DIN 7716 (guideline for storage, maintenance and cleaning of rubber products) applies to the storage of O-rings. Proper storage is important. The service life of O-rings can be affected by many influences, such as light, heat, humidity, oxygen, ozone, etc., and thus changed. The ideal temperature for storage is between + 5 and + 20 degrees C. In general, storage in polyethylene bags welded together is considered optimal. We recommend not to exceed the following storage times significantly:
|4 years||4 years||6 years||10 years||10 years|
The following guidelines (excerpt from DIN 7716) apply to rubber products in pure and composite form with other materials, namely to elastomers made of natural and/or synthetic rubber as well as to adhesives and solutions. The guidelines in accordance with DIN 7716 Sections 3 and 4 primarily apply as requirements for long-term storage (generally longer than 6 months). For short-term storage (less than 6 months) - such as in production and delivery warehouses with continuous material outflow - the provisions of DIN 7716 shall apply mutatis mutandis, with the exception of the general requirements for storage space in accordance with Sections 3 and 3.1, as long as the appearance and function of the products are not adversely affected thereby (see DIN 7716 Section 2) and as long as there is no contradiction to the special requirements of this standard for expressly short storage periods for rubber products (see DIN 7716 Section 4.2.b).
Under unfavourable storage conditions or improper handling, most rubber products change their physical properties. They can, for example, become unusable due to excessive hardening, softening, permanent deformation as well as flaking, cracking or other surface damage. The changes can be caused by the effects of e.g. oxygen, ozone, heat, light, moisture, solvents or storage under voltage. Properly stored and treated rubber products remain almost unchanged in their properties over a long period (several years).
The storage room should be cool, dry, dust-free and moderately ventilated.
The storage temperature should be +15°C and must not exceed +25°C, otherwise the physical properties may harden or the service life may be shortened. The storage temperature should not be below -10°C either. Lower temperatures are generally not harmful to rubber products, but they can become very stiff at lower temperatures. Strongly cooled products must be brought to a temperature of more than +20°C for a longer period of time before commissioning. Adhesives and solutions must not be stored colder than 0°C. Rubber products made of certain chloroprene rubber types may not be stored colder than +12°C.
When heating the storage room, radiators and pipes must be screened. The heat sources in the storage rooms should be designed so that the distance between the radiator and the stored goods is at least 1 m.
Rubber products should not be stored in damp storage rooms. Make sure that no condensation occurs. The relative humidity is best below 65%.
The rubber products should be protected from light, in particular from direct sunlight and from strong artificial light with a high ultraviolet content. For this reason, the windows of the storerooms must be provided with a red or orange (under no circumstances blue) protective coating. All light sources emitting ultraviolet rays, such as openly installed fluorescent tubes, are particularly harmful because of the ozone formation associated with them. Room lighting with normal incandescent lamps is preferable.
Rubber products shall be protected against air changes, especially draughts, by wrapping, by storage in airtight containers or by other means. This applies especially to articles with a large surface area in relation to volume, such as rubberized fabrics or cellular articles. Since ozone is particularly harmful, storage rooms must not contain any ozone-generating devices such as fluorescent light sources, mercury vapour lamps, electric motors or other devices that can produce sparks or other electrical discharges. Combustion gases and vapours which can lead to ozone formation through photochemical processes should be eliminated. Solvents, fuels, lubricants, chemicals, acids, disinfectants, etc. must not be stored in the storage room. Rubber solutions must be stored in a special room in compliance with official regulations on the storage and transport of flammable liquids.
It must be ensured that rubber products are stored stress-free, i.e. without tension, compression or other deformations, since stresses promote both permanent deformation and cracking. Certain metals, in particular copper and manganese, have a damaging effect on rubber products. Therefore, rubber products must not be stored in contact with these metals but must be protected by packaging or by sealing with a layer, e.g. paper or polyethylene. The materials of the containers, packaging and covering material must not contain any components harmful to rubber products, e.g. copper or copper-containing alloys, petrol, oil and the like. Films containing plasticizers must not be used for packaging. If rubber products are powdered, the powder must not contain any components harmful to the rubber products. Suitable for powdering are talcum, slurry chalk, fine-grained mica powder and rice starch. Mutual contact between rubber products of different compositions should be avoided. This is especially true for rubber products of various colours. Rubber products should remain in stock for as short a time as possible. In the case of long-term storage, care must be taken to ensure that new products are stored separately from existing ones. At this point we refer to the DIN 9088 Aerospace Guidelines for the permissible storage times of products made of elastomers.
CLEANING AND MAINTENANCE
Rubber products can be cleaned with soap and warm water. Cleaned articles must be dried at room temperature. After a longer storage (6 to 8 months) the products can be cleaned with a 1.5% sodium carbonate solution. The residues of the cleaning liquid must be rinsed off with water. Effective and particularly gentle cleaning agents are recommended by the manufacturer. Solvents such as trichloroethylene, carbon tetrachloride and hydrocarbons must not be used for cleaning. The use of sharp-edged objects, wire brushes, emery paper etc. is also prohibited. Reproduced with permission of the German Standards Committee. The most recent edition of the standard sheet in A4 format, which was published at the Beuth distribution GmbH is available.