Through-flow impeders

Standard impeders have outer casings that fully enclose and protect the ferrite. Exposed ferrite impeders are used where weld spume or coatings such as aluminium or zinc tend to build up on conventional impeders and shorten their life. Exposed ferrite impeders often permit a larger impeder to be used, since there is no casing at the narrowest part of the tube. These impeders also work well in air or gas-cooled installations. Laminar flow of coolant over the exposed ferrite makes these impeders self-cleaning, and therefore highly resistant to damage from weld spume.

Casing types

Epoxy glass

Epoxy glass casing is a high strength, glass fibre-reinforced epoxy resin composite with excellent wear properties, and extended life at high temperatures. It is widely used and is the least expensive type of casing for most impeder sizes. G-11 epoxy glass will withstand temperatures 100 °F (40 °C) higher than the more common G-10 material.

Ferroglass™

Ferroglass is a high temperature, ferrite-impregnated glass fibre tube made specifically for use in impeders. The extra ferrite in the casing can increase weld speeds by up to 40%. This improved efficiency is most noticeable at small diameters. Ferroglass also has the best wear resistance of all materials normally used in impeders.

S300 Weld Guard (S300WG)

S300WG is a fluoro polymer coated high temperature epoxy casing we use for our range of small diameter impeders with increased ferrite mass. By increasing ferrite mass we are forced to reduce wall thickness of the impeder casing, to counteract this we apply a special white coating to the casing which is cured using a precise thermal process in a controlled environment. This unique coating gives the impeder a ‘low friction’ surface reducing the chance of weld spume/spatter sticking to the casing. Weld guard impeders are available from 10mm to 18mm outside diameter in our standard range.

Cooling requirements

Coolant should be clean, preferably filtered. A pressure of 3 bar (45 PSI) will ensure adequate cooling under most operating conditions. Coolant flow requirements vary widely due to inlet temperature, weld power, frequency and weld area geometry. In high power density situations and at high ambient temperatures, a small chiller for impeder and work coil coolant can greatly improve efficiency. Cooling by air or other gas is not recommended, but can be useful in special situations where the presence of water inside the tube cannot be tolerated. Gasses such as nitrogen have a density that is at least 1,000 times less than water, so coolant volume must be increased accordingly. An impeder cooled using half a gallon (1.9 litres) of water per minute would require a minimum of 15 cubic feet (0.42 m3) per minute of nitrogen. The cost of this is prohibitive in most cases.

Heavy duty impeders

The limiting factor in impeder efficiency is the total amount of magnetic flux that the impeder can support. This varies with temperature & ferrite/ferrite amount. Placing a larger mass of ferrite within an impeder will increase welding efficiency. This becomes important with high powered welders, especially those operating at lower frequencies. ENRX’s heavy duty impeders use up to 50% more ferrite than comparable standard impeders & can greatly reduce the amount of power required for a satisfactory weld. Most heavy duty impeders also have thicker outer casing & improved cooling to extend operating life.