Taboo 1: The main materials, equipment and products used in construction are lack of technical quality identification documents or product certificates that meet the current national or ministerial standards.

Consequences: The project quality is unqualified, there are potential accidents, and it cannot be delivered for use on schedule, and it must be reworked and repaired; The construction period is delayed and the labor and material input is increased.

Measures: The main materials, equipment and products used in the water supply and drainage and heating and sanitation engineering should have technical quality identification documents or product certificates that meet the current standards issued by the state or ministry; The product name, model, specification, national quality standard code, delivery date, name and location of manufacturer, and inspection certificate or code of ex-factory products shall be indicated.

Taboo 2: The soft seal butterfly valve is not subject to necessary quality inspection before installation.

Consequences: During the system operation, the soft seal butterfly valve switch is not flexible, the closing is not tight, and water (steam) leakage occurs, resulting in rework and repair, and even affecting the normal water supply (steam).

Measures: Before the installation of the soft seal butterfly valve, the pressure strength and tightness test shall be carried out. 10% of each batch (the same brand, specification and model) shall be sampled for the test, and no less than one. For closed-circuit soft seal butterfly valves installed on the main pipe to cut off, strength and tightness tests shall be carried out one by one. The strength and tightness test pressure of the soft seal butterfly valve shall comply with the provisions of Code for Acceptance of Construction Quality of Building Water Supply, Drainage and Heating Engineering (GB 50242-2002).

D71X manual wafer type soft seal butterfly valve

Taboo 3: The specification and model of installing the soft seal butterfly valve do not meet the design requirements. For example, the nominal pressure of the soft seal butterfly valve is less than the system test pressure; When the pipe diameter of the water supply branch pipe is less than or equal to 50mm, the gate valve is used; The main and riser pipes of hot water heating adopt stop valves; The suction pipe of fire pump adopts butterfly valve.

Consequence: It affects the normal opening and closing of the soft seal butterfly valve and the adjustment of resistance, pressure and other functions. Even in the system operation, the soft seal butterfly valve was damaged and forced to be repaired.

Measures: Be familiar with the application scope of various soft seal butterfly valves, and select the specifications and models of soft seal butterfly valves according to the design requirements. The nominal pressure of the soft seal butterfly valve shall meet the requirements of the system test pressure. According to the requirements of construction specifications: stop valves shall be used for water supply branch pipes with diameter less than or equal to 50mm; Gate valve shall be used when the pipe diameter is greater than 50mm. Gate valves shall be used for dry and vertical control valves of hot water heating, and butterfly valves shall not be used for suction pipes of fire water pumps.

Taboo 4: The installation method of soft seal butterfly valve is wrong. For example, the water (steam) flow direction of the stop valve or check valve is opposite to the sign, the valve rod is installed downward, the check valve installed horizontally is installed vertically, the handle of the rising stem gate valve or butterfly valve has no opening and closing space, and the valve rod of the concealed soft seal butterfly valve does not face the inspection door.

Consequences: The soft seal butterfly valve fails, the switch is difficult to repair, and the valve stem is downward, which often causes water leakage.

Measures: The installation shall be carried out in strict accordance with the installation instructions of the soft seal butterfly valve. The rising stem gate valve shall have sufficient valve stem extension opening height. The butterfly valve shall fully consider the handle rotation space. The various soft seal butterfly valve stems shall not be lower than the horizontal position, let alone downward. Concealed soft seal butterfly valve shall not only be equipped with inspection door meeting the opening and closing requirements of soft seal butterfly valve, but also the valve rod shall face the inspection door.

Taboo 5: The butterfly valve flange shall be ordinary soft seal butterfly valve flange.

Consequences: The size of the butterfly valve flange is different from that of the ordinary soft seal butterfly valve. Some flanges have small inner diameter, while the butterfly valve disc is large, which causes the soft seal butterfly valve to be damaged because it cannot be opened or hard to open.

Measures: The flange plate shall be processed according to the actual size of the butterfly valve flange.

Taboo 6: There are no reserved holes and embedded parts in the construction of building structure, or the reserved holes are too small and the embedded parts are not marked.

Consequences: During the construction of the heating and sanitation project, the building structure is chiseled, and even the stressed reinforcement is cut off, affecting the safety performance of the building.

Measures: Be familiar with the construction drawings of heating and sanitation works, actively and carefully cooperate with the construction of reserved holes and embedded parts in the building structure according to the needs of the installation of pipes and supports and hangers, and refer to the design requirements and construction specifications for details.

Taboo 7: During pipe welding, the staggered joint of the pipe is not on the same center line after the alignment, no gap is left for the alignment, the thick wall pipe is not beveled, and the width and height of the weld do not meet the requirements of the construction specification.

Consequence: The misalignment of the pipe is not at the same center line, which directly affects the welding quality and appearance quality. There is no gap in the butt joint, the thick wall pipe is not beveled, and the welding cannot meet the strength requirements when the width and height of the weld do not meet the requirements.

Measures: After welding the pipe butt joint, the pipe shall not be staggered, and the butt joint shall be on a central line. The gap shall be reserved. The thick wall pipe shall be beveled. In addition, the width and height of the weld shall be welded according to the specification requirements.

Taboo 8: The pipeline is directly buried on frozen soil and untreated loose soil, and the spacing and position of pipeline buttresses are improper, even in the form of dry bricks.

Consequence: due to the unstable support, the pipeline was damaged in the process of backfill compaction, resulting in rework and repair.

Measures: The pipeline shall not be buried on frozen soil and untreated loose soil. The spacing of buttresses shall meet the requirements of construction specifications. The buttresses shall be firm, especially at the pipeline interface, and shall not bear shear force. Brick buttress shall be built with cement mortar to ensure integrity and firmness.

Taboo 9: The expansion bolt used to fix the pipe support is of poor material, the hole diameter for installing the expansion bolt is too large, or the expansion bolt is installed on the brick wall or even the light wall.

Consequence: The pipe support is loose, and the pipe is deformed, even falling off.

Measures: The expansion bolts must be qualified products. If necessary, samples shall be taken for test and inspection. The hole diameter of the expansion bolts installed shall not be greater than the outer diameter of the expansion bolts by 2mm. The expansion bolts shall be applied to the concrete structure.

Taboo 10: The strength of the flange plate and gasket connected to the pipeline is not enough, and the connecting bolt is short or the diameter is thin. Rubber gaskets are used for heating pipes, asbestos gaskets are used for cold water pipes, and double-layer gaskets or inclined gaskets are used. Flange gaskets protrude into the pipes.

Consequence: The flange connection is not tight, even damaged, and leakage occurs. The flange gasket protrudes into the pipe, which will increase the water flow resistance.

Measures: The flange plate and gasket of the pipeline must meet the requirements of the design working pressure of the pipeline. The flange gasket of heating and hot water supply pipeline should be rubber asbestos pad; The flange gasket of water supply and drainage pipeline should be rubber gasket. The gasket of the flange shall not protrude into the pipe, and its outer circle shall reach the flange bolt hole. Bevel pad or several gaskets shall not be placed in the middle of the flange. The diameter of the bolt connecting the flange should be less than 2mm than the hole diameter of the flange plate. The length of the bolt rod protruding from the nut should be 1/2 of the nut thickness.

Taboo 11: During the hydraulic strength test and tightness test of the pipeline system, only observe the pressure value and water level change, and the leakage inspection is not enough.

Consequence: leakage occurs after the pipeline system operates, affecting the normal use.

Measures: 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 necessary to carefully check whether there is leakage.

Taboo 12: sewage, rainwater and condensate pipes shall be concealed without closed water test.

Consequence: It may cause water leakage and user losses.

Measures: The closed water test shall be inspected and accepted in strict accordance with the specifications. The concealed sewage, rainwater and condensate pipes buried underground, in the ceiling and in the pipe room shall ensure no leakage.

Taboo 13: The pipeline system is not washed carefully before completion, and the flow and speed cannot meet the requirements of pipeline flushing. Even the hydraulic strength test is used to discharge water instead of flushing.

Consequence: The water quality can not meet the operation requirements of the pipeline system, which often leads to the reduction or blockage of the pipeline section.

Measures: flush with the maximum set juice flow in the system or the water flow rate that should not be less than 3m/s. The color and transparency of the outlet water shall be consistent with that of the inlet water through visual inspection.

Taboo 14: water pressure test shall be conducted under negative temperature during winter construction.

Consequence: The pipe freezes due to the rapid freezing in the pipe during the hydraulic test.

Measures: try to carry out the hydraulic test before winter construction, and blow out the water after the pressure test, especially the water in the soft seal butterfly valve must be cleaned, otherwise the soft seal butterfly valve will freeze and crack. When the hydraulic test of the project must be carried out in winter, it should be carried out at a positive indoor temperature, and the water should be blown out after the pressure test. When the hydraulic test cannot be carried out, compressed air can be used for the test.