Drainage valve, pipeline construction taboos and measures

Taboo 1: The main materials, equipment, and products used for construction are lacking in technical quality appraisal documents or product certifications that meet national or ministerial standards. Consequences: The quality of the project is unqualified and there are potential accidents. It cannot be delivered on schedule and must be reworked and repaired. It will result in delays in construction and increase in labor and material inputs. Measures: The main materials, equipment and products used in water supply, drainage, and heat and sanitation projects shall have technical quality appraisal documents or product certifications that meet the current standards issued by the State or the Ministry; the product names, models, specifications, and national quality standards shall be indicated. Code, date of manufacture, manufacturer's name and location, factory product inspection certificate or code number.

    Taboo 2: Before the valve is installed, the necessary quality inspection is not performed as required. Consequences: In the system operation, the valve switch is inflexible, and the phenomenon of lax shutoff and leakage (steam) occurs, resulting in rework repairs and even affecting the normal water supply (steam). Measures: Prior to installation of the valve, pressure strength and tightness tests should be performed. The test shall be randomized by 10% and not less than one in each lot (same brand, same specification, same model). For closed-circuit valves that are installed on the trunk pipe to cut off, strength and tightness tests should be performed one by one. The test pressure of the valve strength and tightness shall be in accordance with the “ Code for Acceptance of Construction Quality of Building Water Supply and Drainage and Heating Engineering” (GB 50242-2002).

    Taboo 3: 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; the water supply branch pipe adopts the gate valve when the pipe diameter is less than or equal to 50mm ; the hot water heating stem and the riser adopt the stop valve ; the fire pump suction pipe uses the butterfly valve . Consequences: affect the normal opening and closing of the valve and adjust the resistance, pressure and other functions. Even causing the system to run, valve damage was forced to repair. Measures: Familiar with the application range of various types of valves, select the valve specifications and models according to the design requirements. The nominal pressure of the valve must meet the requirements of the system test pressure. According to the requirements of construction specifications, the stop valve shall be used when the diameter of the water supply branch pipe is less than or equal to 50 mm, and the gate valve shall be adopted when the diameter of the branch pipe is greater than 50 mm . Hot water heating dry, vertical control valve should be used gate valve, fire pump suction pipe should not use the butterfly valve .

    Taboo 4: Wrong valve installation method. For example, the shutoff valve or check valve water (vapour) flow direction is opposite to the sign, the valve stem is installed downwards, the horizontally installed check valve is installed vertically, the open lever valve or butterfly valve handle does not open and close the space, the valve stem of the valve is concealed Do not face the inspection door. Consequences: Failure of the valve, difficulty in repair and maintenance of the switch, and leakage of the valve stem downward. Measure: Strictly follow the valve installation instructions for installation. The stem valve should be left open for the stem to open. The butterfly valve should fully consider the handle rotation space. Various valve stems must not be lower than the horizontal position, and they must not be downward. The concealed valve must not only be equipped with an inspection door that meets the valve opening and closing requirements, but also the valve stem should face the inspection door.

    Taboo 5: Butterfly valve flange flange with ordinary valve. Consequences: The size of the butterfly valve flange and the ordinary valve flange are different. Some flanges have small internal diameters, and the valve of the butterfly valve is large, causing the valve to be opened or hard to open and causing damage to the valve. Action: The flange plate must be machined to the actual size of the butterfly valve flange.

    Taboo 6: There are no holes and embedded parts in the construction of the building structure, or the size of the holes is too small and the embedded parts are not marked. Consequences: During the construction of the warm and sanitary project, the construction structure was cut out and even the reinforced steel bar was cut off, affecting the safety performance of the building. Measures: Gradually familiarize with the construction drawings of the warm and sanitary project. In accordance with the requirements for the installation of pipelines and support hangers, take the initiative to seriously cooperate with the construction of the structure to reserve holes and embedded parts, with specific reference to the design requirements and construction specifications.

    Taboo 7: When the pipeline is welded, the wrong pipe is not on a centerline after the mouthpiece, and no gap is left between the counterparts. The thick-walled pipe does not dig the groove. The width and height of the weld do not meet the construction specifications. Consequences: Pipe misalignment does not directly affect the quality of welding and perception of quality in a centerline. No gap is left on the counterpart, and the thick-walled pipe does not shovel the groove. When the width and height of the weld do not meet the requirements, the welding cannot meet the strength requirements. Measure: After welding the pipelines to the mouth, the pipes should not be misaligned. A gap should be left on the centerline. The thick-walled pipe must be grooved. The width and height of the welds should be welded in accordance with the specifications.

    Taboo 8: The pipeline is directly buried in frozen soil and loose soil that has not been treated. The distance and location of the piers of the pipelines are improper, and even dry bricks are used. Consequences: Due to unstable support, the pipeline is damaged during the compaction of the backfill soil, causing rework and repairs. Measures: The pipeline shall not be buried in frozen soil and untreated loose soil. The distance between the support piers shall meet the requirements of the construction specifications. The support cushion shall be secure, especially the interface of the pipeline, and shall not be subject to shear forces. Brick support piers should be built with cement mortar to ensure integrity and firmness.

    Taboo 9: The expansion bolts of the fixed pipe brackets are of poor quality, the holes for installing expansion bolts are too large, or the expansion bolts are installed on brick walls or even light walls. Consequences: The pipe supports are loose and the pipes are deformed and even fall off. Measures: The expansion bolts must be selected as qualified products. If necessary, samples should be taken for inspection. The diameter of the installation expansion bolts should not exceed 2mm of the outer diameter of the expansion bolts. The expansion bolts should be applied to concrete structures.

    Taboo 10: The strength of flanges and gaskets for pipe connections is not enough. The connection bolts are short or have a small diameter. The heat pipes use rubber mats, cold water pipes use asbestos mats, and double mats or beveled mats. The flange gasket protrudes inside the pipe. Consequences: Flange joints are not tight or even damaged, causing leakage. The flange gasket protrudes into the tube, increasing the resistance to water flow. Measures: The flanges and gaskets for the pipeline must meet the requirements of the pipeline design work pressure. Flange gaskets for heating and hot water supply pipes should be made of rubber asbestos pads; flange gaskets for water supply and drainage pipes should be rubber pads. The gasket of the flange must not protrude into the pipe. It is advisable to round the flange to the bolt hole of the flange. No bevel pad or several spacers shall be placed in the middle of the flange. The bolt diameter of the connecting flange should be less than 2mm than the flange hole diameter, and the bolt nut protruding length should be 1/2 of the nut thickness.

    Taboo 11: When testing the hydraulic strength and stringency of the piping system, only the pressure and water level changes are observed, and the leakage check is not enough. Consequences: Leakage occurs after the piping system is in operation, affecting normal operation. Measures: When the piping 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 any leakage problem.

    Taboo 12: Contaminated water, rainwater and condensate pipes are concealed without closing the water test. Consequences: May cause water leakage and cause user loss. Measures: Closed water test should be strictly checked and accepted according to specifications. Underground sewage, rainwater, condensate pipes, etc. shall be installed underground, in ceilings, and between pipes to ensure that no leakage occurs.

    Taboo 13: The piping system is not washed properly before it is completed, and the flow rate and speed do not meet the pipeline flushing requirements. Even with water pressure test discharge instead of flushing. Consequences: The water quality does not meet the operational requirements of the pipeline system and often results in reduced or blocked pipe sections. Action: Flush with the maximum juice flow rate in the system or at a flow rate not less than 3m/s. The exit color, transparency and inlet water color and transparency shall be qualified as visual inspection.

    Taboo 14: Water pressure test at negative temperature during winter construction. Consequences: Due to the rapid freezing of the tube during the hydrostatic test, the tube was frozen. Measures: Try to conduct hydrostatic test before winter application, and blow the water after pressure test, especially the water in the valve must be cleared, otherwise the valve will be cracked. The project must be carried out during the hydrostatic pressure test in winter and it should be kept at a positive temperature inside the room. When hydrostatic test cannot be performed, it can be tested with compressed air.