Cochin laboratory

SEDIMENTS ( P 30, D 473, IP 53, ISO 3735)

Knowledge of the sediment content of crude and fuel oils is important both to the refining operations and the buying or selling of the oil. An excessive amount of sediment and water in crude oil is significant because it can cause corrosion of equipment and problems in processing and transporting. An accumulation of sediment in storage tanks and on filter screens can obstruct the flow of oil from the tank to the combustor.

SMOKE POINT (P 31, D 1322, IP 57, ISO 3014)

The smoke point is quantitatively related to the potential radiant heat transfer from the combustion products of the fuel. Because radiant heat transfer exerts a strong influence on the metal temperature of combustor liners and other hot sections of gas turbines, the smoke point provides a basis for correlation of fuel characteristics with the life of these components. It is also an indication of the relative smoke producing properties of kerosene and aviation turbine fuels in a diffusion flame. The smoke point is also related to the hydrocarbon type composition of such fuels. Generally the more aromatic the fuel, the smokier the flame. A high smoke point number indicates a fuel of low smoke producing tendency.

SULFUR

Sulfur compounds contribute to corrosion of refinery equipment and poisoning of catalysts, cause corrosiveness in refined products, and contribute to environmental pollution as a result of the combustion of fuel products. High levels of sulfur compounds adversely affect the fuel performance in the combustion chamber, and the presence of large amounts of oxides of sulfur in the combustion gases is undesirable because of possible corrosion. Some sulfur compounds can also have a corroding action on the various metals of the engine system, varying according to the chemical type of sulfur compound present. Sulfur can cause wear, resulting from the corrosive nature of its combustion by -products and from an increase in the amount of deposits in the combustion chamber and on the pistons. The sulfur content of a diesel fuel depends on the origin of the crude oil from which it is made and on the refining methods. Sulfur can be present test methods in a number of forms, for example, as mercaptans, sulfides, disulfides, or heterocyclic compounds such as thiophenes, all of which will affect wear and deposits. Mercaptan sulfur content has objectionable odor, adverse effects on certain fuel system elastomers, and corrosiveness toward fuel system metals. Following are some of the test method commonly used.

Lamp Method (P 34, D 1266, IP 107)

Wick bold method (D 2485)

XRF method (D 4294, D 2622, IP 336, ISO 20847)

Bomb method (P 33, D 129, IP 61)

Oxidative micro coulometer (D 3120)

UV-Fluorescence method (D 5453)