The installation of stainless steel seamless elbows should pay attention to alignment, sealing, stress prevention, and material protection. After all, it is a key node for pipeline turning, and if not installed properly, it is easy to leak media or deform due to stress, which may also affect the flow of the entire pipeline.
Firstly, the base must be prepared before installation, and the elbow itself should be inspected first. Check if there are cracks or dents on the inner wall, if the sealing surface (whether it is the welding groove or the flange surface) is flat, if there are scratches or oxide scales. If there are problems, do not use it, otherwise it is easy to leak after installation. Then it is necessary to confirm that the specifications, materials, and pipes of the elbow are completely matched. For example, a 304 pipe must be matched with a 304 elbow, and the diameter and wall thickness must also be consistent (for example, a DN50 pipe cannot be matched with a DN40 elbow), otherwise it will not be able to connect and will generate stress. In addition, before installation, the oil stains, dust, and metal debris inside and outside the elbow should be wiped clean, especially at the sealing surface and groove. Impurities can affect welding or flange sealing.
Next is the alignment issue during docking, which is the most crucial step. When connecting elbows and pipes, it is necessary to ensure that their axes are on the same plane and not forcefully bend the pipes to fit the elbows. For example, if it is a 90 ° elbow and forcefully bent into an 85 ° butt joint, it will cause internal stress in both the elbow and the pipe. Over time, the weld joint will crack, and if the flange is connected, the sealing surface will also be crushed. If it is a flange elbow, the bolt holes should be perfectly aligned with the holes of the pipe flange. Do not forcefully tighten the bolts. If they do not match, adjust the position of the pipe instead of bending the elbow.
Then look at the details of the connection method, commonly welding and flange connections. When welding, it is necessary to use welding wire that matches the material of the elbow (such as ER308 welding wire for 304 elbow and ER316 welding wire for 316 elbow). Priority should be given to using argon arc welding as a base to prevent the formation of oxide scale on the inner wall (especially when transporting clean media). During welding, the current should not be too high to avoid burning and deforming the bent part of the elbow. After welding, the welding slag should be cleaned, and the weld should be checked for pores and slag inclusions. If necessary, non-destructive testing should be carried out. For flange connections, the sealing gasket should be selected correctly. For example, nitrile rubber gaskets are used for transporting oil, graphite gaskets are used for high-temperature media, and gaskets should not be installed backwards or damaged; When tightening bolts, they should be tightened diagonally and evenly, 2-3 times to the correct position. Do not tighten a certain bolt at once, otherwise the sealing surface will be subjected to uneven force, and it is easy for medium to leak through the gaps.
During the installation process, it is also necessary to protect the elbow and prevent the bending part of the elbow from being subjected to force and collision. For example, do not use a pry bar to pry the bend during transportation, and do not place the weight of the pipe on the bend during installation. It is best to install brackets on both sides of the bend to distribute the force. In addition, stainless steel is afraid of chloride ion corrosion. During installation, do not touch the elbow with rusty tools, and do not let the elbow come into contact with salt water or cement slurry. If it comes into contact, quickly wipe it clean with clean water to avoid leaving corrosion marks.
After installation, testing is required, such as conducting a water or air pressure test before passing the medium. The pressure should be determined according to the pipeline design requirements, and the pressure should be maintained for a period of time to check for leaks at the welds and flange connections. If there are no problems, normal use can be resumed. Regular inspections should be conducted on the elbow area in the future to see if there is any wear caused by medium erosion or seal loosening due to temperature changes. Early detection and treatment are necessary.