Which fitting type incorporates an O-ring at the face of the fitting and is commonly manufactured using Buna-N or Viton seals?

Which fitting type incorporates an O-ring at the face of the fitting and is commonly manufactured using Buna-N or Viton seals?

• A. O-ring Boss fittings
• B. Orifice
• C. ORFS
• D. Union

Answer: (C)

ORFS, or O-Ring Face Seal, is the fitting style described. The key feature is an O-ring seated on the face of the fitting that seals against a flat mating surface when the parts are bolted together. This face-to-face seal distributes load evenly and provides a reliable leak-tight connection, even if there are small imperfections on the mating faces. The elastomer seal is typically Buna-N (nitrile) or Viton (fluorocarbon), chosen for oil compatibility and temperature range. This is different from other fittings where the seal is along threads or in a different location; for example, O-ring Boss uses an O-ring in the boss area, while an orifice is a flow-restriction element and a Union is a generic coupling type.