In many applications Fluxtrol concentrators work longer than the copper they are attached to. When they do fail, the cause is usually one of three things, and each is preventable.
Why concentrators fail
- Mechanical damage by the part or during coil installation. This is one of the main factors in coil and concentrator failure.
- Material overheating, which leads to crumbling. Causes include insufficient coil cooling, improper design and manufacturing, or separation of the concentrator from the coil tubing when the glue cracks.
- Electrical break, which trips the power supply protection or causes arcing and burning. Causes include improper coil design, wrong material selection (for example Fluxtrol 50 instead of Ferrotron 559H) and metallic particles accumulating on the coil surface.
What to check during maintenance
Each check below maps to one of the failure modes above.
- Mechanical condition. Look for chips, cracks and impact marks, and check the concentrator position relative to the coil, fixtures and moving parts. Check carbide shoes or other components that provide the required gap.
- Thermal path. Confirm that cooling flow is normal and that the concentrator is still bonded to the copper, since glue cracks cut heat transfer. Signs of crumbling or discoloration indicate overheating.
- Electrical cleanliness. Remove metallic particles and debris from the coil surface, and check for arcing marks. Multi-turn coils need the concentrator insulated from the turns and studs to avoid current leakage.
- Surface condition. Machined surfaces can rust where the smeared layer exposes iron particles. Etching and coating are described under protection .
- Grade. Confirm the material on the coil matches the drawing, since the wrong grade can cause electrical break.
Understanding concentrator heat
Concentrators generate heat from magnetic losses and absorb it from the hot part and, sometimes, the copper. This is normal as long as the material stays below its rated temperature. Heat leaves mainly by conduction into the water-cooled copper, so adhesive thickness, gap filling and thermal conductivity decide how well it is removed. In heavily loaded cases, a thin layer of thermally conductive epoxy is essential, and water channels inside the SMC give direct cooling. For vacuum furnaces, pay special attention to cooling because there is no convection.
Reuse and removal
Do not plan on reusing concentrators glued to hardening coils with epoxy, because removing the glue with a furnace or flame can damage them. Coils with mechanical attachment only, or with silicone rubber glue, can be disassembled and the concentrators reused if there is no overheating. Fasteners can be brass or non-magnetic stainless steel, such as 304, for strength and temperature, or plastic and fiberglass-reinforced polymer (G10/G11) when electrical isolation from the coil is wanted.
Compatibility with quench and the environment
Fluxtrol materials work in hot water, polymer solutions and quenching oil. Coatings, etching and impregnation extend life in harsh environments, and published testing found that properly coated SMCs showed no degradation in a standardized humidity test. See Protecting SMC Flux Controllers .
Talk to the engineers
If a coil is failing early, contact Fluxtrol to diagnose the cause, or order replacement material through the SMC order form .