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What recommendation do we have for applications using Low Sulfur Diesel Fuel?

Diesel Fuel Can Shorten Life of Buna-N or Nitrile Seals

Square D / Schneider Electric has recently been made aware of leaks in an installation using pressure switches containing nitrile or Buna N diaphrams. Replacements appeared to experience the same failure in a relatively short time, while other installations in the same plant operated successfully. The only apparent difference between locations was the material being monitored. The leaks all occurred in a system monitoring low sulfur diesel fuel.

Research resulted in the discovery of documentation of a mandated change in the composition of low sulfur diesel fuel, which was issued by the Environmental Protection Agency (EPA) in 1990. The change in composition of the fuel results in a product (chemical?) that attacks Buna N or nitrile.

Pending further investigation, Square D / Schneider Electric recommends using Viton seals as an alternative where float switch or pressure switch installations will be exposed to low sulfur diesel fuels.


Current Installations: Replace leaking diaphrams or seals with Viton replacements on a case by case basis. On products such as 9013, where no Viton is available, customers should replace these devices with 9012 which does have the Viton diaphram option.

New Installations: Request forms which use Viton seals on new float and pressure switch installations where Low Sulfur Diesel fuel may be encountered. Choose 9012 pressure switches with Viton diaphrams in lieu of 9013, as Viton diaphrams are not available for 9013.

We have requested return of several pressure switches exposed to low sulfur diesel fuel, and will begin tests on their arrival.

Note: When substituting 9012 devices with Viton seals for 9013 devices using Buna-N or nitrile, an interposing relay may be required as the 9012 is control voltage rated, not horsepower rated.

CTA-ID : 12279
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