Taboos and Measures of Drainage Valve Pipeline Construction
1: The main materials, equipment and products used in construction are short of technical quality appraisal documents or product certificates that meet the current standards issued by the state or ministry. Consequences: The quality of the project is not up to standard, there are hidden dangers of accidents, can not be delivered on time for use, must be repaired, resulting in delays in the construction period, increased investment in labor and materials. Measures: The main materials, equipment and products used in water supply, drainage and heating and sanitation projects shall be technical quality appraisal documents or product qualification certificates issued by the state or ministry in accordance with the current standards; the product name, model, specifications, national quality standard code, date of departure, name and location of the manufacturer, inspection certificate or code of the manufacturer shall be marked.
2: The necessary quality inspection is not carried out before the valve is installed. Consequences: In the operation of the system, the valve switch is not flexible, the closure is not strict and the phenomenon of water leakage (steam) occurs, resulting in rework repair, and even affecting the normal water supply (steam). Measures: Before valve installation, compressive strength and tightness test should be done. The test shall be carried out in 10% of the quantity of each batch (same brand, same specification, same model), and not less than one batch. Strength and tightness tests should be done one by one for the closed-circuit valves installed on the main pipe to cut off. Valve strength and tightness test pressure should comply with the “Code for Acceptance and Acceptance of Construction Quality of Building Water Supply and Drainage and Heating Engineering” (GB 50242-2002) Or other required ISO/EN/ANSI standard.
3: Installation valve specifications, models do not meet the design requirements. For example, the nominal pressure of the valve is less than the system test pressure; when the diameter of the feedwater branch pipe is less than or equal to 50 mm, the gate valve is used; the dry and riser of hot water heating adopts the stop valve; and the suction pipe of fire pump adopts the butterfly valve. Consequences: Affect the normal opening and closing of valves and adjust resistance, pressure and other functions. Even in the operation of the system, valve damage is compelled to be repaired. Measures: Familiar with the application scope of various types of valves, according to the design requirements to select the specifications and models of valves. The nominal pressure of the valve should meet the requirements of the system test pressure. According to the requirements of construction specifications: cut-off valves should be used when the diameter of feedwater branch pipe is less than or equal to 50 mm, and gate valves should be used when the diameter of pipe is greater than 50 mm. Gate valves shall be used for hot water heating, dry and vertical control valves, and butterfly valves shall not be used for fire pump suction pipes.
4: Error in valve installation. For example, the water (steam) flow direction of globe valve or check valve is opposite to the mark, the stem is installed downward, the check valve installed horizontally is installed vertically, the open stem gate valve or butterfly valve handle has no open or closed space, and the stem of the concealed valve does not face the check door. Consequences: Valve failure, switch maintenance difficulties, valve stem downward often cause leakage. Measures: Install the valve strictly according to the installation instructions. Open-stem gate valve keeps the stem elongation open height. Butterfly valve fully considers the rotating space of the handle. Various valve rods should not be lower than the horizontal position, let alone downward. Undercover valves should not only be equipped with check doors to meet the needs of valve opening and closing, but also the stem should be oriented towards the check door.
5: butterfly valve flange with ordinary valve flange. Consequences: The size of butterfly valve flange is different from that of common valve flange. Some flanges have small inner diameter, while the butterfly valve disc is large, which results in valve failure or rigid opening. Measures: According to the actual size of butterfly valve flange processing flange.
6: No holes and embedded parts are reserved in the construction of building structures, or the size of the reserved holes is too small and the embedded parts are not marked. Consequences: In the construction of heating and sanitation projects, the safety performance of buildings is affected by chipping the building structure, or even cutting the stressed steel bars. Measures: Familiar with the construction drawings of heating and sanitation projects, according to the installation needs of pipelines and hangers, actively and conscientiously cooperate with the reserved holes and embedded parts in the construction of building structures, referring specifically to the design requirements and construction specifications.
7: When the pipeline is welded, the misalignment of the pipe behind the counterpart is not on a central line, the gap is not left in the counterpart, the groove of the thick-walled pipe is not shoveled, and the width and height of the weld seam do not meet the requirements of the construction specifications. Consequences: The absence of pipe misalignment in a central line directly affects the welding quality and sensory quality. When the width and height of the weld do not meet the requirements, the weld strength can not meet the requirements. Measures: After welding the pipe alignment, the pipe should not be misaligned. In a central line, the pipe alignment should be cleared, and the thick-walled pipe should be shoveled. In addition, the width and height of the weld should be welded in accordance with the specifications.
8: Pipeline is directly buried in frozen soil and untreated loose soil. Pipeline pier spacing and location are inappropriate, even in the form of dry bricks. Consequences: Pipeline is damaged during backfill compaction due to unstable support, resulting in rework repair. Measures: Pipeline shall not be buried in frozen soil or untreated loose soil, pier spacing shall conform to the requirements of construction specifications, and supporting cushions shall be firm, especially at pipe interfaces, and shall not bear shear stress. Brick piers should be built with water and sediment slurry to ensure integrity and firmness.
9: The material of expansion bolt for fixing pipe bracket is inferior, the hole diameter of expansion bolt is too large or expansion bolt is installed on brick wall or even light wall. Consequences: Pipeline support loosened, pipeline deformation, or even fall off. Measures: Expansion bolts must select qualified products, and should be sampled for testing if necessary. The hole diameter of the expansion bolts should not be greater than 2 mm. Expansion bolts should be applied to concrete structures.
10: Pipeline connection flange and gasket strength is not enough, connecting bolt short or thin diameter. Rubber cushion is used in thermal pipe, asbestos cushion is used in cold water pipe, double cushion or inclined cushion is used, and flange cushion is protruded in pipe. Consequences: The flange connection is not tight, or even damaged, resulting in leakage. Flange liner penetrating into the pipe will increase the flow resistance. Measures: Flange and liner for pipeline must meet the requirement of pipeline design working pressure. Rubber asbestos pad is suitable for flange pad of heating and hot water supply pipeline, and rubber pad is suitable for flange pad of water supply and drainage pipeline. The liner of the flange shall not protrude into the pipe, and the outer circle of the liner shall reach the bolt hole of the flange. No oblique cushion or several gaskets should be placed in the middle of the flange. The bolt diameter of connecting flange should be less than 2 mm than that of flange hole, and the length of bolt protruding nut should be 1/2 of the nut thickness.
11: In the hydraulic strength test and tightness test of pipeline system, only the change of pressure and water level is observed, and the leakage inspection is not enough. Consequences: Leakage occurs after pipeline system operation, which affects normal operation. Measures: When the pipeline system is tested according to the design requirements and construction specifications, besides recording the pressure or water level changes within the specified time, it is particularly necessary to carefully check whether there is leakage.
12: Sewage, rainwater and condensate pipes are concealed without water closure test. Consequences: It may cause leakage and user losses. Measures: Closed water test should be checked and accepted strictly in accordance with the specifications. Underground burial, suspension roof, pipes and other hidden sewage, rainwater, condensate pipes, etc. to ensure that no leakage.
13: Pipeline flushing before completion is not serious, flow and speed can not meet the requirements of pipeline flushing. It even replaces flushing with hydraulic strength test. Consequences: Water quality can not meet the operation requirements of the pipeline system, often resulting in the reduction or blockage of the pipeline cross-section. Measures: Rinse with the maximum set juice flow rate or flow rate not less than 3m/s in the system. The discharge water color, transparency and the intake water color, transparency visual measurement should be qualified.
14: Water pressure test under negative temperature for winter construction. Consequences: Because the tube freezes quickly during the hydraulic test, the tube is frozen out. Measures: Water pressure test should be carried out as far as possible before winter operation, and water should be blown clean after pressure test, especially the water in the valve must be cleared, otherwise the valve will freeze and crack. The project must be carried out under positive indoor temperature during hydraulic test in winter, and the water should be blown clean after pressure test. Compressed air can be used when hydraulic test cannot be carried out.