Weld ring gaskets

Weld ring gaskets are used in the most critical flange connections where a welded seal is required—typically due to the hazardous nature of the medium or the risk posed by loss of functionality. While the connection must offer extreme sealing performance and safety, it also needs to be detachable to some degree. In such cases, a weld ring gasket is an optimal solution: the connection can be disassembled, but it requires cutting the weld as well as unbolting the flanges—thus, the gasket is considered semidetachable.

Welded flange joints meet the highest sealing requirements and are mandatory particularly when process conditions or the conveyed medium are exceptionally dangerous. Weld ring gaskets are generally made from the same or a compatible material as the pipe or flange, and they are always used in pairs.

Each weld ring gasket consists of two halves: one half is first welded to each flange side, and then the two halves are welded together to form the final seal.

Profiles and Weld Seams

The selection between different weld ring profiles depends on the operating conditions—such as pressure, temperature, and mechanical stress. Profiles A21 to A25 represent the most common shapes, and their typical features are presented in a separate table.

• The attachment seam refers to the weld joint between a gasket half and the flange. Depending on the gasket type, the attachment seam may be internal, external, or both.
• The seal seam always refers to the weld between the two gasket halves, ensuring a tight and secure connection.

Profile	Internal “attachment seam” Crevice corrosion between weld ring and flange is avoided	External “attachment seam” Re-welding or disassembly possible	Capacity of radial differential expansion	Undo and re-weld
	Usual	Not possible	Depending on the thickness of the wall of the torus, to a max. ∆ r ~ 5 mm	Easy to separate with a 2 mm cutting wheel. Can be re-welded 2 to 4 times
	Possible to have additional attachment. Intermittently welded	Usual	Depending on the thickness of the wall of the torus, to a max. ∆ r ~ 5 mm	Easy to separate with a 2 mm cutting wheel. Can be re-welded 2 to 4 times
	Only as an additional attachment. Intermittently welded if there is a danger	Usual setup – Only as an additional attachment aid. Intermittently welded of corrosion	Only low capacity due to the small lip. max. ∆ r ~ 0,5 mm	Difficult to separate. Can be re-welded 1 to 3 times
	Only as an additional attachment. Intermittently welded if there is a danger	Usual setup – Only as an additional attachment aid. Intermittently welded of corrosion	Not really possible. max.. ∆ r ~ 0,1 mm	With cutting wheel Separation loss 2 to 3 mm respectively. Can be re-welded of corrosion 3 to 5 times
	Usual	Not possible Flange form M in accordance with DIN 2526 also	Modest capacity Depending on projection max.. ∆ r ~ 0,3 mm	With cutting wheel Separation loss 2 to 3 mm respectively. Can be necessary re-welded 2 to 4 times