Synthetic oils destroy traditional Nitrile seals

A new range of rotary shaft seals has been introduced to provide a higher performance alternative to traditional Nitrile seals, which tend to fail prematurely when exposed to modern synthetic oils

A new range of rotary shaft seals from Dichta has been introduced to provide a higher performance alternative to traditional Nitrile seals, which tend to fail prematurely when exposed to modern synthetic oils.

The new Viton-based designs offer a longer service life at higher temperatures, and an increased speed capacity of up to 6,000 rpm.

Six models are available, providing varying degrees of pressure capacity, dust protection, and resistance to misalignment.

The standard size range will accommodate shaft diameters from 10-500 mm.

Constant demand for longer life and higher operating speeds from machinery has led to the widespread use of synthetic lubricants, this is causing a serious problem with existing Nitrile seals, as synthetic oils weaken the material structure of these products.

A spokesman explained: "The result is a premature seal failure that can cause extended down time due to leaks, product contamination and lost production.

Nitrile seals are still being used in preference to higher performance sealing designs, using Viton lip elements, because of their comparatively low initial cost".

"The cost implications of a seal failure far outweigh the cost of a better quality seal, making this practice a false economy and underlining the reason for the introduction of the new Dichta range of high-quality Viton-based rotary shaft seals".

Viton is said to offer excellent resistance to both mineral oils and advanced synthetic types - such as high-alloyed hypoid oil - and to ozone and weathering, providing longer operating life and reducing the chance of machine failure.

Traditional Nitrile based seals typically have an operating temperate range of up to 160C while Viton maintains sealing performance in applications where temperatures reach 200C, and shaft speeds exceed 6,000 rpm.

The new range includes more than 200 metric sizes in six basic types, including seals with rubber-covered metal inserts for speedy installation, types with dust lips for additional protection from contaminants, and models with reinforcing caps to withstand pressures in excess of 10 bar.

Standard designs are available to fit bore sizes from 10-500 mm, and with garter springs manufactured from either harmonic spring steel or stainless-steel for more demanding applications.

Variations include twin lip types with two garter springs for additional protection, designs that offer right rotation, left rotation, and bi-directional hydrodynamic lips.

The hydrodynamic design produces a spiralling effect for recycling the lubricant from the lip back into the system, therefore minimising the risk of leakage and contamination.

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