A valve is a device used in a fluid system to control the direction, pressure, and flow of the fluid. It is a device that allows the flow or stopping of the pipe and the medium (liquid, gas, powder) in the pipe and the equipment and the control of its flow rate. In the process of construction, the way of valve installation will directly affect the normal operation or not in the future. The article recommended today will sum up some matters needing attention in valve installation.
Taboo 1: The main materials, equipment and products used in construction are lack of technical quality appraisal documents or product certificates that conform to the current national or ministerial standards.
The result: The quality of the project is not up to standard, the hidden trouble of accident exists, it cannot be delivered on time, it must be reworked and repaired; the construction period is delayed and the input of labor and material is increased.
Measures: the main materials, equipment and products used in water supply, drainage and heating and sanitary works shall have technical quality appraisal documents or product certificates issued by the State or the Ministry that meet the current standards; their product names, models and specifications shall be indicated. National quality standard code, factory date, manufacturer name and location, factory product inspection certificate or code name.
Taboo 2: The valve does not carry on the necessary quality inspection according to the stipulation before the valve is installed.
Result: Valve switch is inflexible, close is not strict and leakage (steam) appears in the operation of the system, which causes rework and repair, even affects normal water supply (steam).
Measures: pressure strength and tightness test should be done before valve installation. The test shall be carried out on a random basis in each lot (number, specification, model) and not less than one. Strength and tightness tests shall be performed one by one for closed-circuit valves installed on trunk pipes. Valve strength and tightness test pressure shall conform to the Code for acceptance of Construction quality of Building Water supply, drainage and heating Engineering (GB50242-2002).
Taboo 3: Installation valve specifications, models do not meet the design requirements. For example, the nominal pressure of the valve is less than the test pressure of the system; the feed water supply branch adopts the gate valve when the diameter of the pipe is less than or equal to 50mm; the stem of the hot water heating adopts the stop valve; the suction pipe of the fire water pump uses the butterfly valve.
Result: Affect the normal valve opening and closing and regulating resistance, pressure and other functions, and even cause the operation of the system, valve damage is forced to repair.
Measures: be familiar with the application range of various valves, select the specifications and models of the valve 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 pipe diameter of the water supply branch pipe is less than or equal to 50mm, the cut-off valve should be adopted; when the pipe diameter is greater than 50mm, the gate valve should be adopted. The hot water heating dry, the vertical control valve should be used. Use gate valve, fire pump suction pipe should not use butterfly valve.
Taboo 4: Valve installation method is wrong. For example, the water (steam) direction of the globe or check valve is opposite to the mark, the stem is mounted downward, the horizontally installed check valve is installed vertically, the lever of the lever gate or butterfly valve is not opened, closed space, and the stem of the hidden valve does not face the inspection door.
Result: Valve failure, switch maintenance difficulties, stem down often cause leakage.
Measures: strictly according to the valve installation instructions, open gate valve full stem elongation opening height, butterfly valve full consideration of handle rotation space, all kinds of valve rods can not be lower than horizontal position, not down. The hidden valve should not only be equipped to meet the needs of valve opening and closing, but also the stem should be oriented towards the inspection door.
Taboo 5: Butterfly valve flange with ordinary valve flange.
Result:Flange of butterfly valve and flange of common valve differ in size, some flanges have small inner diameter, and the disc of butterfly valve is large, causing failure to open or hard to open and damage the valve.
Measures: the flange should 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 the building structure, or the size of the reserved holes is too small and the embedded parts are not marked.
Result: In the construction of warm-and-guard project, chisel construction structure, even cut off the stressed steel bar, affect the safety performance of the building.
Measures: to be familiar with the construction drawings of warm and sanitary engineering, according to the needs of installation of pipes and suspensions, to actively and conscientiously cooperate with the construction of building structures to reserve holes and embedded parts, and to refer to the design requirements and construction specifications.
Taboo 7: When the pipe is welded, the wrong mouth of the pipe is not on the center line, the gap is not left, the width and height of the weld do not meet the requirements of the construction code.
The result: the wrong mouth of the pipe directly affects the welding quality and perception quality without a central line. Without clearance, thick wall pipe without shovel groove, weld width and height do not meet the requirements of welding strength requirements.
Measures: After welding pipe, the pipe can not be wrong, in a central line, the corresponding should be left clearance, thick wall pipe to shovel groove, in addition, weld width and height should be in accordance with the requirements of the code welding.
Taboo 8: Pipelines are directly buried on frozen soil and untreated loose soil, the spacing and position of piers are improper, and even dry code bricks are used.
Result: The pipe is damaged in the process of backfill compaction due to unstable support, resulting in rework and repair.
Measures: pipes should not be buried on frozen soil and untreated loose soil, the spacing of piers should conform to the requirements of construction code, and the support pad should be reliable, especially in the connection of pipeline, should not bear shear force. Brick piers should be built with cement mortar to ensure integrity and solidity.
Taboo 9: Fixed pipe support expansion bolt material poor, installation expansion bolt aperture too large or expansion bolt installed on brick wall or even light wall.
Result: pipe support loose, pipeline deformation, or even fall off.
Measures: the expansion bolt must choose the qualified product. When necessary, the test should be carried out by sampling. The aperture of the expansion bolt should not be larger than the outer diameter of the expansion bolt 2mm, and the expansion bolt is applied to the concrete structure.
Taboo 10: Pipe connection flange and pad strength is not enough, connecting bolt short or fine diameter. Rubber cushion is used for heat pipe, stone pad is used for cold water pipe, and double cushion or sloping cushion is used for flange lining.
Result: flange joint is not tight, even damaged, leakage phenomenon. The flange liner will increase the flow resistance by projecting into the pipe.
Measures: Pipe flanges and gaskets must meet the pipe design pressure requirements. The flange gasket of heating and hot water supply pipeline should adopt rubber stone cotton cushion, and the flange liner of water supply and drainage pipe should adopt rubber cushion. The gasket of the flange shall not penetrate into the pipe, and its outer circle shall be appropriate to the bolt hole of the flange. Sloping pads or several gaskets shall not be placed in the middle of the flange. The diameter of the bolt connecting the flange shall be less than 2mm than the diameter of the flange, and the length of the bolt rod and nut shall be 1 / 2 of the thickness of the nut.
Taboo 11: In 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.
Result: leakage occurs after the operation of the pipeline system, 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 especially necessary to check carefully whether there are leakage problems.
Taboo 12: Sewage, Rain Water, condensate pipes do not do closed water test to do covert.
Result: May cause leakage and user losses.
Measures: closed water test work should be strictly in accordance with the standard inspection and acceptance. Underground, ceiling, pipe and other hidden sewage, Rain Water, condensation pipe to ensure that no leakage.
Taboo 13: Pipe system before completion of washing is not serious, flow and speed can not meet the requirements of pipe washing. Water pressure strength test is even used to drain water instead of washing.
Result: water quality can not meet the operational requirements of the pipeline system, and often lead to pipeline cross-section reduction or blockage.
Measures: Flush with maximum juice flow rate or no less than 3m/s flow rate in the system. Should be discharged saliva color, transparency and inlet water color, transparency is consistent with the standard.
Taboo 14: Water pressure test under negative temperature during winter construction.
Result: Due to the water pressure test, the tube will freeze quickly.
Measures: try to carry out water pressure test before winter application, and after pressure test to clean water, especially in the valve must remove Yu Jing, otherwise the valve will freeze crack. The project must be carried out at positive indoor temperature during water pressure test in winter, and the water should be blown clean after the test. When water pressure tests cannot be carried out, compressed air can be used for testing.