Selecting ORFS Fittings by Application, Pressure, and Temperature

System design is the first step in leak prevention. ORFS fittings are often a strong choice for hydraulic systems, and in some applications they may be the practical connection style when leakage has to be minimized.

The fitting selection should be made before the system is built or repaired, not after a leak appears. Application, pressure, temperature, seal material, and operating shock all affect the right choice.

Application and Environment

The environment helps determine the ORFS fitting material and finish. Steel fittings commonly use electroplated zinc to resist rust from oxygen, moisture, and acidic gases.

In highly corrosive environments, stainless steel may be the better choice. Offshore service, chemical exposure, washdown areas, and caustic materials can justify a material upgrade instead of relying only on a protective coating.

O-Ring Material

The O-ring material also has to match the system conditions. Buna-N may be suitable for many hydraulic applications, but a fluorocarbon or other seal material may be needed where temperature, fluid compatibility, or chemical exposure demands it.

A correct fitting body with the wrong seal can still create a weak connection. Seal compatibility should be checked with the media and the expected temperature range.

Pressure Rating

The dynamic pressure rating of the ORFS fitting assembly should be equal to or higher than the system pressure. Normal operating pressure is only part of the check because shock and vibration can raise the stress on the connection.

ORFS fittings are commonly discussed with a 4:1 design ratio for normal operating conditions with moderate hydraulic and mechanical shock. Severe vibration or shock may require a de-rating factor applied to the dynamic pressure rating.

Temperature Range

Operating temperature depends on the metal material, plating, and O-ring material. The fitting and the seal both need to remain within their rated temperature limits.

Temperature problems can change seal hardness, reduce service life, or affect the protective finish. The temperature check should include fluid temperature and the surrounding environment.

Other System Design Checks

Other selection factors include contamination, environment, fluid velocity, media, shock, tube outside diameter, tube wall thickness, and vibration.

Those details help determine whether an ORFS connection can maintain the intended seal and whether the surrounding tube, hose, or port can support the connection over time.