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Fourteen items for attention in valve installation


When installing the valve, pay attention to the following fourteen items:
The main materials, equipment and products used in the construction lack technical quality appraisal documents or product qualification certificates that meet the current standards issued by the state or the ministry.

Consequences: The quality of the project is not up to standard, there are hidden dangers of accidents, and it cannot be delivered on time and must be reworked for repairs; resulting in delays in the construction period and increased labor and material input.

Measures: The main materials, equipment and products used in water supply and drainage and heating and sanitary projects should have technical quality appraisal documents or product qualification certificates that meet the current standards issued by the state or the ministry; their product names, models, specifications, and national quality standards should be marked. Code, date of manufacture, name and location of the manufacturer, inspection certificate or code of the manufactured product.

two,valveNecessary quality inspections are not carried out as specified before installation.

Consequences: The valve switch is not flexible during the system operation, the closing is not strict and water (steam) leakage occurs, resulting in rework and repair, and even affecting the normal water supply (steam).

Measures: Before the valve is installed, the compressive strength and tightness test should be done. For the test, 10% of the quantity of each batch (same brand, same specification, same model) shall be randomly checked, and not 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. The strength and tightness test pressure of the valve shall comply with the “Code for Acceptance of Construction Quality of Building Water Supply and Drainage and Heating Engineering” (GB 50242-2002).

three,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; when the water supply branch pipe diameter is less than or equal to 50mm, thegate;Dry and riser pipes for hot water heating useShut-off valve;fire pumpSuction pipe adoptsButterfly valve.

Consequences: 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.

Measures: Be familiar with the application range of various valves, and select the specifications and models of the valves according to the 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.

Four,Valve installation method is wrong.such as shut-off valves orcheck valveThe water (steam) flow direction is opposite to the sign, the valve stem is installed downward, the check valve installed horizontally is installed vertically, the handle of the gate valve or butterfly valve has no opening and closing space, and the valve stem of the concealed valve is not facing the inspection door.

Consequences: the valve fails, the switch is difficult to repair, and the valve stem is facing down, which often causes water leakage.

Measures: Strictly follow the valve installation instructions to install, the rising stem gate valve leaves enough valve stem to extend the opening height, the butterfly valve fully considers the handle rotation space, and the 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.

five,Common valve flanges are used for butterfly valve flanges.

Consequences: the size of the flange of the butterfly valve is different from that of the ordinary valve. 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.

Measures: Process the flange according to the actual size of the butterfly valve flange.

six,There are no reserved holes and embedded parts in the construction of the building structure, or the size of the reserved holes is too small and the embedded parts are not marked.

Consequences: During 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.

Measures: 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.

seven,When the pipes are welded, the staggered joints of the pipes are not on the same center line after the counterparts, no gaps are left for the counterparts, and the thick-walled pipes are not shoveled, and the width and height of the welds do not meet the requirements of the construction specification.

Consequences: the misalignment of the pipe directly affects the welding quality and visual 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.

Measures: After welding the counterparts of the pipes, the pipes should not be staggered. They should be on the same center line, and the counterparts should be left with a gap. 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.

Eight,The pipeline is directly buried on the frozen soil and untreated loose soil, and the spacing and position of the pipeline piers are improper, even in the form of dry yard bricks.

Consequences: Due to the unstable support, the pipeline was damaged during the backfill compaction process, resulting in rework and repair.

Measures: The pipeline shall not be buried on the frozen soil and untreated loose soil, the spacing of the buttresses shall meet the requirements of the construction specification, and the support pads shall be firm, especially the pipe joints, which should not be subjected to shearing force. Brick buttresses shall be built with cement mortar to ensure integrity and firmness.

Nine,The material of the expansion bolts for fixing the pipeline supports is poor, the hole diameter of the expansion bolts is too large, or the expansion bolts are installed on brick walls or even lightweight walls.

Consequences: the pipe support is loose, the pipe is deformed, or even falls off.

Measures: Qualified products must be selected for expansion bolts, and samples should be tested for inspection if necessary. The diameter of the installation expansion bolts should not be larger than the outer diameter of the expansion bolts by 2mm, and the expansion bolts should be used on concrete structures.

ten,The flanges and gaskets of the pipeline connection are not strong enough, and the connecting bolts are short or small in diameter. Rubber pads are used for heat pipes, asbestos pads are used for cold water pipes, and double-layer pads or inclined pads are used, and the flange gaskets protrude into the pipes.

Consequences: The flange connection is not tight, or even damaged, and leakage occurs. Flange gaskets protrude into the pipe, increasing the resistance to water flow.

Measures: The flanges and gaskets used for the pipeline 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 connecting the flange should be smaller than the diameter of the flange plate by 2mm, and the length of the nut protruding from the bolt rod should be 1/2 of the thickness of the nut.

eleven,In the hydraulic strength test and tightness test of the pipeline system, only the pressure value and the water level change are observed, and the leakage inspection is not enough.

Consequences: leakage occurs after the operation of the pipeline system, which affects 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 the water level change within the specified time, it is especially necessary to carefully check whether there is any leakage problem.

twelve,Sewage, rainwater and condensate pipes are concealed without a closed water test.

Consequences: It may cause water leakage and cause user losses. 90

Measures: 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.

Thirteen,Before the completion of the pipeline system, the flushing is not serious, and the flow and speed cannot meet the requirements of pipeline flushing. Even flushing is replaced by water pressure test drainage.

Consequences: 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.

Measures: Flush with a larger juice flow rate in the system or a water flow rate 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.

fourteen,In winter construction, the hydraulic test is carried out at negative temperature.

Consequences: The tube freezes due to the rapid freezing of the tube during the hydrostatic test.

Measures: try to carry out the water pressure test before winter application, and blow the water after the pressure test, especially the water in the valve must be cleaned, 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.
The above are the fourteen items that must be paid attention to when installing the valve.


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