Storage and Shelf Life

Storage and Shelf Life of Seal Items

Seal system components just like wiper seals, seals (dynamic and static), wear rings and anti-extrusion rings are made of different polymers. Seals are considered as spare parts, which are often stored on shelf for a longer time before installation.

Typical materials are elastomers (vulcanized rubbers), polyurethanes, fluoroplastics, and hard plastics what tend to change their properties as a result of either chemical reaction or physical impact.  Such changes in material properties can lead to degradation of seal conditions and they can become unserviceable. This might be due to aging, hardening, cracking, softening, crazing, and other possible degradations.

Seal material characteristic changes can be the result of different physical and/or chemical factors: heat, humidity, light, oxygen, ozone, and exposure of chemicals or physical contact with different metals,  further physical impact, which can result in permanent deformation of the components.

Polymers will maintain their original  properties for a certain, limited time without significant changes in case, if they are stored and protected properly. Otherwise faster degradation can be occurred.

Useful information and guide  on packaging, storage and cleaning of polymer components are provided by industrial standards, such as ISO 2230 and DIN7716. Polymer products should be stored according to described suggestions, helping to maintain the optimum, serviceable properties of the seals through the entire recommended shelf life.

TEMPERATURE

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsThe preferred storage temperature is between 15°C and 25°C . Close distance to any source of heat (radiator, boiler or any heater), and direct sunlight exposure should be avoided. If the storage temperature is below 15°C , care should be taken during handling in order to avoid any distortion or significant deformation, as they might have stiffened. In such case the seals should be slowly warmed up to 20°C or to ambient temperature.

Oxygen and ozone

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsPolymer materials should be protected from circulating air. Ozone deteriorates many elastomers, so storerooms should be ozone-free and avoid to keep any equipment that can  generating ozone (just like high voltage electric equipment, electric motor, or mercury vapor lamps).

Inspection after storage

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsElastomer products should be checked before installation, in order to ensure their proper condition. Physical changes due to improper storage or excessive storage time can normally be detected by visual inspection, such as  dirt/dust deposits, , hardening or softening, stickiness or discoloration and cracking. (Following an inspection of these characteristics, the recommended maximum storage period might be extended).

HUMIDITY

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsThe relative humidity in the storeroom should be below 65%. Extreme moist and too dry conditions should be avoided and condensation should not occur.

Deformation

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsSeals should be stored in a relaxed condition. Compressive or  tensile strain or any other type of mechanical deformation should be avoided, as cracking might occur. Generally, delivered articles are packed in deformation/stress-free condition, so it is recommended to store them  in the original packaging.

Contact with non-metals

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsDirect  contact between elastomer products or rubber and plastic products with plasticizers must be avoided,  because of possible transfer of plasticizer or any other ingredients. Exposure by chemicals: Lubricants (oils and greases) or different solvents might chemically attack and cause damage to polymer seals. Direct contact between seals and such chemicals must be avoided in storage.

Cleaning of elastomer seals

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsElastomer seals can be cleaned gently by using clean cloth and hand warm water (exception fabric-reinforced rubbers). Benzene, gasoline and similar substances are not suitable. Drying near to direct heat sources (radiator etc.) should be avoided. Sharp-edged or abrasive objects (sand paper, steel brushes) should not be used for cleaning.

LIGHT AND RADIATION

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsElastomer seals must be protected against light sources, especially  sunlight or artificial light with high UV radiation. Individual storage bags offer good protection if they are made of UV-resistant polyethylene. All type of radiations such as radioactive or gamma radiation must be avoided.

Contact with metals

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applicationsDirect contact with certain metal gardes should be avoided, as they can degrade  elastomers. Such metal are iron, copper and its alloys (brass) ,and manganese.

Shelf life

High Performance Sealing Solutions SealFluid Storage and Shelf Life - for Fluid Power Hydraulic and pneumatic applications
When elastomer seals are stored in the recommended conditions described above, seal components retain their typical properties. Recommended shelf life by material grade can be found in the chart below:

Material grade Typical shelf life
Thermoplastic polyurethanes 10 years
Hydrogenated nitrile (HNBR), nitrile (NBR) and chloroprene (CR) 6 years
Ethylene propylene (EPDM) 8 years
Neoprene with cotton 1 year
Nitrile with cotton 1 year
Fluorocarbon (FKM), silicone (VMQ) and fluorosilicone (FVMQ) 10 years
Perfluorelastomer (FFKM) 13 years
Polytetrafluoroethylene (PTFE) virgin and filled unlimited
Polyether ether ketone (PEEK) unfilled and filled unlimited
Ultra-high-molecular-weight polyethylene (UHMWPE) 20 years
Polyester resin 5 years
Polyacetal (POM) 5 years
Polyamide (PA) 5 years
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