In industrial production, certain continuously operating equipment, such as pipes, valves and containers, leak for a variety of reasons. These leaks compromise the stability of normal production and product quality, pollute the production environment and cause unnecessary waste.
In more serious cases, the leakage of certain substances, such as toxic gases and oils, can pose significant risks to the safety of operations and the environment.
3. Top flux welding method
Some leaks occur due to corrosion and wear. In these cases, direct welding at the leak site should be avoided as it may cause larger holes. Instead, spot welding should be performed in suitable positions adjacent to or below the leak. These areas, which do not present leaks, serve as the basis for the establishment of a weld pool.
Then, in the same way that swallows build nests with mud, gradually surround the leak with welding, gradually reducing the area of the leak. Finally, seal the leak using a small diameter welding rod with an appropriate welding current, as illustrated in Figure 2.
4. Bypass welding method
This method is applicable for welding when the leakage area is large, the flow rate is high, or the pressure is substantial, as shown in Figure. A patch with closure device is created based on the shape of the leak.
For severe leaks, the shutoff device utilizes a section of diverter pipe equipped with a valve; for small leaks, a nut is pre-welded onto the patch. The patch area must exceed the leak area and the closure device on the patch must directly face the leak.
A layer of sealant is applied around the contact area of the patch and leak, allowing leaked media to escape through the bypass tube, reducing leakage around the patch. Once the patch is properly welded, the valve is closed or the screw is tightened.
5. Sleeve tube welding method
When a pipe leaks extensively due to corrosion or wear, a sleeve pipe of the same diameter or that can precisely enclose the leaking pipe is used. The length of the sleeve tube is determined based on the area of the leak.
The sleeve tube is symmetrically cut into two halves and a bypass tube is welded, using the same welding procedure as bypass welding. In terms of the welding sequence, the circumferential seam between the tube and the sleeve should be welded first, followed by the welding seam of the sleeve itself, as illustrated in the figure below.
6. Welding of oil seepage containers
Continuous welding cannot be used; It is crucial to ensure that the temperature of the weld seam does not rise too high. Spot welding is implemented, followed by immediate cooling. For example, after spot welding of some points, the welded points are immediately cooled with gauze moistened with water.
Sometimes it may be necessary to combine several methods to stop leaks. The welding process to stop leaks requires flexibility to ensure success.
However, not all metal materials are suitable for the welding tightness method. Only common low-carbon steel and low-alloy steel can implement these leak-stopping methods.
Austenitic stainless steel can only be repaired by welding if it is confirmed that the base metal near the leak point can undergo significant plastic deformation. Otherwise, it cannot be repaired by welding.
The medium inside the heat-resistant steel tube is generally high-temperature and high-pressure steam. Leaks that occur after long-term service cannot be repaired under pressure. Low temperature steel does not allow for pressure welding repairs.
All the methods of stopping welding leaks mentioned above are temporary measures. They do not have the mechanical properties that welding can normally achieve in the strictest sense.
When the equipment is not under pressure and is not equipped with medium, it is necessary to completely remove this temporary tight weld state and re-weld or otherwise repair it to meet the product usage requirements.
Conclusion
Anti-leakage welding technology is a necessary emergency technique in the continuous production process with the development of modern production.
Handling leak accidents requires punctuality, and subsequent complete replacement processing must be carried out at the leak site. Applying leak-blocking technology requires flexibility.
Various methods can be combined for welding to treat leaks, with the main objective of having no leaks after welding.
