Gaskets flexible graphite

Gaskets, flexible graphite being preferred, but also including soft metal seals such as copper. VolatQe metals and metals which have a low melting point must be avoided (e.g., tin, lead, zinc, cadmium, indium). 

Gaskets uti1i2ed in ethyleneamine service generally are made of Grafod flexible graphite or polytetrafluoroethylene (TEE). There is no single elastomer that is acceptable for the entire product line, although TEE may be considered as an alternative to elastomers across the product line. However, because TEE is not a tme elastomer, it may not always prove suitable as a replacement. 

Baked phenolic-lined earhon steel is acceptable for storage of many pure ethyleneamincs. except EDA. Gaskets utilized in ethyleneamine service generally are made of Grafoil flexible graphite or polylclrafluoroelhy-lene (TFE). 

To demonstrate that flexible graphite gaskets can accommodate some difference in the degree of expansion between the membrane and module components, the experiment was repeated using feed-charmel and permeate-channel frames made of 304 stainless steel, while the membrane support remained Monel. Cyclic durability was very good, and the membranes remained devoid of visible wrinkles. 

Other areas of corrosion concern are the membrane seals. If the seals are composed of flexible graphite, a preferred sealing material as discussed above, then corrosion by the common feed stream constituents is not a problem. However, with any metal seal - whether it be a brazed, welded, or soft-metal gasket seal - it is prudent to evaluate the potential for corrosion specifically at the seal. This evaluation is complicated by the fact that with brazed and welded seals, the metallurgy of the seal is influenced by the addition of the membrane alloy to the liquid braze alloy or weld pool. Experience has shown that welded seals to Pd—40Cu membranes, in which the membrane is welded to either Monel or 304L stainless steel, rapidly fail when subjected to 50 ppm hydrogen sulfide at 400 °C. 

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