date of manufacture, manufacturer’s name and location, factory product inspection certificate or code number.
Installation taboo 2:
Taboo:
Failure to carry out necessary quality inspections according to regulations before valve installation.
Consequences:
During system operation, the valve switches are inflexible, closed tightly and water (steam) leaks occur, causing rework and repair, and even affecting the normal water supply (steam).
Measures:
Before installing the valve, pressure strength and tightness tests should be carried out. The test should randomly check 10% of each batch (same brand, same specification, same model), and no less than one. For closed-circuit valves installed on main pipes with a cutting function, strength and tightness tests should be conducted one by one.
Installation taboo 3:
Taboo:
The specifications and models of the installed valves do not meet the design requirements. For example, the nominal pressure of the valve is less than the system test pressure; gate valves are used when the pipe diameter of the water supply branch pipe is less than or equal to 50mm; stop valves are used for dry and standpipe pipes of hot water heating; butterfly valves are used for fire water pump suction pipes.
Consequences:
Affecting the normal opening and closing of the valve and regulating resistance, pressure and other functions. It may even cause the valve to be damaged and have to be repaired while the system is running.
Measures:
Be familiar with the application range of various types of valves, and select valve specifications and models according to design requirements. The nominal pressure of the valve must meet the system test pressure requirements. According to the requirements of construction specifications: when the diameter of the water supply branch pipe is less than or equal to 50mm, a stop valve should be used; when the pipe diameter is greater than 50mm, a gate valve should be used.
Gate valves should be used for hot water heating dry and vertical control valves, and butterfly valves should not be used for fire water pump suction pipes.
Installation taboo 4:
Taboo:
The valve installation method is wrong. For example, the water (steam) flow direction of the stop valve or check valve is opposite to the sign, and 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. The stem of the concealed valve is installed. Not toward the inspection door.
Consequences:
The valve fails, the switch is difficult to repair, and the valve stem points downward, often causing water leakage.
Measures:
Install strictly in accordance with the valve installation instructions. For rising-stem gate valves, leave sufficient valve stem extension opening height. For butterfly valves, fully consider the handle rotation space. Various valve stems cannot be lower than the horizontal position, let alone downward. Concealed valves must not only be equipped with an inspection door that meets the valve opening and closing requirements, but also the valve stem should be facing the inspection door.
Installation taboo 5:
Taboo:
Use ordinary valve flanges for butterfly valve flanges.
Consequences:
The size of the butterfly valve flange is different from that of the ordinary valve flange. Some flanges have a small inner diameter, while the butterfly valve has a large valve disc, causing the valve to fail to open or open hard, causing damage to the valve.
Measures:
Process the flange plate according to the actual size of the butterfly valve flange.
Installation taboo 6:
Taboo:
When welding pipes, the staggered joints of the pipes after matching are not on the same center line, no gap is left for the matching, thick-walled pipes are not beveled, and the width and height of the weld do not meet the requirements of the construction specifications.
Consequences:
The misalignment of the pipe joints directly affects the welding quality and visual quality. If there is no gap between the joints, no beveling of thick-walled pipes, and the width and height of the weld do not meet the requirements, the welding will not meet the strength requirements.
Measures:
After welding the joints of the pipes, the pipes must not be misaligned and must be on a center line. There should be a gap between the joints. Thick-walled pipes must be beveled. In addition, the width and height of the weld should be welded in accordance with the specifications.
Installation taboo 7:
Taboo:
Pipelines are buried directly in frozen soil and untreated loose soil, the spacing and position of pipeline buttresses are improper, and even dry-coded bricks are used.
Consequences:
Due to unstable support, the pipeline was damaged during the tamping process of backfill soil, resulting in rework and repair.
Measures:
Pipes must not be buried in frozen soil or untreated loose soil. The spacing between buttresses must comply with the requirements of construction specifications. The support pads must be firm, especially the pipe interfaces, which should not bear shear force. Brick buttresses must be built with cement mortar to ensure integrity and firmness.
Installation taboo 8:
Contraindications:
The expansion bolts used to fix pipe supports are made of poor quality, the holes for installing expansion bolts are too large, or the expansion bolts are installed on brick walls or even lightweight walls.
Consequences:
The pipe supports are loose and the pipes are deformed or even fall off.
Measures:
Qualified products must be selected for expansion bolts. If necessary, sampling should be carried out for test inspection. The hole diameter for installing expansion bolts should not be larger than the outer diameter of the expansion bolts by 2 mm. Expansion bolts should be used on concrete structures.
Installation taboo 9:
Taboo:
The flange and gasket of the pipe connection are not strong enough, and the connecting bolts are short or thin in diameter. Use rubber pads for heating pipes, asbestos pads for cold water pipes, double-layer pads or bevel pads, and flange pads protruding into the pipes.
Consequences:
The flange connection is not tight, or even damaged, causing leakage. The flange gasket protrudes into the pipe and increases flow resistance.
Measures:
Pipe flanges and gaskets must meet the requirements of the pipeline design working pressure. Rubber asbestos pads should be used for flange linings of heating and hot water supply pipes; rubber pads should be used for flange linings of water supply and drainage pipes.
The flange gasket must not protrude into the pipe, and its outer circle should reach the flange bolt hole. Bevel pads or several pads must not be placed in the middle of the flange. The diameter of the bolt connecting the flange should be less than 2mm than the flange plate hole diameter. The length of the bolt rod protruding from the nut should be 1/2 of the nut thickness.
Installation taboo 10:
Taboo:
During the hydraulic strength test and tightness test of the pipeline system, only the pressure value and water level changes are observed, and leakage inspection is not enough.
Consequences:
Leakage occurs after the pipeline system is in operation, affecting normal use.
Measures:
When the pipeline system is tested in accordance with the design requirements and construction specifications, in addition to recording the pressure value or water level changes within the specified time, special attention should be paid to carefully checking whether there is any leakage problem.
Installation taboo 11:
Taboo:
Sewage, rainwater, and condensate pipes should be concealed without performing water closure tests.
Consequences:
Water leakage may occur and user losses may occur.
Measures:
The closed water test work should be inspected and accepted strictly in accordance with the specifications. Concealed sewage, rainwater, condensate water pipes, etc. buried underground, in suspended ceilings, between pipes, etc. must be ensured to ensure no leakage.
Installation taboo 12:
Taboo:
The pipeline system is not flushed carefully before completion, and the flow rate and speed cannot meet the pipeline flushing requirements. Even water pressure test draining is used instead of flushing.
Consequences:
The water quality does not meet the operating requirements of the pipeline system, which often results in reduced or blocked pipeline cross-section.
Measures:
Use the maximum juice flow rate in the system or a water flow speed of not less than 3m/s for flushing. The discharge water color and transparency should be consistent with the color and transparency of the inlet water according to visual inspection.
Installation taboo 13:
Taboo:
During winter construction, hydrostatic tests should be carried out under negative temperatures.
Consequences:
Because the pipe quickly freezes during the hydraulic pressure test, the pipe freezes.
Measures:
Try to conduct a hydraulic pressure test before winter application, and blow out the water after the pressure test. In particular, the water in the valve must be cleared, otherwise the valve will freeze and crack. When the water pressure test of the project must be carried out in winter, the indoor temperature must be maintained at a positive temperature, and the water must be blown away after the pressure test. When hydraulic testing is not possible, compressed air can be used for testing.
