Gasket function

Resistance to creep/stretch Stability of edges Resistance to abrasion Stability to vibration Dimensions of available supplies Ability to be fabricated Sealing/gasketing function... 

Thiols iateract readily with many mbber-containing materials. For this reason, care should be taken ia the selection of gasket and hose materials. Teflon, Kel-F, Viton, or other suitable fluoroelastomers function as gasket materials. Viton is suitable for hoses. Carbon steel is useful for many thiols, although some thiols become very discolored when carbon steel is utilized. In these cases, the use of stainless steel is very desirable. Isolation from air and water also minimizes color formation. 2-Mercaptoethanol and 1,2-ethanedithiol should be stored ia stainless steel (61). 

Chemical compatibility is another important factor to reckon with in material selection as in the case of butterfly valves which are frequently used in industrial fluid flow systems where the valves are operated to load and unload different kinds of fluids for shipment or storage. These applications include tank trailers for transportation of fluids from one location to another as well as fluid flow pipelines. A typical butterfly valve usually incorporates a resilient rubber seal component which the valve pivots to seal off the flow lines and when opened allows the fluid to be conveyed to the flow line. The chemicals transported in tanks using butterfly valves are often caustic or acidic. These chemicals corrode the pivot area of the valve making its function ineffective. The rubber gasket material prevents leakage while the valve chamber is protected by a chemically resistant rubber material. 

In order to extend the analytical equations to a fractal lattice, we will need the radial distribution function rdf(r) of the Sierpinski gasket, rdf(r) dr being the average number of sites with distance between r and r + dr from a given site. For fractal lattices one has... 

In order to determine the constant 7, we computed the radial distribution functions for the two types of the Sierpinski gaskets under consideration. In Fig. 6.6 these functions are plotted, as averaged over all sites of the finite gaskets at the 11th stage. Due to the finite size of the structures, deviations... 

Fig. 6.6. Radial distribution functions rdf(r) for the two types of the Sierpinski gaskets a and b (dots) and ideal rdfs (solid curves) with d = 1.58 and 7 = 3.65 (a) or 7 = 5.2 (b) (see equation (6.1.30)). Note, that both axes are logarithmic.

All valves contain rubber components (gaskets, tank seals, seats, or sleeves) and at least one stainless steel part (spring). Both are vital to valve functionality. Some types of valves contain more plastic or stainless steel components than others. Drawings of individual subcomponents of the valve should be on hand for reference to the incoming components. Periodic checking of the rubber or other components may be needed to ensure that the supplier has not changed any compositions or processing procedures. 

The basic principle of the DAC is extremely simple [6,7] an anvil is made of a brilliant cut diamond with the tip cut to form a small flat part, the culet. In a DAC, two such anvils are placed in front of each other, with the culets parallel. The experimental volume is a cylindrical hole drilled in a metallic foil, the gasket. In that volume are the sample, a pressure gauge, normally a ruby chip, whose luminescence is calibrated versus pressure, and a pressure transmitting medium whose function is to ensure the stresses on the sample are as homogeneous as possible (FIGURE 2). All DACs work with the same principle. They differ only in the way the force is applied on the diamonds. 

The rapid development of carborane chemistry is mainly due to their practical applications. For instance, the potential utility of carborane polymers as gaskets, O-rings, and electrical connector inserts has been reported. Their functionality for solvent extraction of radionuchdes as well as the potential medicinal value of the isoelectronic and isostructural boron analogues of biologically important molecules has been the subject of many review articles. For example, a number of boron compounds have been found to possess anti-inflammatory and antiarthritic activity in animal model studies. Boron compounds have also been implicated in studies designed to probe the importance of the so-called anionic subsite of acetylcholine esterase and Ach receptors. But, by far the most interesting practical apphcations of carboranes are in areas of boron neutron capture therapy (BNCT) and supramolecular assembly. 

The elastomeric sealing components of the metering valve are particularly critical. In those valves used with CFC propellants, the elastomeric seals have typically been formed from an acrylonitrile/butadiene rubber, which has been cured with sulfur. These rubber seals may not be fully compatible with HFA propellants hence, alternative elastomeric materials have been used. These materials include peroxide-cured acrylonitrile/ butadiene, ethylene-propylene diene monomer (EPDM), and chloroprene and thermoplastic elastomers (TPE). The elastomeric materials used to form the dynamic seals around the stem and the static gasket seal between the can and valve may differ based on the required properties of the rubber for the specific function of the seal. The most important characteristics of the elastomeric seals... 

The metering valve in an MDI is the critical component in the design of an effective delivery system. The main function of the metering valve is to reproducibly deliver a portion of the liquid phase of the formulation in which the medication is either dissolved or dispersed. The valve also forms the seal atop the canister to prevent loss of the pressurized contents. The valves generally comprise at least seven components that are constructed from a variety of inert materials. Typical materials of construction are acetal or polyester for the valve body, stainless steel or acetal for the valve stem, generally anodized aluminum for the ferrule, and butyl, nitrile, or neoprene for the elastomers used in the seals and gaskets [43],... 

Depth Stop. Use a depth stop adapted to various kinds of valves and pumps. The shape of the depth stop must be designed according to the external shape of the valve ferrule. The depth stop has three functions. It transmits the necessary force to compress the sealing gasket it enables adjustment of the crimping height and it positions the valve ferrule correctly inside the crimp collet. The result is a good concentric crimp. 

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