Damping fluid

This indicated the necessity to completely clean the system when changing between different parts to be cleaned. A typical cleaning process involves performing a 1 hour SCF run with an empty chamber. Cross-contamination can be a problem when using one piece of equipment to clean multiple contaminants, especially when one of those materials is being collected for reuse. 

---

Silicone Fluids. Sihcone fluids are used in a wide variety of appHcations, including damping fluids, dielectric fluids, poHshes, cosmetic and personal care additives, textile finishes, hydraiflic fluids, paint additives, and heat-transfer oils. Polydimethylsiloxane oils are manufactured by the equihbrium polymerisation of cycHc or linear dimethyl silicone precursors. Trifunctional organosilane end groups, typically trimethylsilyl (M), are used, and the ratio of end group to chain units (D), ie, M/D, controls the ultimate average molecular weight and viscosity (112). Low viscosity fluids,... 

Oligosilsesquioxanes with long-chain alkyl substituents have been offered as water-repellents and adhesives for pearlite heat-insulating plates and materials and as damping fluids and structural plasticizers for polymeric ceramic materials which allow to control the properties of the latter in the manufacture of the items concerned. 

Ferrofluids find several technical applications, which include rotary shaft seals, damping fluids, accelerometers, optical switches and shutters, and magnetic inks. The earliest application was in the construction of wear-free seals for rotary shafts. A similar seal is used in computer disc drives. Using ferrofluids, high-pressure differential seals which work in multiple stages have been constructed. When the seal is pressurized, each stage develops a momentary leak into the next chamber. The total pressure that can be contained is the sum of the pressure differences across all the stages. Pressure seals... 

Sheng Jiang is pungent and slightly warm, and enters the Stomach and Spleen meridians. It can soothe the Stomach-Qi, subtly disperse accumulation of dampness, fluid and phlegm in the Stomach, and can therefore promote digestion. Da Zao is sweet and warm, and can tonify the Qi and blood. These two herbs are often selected as assistants in the formula... 

Momentum control gyroscopes and precision guidance instruments are used to control and detect movement in satellites, space probes and platforms, airplanes and missiles. They are, composed of a number of extremely complex electromechanical systems with circuit card assemblies, wire windings, lamination stacks, ball, roller, and gas bearings, and potted components which contain small voids and crevices. Tolerances on these assemblies can be in the microinch range. These instruments can contain lubricants and the previously discussed damping fluids. 

Perfluoropolyether fluids (ex., Krytox ) are commonly used as lubricants, dielectric fluids or heat transfer fluids in a number of space and military products. These fluids and other perfluorolubricants are almost impossible to dissolve in solvents other than halocarbons. Additionally, other halogenated damping fluids have compatibility problems with some of the common solvents which can dissolve the fluid. Early experiments with supercritical carbon dioxide indicated that it would dissolve both halogenated damping fluids and perfluoropolyether lubricants and thus was a candidate as a replacement solvent cleaning process. 

After the SCF system was operational, it was necessary to determine process parameters for removal of the common contaminants. Temperature, pressure, flow rate and time were identified as critical parameters and a number of experiments were designed using Taguchi methods to minimize the number of experiments necessary to accurately determine the effects of these parameters on the cleaning effectiveness. Damping fluid, Krytox 143AZ lubricant, and hydrocarbon vacuum pump oil were selected as the contaminants for removal. 

The results of the these experiments showed that the damping fluid, Krytox , and hydrocarbon oils all could be successfully removed using supercritical carbon dioxide at pressures in the range of 1200-3000 psi and temperatures in the range of 90 to 185°F. The Krytox lubricant was easily removed at the lower extremes, while the hydrocarbon oil was the most difficult to remove. 

With over three years invested in the development and qualification of the supercritical cleaning process, the next phase of the implementation plan was cleaning of production hardware. The two key operations which had been identified early on as potential applications were the cleaning of end housings and the removal of bulk amounts of damping fluids from fill system fixturing. 

The ability of SCF to remove contaminants is directly related to the number of volume exchanges of SCF within the cleaning chamber and the amount of contaminant. Previous experiments in removal of damping fluid indicated that it would take approximately 3-4 hours at 3500 psi and 185°F with a flow of 1.0 Actual Cubic Feet per Minute (ACFM) to clean fill stand hardware. This was performed in the small (2.4 liter) chamber. Since the volume of the new chamber (14.9 liter) was much greater than the previous chamber, it was anticipated that... 

Use Corrosion control, contamination prevention, insulation, electrical equipment, molded and fabricated industrial equipment, lubricants, gyro and damping fluids. Especially useful under extreme conditions, including jet and space technology. 

---