O-Ring Shelf Life Recommendation per ARP 5316
The Chart below provides the recommended shelf life for various materials of elastomer (rubber) seals, per SAE’s Aerospace Recommended Practice ARP 5316. Global O-Ring and Seal has accepted ARP 5316 as the most comprehensive basis for establishing shelf life, however, it is not a binding Specification. This information is to be used simply as a basis upon which companies can form their own shelf life requirements.
|Elastomer Family||ASTM||Shelf Life|
|Butyl Rubber, Isobutylene Isoprene||IIR||Unlimited|
|Chloroprene (Neoprene®)||CR||15 Years|
|Ethylene Acrylic (Vamac®)||AEM||15 Years|
|Ethylene Propylene, EPDM or EP||EP||Unlimited|
|Hydrogenated Nitrile, HNBR or HSN||HNBR||15 Years|
|Nitrile (Buna-N or NBR)||NBR||15 Years|
|Polyurethane (Polyester or Polyether)||AU / EU||5 Years|
|Styrene Butadiene (Buna-S)||SBR||3 Years|
These limits are based on examination and testing of rubber seals with extensive shelf age, in some cases more than 30 years. In addition to practical experience, these recommendations also conform to theoretical expectations: those materials with unlimited shelf lives show no chemical potential for degradation due to atmospheric exposure and are chemically and physically stable.
Age control of elastomeric seals and assemblies started after World War II on hydraulic, fuel and lubrication seals on aircrafts. The first document on age control was released in 1958 and was a compilation of several studies on age control done since WWII. After several more studies and papers, MIL-STD 1523 was released in 1973 and gave 12 quarters as maximum shelf life. This was extended to 40 quarters in 1984 with the release of MIL-STD-1523A. This standard was cancelled in 1995 when the release of AS1933 was issued. AS1933, “Age Controls for Hose Containing Age-Sensitive Elastomeric Materials” only addressed elastomeric hoses and seals were essentially released from control.
In the past, MIL-HDBK-695C, MIL-STD-1523A, and its replacement, AS1933, were applied to rubber seals. MIL-STD-1523A was cancelled in 1995; the cancellation notice referred to AS1933 as a potential replacement. However, AS1933 specifically deals with rubber hose, and does not deal directly with the concerns of the seal industry. In like manner, MIL-HDBK-695C applies to any and all rubber goods — but does not satisfy the needs of the seal industry. ARP 5316 was written to “fill the void” and provide a foundation upon which seal manufacturers, distributors, and users could generate realistic shelf life criteria.
ARP 5316 does not mention the quarter of cure, but instead refers to the “time of manufacture.” At Global O-Ring, we utilize the last day of the quarter of cure as the time of manufacture.
ARP 5316 recommends individual packaging of rubber seals to protect them and maintain batch traceability. We have found that our bulk packaging accomplishes the same. In addition, the data utilized by the SAE committee was based on the examination of 32-year-old seals. No differences were found between bulk packaged and unit packed seals in this study. Therefore, we feel that unit packaging is not critical for attaining the stated shelf lives; however, it will be available at customer request.
Because ARP 5316 represents the latest and most accurate information concerning shelf life of elastomer seals, Global O-Ring and Seal recommends that all distributors and customers work to incorporate the new guidelines in the most appropriate manner. ARP 5316 is a copyrighted document. Copies of ARP 5316 may be purchased from SAE by calling (724) 776-4970 or at http://standards.sae.org/arp5316c/.