Figure 3.22. Designations of Compromise Bars.
3.31. INSULATED JOINTS
Insulated joints are found in automatic block territory on each track at block limits, on all
crossovers and turnouts, and where highway crossing gates or lights are electrically operated.
They are also used to isolate spurs on which gasoline is to be unloaded from track used in
electric circuits. Joints connecting rail of the same section and those known as compromise
joints are insulated where necessary. They are called insulated same-section joints and insulated
compromise joints, respectively.
To insulate a joint, the procedure is as follows. A fiber insulator is placed between the
rail base and the joint bar base; insulating bushings are placed around the bolts securing the bar;
fiber washers are placed under the nuts; and fiber end post insulators, shaped like the rail, are
placed between the two rail ends with no room for expansion.
Insulated joints are the source of continual maintenance annoyance; of all rail joints, they
are said to be the weakest. To keep insulated joints in good. condition, the bolts must be kept
tight and the ties under the joints should be the best; they must be well tamped with clean ballast
and well drained to prevent the joint from pumping and churning and to prevent excessive wear
of the fiber. Loose ties cause the fiber to wear out quickly, and this may cause failure of the
signal.
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