Pumps, metering

Process and Equipment. Rigid polyurethane foam processes use the same high or low pressure pumping, metering, and mixing equipment as earher described for flexible foams. Subsequent handling of the mixture is deterrnined by the end product desired. 

Prepare solvent bank by carrying out the steps below in sequence 2.1.1 Select correct pump 2.1.2 Set pump meter to zero and enter the required amount of solvent 2.1.3 Connect up hose... 

Others, e.g., air pump, metered Advantages Deeouples aerosol generation from patient... 

Poly (3,3-Bis(Chloromethyl)Oxetane) This is marketed by Hercules as Penton chlorinated polyether. Its thermal, flame, and chemical resistance are used primarily for corrosion-resistant equipment in the process industries, such as valves, fittings, pumps, meters, and linings for steel pipe and tanks, for service in many corrosive atmospheres up to 250°F. or higher. At 4.50/pound, growth possibilities appear limited by increasing competition from lower-cost materials. 

Rotary positive-displacement pumps with no valve action gear pumps, lobe pumps, screw pumps, eccentric-cam pumps, metering pumps... 

Single system convenience. All elements for pumping, metering, mixing, and controlling mounted within one unit result in minimal floor space requirement and if layout is appropriate, allows easy maintenance. 

Patient inhalation Other (air pump, metered propellant, electrical, other)... 

The spin pump (metering pump) delivers the molten polymer to a spin pack, which consists of a top cap and a breaker plate to distribute polymer evenly, then into a filtration media and out of the spinneret. The filtration media contains either different layers of special sand, layers of different size of stainless steel screens, or sintered metals. In addition to removing the foreign particles, gel particles and undesirable conglomerate additives, filtration may also improve the polymer melt homogeneity due to its torturous path and high shear of the filtration media. 

Any moisture contamination of the cell has a deleterious effect on its operation. Therefore, all cell assembly operations are usually carried out in a dry room or dry box. Alternatively, the cell then may be put in a heated vacuum oven for 16-24 h in order to extract residual water from the cell core before electrolyte filling. In the next process, the cell is filled with the electrolyte using a vacuum injection apparatus. Electrolyte is added to the cell by a precision pump and then vacuum filled to ensure that the electrolyte permeates and completely fills the porosity in the separator and electrode structures. Precision pumps meter the exact amount of electrolyte needed for good cell operation. The electrolyte salt usually is LiPF dissolved in a... 

Because the NCO/OH equivalents ratio must be accurately held, it is important that the pumps meter precisely and thoroughly mix the polyol and isocyanate, in order that their end-groups come into intimate contact... 

Polymers. Foam is often a particular problem in the production of polymers. There are numerous situations where foam can reduce the production capacities of vats and vessels and cause problems in pumps, meters, and other equipment, particularly distillation and evaporation equipment. Foam is frequently a problem when stripping off a monomer from a polymer. Examples are in the production of styrene-butadiene [9003-55-8] and acrylonitrile-butadiene [9003-18-3] rubber latices. These latices are stabilized by surfactants that greatly contribute to foaming difficulties. Another problem foam area is in the stripping of imreacted monomer from poly(vinyl chloride) suspensions. In this process, vinyl chloride [75-01-4], a gas at room temperature, is liquefied by pressure, emulsified in water with surfactants and catalysts, and heated to bring about polymerization. The recovery of unpolymerized monomer by distillation from this mixture produces a severe foaming problem. 

The pumps, metering, mixing and application systems must be adapted to the viscosity of both the components. The viscosities of the two components should be similar in order to get a good mixing effect a very liquid product could not be mixed efficiently with a very thick product. Rheology, of course, must be also adapted the products may be pseudoplastic, thixotropic but never dilatant (for these definitions, refer to Chapter 2 in Volume 1 Technical Characteristics of Adhesives and Sealants ). 

PPE blends with styrenics have found wide application in the automotive, electrical and electronics industries, in manufacture of furniture, business machines, apphances, etc. Owing to low moisture sensitivity and good processability, they are used for water pumps, meters, critical plumbing. 

Dosierpumpe dosing pump, proportioning pump, metering pump... 

Some chlorine dioxide feed systems use a batch generation process. Regardless of the generator used, it fills a batch storage tank. A feed pump meters the chemical to the feed location. Continuous... 

The circuit diagram in Fig. 1 shows the common gear pump metering system. The degree of sophistication governing the driving and monitoring of these devices varies from manufacturer to manufacturer, as does the cost. 

Fig. 1. Gear pump metering circuit. PA—resin metering pump PB—hardener metering pump V—three-way valve M—drive motor C—mixer. A—resin tank, B—Hardener tank.

The basic circuit diagram for this type of metering system is shown in Fig. 2. The resin (A) and hardener (B) tanks can incorporate the same features as described previously for the gear pump metering system, in addition to mixing methods. 

The chemical injection pumps meter the solution into a mixing header with flow rates automatically controlled by continuous monitoring of the boiler load, temperature, and NO, concentration (Nalco, 1990 Epperly and Hofmann, 1989). The concentrated NO,OUT A solution is diluted with water and flows to the injector modules through the distribution piping. Typically, a total of S-7 scfm of plant air per injector has been used for atomization and for the wall-injector outer cooling jackets (Grisko, 1992). When steam is used for atomization, about 50 Ib/hr of 50 psig steam per injector is required. 

Electrolyte is metered into the cell by a precision pump and vacuum filled to ensure that the electrolyte permeates and completely fills the available porosity in the separator and electrode stmctures. Precision pumps meter the exact amount of electrolyte needed for good ceU operation. The amount of electrolyte is generally arrived at by trial and error, based on the performance of the cells. The electrolyte is invariant (same number of Li" ions enter as leave the electrolyte during charge and discharge). The electrolyte salt is usually LiPFe dissolved in organic carbonate solvents (see the ch ter on Liquid Electrolytes by J. Yamaki). Each manufacturer has a different combination of solvents with ethylene carbonate (EC) being a common denominator for most... 

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