Return Flow Impedors




Our RFI (Return Flow Impeders) are used for applications where the inside of the tube must be kept as dry as possible. Examples of this are galvanised tubes (to prevent ‘white rust’ formation) and also stainless steel tubes (to avoid coolant in the welding zone). EHE Consumables RFI impedors are fully repairable by the simple loosening of 2 x set screws enabling replacement of the casing and /or ferrite core.
Replacement cut-to-length casings and ferrite cores are available from stock. We now also offer RFI impedors with our S300WG casings. This unique white fluoro polymer offers excellent non-stick properties and increases casing temperature endurance by almost 100ºC.

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RFI impedors have significant advantages over other return flow designs such as:
• Rugged CNC machined brass internal assemblies
• Centre tube pinned to end plug avoiding any possible detachment during production
• High temperature Silicone glass casing with Fluoro Polymer coating
• Both ends sealed with high specification silicone O rings
• NPT tapered thread connections to ensure full leak proof connection
• No drilled holes or fasteners in casing body



We also offer simple couplings for our RFI impedors which can be supplied with or without ‘hanger blades’ for fixing in place.

RF coupling











Return flow impeder cooling
Return-flow impeders may offer more resistance to coolant flow than through-flow types, a higher coolant pressure is therefore recommended.  A minimum pressure of 4 bar (60 PSI) ensures adequate cooling under most operating conditions. Coolant flow requirements vary widely due to inlet temperature, weld power, frequency and weld area geometry.  Clean filtered coolant is recommended when using return-flow impeders. Since coolant flow can be reduced at lower inlet temperatures, it is beneficial to keep the inlet temperature as low as possible. This may require the use of a heat exchanger or refrigerative cooler when using return-flow impeders. Coolant temperature entering the impeder should not exceed 25°C (75°F). Higher temperatures will result in lower welding efficiency and impeder life.