Blow Molding Fuel Tanks
Blow Molding Containers
“Fuel tanks of thermoplastic materials are in principle to be impermeable in relation to hydrocarbons. They are usually produced from multi-layer co-extrudates which include barrier layers for hydrocarbons. The plastic materials used for the production of plastic fuel tanks, for example polyethylene, are in principle not diffusion-tight in relation to hydrocarbons. In addition those plastic materials have a tendency to swell in the presence of fuel. For that reason the known fuel tanks of plastic material are provided with a multi-layer wall in which an EVOH layer is embedded as a barrier to hydrocarbons. In that respect the lack of diffusion-tightness of the base material used does not represent a problem.
Usually however fuel tanks are provided with installation fitments which have air intake and venting conduits as well as electrical connections. To produce passage means which pass through the tank wall, it is known for the finished tank to be provided with marked-out circles into which connecting nipples, valves or the like are fitted. The valves, valve covers and nipples are welded to the outside wall of the tank in such a way as to cover the respective opening. Such connecting locations on a plastic tank represent potential leakage points. In order to avoid leakage paths at connections of the fuel tank it is known for connecting nipples and valves to be produced in the form of complicated and expensive two-component structural members, wherein generally those structural members have at least one part comprising a plastic material which is weldable to the tank wall, whereas functional parts on such members usually comprise plastic materials which do not swell in the presence of fuel. Those plastic materials (ABS, POM) generally cannot be welded to the plastic materials used for the tank wall.
Frequently installation fitments, valves and connecting nipples have to be connected to the tank in a manual manufacturing stage after the tank is finished. It is known for example for parts of valves to be latched on the inside of the tank wall and to be connected in positively locking relationship on the outside to weld-on covers, weld-on nipples or the like. The complication and expenditure involved in assembly is considerable.”
[Borchert et al, US Patent 8,287,799 (10/16/2012)]
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Roger D. Corneliussen
Maro Polymer Links
Tel: 610 363 9920
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Copyright 2012 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
* Date of latest addition; date of first entry is11/1/2012.