AAR & DOT SHELF COUPLERS

All hazardous material cars must be equipped with couplers having top and bottom shelves projecting from head end front faces.  The purpose of the shelves is to prevent vertical coupler disengagement during train derailment and thereby minimize the potential for tank car shell puncture.  All AAR standard E, E/F and F couplers are available with top and bottom shelves.  These are identified by prefixes to the coupler catalog numbers as follows:

SE – Double Shelf (Top & Bottom) E and E/F Couplers

SF – Double Shelf (Top & Bottom) F Couplers

All new and rebuilt cards must be equipped with couplers having a bottom shelf as a minimum requirement.  The bottom shelf serves to support a mating coupler suffering a pull-out from car sill and this keeps it from falling to the roadbed and presenting a derailment hazard.  The shelf also serves to prevent vertical coupler disengagement during derailment, as related to the mating coupler.  The bottom shelf is effective when the 10-A contours of the mating couplers are within AAR specified condemning limits.  Bottom shelf couplers are identified by prefixes:

SBE – Bottom Shelf E Couplers