Forvarmings

Forvarmings, sometimes written förvärmning in Swedish, refers to the intentional raising of the temperature of a component, system, or material before its normal operation. The purpose is to improve performance, efficiency, safety, or reliability by avoiding thermal shock, reducing friction, or shortening warm-up periods. The term comes from for- (before) and varme (warmth).

In mechanical engineering and automotive contexts, forvarmings is common in engines, especially diesel: engine block heaters or glow plugs preheat the combustion chamber to improve cold starts, reduce wear, and lower emissions. Preheating of air or fuel-air mixtures can also improve starting in extremely cold climates.

In welding and metalworking, preheating (forvarmings) of steel or other alloys reduces thermal gradients, lowers the risk of cracking, and improves weld quality. In forging and heat treatment, preheating stabilizes material properties before forming.

In HVAC and laboratory settings, preheating may refer to bringing rooms, cabinets, or glassware to a target temperature to prevent condensation, thermal shock, or delays in achieving stable conditions.

In power generation and process industries, air preheaters and feedwater preheating raise incoming temperatures to improve overall efficiency and reduce fuel consumption.

While forvarmings offers efficiency and safety benefits, it also consumes energy and can cause damage if misapplied, such as overheating components or distorting tolerances. Standards and best practices emphasize appropriate target temperatures and gradual heating rates.