Gaskets material selection

Membrane manufacturers frequently have as much technology and art invested in the selection and processing of the tubesheet and sealants as in the membrane itself. Understandably, much of the details about tubesheet and gasket material selection and processing is considered proprietary and trade, or closely guarded, secret information by membrane manufacturers. 

The values in Table are for ambient conditions oniy The gasket material selection is based on the design temperature and the process conditions. The properties for seating and seaiing of the gasket should be based on the ambient properties. 

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). 

The following factors must be considered when selecting a gasket material ... 

Confirm the selection of membrane and gasket material for a full-scale facility. 

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. 

Table 9 presents information on the corrosion resistance of some common metals, nonmetals, and gasket materials. Table 10 presents similar information for various types of plastics. These tables can be used as an aid in choosing materials of construction, but no single table can take into account all the factors that can affect corrosion. Temperature level, concentration of the corrosive agent, presence of impurities, physical methods of operation, and slight alterations in the composition of the constructional material can affect the degree of corrosion resistance. The final selection of a material of construction,... 

Gaskets, printed, in hydraulic control equipment, 147 base plates, 151 failure in, 155 load-deflection curves, 149 material selection, 150 polyurethane seal, 149 production, 150 screen printing, 152 specification development, 155 testing and quality control, 154 Gears, plastics, 42-64 bending stresses in, 47, 52 Lewis formula, 52-4... 

There is a considerable possible choice of gasket material in many applications. The decision as to which gasket material is to be selected is often based upon the required gasket width. If the gasket is made too narrow, the unit pressure on it may be excessive. If the gasket is made too wide, the bolt load will be unnece-ssarily increa. A relationship for making a preliminary estimate of the proportions of the gasket may be derived as follows ... 

Figure 12.28 shows the partuil design of a pressure vessel. Determine the ma.ximuin Of rating pressure for the vessel based upon the shell dimensions and material (see OI apter 13 for allowable stresses and code equations). For this pressure select a suitable gasket material and determine the optimum number and size of the bolts assuming a hub thickness, equal to 3 in. The service temperature is 400" F. 

Besides the bipolar plate, the gasket material is an important component of the fuel cell stack and tends to be heavily underestimated. It plays a key role in the mechanical properties of the stack, compensated tolerances and partially determines the mechanical compression of the MEA. Inappropriately selected gasket materials may cause failure of the MEA or fracture of the bipolar plates. Despite the fact that the gasket has only to seal the stack, it is a highly challenging issue due to the tolerances of the other components which have to be managed. And last but not the least, the gasket has to be cost attractive. 

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