Valves are the most common equipment in chemical enterprises. Installing valves may seem easy, but if not carried out according to relevant technical standards, it can lead to safety accidents. Today, we would like to share some experience and knowledge about valve installation with you.

I. Conduct a water pressure test during winter construction at negative temperatures.

• Consequence: Due to the rapid freezing inside the pipe during the hydrostatic test, the pipe is damaged by freezing.
• Measures: Try to conduct a water pressure test before winter construction, and blow out the water after the test, especially the water inside the valve must be completely removed, otherwise the valve may rust or even freeze and crack. When conducting a water pressure test in winter, the project must be carried out at a positive temperature indoors, and the water must be blown out after the test.

II. The pipeline system is not washed carefully before completion, and the flow and speed cannot meet the requirements of pipeline flushing.

• Consequences: Water quality cannot meet the operational requirements of the pipeline system, often resulting in reduced pipeline cross-sections or blockages.
• Measures: flushing should be carried out with the maximum design flow rate in the system or a water flow rate of not less than 3m/s. It should be considered as qualified if the water color and transparency at the outlet are visually consistent with those at the inlet.

III. Sewage, rainwater, and condenser pipes are concealed without undergoing a closed water test.

• Consequences: It may cause water leakage and cause losses to users.
• Measures: The closed water test work should be strictly inspected and accepted according to the specifications. The concealed installation of sewage, rainwater, condenser pipes, etc. in underground burial, ceiling, and between pipes should ensure no leakage.

IV During the hydraulic pressure strength test and tightness test of the pipeline system, the leakage inspection is not sufficient.

• Consequence: Leakage occurs after the pipeline system is running, affecting normal use.
• Measures: When testing the pipeline system according to design requirements and construction specifications, in addition to recording pressure values or water level changes within the specified time, it is particularly important to carefully check for leakage problems.

V. The flange plate of the butterfly valve is made of ordinary valve flange plate.

• Consequences: The dimensions of the flange plates for butterfly valves and ordinary valves are different. Some flanges have a small inner diameter, while the butterfly valve's disc is large, causing it to be unable to open or to open forcibly, resulting in damage to the valve.
• Measures: The flange plate should be processed according to the actual size of the butterfly valve flange.

VI. The valve installation method is incorrect.

For example, the water (steam) flow direction of the stop valve or check valve is opposite to the mark, the valve stem is installed downward, the horizontally installed check valve is installed vertically, the handle of the open-stem gate valve or butterfly valve has no space for opening and closing, and the valve stem of the concealed valve does not face the inspection door.

• Consequences: Valve malfunction, difficulty in switch maintenance, and often water leakage caused by the valve stem pointing downwards.
• Measures: Install the valve strictly according to the installation instructions. For the rising stem gate valve, leave enough space for the valve stem to extend and open. For the butterfly valve, fully consider the space for rotating the handle. The valve stem should not be lower than the horizontal position, and it should not be downward. For concealed valves, not only should there be an inspection door that meets the needs of opening and closing the valve, but also the valve stem should face the inspection door.

VII. 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; gate valves are used for water supply branch pipes with diameters less than or equal to 50mm; stop valves are used for hot water heating dry and vertical pipes; and butterfly valves are used for fire pump suction pipes.

• Consequences: It affects the normal opening and closing of the valve and the adjustment of resistance and pressure. It may even cause damage to the valve during system operation and necessitate repairs.
• Measures: Familiarize yourself with the application scope of various valves, and select the specifications and models of valves according to the design requirements. The nominal pressure of the valve should meet the requirements of the system test pressure. According to the construction specifications, when the diameter of the water supply branch pipe is less than or equal to 50mm, a globe valve should be used; when the diameter is greater than 50mm, a gate valve should be used. The hot water heating dry and riser pipes should use gate valves, and the suction pipe of the fire pump should not use butterfly valves.

VIII. The necessary quality inspection is not conducted according to the regulations before the installation of the valve.

• Consequences: The valve switch is not flexible during system operation, resulting in poor closure and leakage (steam) phenomena, causing rework and repair, and even affecting normal water (steam) supply.
• Measures: Before the installation of valves, pressure strength and tightness tests should be conducted. The tests should be conducted on 10% of each batch (of the same brand, same specification, and same model) and no less than one. For closed-circuit valves installed on the main pipe to cut off, strength and tightness tests should be conducted one by one. The pressure for valve strength and tightness tests should comply with the provisions of the Code for Acceptance of Construction Quality of Water Supply Drainage and Heating Works (GB 50242-2002).

IX. Improper installation of valves in high temperature environment.

• Consequence: leakage accident
• Measures: For high temperature valves over 200℃, they are at normal temperature during installation, but after normal use, the temperature rises, the bolts expand due to heating, and the gap increases, so they must be tightened again, which is called "hot tightening". Operators should pay attention to this work, otherwise leakage is likely to occur.

X. Valve flip-chip

• Consequences: Valves such as stop valves, throttle valves, pressure reducing valves, and check valves all have directionality. If installed upside down, the throttle valve will affect the effectiveness and lifespan of the valve; the pressure reducing valve will not work at all, and the check valve may even pose a danger.
• Measures: General valves have directional signs on the valve body; if not, they should be correctly identified based on the working principle of the valve. The valve cavity of the globe valve is asymmetric left and right, and the fluid should be allowed to pass through the valve port from bottom to top, which reduces fluid resistance (determined by shape) and saves effort when opening (due to the upward pressure of the medium). After closing, the medium does not press on the packing, which is convenient for maintenance. This is why the globe valve cannot be installed backwards. Gate valves should not be installed upside down (i.e., with the handwheel facing down), otherwise the medium will remain in the valve cover space for a long time, which can easily corrode the valve stem and is also prohibited for certain process requirements. At the same time, it is extremely inconvenient to replace the packing. For rising stem gate valves, do not install them underground, otherwise the exposed valve stem will be corroded due to moisture. For lift check valves, ensure that their valve discs are vertical during installation to facilitate flexible lifting. For swing check valves, ensure that their pin shafts are horizontal during installation to facilitate flexible swinging. Pressure reducing valves should be installed upright on horizontal pipelines, and should not be tilted in any direction.