Connection Types: ORB (O-Ring Boss)
What are ORB Fittings?
ORB,or(SAE Straight ThreadO-ring Boss) fittings,incorporate a port connection as recommended by the National Fire Protection Association (N.F.P.A.) for leak prevention in medium and high pressure hydraulic systems.ORBconnectionsare commonly manufactured in carbon, nickel plated carbon & stainless steel andtypically use Buna-N or Viton, 90 Durometer O-rings.The male connection is astraight UNFthread with an O-ring. The female port has a straight thread and a machined surface to provide a smooth, flat, accurately located surface (minimumspotface), along with a chamfer where the O-ring seats.The seal is createdwhen the O-ring is compressed into the chamfer when mating the maleand femaleconnectionprovidinga leak-tight seal.
Disadvantages of ORB Fittings
- The relevant temperature rating is limited by the o-ring seal material making these fittings ineffective in high temperature applications
- The O-ring can be improperly installed resulting in a cut or pinch
- The fitting could be improperly torqued
- The threaded portion of the fitting may be longer than SAE specification resulting in the fitting bottoming out in a port before the o-ring can be fully compressed
Advantages of ORB Fittings
- They’re readily available and offer a large variety of sizes, shapes, combinations and materials
- Provide optimal sealing performance in medium to high pressure systems
- The nature of ORB fittings resists complications associated with over-assembly
- The straight thread connection design coupled with the replaceability of the o-ring makes these fittings reusable and easily maintainable
- Are either adjustable or non-adjustable
Adjustable o-ring fittings are typically elbows or tees that are installed in a fixed direction. Non-adjustable o-ring fittings are usually plugs and straight connectors that are fitted into a port without the need for alignment. Options like these make ORB fitting orientation easier than some other fittings because the o-ring is the sealing factor and not the threads.
ORBfittingscan be confused with other connection systems, such as NPTor even JIC.For example,this straight thread connection uses the same threads as the JIC 37° fitting. However, the 37° flare has been removed and ano-ringhas been added.So,while threads of different connectors sometimes fit, ORBconnectionsshould never be used with any other type of connectors as leaks are likely.For these reasonscare needs to be taken to properly identify the right connection to create a safe and leak resistant seal.
