Common use of SULFUR Clause in Contracts

SULFUR. Sulfur occurs in fuels as combustible organic compounds yielding sulfur oxides on combustion. These combine with any traces of sodium or potassium present to form alkali sulfates; a principal source of hot corrosion. The sulfur level in a fuel cannot be lowered enough by refining to avoid the formation of alkali sulfates, so that they must be controlled by limiting the sodium and potassium levels in the fuel. Gas turbine installations utilizing exhaust heat recovery equipment could have metal temperatures below the dewpoint of sulfuric acid, and in these cases it is necessary to know the sulfur level in the fuel to avoid acid corrosion of heat transfer surfaces. The maximum allowable sulfur to avoid sulfuric acid condensation will depend on the specific heat recovery equipment used. For fuels exceeding this maximum level, the operating temperature of the heat recovery equipment could be changed accordingly to avoid condensation of acid products. The sulfur level of liquid fuels is regulated in many localities as a means of controlling the emission of sulfur oxides in the exhaust gases. Crude oils burned directly as fuels may also contain active sulfur in the form of hydrogen sulfide or mercaptans. These substances, especially in the presence of water, may cause corrosion to fuel system components. For this reason, the water content of such fuels should be kept as low as possible.