Effect of a Heavy Distillate Fuel on U-700

Uncoated R77 (U-700) first stage buckets have seen 8800 h of satisfactory service in a General Electric model MS-5000 gas turbine at Progil burning a heavy distillate fuel. Although this alloy is quite sensitive to hot corrosion by sodium sulphate, these buckets emerged in excellent condition as shown by metallographic examination. Levels of sodium, vanadium, etc., in the fuel were reported to be less than 0.1 ppm for most of the shipments. It appears that thoughtful handling can maintain distillate fuels clean enough to permit satisfactory operation.