CEMP-E
TI 850-02
AFMAN 32-1125(I)
1 MARCH 2000
(3) Size and Designation. Derails must be ordered for the size of rail on which they are to be
installed. The number of the derail usually indicates the distance (in inches) from the top of the rail to the
top of the tie (including tie plate thickness). Derails generally come in even 1-in. sizes and can be
shimmed up to a height of 0.5 in. (or the ties on which the derail is attached can be added up to 0.5 in.
deep) to accommodate height variations.
(4) Direction. Derails are designed as either left-hand or right-hand. The proper direction is
determined by looking in the direction that the rolling stock to be derailed would be moving. A right hand
derail is installed on the right hand rail and derails the cars off the right side of the track, while a left-hand
derail is installed on the left-hand rail and always derails to the left.
b. Bonded and Grounded Track.
(1) Wherever cars carrying fuel, ammunition, or other flammable or explosive materials are unloaded,
or where track is located adjacent to electrical equipment, the rails (and related track materials capable of
conducting electrical current) must be bonded, grounded and insulated from the remaining track. This
bonding and grounding helps prevent the discharge of static electricity during the loading or unloading of
these hazardous materials. General requirements for bonding and grounding are given below; additional
details are found in chapter 33, part 7 of the AREMA Manual.
(2) When a side track, or section of running track, is to be bonded and grounded, an insulated joint
should be provided on each rail at the first rail joint beyond the turnout of the adjacent main track at either
end of the main track. The rails at all other joints in the track beyond or between the insulated joints will
be bonded together with bond wires and both rails of the bonded track will be connected by grounding
connectors to a single driven ground rod.
(3) An exothermic type rail bond ("cadweld bond") is recommended for the application of rail bonds
on military track. Bond cables should be flexible bare copper stranded 1/0 AWG cables with preformed
ends and should conform to the applicable requirements.
(4) Grounding rods should be 0.75-in. diameter copper clad steel rods or 1-in. diameter zinc coded
steel rods. The minimum length of ground rods should be 8 ft. Ground rods should be driven vertically
for their full length, and the top of the ground rod should be located a minimum of 12 in. below the top of
the subgrade at the toe of the ballast slope. The maximum allowable resistance of grounded rail or
structures is 25 ohms.
(5) All electrical connecting hardware should be bronze pressure type materials and have no rotating
parts coming in direct contact with the conductors.
(6) Rail cross bonds are required to bond the two rails together and to connect the rails to the
grounding rods. Rail cross bonds should be installed using exothermic type bonds and 1/0 AWG flexible
bare copper stranded cable. The cross bond should be applied to the rail head or rail web and the cable
for the cross bonds installed a minimum of 12 in. below the bottom of the ties. One cross-bonded ground
rod should be installed at 100-ft intervals along tracks designated for the loading and unloading of fuel,
ammunition, and other volatile or hazardous materials.
(7) Defective bonds will be removed by shear cutting old cables immediately adjacent to the weld or
pin. Flames or torches will not be used to remove defective or out-of-service bonds.
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