Foam preventative Antifoaming agent

Foam Preventative. See Foam Inhibitor, Antifoaming Agent. 

In addition, even where foaming is not a specific problem in a boiler, carryover may occur, especially in lower pressure boilers with very high TDS (i.e., over 10,000 to 15,000 ppm TDS) because of the collapse of surface bubbles. This leads to BW aerosol generation and entrainment of the spray in steam. Under these circumstances, antifoam agents such as polyamides are useful in preventing these entrainment problems. Furthermore, the antifoaming action of polyamides is often enhanced by protective colloid materials such as tannins, and consequently, formulations containing polyamide emulsions in an alkaline tannin base are available. 

Antifoaming agent A chemical that is added to a liquid mix to prevent formation of foam, or added to the foam itself to break a foam already formed. 

Foam Control. Fermentations tend to froth because metabolites have surfactant properties. Prevention commonly is by addition of antifoam agents such as oils, heavy alcohols, fatty acids, or silicones. High-speed rotating impellers destroy bubbles by direct impact and by throwing them against the wall of the vessel. 

The presence of oil in boiler water is intolerable, as it causes foaming and cany-over. Steps should be taken to prevent its entiy into the boiler through the feedwater system or leakage through pressure seals and joints. Organic antifoaming agents are a recent development with some successful application. However, their use should not be considered a cure-all. 

Antifoam agents Prevent foam formation. Foaming of lubricants is detrimental for two reasons. First, in an oil-circulation system foaming may lead to a break-down of the lubrication transport. Second, the increased surface area in a foam accelerates oxidation. 

The prevention of foaming and the destruction of existing foams is often a matter of practical importance for example, polyamides and silicones find use as foam inhibitors in water boilers. Antifoaming agents act against the various factors which promote foam stability (described above) and, therefore, a number of mechanisms may be operative. 

Any agent that acts to prevent foaming. Also termed foam preventative . A more general term is antifoaming agent . See also Antifoaming Agent. 

Recently, emulsions based on oligomethylsiloxane liquids have been widely used as antifoaming agents to suppress or prevent foam in aqueous, nonaqueous and low-aqueous solutions, and as separating lubricants in pressure molds for tyre production. They are also used in foundry work to manufacture rods and in the production of elastomers and plastics. 

On the other hand, some substances, even in minute concentrations, promote coalescence. Some of the non-ionic surfactants often used as antifoaming agents are so effective that a concentration of 3 ppm is sufficient to halve the kLaL of pure water (Zlokarnik, 1979). Clearly the use of surfactants for foam prevention should be avoided whenever possible, and an efficient mechanical foam breaker should be used (Zlokarnik, 1986). 

An important issue is the proper design of the distributors for the solvent and an adequate liquid holdup in the pump sump to balance fluctuation in the liquid flow sometimes caused by foaming. Foaming may require addition of suitable antifoaming agents. To reduce the mechanical energy demand the laden solution is depressurized over a hydraulic turbine mounted on the pump shaft. In processes which need addition of inhibitors to prevent corrosion, careful control of inhibitor concentration is required. 

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