O-Ring Shelf Life and Elastomer Storage RecomendationsElastomer and O-Ring Shelf Life Recommendation Summary with Proper Storage:
Experience demonstrates that storage conditions impact the useful life of O-rings than generalized shelf life time. SAE-ARP5316 is the most widely referenced guide for data recording procedures, packaging, and storing of aerospace elastomeric seals. Previously MIL-HDBK-695E and MIL-STD-1523A were also references. SAE-ARP5316 and Industry shelf life recommendations:
FKM, FFKM, Silicone, Fluorosilicone, EPDM, Butyl, FEPM
NBR Buna-N, HNBR, Chloroprene, Hypalon, ACM Polyacrylate
5 or 10 Years
Polyurethane depending on type
Bonded joint O-Ring shelf life is typically the same as the base material since like polymer based adhesives are typically used.
Elastomer and O-Ring Expiration Date Calculation Summary:
The rubber industry uses old US military specs and current SAE Aerospace recommendations to calculate elastomer and O-Ring shelf life in quarter year units presented as 1Q20 meaning first quarter of year 2020. Since the actual manufacturing cure date can occur anytime within the 3 month quarter, the shelf life expiration time does not begin until after the first fully complete quarter. An elastomer cured on November 15th 2020 would have a cure date presented as 4Q20 but would not begin aging for expiration date purposes until January 1st (1Q21). Meaning with a 3 year shelf life it would expire Jan 1st 2024 (1Q24).
Rubber shelf life is not an exact science since it is significantly impacted by storage and handling. For a more relatable example, if milk has an expiration date of today, what time does it expire? Could it spoil earlier? Can it be safe to drink past the expiration date? We will label shelf life and expiration to customer request based on their expertise and judgement of their own storage, handling and usage application judgement.
Elastomer and O-Ring Storage Recommendation Summary:
- Store without stretch or tension including hanging
- Store free from compression or deformation
- Dry contamination free environment less than 25°C (77°F) and 75% humidity
- Protect from direct sun and artificial light, UV and other radiation
- Protect from ozone (generated from some electrical devices)
SAE-ARP5316 Shelf Life and Storage Reference
Experience demonstrates that storage conditions impact the useful life of O-rings than generalized shelf life time. SAE-ARP5316 is the most widely referenced guide for data recording procedures, packaging, and storing of aerospace elastomeric seals. Previously MIL-HDBK-695E and MIL-STD-1523A were also references. SAE-ARP5316 recommendations:
Temperature: The storage temperature shall be below 100°F (38°C), except when higher temperatures are caused by temporary climate changes, and articles shall be stored away from direct sources of heat such as boilers, radiators, and direct sunlight.
Humidity" The relative humidity shall be such that given the variations of temperature in storage, condensation does not occur. If the elastomers are not stored in sealed moisture proof bags, the relative humidity of the atmosphere in storage shall be less than 75% relative humidity, or if polyurethanes are being stored, shall be less than 65% relative humidity.
Light: Elastomeric seals shall be protected from light sources, in particular direct sunlight or intense artificial light having an ultraviolet content. The individual storage bags offer the best protection as long as they are UV resistant. Note: It is advisable that windows of storage rooms where elastomers are stored in bulk be covered with a red or orange coating.
Radiation: Precautions shall be taken to protect stored articles from all sources of ionizing radiation likely to cause damage to stored articles.
Ozone: As ozone is particularly damaging to some elastomeric seals, storage rooms shall not contain any equipment that is capable of generating ozone such as mercury vapor lamps, high voltage electrical equipment giving rise to electrical sparks or silent electrical discharges. Combustion gases and organic vapor shall be excluded from storage rooms as they may give rise to ozone via photochemical processes.
Deformation: Elastomeric seals shall be stored free from superimposed tensile and compressive stresses or other causes of deformation. Where articles are packaged in a strain-free condition, they shall be stored in their original packaging. O-rings of large inside diameter shall be formed into at least three superimposed loops so as to avoid creasing or twisting. Note: It is not possible to achieve this condition by forming just two loops, three are required.
Contact with Liquid and Semi-Solid Materials: Elastomeric seals shall not be allowed to come in contact with liquid or semi-solid materials (for example, gasoline, greases, acids, disinfectants, and cleaning fluids) or their vapors at any time during storage unless these materials are by design an integral part of the component or the manufacturer's packaging. When elastomeric seals are received coated with their operational media, they shall be stored in this condition.
Contact with Metals: Certain metals and their alloys (in particular, copper, manganese, and iron) are known to have deleterious effects on elastomers. Elastomeric seals shall not be stored in contact with such metals (except when bonded to them) but shall be protected by individual packaging.
Contact with Dusting Powder: Dusting powders shall only be used for the packaging of elastomeric items in order to prevent blocking or sticking. In such instances, the minimum quantity of powder to prevent adhesion shall be used.
Contact between Different Elastomers: Contact between different elastomers and elastomers of different seals shall be avoided.
Elastomeric Seals bonded to Metal Parts: The metal part of bonded elastomeric seals shall not come in contact with the elastomeric element of another seal. The bonded seal shall be individually packaged. Any preservative used on the metal shall be such that it will not affect the elastomeric element or the bond to such an extent that the seal will not comply with the product specification.
Stock Rotation: Elastomeric seal stock should be rotated on the FIFO (First In, First Out) principle.
ISO 2230: Rubber products – Guidelines for storage
Additional references for storage conditions and maximum life of elastomer parts can be found in the ISO 2230: Rubber products – Guidelines for storage. This guideline differs slightly from SAE-ARP5361 recommending:
An appropriate packaging material should be free from substances having a degrading effect on the rubber. Heat sealable opaque materials should be used unless not practical to prevent distortion of the packaged product. Suitable materials are polyethylene (PE)-coated Kraft paper, aluminum foil/paper/PE laminate and opaque PE film. PVC film or any other film containing plasticizer is not recommended for direct contact with rubber. PE is suitable as a single wrapping and should be at least 0,075 mm thick. Where there is a serious risk of ingress of moisture, aluminum foil/paper/PE laminate or other similar means of protection should be used to ensure protection.
The major differences from the SAE-ARP5361 storage guidelines are:
- Store in temperature below 25°C, away from direct sources of heat.
- In temperatures below 15°C elastomers can stiffen and should be handled with care to prevent damage. Careful heating to 30°C prior to installation if practical.
- Relative humidity in storage should be less than 70%, for polyurethanes less than 65%
The ISO 2230 standard splits the maximum storage time into an initial storage period and an extended storage period which may be applied after representative samples of the stored products were inspected. Inspection should be in accordance with the relevant production specification. A visual inspection should not show permanent distortions (like creases or flats), mechanical damage (cuts, tears, abraded areas), surface cracking when viewed under a magnification of 10X or changes in surface condition such as hardening, softening or tackiness. Testing can show if the relevant performance characteristics are within the acceptable limits. If the storage temperature is over or under 25°C the storage life will be influenced. Storage at a 10°C higher temperature will reduce the storage time by about 50% and storage at a 10°C lower temperature will increase storage time by about 100%.