Attention should be paid to the following precautions for installing valves:
- Confirm that the valve meets the design requirements and relevant standards before installing the valve.
- When moving and installing the valve, prevent bumps and scratches of the valve.
- Before installing the valve, clean the inside of the pipeline to remove iron filings and other impurities to prevent foreign matter from getting into the valve's sealing seat. In addition, the valve should be closed during installation.
- When the valve is lifted, it should be lifted correctly at the designated lifting position, and it should not be lifted or pulled only under partial force.
- When the valve is installed, it is necessary to confirm whether the flow direction of the medium, the installation form and the position of the handwheel comply with the regulations.
- Install the valve with flange connections.
(1) The flange surface of the valve and pipe should be free from damage, scratches, and kept clean. The grooving of the flange should match the gaskets, especially when metal elliptical or octagonal gaskets are used. Red lead should be applied for matching and grinding to ensure good sealing.
(2) The perpendicularity of the flange surface of the pipe to the center line of the pipe and the error of the flange bolt's hole should be within the allowable range. The center line of the valve and pipe must be consistent before installation.
(3) When two flanges are connected, the sealing surface of the flange and the gasket must first be evenly compressed so as to ensure that the flanges are connected by the same bolt stress.
(4) When tightening the bolts, use a wrench that matches the nut. When tightening by hydraulic or pneumatic tools, be careful not to exceed the specified torque.
(5) The flanges should be tightened without uneven force. They should be tightened in the asymmetrical and intersecting direction.
(6) After the flange is installed, make sure that all bolts and nuts are firm and even.
(7) The materials of bolts and nuts must comply with regulations. After tightening, the bolt head should show two pitches from the nut.
(8) In order to prevent loosening caused by vibration, when bolts are tightened, washers should be used. In order to avoid adhesion between threads at high temperatures, the threaded part should be coated with an anti-sticking agent (molybdenum disulfide) during installation.
(9) For valves used at a temperature of above 200 degrees Celsius, after the temperature rises, the flange connecting bolts, bonnet fastening bolts, pressure sealing bolts and packing cap bolts must be tightened again.
(10) Low-temperature valves are at atmospheric temperatures when they are installed. In actual application, when the medium passes through, it becomes a low-temperature state. The flanges, gaskets, bolts and nuts will shrink due to the temperature difference. Because the materials of these parts are different, their respective linear expansion coefficients are also different, forming environmental conditions that are very easy to leak. Considering this objective situation, when bolts are tightened at atmospheric temperature, a torque that takes into account the shrinkage of various parts at low temperatures must be used.
(2) The perpendicularity of the flange surface of the pipe to the center line of the pipe and the error of the flange bolt's hole should be within the allowable range. The center line of the valve and pipe must be consistent before installation.
(3) When two flanges are connected, the sealing surface of the flange and the gasket must first be evenly compressed so as to ensure that the flanges are connected by the same bolt stress.
(4) When tightening the bolts, use a wrench that matches the nut. When tightening by hydraulic or pneumatic tools, be careful not to exceed the specified torque.
(5) The flanges should be tightened without uneven force. They should be tightened in the asymmetrical and intersecting direction.
(6) After the flange is installed, make sure that all bolts and nuts are firm and even.
(7) The materials of bolts and nuts must comply with regulations. After tightening, the bolt head should show two pitches from the nut.
(8) In order to prevent loosening caused by vibration, when bolts are tightened, washers should be used. In order to avoid adhesion between threads at high temperatures, the threaded part should be coated with an anti-sticking agent (molybdenum disulfide) during installation.
(9) For valves used at a temperature of above 200 degrees Celsius, after the temperature rises, the flange connecting bolts, bonnet fastening bolts, pressure sealing bolts and packing cap bolts must be tightened again.
(10) Low-temperature valves are at atmospheric temperatures when they are installed. In actual application, when the medium passes through, it becomes a low-temperature state. The flanges, gaskets, bolts and nuts will shrink due to the temperature difference. Because the materials of these parts are different, their respective linear expansion coefficients are also different, forming environmental conditions that are very easy to leak. Considering this objective situation, when bolts are tightened at atmospheric temperature, a torque that takes into account the shrinkage of various parts at low temperatures must be used.
(1) Grooves processing of socket welding and butt welding should be correct, and they should comply with relevant standards.
(2) Prevent iron filings and welding beans from getting into the pipe during welding, and tungsten inert gas shielded welding should be used.
(3) During welding, the valve should be opened slightly.
(4) The welding materials should be selected correctly according to the valve and pipe materials. When using welding rods, check the storage conditions of the welding rods and confirm whether the drying treatment suitable for them has been adopted.
(5) The personnel engaged in electric welding operation should meet the requirements of electric welding technicians.
(6) When heat treatment is required after welding, check the time and temperature curve record of the heat treatment.
(7) Visual inspection or non-destructive inspection should be carried out on the welding part to confirm that there are no harmful defects such as cracks, weld beading, undercut and so on.
(2) Prevent iron filings and welding beans from getting into the pipe during welding, and tungsten inert gas shielded welding should be used.
(3) During welding, the valve should be opened slightly.
(4) The welding materials should be selected correctly according to the valve and pipe materials. When using welding rods, check the storage conditions of the welding rods and confirm whether the drying treatment suitable for them has been adopted.
(5) The personnel engaged in electric welding operation should meet the requirements of electric welding technicians.
(6) When heat treatment is required after welding, check the time and temperature curve record of the heat treatment.
(7) Visual inspection or non-destructive inspection should be carried out on the welding part to confirm that there are no harmful defects such as cracks, weld beading, undercut and so on.
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