Storage is the most important process that affects the life of the seal from production to installation. Correctly stored parts can remain ready for use for many years without any problems.
Especially for rubber parts, storage in accordance with ISO 2230 standard is recommended. If these requirements are followed, shelf life values for rubber products are shown in the table. In the table, all rubber types are divided into three groups and first shelf life and extended shelf life are defined for each group. At the end of the relevant shelf life, the rubber parts are checked according to the criteria to be determined by the user or manufacturer (visual inspection, testing, etc.). If appropriate, the shelf life of the table is extended by the extension time. At the end of each period, the relevant parts are periodically checked again. Controls can be performed on representative samples of stored products.
As a simple example, if an NBR-based material is stored under appropriate standard conditions according to the table, the initial shelf life is 7 years from the date of manufacture. At the end of this period, the shelf life is prolonged by 3 years with the appropriate control.
|A||BR, NR, IR, SBR, AU, EU||5||2|
|B||NBR, NBR/PVC, XNBR, HNBR, CO, ECO, ACM, CR, IIR, BIIR, CIIR||7||3|
|C||CM, CSM, EPM, EPDM, FKM, Q, PMQ, PVMQ, MQ, VMQ||10||5|
If the storage temperature is 25 oC or more, the shelf life is reduced by approximately 50% over the mentioned values. If the temperature is 10 oC C or less, the shelf life is increased by approximately 100% from the above values.
The temperature in the storage area should be below 25°C. Higher temperatures trigger material aging, resulting in shortens the shelf life.
In general, low temperature is not very common, but especially at temperatures below 15 ° C, the rubber hardens and becomes relatively brittle, so at these temperatures to avoid damage care should be taken. Increasing the temperature of the rubber parts stored at such low temperatures to room temperature before installation in the field, would be beneficial during the installation and prevent cracking, tearing and breaking.
Relative humidity should be below 70%. This limit value for polyurethanes is 65%.
Condensation builds up on parts stored in high humidity and low temperature environments. Some rubber types can collect water by being affected by moisture in the environment even without condensation. This is generally reversible, but water oxidation can permanently break down and degrade some components in the rubber.
Sunlight and high UV content illuminate the rubber to early aging. When possible, it is recommended to keep the area where rubber parts are stored away from direct sunlight, and to cover the windows with films that prevent UV.
In practice, there is not a high amount of storage throughout the area, it should be known that any radiation has a corrosive and disruptive effect on rubber products.
Rubber parts must be protected from ozone as it causes oxidation and triggers deterioration of the rubber surface. For this reason, the products should be kept in their original packaging, there should be no lighting and equipment in the storage area that produce a high percentage of ozone. In addition, it should be noted that the waste gas produced by fuel-powered forklifts or similar stacking equipment has the effect of triggering ozone formation.
Products should not be stacked that they crush each other in the storage area or crush under heavy parts. Seals should not be hung on tools such as nails, hooks, wire, rope and so on. Soft products should not be folded by hand unless they are folded in their original packaging. Products should not be positioned on their sharp edges or corners.
If necessary, load distributing separators should be used to prevent possible crushing on sensitive walls of the product. The elastic deformation on the rubber is generally reversible, but the deformation on some rubbers may not be 100% reversible. Furthermore, permanent damage or plastic deformation may occur on the part. If this damage occurs in a critical area, there may be early leakage in the application.
Rubber parts should not be kept out of their original packaging and must not be allowed to contact with cleaning chemicals, solvents, fuels, unidentified oils, alcohols or acid derivatives. It should not contact with various dense gases other than liquids or some special solid metal surfaces (e.g. copper or alloys). Oil seals should not be kept in lubricants or fuel derivatives that are unsuitable for the rubber, and should not be lubricated with undefined grease or similar chemicals.
Products should not be stored outside their packaging in such a way that contacting with dust. Seals stored outdoors in a manufacturing area where there is lots of dirt or dust, easily hold dust and dust particulates accumulated especially in areas such as lip trace tape, after installation disrupt the oil film. This causes early leakage.
The storage and release system should comply with the ‘first in, first out’ principle to ensure optimal shelf life.