3.10 Accessories

Gaskets and O-rings

For flanged connections at ambient conditions it is recommended to use gaskets of PTFE [poly(per)tetrafluoroethylene] or graphite with a reinforced rim inside. O-rings in ethylbenzene service should be made from a co-polymer of fluorinated ethylene and fluorinated propylene. Rubber or other ethylbenzene soluble materials and PTFE encapsulated O-rings should be avoided. For gland sealing, graphite (optionally PTFE) is the material of choice.

Filters

Since small amounts of foreign matter may enter a storage tank from various sources, a filter in the transfer piping between tank and processing equipment is recommended. A replaceable cartridge or filter is recommended. Suitable materials are polyester and nylon. Especially for seal-less pumps, an inline basket strainer is recommended. The strainer will have adjacent isolation valves and connections for blowing it clear, for safe removal and cleaning.

Flexible Transfer Hoses

To avoid product contamination, the most important aspects for transfer facilities are easy cleaning and product compatibility. Therefore lightweight aluminum pipe and swing joints, with seals of fluoroelastomer are preferred. Composite hoses, which are static-conductive, and flexible metal hoses (woven metal type) are satisfactory, but they require more care and attention to keep them properly clean and to prevent damage or breakage during use. Hoses from fluoro-olefin elastomers give the best service and are the most widely used of the composite hoses. Neoprene elastomer synthetic hoses do not have sufficient resistance to aromatics and are therefore not recommended for ethylbenzene service. Multi-layered polypropylene and PTFE hoses are flexible and chemically resistant, and are therefore recommended materials. Because ethylbenzene can attack the interior of a hose, it should never be allowed to stand in any of the composite hoses. All residual ethylbenzene should be drained, and all intermittently used transfer lines should be thoroughly cleaned to prevent formation of undesirable reaction products. All transfer lines and hose connections should be properly grounded to prevent build up of static electricity. Regular preventive maintenance is recommended for flexible transfer lines.

Further details on material compatibility with ethylbenzene are found in Appendix 3.

CEFIC
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Patrick Detournay
T +32 2 676 72 05
E pdt@cefic.be