Antifoaming additives to turbine oils

Abstract

In the current design of oil reservoirs the presence of foam affects only the oil level and increases its consumption due to losses through the ventilation openings. Aeration of the oil represents a more serious hazard. The deaerating properties of turbine oils deteriorate in the presence of siloxane additives, which are added to prevent excessive foaming [3]. These additives effectively destroy surface foam, however, they enhance the formation of a highly dispersed air-oil emulsion and reduce significantly its sedimentation rate. The search for new additives which would inhibit foaming and at the same time would not affect negatively the deaerating properties therefore represents an acute task. From thermodynamic concepts it follows that single-component liquids are not capable of forming a stable foam; it breaks down rapidly, regardless of the surface tension. A stable foam can occur 0nly in a multicomponent system, where even one of the components possesses surface-active properties and is capable of adsorbing at the interface. Lubricating oils .represent complicated multicomponentsystems which contain different surfactants in the base oil as well as in the additives. Consequently, many oils are inclined to foaming in the exploitation process which leads to the need of adding antifoam agents. Turbine oils manufactured according to GOST 9972-74 contain the antifoam PMS-200A organosilicon additive. Organosilicon compounds are being widely used as antifoaming agents. They are chemically inert, stable and effective at high temperatures~ available~ and inexpensive. Their viscosity and surface tension vary within wide limits [4]. The antifoaming properties of siloxane polymers are due to the unusually low surfice strength of their films and to the ability of displacing the not strongly enough adsorbed molecules of the foam stabilizer. The mechanical strength of the mixed adsorbed film is lost due to deep changes related to the occurrence of weakened sections. These sections are the first to break down under