Seals flexible graphite

A simple, but efficient reactor concept was developed based on the insertion of metallic wires that serve as a catalyst into a micro channel. The wire extends over the channel length and can thus be contacted electrically for heating purposes. It is sealed by graphite seals at both reactor ends. In this way, an easy, flexible and cheap concept for catalyst exchange and reactor assembly is provided. 

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). 

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. 

Graphite is offered moreover in flexible sheets (e.g. Sigraflex of the SGL-Carbon Group). This is primarily a sealing material, but it is suitable also as electrode or corrosion resistant current feeder (erosion in case of gas evolution is possible). 

Now many composite materials are used in aircrafts (Fig. 18). Graphite/epoxy and graph te/Kevlar are commonly used. For these materials, polysulfides (120) have been used as sealants. To provide airframe integrity, everything has to be sealed, preferably with flexible sealants that allow joint movement, fuel and weather resistance, and corrosion prevention. Today airframes are guaranteed to have a service life of 20 years without any corrosion damage. For this reason, the inhibited polysulfides are used to prevent corrosion between aluminum and graphite/epoxy composite parts. 

The motor is coupled to the pump by means of a flexible spacer type gear coupling. The coupling is provided with a spacer sleeve of sufficient length to ensure easy maintenance of the shaft seals and the graphite bearing. 

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