Taboos and Correct Remedial Measures for Installation of Valves

Date:Aug 23, 2019

Many of the valves on the factory pipes are installed by professional valve installation companies. This article is mainly for the owners of valve installations and the owners who are prone to problems with valves.

There are many factors that cause the valve to be easily damaged, such as the quality of the valve itself, the improper selection of the valve, or the influence of the environment on the valve. In order to enable the valve to operate normally for a long time and avoid unnecessary losses in production, in addition to the factors mentioned above, we must do the corresponding measures in the early stage of valve operation. The canal valve lists the results of improper operation of some common valves and the corresponding remedies:

Taboo 1. The winter building is subjected to hydrostatic pressure test at negative temperature.

Consequences: Due to the hydrostatic test, the pipe quickly freezes.

Measures: Try to test the water pressure before the winter, and test the pressure to clean, especially in the valve water, the net must be removed, otherwise the valve will be frozen and cracked. The project must be hydrostatically tested during the winter to maintain room temperature and to be flushed after testing pressure. When the hydrostatic test is not possible, compressed air can be used for testing.

Contraindications 2. The piping system is not severe before it is flushed, and the flow rate and speed do not meet the requirements for pipeline flushing. Even if you use the hydraulic strength test discharge, do not rinse.

Consequences: The water quality does not meet the operational requirements of the pipeline system, which often leads to a reduction or blockage of the pipeline.

Action: Flush with maximum juice flow in the system or flow should not be less than 3 m/s. It should be defined by the visual consistency of the water color of the outlet, the transparency and the transparency of the entrance.

Taboo 3, sewage, rainwater, condensate water pipes do not do confined water to try to conceal.

Consequences: May cause leakage and loss of users.

Measures: The closed water test should be carried out in strict accordance with the standard. Underground burial, ceiling, Prince and other dark sewage, rainwater, condensate water pipes, etc., to ensure no leakage and leakage.

Contraindications 4, hydraulic strength test and tightness test of the pipeline system, only the pressure value and water level change are observed, and the leak check is insufficient.

Consequences: Leakage occurs after the piping system is in operation, affecting normal use.

Measures: The piping system is tested according to the required design and construction specifications. In addition to recording pressure or water level changes at specified times, it is especially necessary to carefully check for leaks.

Taboo 5, butterfly valve flange and ordinary valve flange.

Consequences: Butterfly valve flange and common valve flange size, some flange diameter is small, butterfly valve disc is large, causing open or hard opening and valve damage.

Action: Follow the actual size of the butterfly valve flange to machine the flange.

Contraindications 6. There are no reserved holes and embedded parts in the structure of the structure, or the size of the reserved holes is small, and the embedded parts are not marked.

Consequences: During the construction of the preheating project, the structure was cut and the joint reinforcement was cut off, which affected the safety performance of the building.

Measures: Be familiar with the construction drawings of the warm engineering project. According to the needs of the installation of the pipeline and the supporting hanger, actively cooperate with the reserved holes and embedded parts of the building structure, with specific reference to the design requirements and construction specifications.

Taboo 7, tube welding, after the wrong mouth is not the center line, relatively no gap, thick wall tube is not shovel, weld width, height does not meet the construction specifications.

Consequences: The wrong port of the pipe does not directly affect the quality of the weld and the quality of the perception. Relatively no gap is left, the thick-walled pipe does not shovel, the weld width and height do not meet the requirements, the welding does not reach the strength requirement.

Measures: After the welded pipe, the pipe can not be staggered, to a neutral line, the corresponding side should leave the gap, the thick wall pipe to the shovel, the width of the weld, the height should be welded according to the required specifications.

Taboo 8, the pipeline is directly buried in the frozen soil, no treatment, the spacing and position of the pipe pier is not appropriate, even in the form of dry code bricks.

Result: Due to the instability of the support, the pipeline is damaged and the repair of the rework is caused by the backfill compaction process.

Measures: The pipeline should not be buried in the frozen soil, and the loose soil should not be treated. The distance between the piers should meet the requirements of the construction code. The support pads should be reliable, especially the pipeline interface, and should not be subjected to shearing force. The brick piers are made of cement mortar to ensure integrity and sturdiness.

Confinement 9. The expansion bolts of the fixed pipe racks are of poor quality, the expansion bolts have too large a hole diameter, or the expansion bolts are installed on the brick wall or even on the lightweight wall.

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

Measures: The expansion bolts must be qualified products. If necessary, the test should be carried out. The expansion bolts should not be larger than the diameter expansion bolts 2mm. The expansion bolts are applied to the concrete structure.

Contraindications 10, the pipe joint flange and the liner are not strong enough, and the connecting bolts are short or thin. Heat pipes use rubber mats, cold water pipes use asbestos mats, and double-sided mats or beveled mats, and flanged gaskets burst into the tubes.

Result: The flange connection is not tight, even damaged, and there is leakage. Flange gaskets into the tube will increase flow resistance.

Action: Pipe flanges and gaskets must meet the pressure requirements for piping design. The flanged lining of the heating and hot water supply piping shall be made of rubber asbestos gasket; the flanged lining of the drainage piping shall be made of rubber gasket. The gasket of the flange should not burst into the tube, and the outer circle to the flange bolt hole is appropriate. Do not place a bevel pad or a few pads in the middle of the flange. The diameter of the connecting flange bolt should be less than 2mm than the flange diameter. The length of the bolt rod nut should be 1/2 of the thickness of the nut.

Taboo 11, the valve installation method is wrong. For example, the check valve or check valve water (steam) is reversed, the stem is installed, the horizontally mounted check valve is installed vertically, the stem valve or butterfly valve handle is not open, the closed space, the flush valve stem does not face the inspection door.

Consequences: Valve failure, switch maintenance is difficult, the valve stem is often caused by leakage.

Measures: Install in strict accordance with the valve installation instructions. The stem stem valve has sufficient stem elongation to open. The butterfly valve fully considers the handle rotation space. The various valve stems cannot be lower than the horizontal position, but not downward. The flush valve should not only be provided with an inspection door that meets the valve opening and closing requirements, but the valve stem should face the inspection door.

Taboo 12, valve installation 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 pipe diameter is less than or equal to 50 mm, the gate valve is used; the dry and vertical pipes heated by the hot water are the shut-off valves; and the fire pump suction pipe adopts the butterfly valve.

Consequences: Affect the normal opening and closing of the valve and adjust the resistance and pressure. It even caused the system to run, the valve was damaged, and was forced to repair.

Measures: Familiar with the application of various types of valves, valve specifications and models can be selected according to design requirements. The nominal pressure of the valve should meet the requirements of the system test pressure. According to the requirements of the construction code: The water supply pipe diameter is less than or equal to 50mm and should be used as a shut-off valve. When the diameter exceeds 50mm, the gate valve should be used. The hot water is heated and dried, the vertical control valve should use the valve, and the fire pump suction pipe should not use the butterfly valve.

Contraindications 13. Quality inspection is required before the valve is installed.

Consequences: System operated valve switches are inflexible, closed and leaking (steam), resulting in rework and repair, even affecting normal water supply (steam).

Action: Pressure strength and tightness tests should be performed prior to valve installation. The test should be 10%, not less than one, per batch (same grade, same specification, same model). For closed valves installed on the main pipe, the strength and tightness tests shall be performed one by one. The valve strength and sealing test pressure shall be in accordance with the “Code for Acceptance of Construction Water Supply and Drainage and Heating Engineering Construction Quality” (GB 50242-2002).

Taboo 14, the main materials, equipment and products used in construction, lack of technical quality identification documents or product certification in line with current national or departmental standards.

Consequences: The quality of the project is unqualified, there are hidden accidents, it cannot be delivered on time, the repair must be reworked, delays are caused, and labor and material inputs are increased.

Measures: The main materials, equipment and products used in the water supply and drainage heating project shall be in accordance with the technical quality appraisal documents or product certificates issued by the state and the department, and indicate the product name, model, specification, national quality standard code, date of manufacture, manufacture. Trade name and location, inspection certificate or factory product code.

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