Oil seals, also known as rotary shaft seals, are a type of gasket used to prevent lubricant leakage and contamination in rotating machinery by creating a barrier between the moving and stationary parts.
First, an elastomer, most often nitrile, is vulcanised to a metal ring. This creates a stiffening effect that includes a specialised metal tension spring directly behind the sealing lip, keeping the oil seal firmly in place against the moving part.