A weld ring gasket, also commonly referred to as a welded lip seal, consists of a pair of metallic rings. Each individual ring is first welded to its respective flange face. Upon assembly of the joint, the two rings are then welded together at their outer periphery to complete the seal.
The use of weld ring gaskets is recommended when conventional gasket types are considered unsuitable and when joint disassembly is infrequent. These gaskets are generally classified as semi-detachable, since the welded connection between the sealing rings must be cut in addition to removing the flange bolts to open the joint.
Several designs of weld ring gaskets are available, including:
Membrane weld ring gaskets
Profiled weld ring gaskets
Hollow-lip weld ring gaskets
Membrane weld ring gaskets and weld ring gaskets are not suitable for accommodating significant radial differential expansion between the connected components. Depending on the specific design of the gasket, the allowable radial movement can be as low as 0.1 mm (0.004 inches) and should not exceed 0.5 mm (0.02 inches).
A membrane weld ring gasket typically consists of two matching metal rings, each with a thickness of approximately 4 mm (0.16 inches). These rings are made from materials that are either identical or compatible with the flange materials, in order to ensure:
chemical and weld compatibility,
thermal conductivity alignment,
and minimization of radial differential stresses.
Each ring is individually welded to its corresponding flange using an internal joint weld. After both rings are secured, a second welding step is performed along the outer diameter, creating a fully welded, sealed joint.
The welds used in this configuration are classified as seal welds, meaning they are intended to ensure leak-tightness, rather than to provide structural strength.
The width of the weld ring gasket must be engineered to withstand internal pressure, particularly acting in the circumferential (hoop) direction, ensuring mechanical stability and integrity under operating conditions.
