Elastomer materials are more sensitive to fluids than other sealing compounds. Chemical reaction can cause damage to the seal, affecting physical properties. Specifically in hydraulic applications, selection of the optimum elastomer material for a given hydraulic fluid is critical. Not only must the oil used be taken into account but also the additives, as these can cause adverse behaviour. It may be necessary to conduct a soak test at elevated temperature in order to verify the performance in application.
Turel® Compounds are available to operate in temperatures from -73°C to +260°C / -100°F to +500°F. Most will therefore meet the temperature requirements of AS4716 type II systems, specified as -54°C to +135°C / -65°F to +275°F. The use of spring- energized Variseal® can expand the temperature range even further. In addition, for high-temperature applications, Isolast® J8325 has an operating temperature up to +325°C / +617°F.
The effect of temperature cycling on elastomer seals can result in compression set. This means that the elastomer material loses its elasticity over time. For Turel® materials, this effect is kept to an acceptable minimum if they are specified for applications with operation temperatures within the indicated parameters. The low-temperature dynamic cycling limits vary according to elastomer type.
Elastomer materials from Trelleborg Sealing solutions are specifically engineered to give maximum performance in cold conditions.
Elastomer materials contract approximately ten times more than steel in cold environments. The material becomes stiffer and loses its flexibility at cold temperatures. When passing the lower limit it reaches the glass transition stage, when it becomes extremely brittle. Physical properties will recover when temperatures elevate again. Increased squeeze can improve performance at low temperatures.
Elastomer materials soften and lose their physical properties if the upper temperature limit is exceeded. Physical properties will not recover and the seal will take on a permanent compression set. The compression set also varies with the type of media to which the elastomer is exposed. Continuous exposure to temperatures higher than those recommended can permanently damage the seal.
In general, the speed of the dynamic surface in contact with an elastomer seal should be kept below 9.8 ft/s / 3 m/s to avoid damage to the elastomer.
The maximum recommended storage and shelf time can be seen in our Aerospace Sealing Systems Product Catalog and Engineering Guide. These values are only valid if the elastomer is stored under controlled conditions in light-proof and airtight packaging.
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