Sealing welds are used to prevent leakage and contain gas or liquid substances. They are applied to galvanized joints, but must not affect joint flexibility or ultrasonic inspections. Proper welding practices must be followed to ensure complete fusion. Sealing welds are commonly used in food processing and engineering industries.
A sealing weld is a weld that performs the primary function of sealing joints. Seal welds are commonly used in gas or liquid containers to contain the gas or liquid substances and to prevent leakage. The presence of sealing welds also prevents gases or fluids from entering specific, prohibited areas where they can cause corrosion or other damage.
Sealing welds are applied to parts that are to be galvanized. There are two types of ready galvanized joints, regular and ventilated, which can be welded together respectively with sealing welding; there is also a ready-to-use galvanized third joint that does not require sealing welding. With regular joints, care must be taken to ensure that the sealing welds are not so porous as to allow any type of leak. Vented joints are joints that have vents or holes to allow the gas to escape. When applying seal welds to vented joints, it is important to ensure that the vents are placed in suitable locations; a buildup of gas could damage the joints otherwise.
It should be borne in mind that sealing welds are placed only as a containment measure and should not be expected to increase the strength of the joint. It is essential that the designer and manufacturer verify that gasket placements comply with code requirements specified by the American Welding Society (AWS), although in some cases code violations are permitted that could affect joint flexibility. You also need to ensure that the sealing weld does not inadvertently end up performing some unwanted structural function, or that the presence of the sealing welds does not affect ultrasonic inspections too negatively.
The welder must be well qualified to do the job and must follow good welding practices when making sealing welds. Watertight welding practices include adhering to specified weld sizes and heat inputs, selecting the correct electrode shape, and following proper welding procedures. The proper heating time and weld pressure are necessary to ensure that complete fusion is achieved and that there is no possibility that the gasket weld could crack.
The application of sealing welds is common in the food processing and engineering industries. In addition to pipes and containers, the exposed steel elements are tightly welded before being painted to prevent rust. A pinch weld seal, also known as a trim seal or rubber block, is used in both refrigerator and car doors.
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