Green dery seal failures
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• Operators in the US have experienced a nationwide rash of fuel seal failures since the introduction of low-sulphur diesel on 1 October. All US road-going vehicles must use the cleaner diesel from that date as part of the forthcoming 1994 US Environmental Protection Agency (EPA) emissions limits. The low-sulphur fuel is needed to reduce exhaust particulate emissions to a maximum of 0.1g/bhp/h.
The seals affected are made from nitryl rubber and some appear to be failing after as little as three weeks use with the new fuel, according to the US trucking industry newspaper Transport Topics. The problem does not appear to be confined to any one manufacturer: reports indicate that Navistar, Caterpillar and Cummins engines have all been affected. Cummins PT fuel pump, throttle shaft and front housing seals appear to have suffered a number of failures.
Cummins has suggested that in time, nitryl seals will swell when exposed to highsulphur, high-aromatic-content fuel. Then, when the aromatic level is reduced to that needed by the new EPA limits, the seals shrink and crack, causing leakage. Fuel and seal manufacturers are working to find the cause of the problem.
Many transport fleets have suffered major disruption because of the number of vehicles off the road. The cost of the repairs is relatively small but operators are reporting as many as half their fleet off the road at one time.
The problem does not seem to have affected operators using low-sulphur fuel in Europe. Andrew Owens of low-sulphur fuel supplier Greenergy says: "I'm aware of it, but we've not come across it in Europe. There's a lot of theory as to what's causing it but no hard answer. It's more related to the manufacture of the fuel pump than the engine."
The Lane Group has been using Greenergy low-sulphur fuel in nine Volvos running on the Body Shop contract since May. Fleet Engineer Ken Riggs reports no fuel pump leaks from the vehicles during that time.