TO: Maintenance professionals. FROM: The Fluid Power Safety Institute™. SUBJECT: Caution: There is a difference between O-Rings for SAE Straight Thread Tube Fittings and Standard O-Rings. What's the problem? - It has been brought to the attention of the FPSI™ that many maintenance professionals are unaware that O-rings for SAE straight thread fittings are non-standard. An incorrect O-ring cross section dimension can lead to safety problems: if the cross section dimension is too small, it could cause leakage. If it is too big, the seal could extrude and fail. Tell me more! - The dimension that we are referring to in this safety bulletin is the cross section dimension. This chart shows an example of how the cross section dimension of an SAE O-ring differs from the cross section dimension of a standard O-ring (a 1/2" O-ring is used in the example): Here is an illustration showing the nomenclature for the various dimensions of an O-ring: What must I do to correct the problem? - 1. With immediate effect, advise your colleagues of this problem to avoid further confusion. 2. Advise your purchasing agent(s) with immediate effect. 3. If you know of any fluid power system that has incorrect O-rings, change them immediately. 4. Mark the O-rings in your inventory clearly to avoid accidental misapplication. 5. Refer to the appropriate page in the manufacturer's catalog when ordering O-rings. It will (usually) state clearly: "Standard O-rings," or Standard O-rings for Straight Thread Tube Fittings." Conclusion - An O-ring is such an "insignificant" component, yet it can lead to a host of accidents that can cause severe injury, death, or substantial property damage. Take note when installing O-rings, and if there is ever any uncertainty, ask!

Waiver of Liability -

The Fluid Power Safety Institute™ does everything possible to ensure that the information and drawings contained in this safety notice are accurate, and the suggested procedures are deemed safe and reliable. However, these are general recommendations only and might not be applicable to all situations. You MUST have your engineering department in conjunction with your safety department read these recommendations and make the necessary changes for your application. The Fluid Power Safety Institute™ is not responsible for actions taken by untrained and/or unauthorized persons. Trained, authorized persons only should do ALL fluid power system service, repair, and troubleshooting.