Spray heads

Polyester resin coatings are synthesized with components that introduce unsaturation into the polymer chain (—C=C—). The paint is manufactured by mixing a dissolved polyester resin in styrene monomer with pigment and reaction inhibitor. Additional styrene and peroxide are packaged in a separate container and are mixed with the paint when applied using a dual-headed spray gun. Peroxide serves as a radical polymerization initiator for the polyester resin with monomeric styrene and cross-linking. Figure 13.5 shows the chemical structure of an isophthahc polyester resin. 

To increase the production rate, spray-up technique is used instead of a hand lay-up technique. This technique employs a multiple-headed spray gun. The resin mixture and chopped fibres are discharged simultaneously by using the spay gun on the surface of the mould where they are deposited to a uniform thickness. Sheets, storage vessels, auto body parts, boat hulls, truck bodies and building components are made using this process. 

Fig. 9.6, Sectional view of the Grand Gulf boiling water reactor (courtesy of General Electric Company and Nuclear Engineering International). A, Vent and head spray B, steam dryer C, steam outlet D, core spray outlet E, steam separators F, feedwater inlet G, feedwater sparger H, L.P. coolant injection inlet J, core spray pipe K, core spray sparger L, top guide M, jet pump N, core shroud O, fuel assemblies P, control blade Q, core plate R, jet pump water inlet S, recirculation water outlet T, vessel support skirt U, control rod drives V, in-core flux monitor.

Suction hood Spray head Spray plume... 

Flame Sources Atomization and excitation in flame atomic emission is accomplished using the same nebulization and spray chamber assembly used in atomic absorption (see Figure 10.38). The burner head consists of single or multiple slots or a Meker-style burner. Older atomic emission instruments often used a total consumption burner in which the sample is drawn through a capillary tube and injected directly into the flame. 

Spray. In spray-on appHcations the reactive iagredients are impingement mixed at the spray head. Thickness of the foam is controlled by the amount appHed per unit area and additional coats are used if greater than 2.5 cm (1.0 ia.) thickness is required. This method is commonly used for coating iadustrial roofs or iasulatiag tanks and pipes. 

Thermal or Flame Spray Process. The earliest experiments in metal spray used molten metal fed to a spray apparatus, where it was dispersed by a high speed air jet into tiny droplets and simultaneously blown onto the surface of the part to be covered. The metal solidified on contact. Modem processes use a more convenient source than premelted metal. Spray heads using a flame or an electrical arc to melt metal wires or powders directly are much more convenient. These are the only types used on a large scale in the United States. 

The objective in packaging cool sterilized products is to maintain the product under aseptic conditions, to sterilize the container and its Hd, and to place the product into the container and seal it without contamination. Contamination of the head space between the product and closure is avoided by the use of superheated steam, maintaining a high internal pressure, spraying the container surface with a bactericide such as chlorine, irradiation with a bactericidal lamp, or filling the space with an inert sterile gas such as nitrogen. 

Safety Showers. Safety showers and eyewash fountains or hoses should be installed where corrosive or toxic materials are handled. A large-volume, low velocity discharge from directly overhead should effect continuous drenching, ie, a minimum flow of 20 L/min (50 gal /min). Water to outside showers may be heated to a maximum temperature of 27°C by an electric heating cable. The valves for all safety showers should be at the same height and relative position to the shower head, and they should operate in the same way and direction. The shower station should be identified by paint of a bright, contrasting color. In areas where chemicals harmful to the eyes may be encountered, an eyewash fountain or spray should be available in case of splash accidents. 

The rain test simulates the effects of rainfaU the hydrostatic head on the spray controls the intensity of spraying. The repeUency is rated by the weight of water that penetrates the fabric and is absorbed by a blotter mounted behind the fabric at a specific intensity of spraying (AATCC Test Methods 35 and 42 INDA Standard Test 80.2-92). 

The fluid dehvery in an air-spray system can be pressure or suction fed. In a pressure-fed system, the fluid is brought to the atomizer under positive pressure generated with an external pump, a gas pressure over the coating material in a tank, or an elevation head. In a suction system, the annular flow of air around the fluid tip generates sufficient vacuum to aspirate the coating material from a container through a fluid tube and into the air stream. In this case, the paint supply is normally located in a small cup attached to the spray device to keep the elevation differential and frictional pressure drop in the fluid-supply tube small. 

Vapor-Liquid Separation This design problem may be important for a number of reasons. The most important is usually prevention of entrainment because of value or product lost, pollution, contamination of the condensed vapor, or fouling or corrosion of the surfaces on which the vapor is condensed. Vapor-liquid separation in the vapor head may also oe important when spray forms deposits on the w ls, when vortices increase head requirements of circulating pumps, and when shoiT circuiting allows vapor or unflashed liquid to be carried back to the circulating pump ana heating element. 

Fig. 4. Application of fibrin sealant (arrow points to spray head for applying two-component adhesives) at the time of mastectomy and axillary dissection to reduce seroma formation.

Rail cars, tank trucks, and some reactors and storage tanks were cleaned manually by personnel who entered the vessel fatalities occurred from unexpected or undetected low oxygen content or toxicity. An inherently safer system is a rotating pressurized water spray head that does the cleaning without vessel entry. 

Decoking is a routine daily occurrence accomplished by a high-pressure water jet. First the top and bottom heads of the coke drum are removed then a hole is drilled in the coke from top to hottom.. A rotating stem is lowered through the hole, spraying a jet high-pressure water sidewavs... 

Depending on spray pressure and the strainer, pipeline, and valve resistance, the pumping head is normally in the 16 to 24 m range. 

Chromatograms can be made handleable and storable by treatment with plastic dispersions, based on polyacrylic ester, polyvinyl chloride or polyvinyl propionate, such as, for example, Neatan (Merck) [21 — 23]. In order to avoid clogging the spray head with plastic dispersion residue it is recommended that it be rinsed through immediately after use with tetrahydrofuran or that disposable jets be employed [24]. 

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