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The 14 taboos of valve installation!
May 15, 2018

Installing valves is not an easy task. There are 14 contraindications. Do you know? What are the consequences of violating these taboos? And how to solve it?

Taboo 1

Water pressure test is carried out at negative temperature in winter construction.

Consequence: because the pipe freezes rapidly during the hydraulic test, the pipe is frozen.

Measures: try to test the water before the winter, and clean the water after the test, especially the water in the valve must be cleaned, otherwise the valve will freeze.

The project must be carried out in the water pressure test in winter. It should be maintained at room temperature. After testing, the water should be blown clean. When the hydraulic test is not available, the test can be carried out with compressed air.

Taboo 2

Before the completion of the pipeline system, the flushing is not serious, and the flow and speed can not meet the requirements of pipeline washing. Even the water pressure strength test is used to replace the flushing.

Consequences: water quality can not meet the requirements of pipeline system operation, often resulting in pipe cross-section reduction or blockage.

Measures: flush with the maximum juice flow rate in the system or the flow velocity should not be less than 3m / S. It should be qualified that the water color and transparency of the discharge port are consistent with the water color and transparency of the inlet water.

Taboo 3

Sewage, rainwater and condensate pipes are not concealed.

Consequence: it may cause leakage and cause user loss.

Measures: closed water test should be strictly checked and checked according to specifications. Underground burial, ceiling, pipe and other underground sewage, rainwater, condensate pipes and so on to ensure that no leakage.

Taboo 4

Only when the pressure and water level changes are observed in the hydraulic pressure test and tightness test of pipeline system, leakage inspection is not enough.

Consequence: leakage occurs after operation of piping system, affecting normal operation.

Measures: when the pipeline system is tested according to the requirements of the design and the specification of the construction, the pressure value or the change of the water level are recorded in the prescribed time, and the leakage problem is carefully checked.

Taboo 5

The flange plate of the butterfly valve is used for the common valve flange.

Consequences: butterfly valve flange plate and common valve flange size is different, some flanges small diameter, and the butterfly valve large valve, causing failure to open or hard open and make the valve damage.

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

Taboo 6

No holes and embedded parts are reserved 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: in the construction of warm water projects, it is necessary to chisel the structure of the building and even cut the steel bar to affect the safety performance of the building.

Measures: conscientiously familiar with the construction drawings of the warm health engineering, according to the needs of the pipeline and the support and hanger installation, actively cooperate with the construction structure to reserve the hole and the pre embedded parts, and specifically refer to the requirements of the design and the specification of the construction.

Taboo 7

When the pipe is welded, the error of the pipe is not in the center line, the gap is not left, the thick wall pipe does not shovel the groove. The width and height of the weld are not in accordance with the requirements of the construction specification.

Consequence: the pipe's misalignment is not directly affected by the center line and the quality of welding. There is no gap between the two sides, and the thick wall pipe does not scratch the groove. When the width and height of the weld do not meet the requirements, the welding can not meet the requirements of strength.

Measures: after the welding pipe, the pipe can not be wrong, to the center line, the gap should be left, the thick wall pipe should shovel the groove, and the width and height of the weld should be welded in accordance with the requirements of the standard.

Taboo 8

The pipes are directly buried on frozen soil and untreated loosen soil, and the spacing and location of the piers are improper, even dry code bricks are adopted.

Consequence: the pipeline is damaged due to unstable support, resulting in rework and repair.

Measures: the pipe should not be buried in the frozen soil and the untreated pine soil, the pier spacing should conform to the requirements of the construction specifications, the support should be reliable, especially the pipe interface, and should not bear the shear force. Brick pier should be built with cement mortar to ensure integrity and firmness.

Taboo 9

The expansion bolt of the fixed pipe support is inferior in quality, the aperture of the expansion bolt is too large or the expansion bolt is installed on the brick wall or even the light wall.

Consequences: pipe support loosening, pipe 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

The flanges and gaskets connected to the pipes are not strong enough, the connecting bolts are short or the diameter is thin. The thermal pipeline uses rubber mats, cold water pipes use asbestos mats, and double layer pads or inclined pads, and flange gaskets penetrate into the pipes.

Consequences: flange connection is not strict, or even damage, leakage phenomenon. The flange gasket penetrates into the tube, which will increase the resistance of the flow.

Measures: the use of lanes and liners must meet the requirements of piping design working pressure.

Rubber gaskets should be used for flange gaskets in heating and hot water supply pipelines. Rubber gaskets should be used for flange gaskets in water supply and drainage pipelines.

The flange gaskets must not penetrate into the tube, and the outer circle to the flange bolt hole is suitable. In the middle of the flange, no slope pad or several liners should be placed. The diameter of the bolt connecting flange should be less than 2mm, and the length of bolted rod nut should be 1 / 2 of the thickness of the nut.

Taboo 11

The valve installation method is wrong.

For example, the flow direction of the cut-off valve or check valve is opposite to the sign, the stem is mounted downward, the horizontal installation check valve is vertically installed, the rod valve or the butterfly valve handle has no open and closed space, and the valve stem of the dark mounted valve does not face the check door.

Consequences: valve failure, switch maintenance troubleshooting, valve stem tends to cause leakage.

Measures: strictly according to the valve installation instructions to install, the rod valve stem length to open the opening height, the butterfly valve fully consider the handle rotation space, the various valve rods can not be lower than the horizontal position, more can not be down. The hidden valve should not only set up the check door to meet the need of valve opening and closing, but also stem should face the check door.

Taboo 12

The specifications and types of 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 pipe uses the gate valve when the pipe diameter is less than or equal to 50mm; the dry and vertical pipe of the hot water heating uses the cut-off valve; the water suction pipe of the fire pump adopts the butterfly valve.

Consequences: affect the normal valve opening and closing and regulating resistance, pressure and other functions. Even cause the operation of the system, valve damage is forced to repair.

Measures: familiar with the application scope of various valves, and choose the specifications and models of valves according to the design requirements. The nominal pressure of the valve must meet the requirements of the system test pressure. According to construction specifications, the cut-off valve should be adopted when the diameter of water supply branch pipe is less than or equal to 50mm, and gate valve should be adopted when the pipe diameter is larger than 50mm. Hot water heating and vertical control valves should be gate valves, and butterfly valves should not be used for fire pump suction pipes.

Taboo 13

Before the valve installation, the necessary quality inspection is not carried out according to the regulations.

Consequence: the valve switch is inflexible, closed and leaky (steam) occurs during the operation of the system, resulting in rework and repair, and even affects normal water supply (steam).

Measures: pressure and tightness test should be done before valve installation. The test shall be conducted at 10% per batch (the same grade, the same specification and the same type) and not less than one.

For closed circuit valves installed on main pipes, strength and tightness tests shall be done one by one. The test pressure of the valve strength and tightness should conform to the "acceptance criteria for construction quality of building water supply and drainage and heating engineering" (GB 50242-2002).

Taboo 14

The main materials, equipment and products used in construction are lack of technical quality appraisal document or product qualification certificate conforming to the current standards issued by the state or ministry.

Consequences: the quality of the project is not qualified, there is an accident hidden danger, can not be delivered on time, must be reworked and repaired, cause delay in the time of work, and increase the labor and material input.

Measures: the main materials, equipment and products used for water supply and drainage and thermal protection projects should be certified by the state or department in accordance with the current standards for technical quality identification or product qualification; the name, model, specification, national quality standard code, date of factory production, manufacturer's name and place, and factory products shall be marked. A test certificate or code name.