Resources: Engineer FAQs
In 1998, the Society of Aerospace Engineers (SAE) issued Aerospace Recommended Practice (ARP) 5316. It was intended to fully replace Mil-HDBK-695C as the industry standard for the shelf life of aerospace elastomeric seals. However, ARP 5316 can also be used as a useful guideline for shelf life of many industrial and commercial grade elastomers as well. The information in ARP 5316, and the chart below, is intended to be utilized by those organizations that do not already have specific recommendations for the control of elastomeric seals. It should be noted that the packaging of the elastomeric seals prior to assembly into a product is an integral part of the controlled storage procedure. It provides a positive means of product identity from the time of manufacture, to the time of assembly.
ARP 5316 does not establish limitations for storage times in assembled components, nor does it in any way provide a guideline for the operating lifespan of a particular compound.
Elastomers are long chain polymers capable of cross-linking via a process called vulcanization. Vulcanization process cross-links the polymer chains by a chemical bond creating the elastic nature of elastomers. Elastomers are described by family based on polymer used for formulation.
An o-ring is a torus or a doughnut shaped object, generally made from an elastomer. O-rings are one of the most common seals used in machine design because they are inexpensive and easy to make, reliable, and have simple mounting requirements. They are designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. An O-Ring is a means of closing off a passageway and preventing an unwanted loss or transfer of fluid. They can seal tens of MPA (thousands of psi) pressure. The O-Ring seal consists of two elements, the O-Ring itself and a properly designed gland to contain the elastomeric material.