Posted on May 08, 2019

Things to Consider When Selecting an ORFS Fitting

System design is the first consideration for leak prevention in hydraulic systems. The right components must be selected to reduce the incidences of leaks and connection failures. Typically O-ring face seal fittings are the best or sometimes only practical choice. The following are attributes that should be taken in consideration when selecting system connections in the design phase.


The environment will determine ORFS fitting design and selection. The use of stainless steel or a protective coating on steel fittings extends the service life in corrosive environments. The most common finish for steel fittings is electroplated zinc to avoid rusting from the presence of oxygen, acidic gases and moisture. However, stainless steel is the best choice for highly corrosive environments such as off-shore or applications exposed to caustic chemicals. Finally the choice of O-ring material must meet the system conditions and application as well. A fluorocarbon or other material may need to be specified over Buna-N in certain applications, particularly in very high temperatures. 


The dynamic pressure rating of the ORFS fitting assembly is to be equal to or higher than the system pressure. Typically, ORFS fittings are rated at a 4:1 design ratio, which applies to normal operating conditions that can withstand moderate hydraulic and mechanical shock. For severe vibration and shock operating conditions a “de-rating factor” should be applied directly to the dynamic pressure of the fitting.


The operating temperatures for ORFS fittings and O-ring seals are dependent on the metal material, plating and material of the seal. Temperature ranges for fittings and O-ring seal materials are shown in the table table for blog

Other important considerations in system design that must be considered include:

  • Contamination
  • Environment
  • Fluid velocities
  • Media
  • Shock
  • Tube O.D. and Wall Thickness
  • Vibration


This blog is an excerpt from our latest whitepaper, 5 Things You Should Know About O-Ring Face Seal Fittings. Click here or the link below to download your free whitepaper! 

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